# Spindle square



## DPittman (Nov 14, 2021)

Still practicing with milling machine (trial and error)  I made myself a spindle square out of salvaged material.  I loosely used Dale Derrys video series, "Metal tips and tricks" as an inspiration.

The aluminum was cut from an 8" round log of extruded aluminum (soft, gooey stuff), the brass screws





 were made from salvaged water valve stem, and the shank was rod salvaged from an old printer.  

I did some "jeweling" on the back side with a small chunk of scotch Brite pad glued to a piece of wood doweling.  If I would have changed out the scotch Brite pad several times I would have had a better more defined job.  

It was a first attempt with a ball end mill and I'm not happy with the finish it gave but I think at least part of that is the material I was working with.  

I have two different mounting distances for the indicators as I have only a 4" vise on my mill but wanted to get maximum distance for table squaring so I made 3.5" and 5" spaces.


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## gmihovics (Nov 14, 2021)

Looks like you did a good job to me. I've seen these on a bunch of people using these on YouTube channels lately but never a homemade one. what kind of accuracy do you think you will get from this?

Also, I'm amazed at the level of scavenged materials around here. I always keep parts for building printers or machines but never thought to keep it for turning or milling until I joined the forum.


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## Susquatch (Nov 14, 2021)

gmihovics said:


> Looks like you did a good job to me. I've seen these on a bunch of people using these on YouTube channels lately but never a homemade one. what kind of accuracy do you think you will get from this?
> 
> Also, I'm amazed at the level of scavenged materials around here. I always keep parts for building printers or machines but never thought to keep it for turning or milling until I joined the forum.


I only buy new stock when I absolutely have to.

Almost all my stock is salvaged or scrounged or traded.

For the lathe, you will find old bolts are a terrific supply source. Look at equipment company dumpsters, farm machinery shops, highway construction sites, old street-light post anchors. etc. You can get regular Bolts, grade 5 Bolts, grade 8, and of course Stainless. They are usually pretty good steel. Just turn the threads off and or galvanized coating off and use as appropriate. Brass and aluminiun is harder to find that way.


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## DPittman (Nov 14, 2021)

gmihovics said:


> what kind of accuracy do you think you will get from this?


I would expect the accuracy all depends on the indicator repeatability and resolution.


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## YYCHM (Nov 14, 2021)

So, if you find that your head is out of tram how will you correct that?


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## Susquatch (Nov 14, 2021)

gmihovics said:


> what kind of accuracy do you think you will get from this?



I don't have one and have not considered making one either.

For my purposes, I have found that an indicator mounted to the outside of the spindle or in a collet or even a drill chuck is plenty good enough. I cannot get my milling machine trammed in any better than a 1 thou indicator anyway. Any runout in the collets or drill chuck or spindle OD is totally cancelled out if you only use one indicator and turn the spindle by hand using a 3/4" socket and wrench on the Drawbar.


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## DPittman (Nov 14, 2021)

YYCHM said:


> So, if you find that your head is out of tram how will you correct that?


Go to the chiropractor and get an adjustment I guess.

Well the mill has adjustment for tramming the on the x axis but it has no nod adjustment so I guess that would have to be done with shims.


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## DPittman (Nov 14, 2021)

Susquatch said:


> I don't have one and have not considered making one either.
> 
> For my purposes, I have found that an indicator mounted to the outside of the spindle or in a collet or even a drill chuck is plenty good enough. I cannot get my milling machine trammed in any better than a 1 thou indicator anyway. Any runout in the collets or drill chuck or spindle OD is totally cancelled out if you only use one indicator and turn the spindle by hand using a 3/4" socket and wrench on the Drawbar.


Well I could be wrong, but when you calibrate the two indicators to read the same thing in the same spot that accomplishes the same thing as you are doing with using just one indicator.  The spindle square is no better than using just one indicator just more convenient.


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## Susquatch (Nov 14, 2021)

DPittman said:


> Well I could be wrong, but when you calibrate the two indicators to read the same thing in the same spot that accomplishes the same thing as you are doing with using just one indicator. The spindle square is no better than using just one indicator just more convenient.



I think you are absolutely correct on all counts except the convenience part. You might be right on that too, but I think by the time you finish calibrating the two gauges to read the same thing, you could be finished tramming your head. 

Then again, I am so used to dialing in a part on my lathe that I found tramming my mill to be a total cake walk.


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## gmihovics (Nov 14, 2021)

i was just wondering about the the accuracy of the shaft into the main body. if the shaft hole isn't completely perpendicular to the body, wouldnt that introduce some inaccuracy?


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## Susquatch (Nov 14, 2021)

DPittman said:


> but it has no nod adjustment so I guess that would have to be done with shims.



Ya, at first I had trouble with adjusting nod. But as soon as I realized that both front and back measurements move the same way except in magnitude, it got fairly easy too. You just can't use the rule of halves in the normal way.


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## Susquatch (Nov 14, 2021)

gmihovics said:


> i was just wondering about the the accuracy of the shaft into the main body. if the shaft hole isn't completely perpendicular to the body, wouldnt that introduce some inaccuracy?



The body concentricity doesn't matter as long as you don't try to use it. You just use the spindle axis. If that doesn't run true, it's time for a new machine or a major rebuild!


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## Brent H (Nov 14, 2021)

The biggest reason to use this type set up on, say a Bridgeport or clone, is that tramming the mill in the Y-axis is a bit more of a PITA.  This is because of the way the head is off set and any error on the y-axis gets worse very quickly.  It is very quick to get the 2 indicators reading the same.  By using the two indicators I can set up from a head tilt operation in a few minutes.


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## DPittman (Nov 14, 2021)

gmihovics said:


> i was just wondering about the the accuracy of the shaft into the main body. if the shaft hole isn't completely perpendicular to the body, wouldnt that introduce some inaccuracy?


Nope that's what the calibrating the indicators to read the same in the exact same spot accomplishes. Remember this isn't a always turning thing, it just turns 90 degrees to read the two planes concerned with tramming a mill.


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## Susquatch (Nov 14, 2021)

Basically, any part that is solidly attached to the spindle will run as true as the spindle does.


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## Susquatch (Nov 14, 2021)

Brent H said:


> The biggest reason to use this type set up on, say a Bridgeport or clone, is that tramming the mill in the Y-axis is a bit more of a PITA.  This is because of the way the head is off set and any error on the y-axis gets worse very quickly.  It is very quick to get the 2 indicators reading the same.  By using the two indicators I can set up from a head tilt operation in a few minutes.



I confess I'm a bit surprised at you Brent! I would have figured you could do that kind of math in your head without even thinking about it! Mere mortals like me have to do the trigonometry. It's just the two different angles from the front and rear of the table to the head's pivot point! I do an adjustment, look at how much they both moved and then ratio that to get to where they are the same. Two or three adjustments later and you are there. I confess I had to think about that a bit the first time I did it though.... 

I have also thought you might be able to use either of the midpoints with a half rule to get you there too but I never tried it. Then again, maybe not..... I guess I should actually try that last one before I shoot my mouth off.......LOL!


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## Brent H (Nov 14, 2021)

HA HA! @Susquatch : yes - doing some math and calculation is all good but in the couple minutes it takes with the spindle square.........  plus, having ten dial indicators is one thing, but if over half of them have a dedicated purpose - that is another   and when the boss comes out and dials are adjusting and things are spinning about and the work place is happy.....way better than a bunch of sailor language (which I have proper training in ) after over shooting the adjustment a few times.  LOL

Plus it was neat to make ..... one of the joys of shop


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## PeterT (Nov 14, 2021)

DPittman said:


> I would expect the accuracy all depends on the indicator repeatability and resolution.


...and also the arm distance from the spindle post to indicator stem. You could elongate the bar segment for even more accuracy, but most people keep it compact like yours to match the table width in Y direction. Unless you happen to have a nice, long, accurate parallel bar to lay over the table. I use my Noga arm with DTI & mag base stuck to underside of spindle (no tool in). It's quick but still 1-dial rotate operation. The 2 dials would be convenient in nod adjustment mode, just bump-bump till they agree. You can also use this method to check you vise ways relative to table.

Another useful test with your tenths DTI held in quill is run it up & down the fixed jaw of mill vise using quill or knee. Better yet clamp a good 123 block with soft filler on the moveable jaw side. The extra block length will exaggerate the jaw discrepancy beyond its vertical width. The idea here is to see how the fixed jaw aligns to quill axis. If it's out (could be jaw, could be vise bed...) this works against you when it comes to milling square stock despite the roll/rotate the machined part recipe sequence. If the jaw is out, it will be parallelogram-ish at best.


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## Dusty (Nov 14, 2021)

I also designed my hybrid spindle square from Dale Derrys video series, "Metal tips and tricks".

Checks it out here:    









						Spindle Square
					

Finally got around to making my DIY Spindle Square for my small mill/drill although with my lame leg the doing wasn't easy like a half hour here and there.  Material used was a 4 & 1/2" of (oversized .0005") by 1/2" drill rod and a piece of 1"x1"x 6" of aluminum. Two 5/8" long by 1/4" 20NC cap...




					canadianhobbymetalworkers.com


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## gmihovics (Nov 14, 2021)

Susquatch said:


> The body concentricity doesn't matter as long as you don't try to use it. You just use the spindle axis. If that doesn't run true, it's time for a new machine or a major rebuild!





DPittman said:


> Nope that's what the calibrating the indicators to read the same in the exact same spot accomplishes. Remember this isn't a always turning thing, it just turns 90 degrees to read the two planes concerned with tramming a mill.



ok yup, that makes total sense, I didn't think about calibrating both dials on the same spot first. that solves the issue.


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## Susquatch (Nov 14, 2021)

Susquatch said:


> I have also thought you might be able to use either of the midpoints with a half rule to get you there too but I never tried it. Then again, maybe not..... I guess I should actually try that last one before I shoot my mouth off.......LOL!





Brent H said:


> yes - doing some math and calculation is all good but in the couple minutes it takes with the spindle square.........



OK, sometimes I am a sucker for punishment and way too curious about how things work and why they work that way. I just couldn't help myself. So I did some thinking.

There are a few observations that may be obvious to many and not so obvious to others.

First off, I accept that the square tool is both fast and convenient. For those of us without one, the process isn't horrible though - just a lot more rigorous. Here are my thoughts on the matter. 

Unlike a regular clockwise / counterclockwise tram, a nod tram is not done on an axis that transects the bed. That's because the nod center of rotation is located quite a bit rear of the bed.

Therefore a standard split the difference approach to reaching tram square does not work. In fact, I was outright wrong to think it ever could. 

Basically, because the nod center of rotation is behind the bed, all the points that might be used on the bed to determine a tram condition *all increase simultaneously as the head nods up* or they all decrease simultaneously as the head nods down. However, *the rate of increase or decrease changes in linear proportion to how far they are from the center of nod*. The further they are forward toward the user, the faster they change.

This last fact can also be used to advantage to improve tramming accuracy. I think everyone accepts that the longer the distance used to measure points on any plane, the better the obtainable accuracy. When tramming the nod, I think it is better to use the bed in the fully forward position EVEN if that means that the spindle is behind the bed. The reason for this is that moving the bed as far forward as possible, also increases the distance from the center of nod rotation to all the points that might be used and therefore increases the relative accuracy that can be achieved. For this assessment, I arbitrarily chose a point at the front of the bed and a point at the rear of the bed. As long as the head has already been trammed in the X-axis, neither one of the two nod reference points needs to be in line with the spindle. However, they do need to be somewhat consistent. 

It will also be obvious to most others that adjusting nod should be done in the direction that tilts the head up. Just like moving a table or any other machining operation, backlash is best removed when working against the natural forces. In this case, gravity is trying to pull the head down, so it's best to operate the rack in the lifting direction in order to remove all the backlash while turning the nod pinion on the nod rack to change nod.

With these observations in hand, I set my mind to the business of how to tram the nod in a fast rigorous way instead of the trial and error method I have used myself and seen used elsewhere.

As noted above, its best to begin with the head down a bit from square. Then measure a position on the front and rear of the bed sequentially. If I began with the head nodded down a bit, the front bed position will be lower than the rear position. The head can then be lifted while measuring at the front by the entire difference between the two readings. This can be repeated until the difference is zero and then you are trammed.

The number of iterations can also be reduced by lifting the head by more than the difference. However as the difference gets small, this becomes more and more difficult to do. 

If one is extremely careful, the number of iterations can be reduced to two by carefully limiting the extra adjustment to the ratio of the two point distances to the center of rotation of the nod times the difference. 

However, overshooting square is easy to do, so I'm thinking that a somewhat more conservative approach is better. Besides, a few more iterations is a piece of cake if you are only swinging the indicator back and forth from the front to rear of the bed and back. Best of all, if the table is adjusted fully forward during this process, all the readings can be done without needing to go around to the other side of the mill to see the face of the indicator. 

OK, so now I need to get off my butt and make a tram square......... LOL! 

I might not make one that looks the same as a conventional one though. Mine will probably be triangular so I can keep the spindle behind the bed! Or does the improved accuracy really matter? Probably not for most operations. Maybe I'll make a conventional one too!


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## RobinHood (Nov 14, 2021)

Great description of what is happening.

Here are some thoughts:



Susquatch said:


> When tramming the nod, I think it is better to use the bed in the fully forward position EVEN if that means that the spindle is behind the bed.


That takes away from the “self proving“ ability of a rod held in the spindle. You want the spindle centered over the surface you are tramming so that any bend in the rod does not affect the indicator reading because it forces the rotation of said rod in the spindle by 180* in order to measure the opposite position. I think using a triangular shaped dual indicator holder only works if you know for sure that the vertical side is exactly 90* to the horizontal side of the triangle and that the vertical extension into the spindle is proven to be straight. Making such a tool is not without challenges.

One could probably accurately tram a milling machine head without an indicator(s) by using an ordinary fly cutter holder and a rod (clamped in the tool slot), the length of which is equal to 1/2 the table width, and a piece of paper or shim stock. Start by eliminating tilt in the +/- X direction first and then adjust the nod. You are trammed when in any position on the inscribed circle it takes the same amount of force to pull the paper/shim from underneath the rod end. The accuracy is limited by the spindle bearing/straightness (a constant, no matter which method of tramming you use) and the fine feel in your fingers only. No reading parallax or hysteresis of indicator springs to worry about. It would probably take a few tries in each axis to get there.


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## PeterT (Nov 14, 2021)

Maybe some pictures will help. The beauty of the 2-gauge is (once calibrated square & left that way) there is only 1 job: tweak the nod angle until both dial readings read the same. Both are conveniently facing the operator from the side so relative movement & convergence will be pretty obvious. The other thing I notice, at least on my machine, is just tightening the head can influence  position until its fully locked down. That's when its nice to simultaneously have your eye on the needle target to see what's going on.

I just made a fictional dimension example by eyeball to get a feel. This suggests 1 degree of nod is equivalent to 0.140" delta in gage readings. So if the dials are reading within a thou of each other, that's pretty good.

You could build a 'square' like the green sketch if I understand the idea - a vertical pin joined to a bar which is set precisely perpendicular at 90-deg. Which is probably the same or more work than the gage holder. And then what. I think it would be clumsy to implement to rest on the table or blocks or otherwise judging relative gap. The beauty of dials is they are virtually passive to the machine setup. If you need more accuracy, invest in a longer parallel & lay it along the table surface & spread the gages to suite will dramatically enhance the accuracy on same gage resolution.


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## Susquatch (Nov 15, 2021)

RobinHood said:


> That takes away from the “self proving“ ability of a rod held in the spindle. You want the spindle centered over the surface you are tramming so that any bend in the rod does not affect the indicator reading because it forces the rotation of said rod in the spindle by 180* in order to measure the opposite position. I think using a triangular shaped dual indicator holder only works if you know for sure that the vertical side is exactly 90* to the horizontal side of the triangle and that the vertical extension into the spindle is proven to be straight. Making such a tool is not without challenges.



I'm not sure I understand your self proving concept. I assumed (rightly or wrongly) that setting the gauge loads the spindle the same no matter which position it is rotated to. I also assumed that a crooked or loose spindle means you are screwed no matter how much effort you put into tramming.



PeterT said:


> Maybe some pictures will help. The beauty of the 2-gauge is (once calibrated square & left that way) there is only 1 job: tweak the nod angle until both dial readings read the same.



Ya, sorry. I meant to add my drawings but forgot. Your third and fourth are like mine. Except yours are much better looking because mine are hand drawn. 

Yes, after doing my assessment, I appreciate better the value of the 2 gauge tram square. But I need to understand why a triangular unit (think three gauges) wouldn't be better because it would allow the table to be further forward. Maybe after I understand @RobinHood's self proving aspect I will appreciate the situation better. 

I am really loving the mill learning curve. It's a whole new world. I wish I had bought a better mill right around the same time I bought a better lathe!


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## RobinHood (Nov 15, 2021)

Maybe “self proving” is not the correct terminology? It is used when talking about cylinder squares and the fact that they work without error, even though they may not be 100% “square”, due to the fact that you can rotate them through 360* while they are sitting on the surface plate to eliminate the manufacturing error.

The thought I had was that unless you can rotate the measuring tool round the spindle axis, the tool itself must be know to be square to the spindle. So with your idea that the table be at the FWD most position during the nod adjustment (and thus no room to rotate the tool because the spindle axis is off the table) the tool has to have been set perfectly to the spindle axis before the measurement is made as any error will cause the nod angle to be off by the same (or larger) amount as the tool’s error to the spindle axis.

If, on the other hand, one just centers the table underneath the spindle in Y, the measuring tool can be rotated and the “self proving” concept can be taken advantage of and it absolutely does not matter that the tool’s physical axis be dead nuts inline (and it’s measuring axis 90* to that) with the spindle axis because the rotational axis will be in line and that is all that matters.

This principle can be shown with laser centering devices: as long as the laser point is rotated, the axis of the laser pointer itself does not need to be co-axial to the spindle. You just center the light circle over your desired position (center punch mark, hole, edge, etc) and the spindle center will be there as well.

Hopefully this is a more understandable description of what I was on about in the previous post.


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## Susquatch (Nov 15, 2021)

RobinHood said:


> Maybe “self proving” is not the correct terminology? It is used when talking about cylinder squares and the fact that they work without error, even though they may not be 100% “square”, due to the fact that you can rotate them through 360* while they are sitting on the surface plate to eliminate the manufacturing error.
> 
> The thought I had was that unless you can rotate the measuring tool round the spindle axis, the tool itself must be know to be square to the spindle. So with your idea that the table be at the FWD most position during the nod adjustment (and thus no room to rotate the tool because the spindle axis is off the table) the tool has to have been set perfectly to the spindle axis before the measurement is made as any error will cause the nod angle to be off by the same (or larger) amount as the tool’s error to the spindle axis.
> 
> ...



I'm sorry @RobinHood, I still don't understand your point. Maybe I need another good nights sleep. We had 3 of our grandsons here for the weekend (7,10,&13) and they totally whacked me out.

I had thought your point involved relative movement between the indicator tip and the spindle somehow. But with your second attempt, I don't think that was your point afterall. Unfortunately, I am still left without a clear "I see".

Does your point still apply with a single indicator mounted to a swing arm that is solidly fixed to the spindle axis say using a collet on a bent indicator arm that is sweeping back and forth between front, side, and rear? If so, perhaps you could use that mechanism to explain your point because we would both have a common visual in our heads.

If not, then perhaps you could try to use that example anyway because that is the way I have always thought that it was done when one didn't own a two gauge square. So I assume that it is a valid way to do it.

Basically, I assume that a spindle axis that is perpendicular to the plane of the bed on two axis (x & y) would also be square on all other axis on the x/y plane - because that is my understanding of the definition of a plane. If that is not true then I need a refresher in my elementary math.

I also assume that a rotating spindle must be just as square as the spindle axis itself and if it isn't, then the mill badly needs a rebuild. But assuming it is, any movement of the bed in X, in Y, and in any other axis that might be obtained by a rotating spindle is square, and would be so indicated by an indicator rigidly mounted to the spindle axis no matter how long the indicator arm was or where it was used on the bed. This of course is really not quite perfect because the spring on the indicator needle does cause the indicator mounting arm to bend a bit. But if the length and geometry of the arm does not change, then that should be a constant that cancels out.

I suspect, that you think I am not using the spindle itself but perhaps the nose or the housing. That is not the case. I am using an indicator that is solidly attached to the spindle axis and that is rotated (or swept) by turning the spindle.

I am also using an indicator needle that is sweeping the bed surface. I don't have a parallel or a precision plate big enough to cover the whole bed, so some discretion must be used in choosing the best measurement location to avoid nicks and pecker marks.

I don't really see why the spindle can't be behind the bed under these conditions. A plane is a plane whether or not a solid surface is present. An indicator needle that is swept on the surface of that plane should show any non alignment between a plane that is square to the spindle axis, and the plane that is not, no matter where it is. 

Sorry for being so thick.


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## RobinHood (Nov 15, 2021)

Susquatch said:


> When tramming the nod, I think it is better to use the bed in the fully forward position EVEN if that means that the spindle is behind the bed.


 My comments are based on this part of your statement.

If you do that, I can’t see how you can sweep the indicator (either a single one or the tramming tool) and still contact both the front part of the table and, after turning the indicator 180* in the spindle, contact the rear of the table. Both contact points are necessary in order for the sweep method to work and eliminate the instrument mounting error.

If you devised some sort of device so that you can have the table all the way FWD (spindle Center is now behind rear edge of the table), then the measuring device needs to be accurately calibrated beforehand and also mounted in the spindle axis to the head in order for the nod to be eliminated, because you can no longer sweep the plane of the table and thus the set-up is no longer ”self proving”.

Hope that helps.


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## DPittman (Nov 15, 2021)

Don't want to derail the good discussion going on but just a small update on fixing a "problem" on my spindle square that shouldn't have happened.

The stem (not the moving part) of the indicators measures .375" so when I made my holes for mounting I thought "well I'll just use a 3/8" drill bit because that will also give me some clearance as a drill bit usually drills oversize somewhat". The holes ended up being sloppy loose and I hated how the indicators bobbled around until I tightened up the screw.  Ya it probably didn't matter much to the operation but it bugged me, so I bored out new holes and made brass inserts with a REAMED hole that fits perfectly now.  I got to try out my new coaxial indicator for re-entering on the shaft hole.  Yes too much "work/time" for the project but I enjoyed it all.  My shop time makes me a better man.


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## PeterT (Nov 15, 2021)

Susquatch said:


> I don't really see why the spindle can't be behind the bed under these conditions. A plane is a plane whether or not a solid surface is present. An indicator needle that is swept on the surface of that plane should show any non alignment between a plane that is square to the spindle axis, and the plane that is not, no matter where it is.


Sorry, you've lost me too. 
pic-1: I think a single indicator arm rotating about the spindle axis needs to make table contact on both the front & rear side of spindle is because its the difference in readings that will convey nod extent (distance 1 vs distance 2). 
pic-2: A plane is a plane but if the rotated arm (dashed line on right) is off in space, then you have no physical contact reference to the measurement you made on left hand side (solid).


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## Susquatch (Nov 16, 2021)

DPittman said:


> Don't want to derail the good discussion going on but just a small update on fixing a "problem" on my spindle square that shouldn't have happened.
> 
> The stem (not the moving part) of the indicators measures .375" so when I made my holes for mounting I thought "well I'll just use a 3/8" drill bit because that will also give me some clearance as a drill bit usually drills oversize somewhat". The holes ended up being sloppy loose and I hated how the indicators bobbled around until I tightened up the screw.  Ya it probably didn't matter much to the operation but it bugged me, so I bored out new holes and made brass inserts with a REAMED hole that fits perfectly now.  I got to try out my new coaxial indicator for re-entering on the shaft hole.  Yes too much "work/time" for the project but I enjoyed it all.  My shop time makes me a better man. View attachment 18316View attachment 18315View attachment 18314



She is beautiful @DPittman! 

No worries, I think it was my fault that this original thread took a left turn. But it is at least on topic. 

I'll be making something like yours soon enough!


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## 6.5 Fan (Nov 16, 2021)

DPittman that looks great with those brass inserts. I will have to contemplate making one.


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## Susquatch (Nov 16, 2021)

RobinHood said:


> If you do that, I can’t see how you can sweep the indicator (either a single one or the tramming tool) and still contact both the front part of the table and, after turning the indicator 180* in the spindle, contact the rear of the table. Both contact points are necessary in order for the sweep method to work and eliminate the instrument mounting error.





PeterT said:


> A plane is a plane but if the rotated arm (dashed line on right) is off in space, then you have no physical contact reference to the measurement you made on left hand side (solid).



You two guys seem to gang up on me a lot.....  LOL! No worries. I'm a contrary fellow and arguments seem to follow me around! I personally love it as long as it doesn't get nasty. I usually always learn something. Debates have been a healthy part of the way humanity makes progress.

I believe I now see where we seem to fall apart. In both cases, you guys are hung up on the idea that the two indicated points need to be 180° from each other.

To repeat your concerns stated in my words, if the spindle is off the rear of table and the front indication point is at the edge, then the rear point must be off the table too and there is no place to make a measurement. And even if there were, this introduces an instrument error of some kind.

I don't see why being at 180° is necessary nor why there should be an instrument error. (Actually, I do see the instrument error, but as I'll describe later - I believe it disappears at the end.)

Assumption #1 - Imagine for a moment that we lower the table so the spindle and anything attached to it is just kinda out there hanging in space. As you turn the spindle, the tip of an instrument attached firmly to the spindle scribes a "perfect" circle that is absolutely and perfectly square to the spindle axis in all directions. I have called this assumption #1 so you can more easily focus your counterpoints if you wish.

Assumption #2 - all the points on this circle are points that are on a flat plane that extends in all directions to infinity. However, for this discussion, we can limit the plane to a flat plate - either round or square that is hanging in space above the bed. For simplicity and ease of visualization, I'd suggest that we make it a round flat plate the same size as the circle scribed by the indicator tip.

Assumption #3 - If (and only if) the bed has already been trammed in the X direction, and if (and only if the nod has NOT yet been trammed and was started low) one can visually see that the front edge of the plate is closer to the bed than the back edge.  And yes, the plate does extend back behind the bed. But as both of you have pointed out, there is no place to measure the gap there. 

Assumption #4 - one can measure this gap anyplace that one chooses. But, I choose to measure it at the front edge of the bed and at either rear edge of the bed were it intersects the round plate. Neither of these two points are at 180° to the front point. Nonetheless, the gap at these locations will be greater than the gap at the front. Furthermore, if the bed is truly trammed on the X-axis, both rear measurements will be the same. Lastly, a line drawn between all three points will describe a triangle with the rear leg of the triangle parallel to the rear edge of the bed. 

Assumption #5 - as the nod is slowly tilted up, the DIFFERENCE between the front gap (at the front edge of the bed) and the rear gap (at the rear edge of the bed) will slowly disappear. Yes, both will get bigger, but the difference between them will shrink. 

Assumption #6 - (I bet you already know what I am going to say) when the difference between the front and rear measurements gets reduced to 0.0000, the nod is trammed. 

A little more discussion:

The plate does not know or care if the back edge is hanging out. The plate and the bed are either at an angle to each other with a differential gap, or they are parallel with no differential. 

In the singular case of nod adjustment (as I noted 2 posts ago), there is no such thing as halves. Equidistant points have no meaning anymore. The gap at both points (no matter where they are) is either increasing or decreasing. The geometry created by a hinge point so far behind the bed dictates that. It also dictates a ratio on the rate of change - not a differential. 

With respect to instrument mounting errors. I believe such errors may well exist when the plate and bed are at an angle to each other. However, I believe this error (if any) gets cancelled out when tram is reached. Because all points on the circle are in a common plane, any angular error in the instrument is absolutely the same no matter where it is. Therefore it gets cancelled out. 

Please note that I am NOT claiming that either of your methods are wrong. I'm only trying to illustrate that a different method works too. In a perfect world with a huge bed, I would choose to use a 180° differential too. But we don't have that. Since the differential grows with radius distance, I would prefer to pull the bed out as far as it can go because that is where the distances are greatest. 

Assuming that you both now understand what I am suggesting, I may make a triangular tram. 

OK, that's it. I'm done. Hopefully you agree. My flack jacket and hard hat are on. Fire away!


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## Susquatch (Nov 16, 2021)

6.5 Fan said:


> DPittman that looks great with those brass inserts. I will have to contemplate making one.



I dare say that @DPittman's gauge actually looks BETTER than it would have looked if the original holes had been a perfect fit!  Best of all, the indicators won't get scratched!!! I love it!  

Many an advance made is the result of a mistake that really wasn't......

Well done @DPittman !


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## Brent H (Nov 16, 2021)

@Susquatch - is the frown you sent me now upside down? 

Seems like you have embraced the idea of the  spindle square or triangle or tetrahedron or ellipse .....etc


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## Susquatch (Nov 16, 2021)

Brent H said:


> @Susquatch - is the frown you sent me now upside down?
> 
> Seems like you have embraced the idea of the  spindle square or triangle or tetrahedron or ellipse .....etc



Yup, it is. As you said earlier, it isn't really "will it work?"

It's just plain easier and I'm in for that all day every day! Might make an ellipse though..... JFTFOI! How cool would that be!


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## Susquatch (Nov 16, 2021)

Brent H said:


> @Susquatch - is the frown you sent me now upside down?
> 
> Seems like you have embraced the idea of the  spindle square or triangle or tetrahedron or ellipse .....etc



Imagine a deliberately twisted up gnarly looking fixture. With beautiful brass gauge mounts, And maybe a deliberate optical illusion to totally camouflage the hidden plane...... Yup, Lovin it!


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## historicalarms (Nov 16, 2021)

What is this "mill head trammeling" thing y'all are going on about....asks the guy with a big $hit eating grin & solid head mill-drill (the only time he gets to grin when comparing a Bridgeport type to a mill-drill).


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## RobinHood (Nov 16, 2021)

@Susquatch , no need for personal protection gear!

A agree with all your assumptions & points in post #32. It for sure will work.

Not sure if it was you or someone else said that the nod can be trammed out quickly with just a few iterations.

The main purpose of the tool that @DPittman made is to speed up the tramming process (once the tool is calibrated). I think that a tool like that can do that.

I think that’s where @PeterT and I are coming from: is the ”triangle method” advantageous to use?

If you center the spindle over the table in Y and use a point on the front edge and one 180* from it on the rear, you essentially eliminate any out of tram error of the spindle in X (tilt). (It‘s like using a cylinder square - you use two points on it 180* opposite that are at a true 90* to your reference surface, like a surface plate, or in our case the mill table). With your method, if the spindle axis is tilted even the slightest in X, the error of the plane will be magnified with your triangle method and it may be very hard to determine if you are out in the nod, the tilt or both. Is it going to work, for sure. Is it accurate - yes. Is it relatively quick - maybe not.


A little story:

I though I could tram the BP head in both X and Y at the same time when I first got the mill (a long time ago now) by just sweeping a 1/2 tenths indicator on the mill table with the mounting bolts lightly snugged up. I did understand that a plane swept by the indicator needed to be parallel to the table in order for the head to be in tram. Turns out that that is a very difficult operation and I spent a good long amount of time trying to get it. I eventually got it. I was very happy and the mill made nice square cuts.

We then decided that we are going to deck off some old railway track for an anvil (One 12” section for my son and one for me). The cutting forces were much higher than on anything we did before and the head moved. We had to tram again. Same X & Y together method was used - again, it took a long time. It was then suggested that maybe there is a better way (“why is this taking so long, dad?“). He went online to look up tramming a mill head and found that isolating tramming in X (tilt) from Y (nod) was the ticket. X is first. Been doing it like that ever since…


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## RobinHood (Nov 16, 2021)

Speaking of milling heads that are difficult to tram: the Huron style ones are apparently the worst because it is hard (impossible?) to isolate the X and Y directions from one another because of the oblique mounting flange. This is where a calibrated tramming tool shines.


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## Susquatch (Nov 16, 2021)

RobinHood said:


> Not sure if it was you or someone else said that the nod can be trammed out quickly with just a few iterations.



It was me. I was mostly having fun with Brent. Sorry if that caused a storm at sea that shouldn't be. 

But I was also serious. I did both my new to me mills that way. Both were out in both axis. The halves rule handled x adroitly. The nod was also fast, probably because I instinctively interpolated the numbers after one iteration and they zeroed in very quickly. But perhaps I got lucky. 



RobinHood said:


> The main purpose of the tool that @DPittman made is to speed up the tramming process (once the tool is calibrated). I think that a tool like that can do that.



I agree and said so very early in our discussion. If you saw my post to @Brent H , I'll be making something VERY DIFFERENT and fun to use! I hope it will be as entertaining for all of you as I know it will be for me!



RobinHood said:


> I think that’s where @PeterT and I are coming from: is the ”triangle method” advantageous to use



I believe that there are two advantages that have not been fully "flogged". One is the inherent resolution advantages of the arc at a longer radius. The other is the ability to tram both x and y simultaneously. 



RobinHood said:


> With your method, if the spindle axis is tilted even the slightest in X, the error of the plane will be magnified with your triangle method and it may be very hard to determine if you are out in the nod, the tilt or both. Is it going to work, for sure. Is it accurate - yes. Is it relatively quick - maybe not.



Well, given that the method outlined in our discussion only used one indicator, I'll have to concede (and did and actually already conceded that much earlier in this thread) that the two indicator system is much faster. BUT..... I believe that my soon to build and hopefully entertaining three dial system would be faster still because it can do both x and y at the same time. Of course, I never even thought about doing both like that till this orangutan character and his buddy @PeterT pushed my thinking beyond where it was stuck. 



RobinHood said:


> We then decided that we are going to deck off some old railway track for an anvil (One 12” section for my son and one for me).



I DID THAT TOO! About 40 years ago I lived beside a railroad track. They had a 20ft section of track they replaced and shoved the old piece into the ditch. I let it sit till it was overgrown with weeds and then decided it was safe to swipe it. I torched it into 3 short pieces and made an anvil for myself and my friend. I still use my anvil and I still have the remaining piece. It's about 3 ft long. I bet you are wondering how come I only got 2 anvils and a 3 ft piece out of a 20ft section. I'm still wondering that too. I think it probably has something to do with how mass shrinks at speeds close to the speed of light. Which is how fast my years have gone by. I swear on my wife's Fine China that it was at least 20ft long when I was dragging it home all alone..... In the dark...... Waiting for the sirens to start screaming. 

My anvil still looks like a piece of short track. But I didn't have a mill till just recently. I should drag that thing out and make some improvements.......


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## Susquatch (Nov 16, 2021)

RobinHood said:


> Speaking of milling heads that are difficult to tram: the Huron style ones are apparently the worst because it is hard (impossible?) to isolate the X and Y directions from one another because of the oblique mounting flange. This is where a calibrated tramming tool shines.
> 
> View attachment 18321



I'd be willing to place a beer wager that my three gauge triangle idea would make short work of that challenge.

But I truly hope I lose - I'd love the opportunity to get you beer silly! Especially if my gnarly gauge ends up half as twisted as I see it in my minds eye......


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## Susquatch (Nov 16, 2021)

RobinHood said:


> Speaking of milling heads that are difficult to tram: the Huron style ones are apparently the worst because it is hard (impossible?) to isolate the X and Y directions from one another because of the oblique mounting flange. This is where a calibrated tramming tool shines.
> 
> View attachment 18321



Hard to tell what I'm really looking at there. Is that head really sitting on a round angular flange? And what are all those cranks, dials, switches, and knobs for? I'm thinking that thing would create some glorious times for us guys that like playing with a million adjustments! 

Or is that really a space ship in disguise?


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## RobinHood (Nov 16, 2021)

Susquatch said:


> Is that head really sitting on a round angular flange? And what are all those cranks, dials, switches, and knobs for?



It is just a picture I grabbed of the internet - my dream manual machine if one ever came up for sale at a reasonable price.

Yes, it is siting on an angular flange and the whole head is on a swivel behind it.

The dials, cranks, switches and knobs are to control spindle speed, feeds, rapids, etc, both mechanically and electrically.

I probably misread at least one of your posts and did not catch that you were planning on making a tri-gauge tramming tool. Should be a fun project. For sure, once calibrated, it would be the fasted way of tramming a milling head in both X and Y concurrently.


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## PeterT (Nov 16, 2021)

Another application for a dual gage. Tramming to a sine bar reference. If the bar was along X, then I guess here you need reverse procedure - establish nod first & tilt second.


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## Susquatch (Nov 17, 2021)

RobinHood said:


> I probably misread at least one of your posts and did not catch that you were planning on making a tri-gauge tramming tool.



That would have been easy to do. I was carrying on two conversations at once. One with you and @PeterT where I was trying to understand your concerns about tramming nod with the spindle behind the bed, and another simultaneous conversation with @Brent H in the same thread about making a tri-gauge tool. Unless you were following the whole thread as opposed to just those with your user name in them, it would have been easy to miss as those posts very short compared to the books that you and Peter and I seem to like writing...... LOL!

If you skim back, you will see that I threw in the towel on the speed issue almost right away. Perhaps my initial poor attempt to have some fun with Brent wasn't as obvious as it could have been to everyone!

I like to learn. I like to help. And I like to have fun too!

FWIW, the idea of incorporating optical illusions into the tri-gauge fixture that I mentioned to Brent was really just another shot of humour aimed at you that arose out of the difficulty I had visualizing your concerns. 

All is well that ends well!


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## Susquatch (Nov 17, 2021)

PeterT said:


> Another application for a dual gage. Tramming to a sine bar reference. If the bar was along X, then I guess here you need reverse procedure - establish nod first & tilt second.



I like the overall idea, it's a cool looking fixture and setup. 

But I confess that I have no idea right now where or why anyone would want to do this.... 

Nonetheless, I have stored the concept into my cerebral archives as a potential solution to a problem I have not encountered yet...... 

Also, wouldn't this fixture work a bit better with the bars or balls built into the fixture itself and the balls shown here replaced by gauge blocks?


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## Susquatch (Nov 17, 2021)

A question for all regarding spindle squares.

The tables on all 4 of my mills & drills are not perfect. And even if they were, the TSlots make calibrating a gauge or indicator difficult. I have always swung / swept the indicator tip backward to avoid damaging it.

But all this discussion about tramming has me wondering about what I will call a tram plate. Something like a precision ground plate that you set on the bed and then run your indicator (or tram tool once I make one) on that.

I'm thinking that perhaps a premium automotive brake rotor might be a great solution. They are typically ground to be ultra flat when new and they are not outrageously expensive for what you get. 

However, I find myself wondering how well they would work on a mill table. How much would an oil film or a human hair or the one teeny tiny ding my stone didn't catch affect its usefulness?

Anyone have any experience or thoughts on this?


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## Brent H (Nov 17, 2021)

@Susquatch : Typically if you are tramming the head, you do it to a flat surface (like the vice) - not necessarily your mill table.  If I want to tram to the table I will set up a parallel that spans a good distance (say an 8 or 10") and make sure the table is lightly stoned and wiped off.  Set up the parallel in the direction you need to go such that it will span the table imperfections and give you a proper calibration.  

The Sine bar, table etc can be used to set up the head at very accurate angles or a work piece.  Tramming the head to the sine bar will give you that 30.01 degree of accuracy or better depending on you.  

You can also tram with a matched set of 123 blocks etc.

Lots of different options


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## Susquatch (Nov 17, 2021)

Brent H said:


> @Susquatch : Typically if you are tramming the head, you do it to a flat surface (like the vice) - not necessarily your mill table.  If I want to tram to the table I will set up a parallel that spans a good distance (say an 8 or 10") and make sure the table is lightly stoned and wiped off.  Set up the parallel in the direction you need to go such that it will span the table imperfections and give you a proper calibration.
> 
> The Sine bar, table etc can be used to set up the head at very accurate angles or a work piece.  Tramming the head to the sine bar will give you that 30.01 degree of accuracy or better depending on you.
> 
> ...



I'm paying close attention to the advice I got earlier from a certain sailor I know. Lots of ways to do it, so I'm just aiming for fast and easy. Preferably home made and faster and easier than whatever the rest of the crowd uses to increase the pride factor.

Was hoping to be able to make a sweep system to facilitate that. Blocks and parallels will work but still suffer the bump as the needles transition from open space to the gauge surface. I'm thinking here about the initial calibration effort. All the gauges need to be set to show the same measurement at the same place before they can be used in different places to show the difference. I thought a big circular plate like a disk brake rotor might do that job well and as bonus extend back behind the bed too. But that's just a guess.


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## PeterT (Nov 17, 2021)

Susquatch said:


> I like the overall idea, it's a cool looking fixture and setup.
> But I confess that I have no idea right now where or why anyone would want to do this....



Picture any part that is long-ish with angled features that require milling/drilling/whatever. It is easier to rotate the head to the work axis vs angling the work to meet a perpendicular spindle axis. Particularly, headroom becomes diminished & more complex fixturing/clamping arrangement is required.

Or visualize replacing the left sketch blue part with a rotary table assembly. Now more complex parts can be machined in 4 axis independently. These would be very clunky if not impossible to accomplish with a head confined to 2 locked perpendicular axis.


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## Susquatch (Nov 17, 2021)

PeterT said:


> Picture any part that is long-ish with angled features that require milling/drilling/whatever. It is easier to rotate the head to the work axis vs angling the work to meet a perpendicular spindle axis. Particularly, headroom becomes diminished & more complex fixturing/clamping arrangement is required.
> 
> Or visualize replacing the left sketch blue part with a rotary table assembly. Now more complex parts can be machined in 4 axis independently. These would be very clunky if not impossible to accomplish with a head confined to 2 locked perpendicular axis.



I see! So this us all about tramming the head to cut on an angle VS the table. 

I assume that usually means doing most of the cutting work using the Y-axis on the table..... And nod angle adjustments would use the X axis.


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## Susquatch (Nov 26, 2021)

Hey @RobinHood, @PeterT, & @Brent H , & all those others following this thread. I had to go visit the doctor today and had some time to kill waiting for my turn in the torture room..... 

I decided to spend some time looking to see if anyone had ever made a 3 gauge tram system.  I didn't find one, but I did find these interesting ways of going about using two dials. 

One is actually the brake rotor that I thought might work. Apparently someone else had the same idea. And it does work! 

The other is a raised rotor that clears the vice. I really like that too! No need to remove the vise to tram the mill! 











I'm thinking that maybe three custom precision blocks under the rotor would work just fine. 

Lots of room for that illusion I want so badly too...... LOL!


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## RobinHood (Nov 26, 2021)

Those are two very clever solutions!


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## 6.5 Fan (Nov 27, 2021)

Jeeez you could make that raised rotor gizmo yourself. "hey SWMBO, i need to buy a surface grinder" Guess what the answer will be, NO, HELL NO.


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## Susquatch (Nov 27, 2021)

6.5 Fan said:


> Jeeez you could make that raised rotor gizmo yourself. "hey SWMBO, i need to buy a surface grinder" Guess what the answer will be, NO, HELL NO.



She has no idea what a surface grinder is. She didn't even bat an eye when it took two guys to load a rotary table into the back of her jeep. 

Or maybe she does, but she has resigned herself to the fact that she married a crazy man 50 years ago and it's just a matter of waiting for the right moment to push me into the hole. 

I dunno. It's always amazing to me what she accepts and what she fights. I'll never figure her out.


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## Susquatch (Nov 28, 2021)

Found two old car brake rotors in my scrap metal pile this morning. Just for Sh**s & Giggles, I put one in the lathe and checked the runout. Not good as is. Cleaned off the rust on the hub section until bare metal showed and tried it again. Woah, within 8 tenths. And it's a very consistent wobble so even that can be taken out with a few mallet raps. 

With the hub up, it even clears my vise sitting on some 123 blocks. With a little more cleanup, I think we have a winner! 

Just need some 1/2" plate to make that goofy gnarly looking 3 gauge illusion I have in mind and we are in business!


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## ThirtyOneDriver (Jan 17, 2022)

This thread has been helpful - I should add a sine bar to my future purchase list - may be a more accurate means to tilt head for notching roll cage tubing with the annular cutter... probably doesn't matter, a degree or five is close enough... 

Am I visualizing the "triangle tram" idea correctly?



 

Circle radius for this mock-up/visualization is 6" - table is 21" x 6" (there's 3" height/z dimension between circular plane/spindle throat and top of mill table)
The triangle is 11.5" on the x-axis and 5.75" on the y-axis so the "pins" (measurement points?) were visually on the table but for ease of discussion/theory let's agree that they're coincident with the 6" radius (therefore the corners attached to the base/back edge are 12" from one another along the x-axis and 6" from the spindle center to the "front" of the triangle in the y-axis).

How I am perceiving the information presented thus far, is that if the points along the x-axis are equal, then my head is trammed(?) and if the front point is equal to those, then I don't have nod(?) (... essentially my spindle is perpendicular to the table along the x-axis and the y-axis...).

I loosely based these measurements on what I believe (the numbers in my head w/o checking) my table dimensions are (slots aren't correct) - I likely have some good 12.18" rotors on the shelf/know where to get good used (what we [racers] would consider scrap) ones that could be machined flat (they bolt to hubs so there is an open center ~7" in dia).


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## Susquatch (Jan 17, 2022)

Ya, that's all pretty close. I think you did well sifting through the confusion. 

Athough it isn't necessary, it really helps to zero all three indicators on the same spot. That way you can know at a glance where things are because they all read the same. But if your head can handle the translation only looking at the change, it isn't necessary. But for simplicity sake, let's assume you prefer the simple approach. That means the distance to each indicator from the spindle center has to be the same. Your 5.75" works. 

It's unlikely that you can machine a used brake Rotor to be better than it is without a surface grinder. The brake pads themselves are pretty good at making a flat surface. I'd just find a good one and be done with it. 

Keep in mind that this 3 pt tram device of mine is not required. In fact you don't even really need 2 points. You can do the whole thing with a single indicator measuring your bed directly. It's just that two makes it a lot easier and 3 makes it downright simple. I just thought it would be fun to make a 3 gauge unit since I've never seen or heard of anyone using one or making one. 

In reality, you just need to tram your mill with a single gauge and then square your vise with the same gauge held differently, and you are good to go.


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