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Lathe Purchase, move, setup and Lathe Stand build

#24
It’s going to be a while before I get my own tools to make chips. But once I do I will run a bunch of test cuts and let you know how it performs.

Also need to turn a new shear pin and as per a different thread I need to fix the pulley stack on my mill.
 
#28
Played around with the lathe last night and wanted to verify some things before I shared them with you all.

So, when it came to the headstock alignment.... almost all the videos you can find on youtube and most of the suggestions I received, was to cut a dog bone looking thing in the lathe and measure each "bell" and adjust/recut and measure again.

This is fine and dandy and a great method. But, its a PITA if your mounting bolts are hidden behind gears or the motor and such. You will have to unbolt things and rebolt between adjustments. The method we used was simple and didnt require the machine to be under power. It did however require a piece of bar stock that is perfect without a taper.

Disclaimer: This is not my brain child, I had a professional chip maker helping me out with this. KEB6134 just joined the forum and will be able to correct any mistakes I made or help add info.

You take the bar stock and put it in a four jaw chuck with some shims (Shims help create a pivot point in the chuck).
Keeping the saddle locked in place use and indicator on top close to the chuck, hand spin the chuck and make your adjustments to ensure the bar stock is perfectly in the middle. Then move the indicator to the end of the bar stock (Move the indicator NOT the saddle) make your adjustments. Go back and forth between those points until you know your bar stock is running true to the spindle axis.

Now you can unlock your saddle, reposition the indicator to the side of the stock and use the saddle to move the indicator over the stock from front to back to see the alignment of the headstock. Adjust the headstock alignment screws, or use your "precision adjustment hammer" until desired effect. In my case we got it to within 3/10's of a thou. (Over 12") We then tightened all the bolts, verified it measurements by running the saddle back and fourth again. Then called it a day and finished building the lathe.

Last night we finally got around to making some cuts and verified that it is indeed as accurate as we originally thought.

So, I figured I would share this new method that I recently learned because I have not seen it online yet. Hope it helps someone out. Feel free to ask me any questions if I was not clear enough
 
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PeterT

Ultra Member
Premium Member
#29
I’m not a millwright but my own opinion is this whole dog bone / dumb bell / Rollies dad method / offshoot ‘cutting methods’ is introducing more variables than necessary. The issue is that in order to get any kind of distance between the two reference diameters for an accurate comparison, you will surely exceed the cantilever stick out ratio (call it 2-3 times diameter for discussion purposes). You can’t support the end with tail stock because that introduces a new re-centering variable if the tail stock is out. But you can’t reasonably align the tail stock without first aligning the head stock.

So that’s why you hear some guys recommend a 3” diameter drop of aluminum extending say 10-12” from the chuck. They are counting on the aluminum being lower weight, higher strength & easier to cut so the diameter comparison is more meaningful. Next best might be free machining steel like 12L14. Worse is any kind of crap grade CRS. Real bad is any steel that work hardens like stainless. With cutting you still have surface finish and some degree of tool induced deflection to contend with. Better surface finish = larger nose geometry = generally more infeed force = more deflection. Think about it this way, assume your lathe perfect coaxial to begin with & you cut this same log without tail stock support (which you would normally rarely do). Would you realistically expect the outboard end to be a thou or more larger diameter than the chuck end even after spring passes? The answer is yes btw. Well then you cant assume its cylindrical (equal end bell diameter) for the purposes of head stock alignment. Cutting introduces more variables & like you say, every time you adjust the head stock you have to re-cut the coupon to re-reference the diameters.

Test bars come in a few flavors. They are precision ground to very high tolerance & cost a whopping $50 if sourced offshore. About as much (or less) than the log of aluminum. One type is 100% cylindrical. They are best held in 4J chuck like you did. Theoretically you could have a jaw gripping issue where it is not holding the bar parallel to the spindle axis. But unless it’s badly worn jaws or beat up chuck, that should be minimal. Some folks will say you should never grip anything of precision with jaws like this, only between centers. But I guess just use common sense, don’t gronk the tightening or better yet use brass shim.. This might be a reason why its not as referenced as a standard, even in Internetland where generally anything goes.

Another type of test bar that cuts out the middleman chuck has MT taper on one end and 12-14”cylindrical ~1” diameter section on the other. Insert into the head stock socket, indicate along the cylindrical length. Boom, done. You have eliminated the chuck, related mounting, material deflection properties, cutting forces, surface finish and probably some other things I forgot. If your head stock taper is MT5 you will require the converter socket which hopefully came with your lathe. It does introduce some teeny fit-to-fit tolerance but now we are hair splitting. Either bars can be used for tail stock alignment which is the next very important thing. I kind of prefer the MT style for this reason if you don't already own one of either.

I don’t know but I suspect the suggested cutting methods are related to bigger lathes where they just don’t have access to an inexpensive test tool, so this is the legitimate way to do it. But for hobby machines especially with common MT sockets, it’s a waste of material & time IMO. The cutting method also tells you nothing about an upward or downward pointing spindle or tailstock axis. Yes this form of misalignment has a muted effect on actual taper cutting runout, but again I would prefer to measure it rather than wonder.
 
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#30
I’m not a millwright but my own opinion is this whole dog bone / dumb bell / Rollies dad method / offshoot ‘cutting methods’ is introducing more variables than necessary. The issue is that in order to get any kind of distance between the two reference diameters for an accurate comparison, you will surely exceed the cantilever stick out ratio (call it 2-3 times diameter for discussion purposes). You can’t support the end with tail stock because that introduces a new re-centering variable if the tail stock is out. But you can’t reasonably align the tail stock without first aligning the head stock.

So that’s why you hear some guys recommend a 3” diameter drop of aluminum extending say 10-12” from the chuck. They are counting on the aluminum being lower weight, higher strength & easier to cut so the diameter comparison is more meaningful. Next best might be free machining steel like 12L14. Worse is any kind of crap grade CRS. Real bad is any steel that work hardens like stainless. With cutting you still have surface finish and some degree of tool induced deflection to contend with. Better surface finish = larger nose geometry = generally more infeed force = more deflection. Think about it this way, assume your lathe perfect coaxial to begin with & you cut this same log without tail stock support (which you would normally rarely do). Would you realistically expect the outboard end to be a thou or more larger diameter than the chuck end even after spring passes? The answer is yes btw. Well then you cant assume its cylindrical (equal end bell diameter) for the purposes of head stock alignment. Cutting introduces more variables & like you say, every time you adjust the head stock you have to re-cut the coupon to re-reference the diameters.

Test bars come in a few flavors. They are precision ground to very high tolerance & cost a whopping $50 if sourced offshore. About as much (or less) than the log of aluminum. One type is 100% cylindrical. They are best held in 4J chuck like you did. Theoretically you could have a jaw gripping issue where it is not holding the bar parallel to the spindle axis. But unless it’s badly worn jaws or beat up chuck, that should be minimal. Some folks will say you should never grip anything of precision with jaws like this, only between centers. But I guess just use common sense, don’t gronk the tightening or better yet use brass shim.. This might be a reason why its not as referenced as a standard, even in Internetland where generally anything goes.

Another type of test bar that cuts out the middleman chuck has MT taper on one end and 12-14”cylindrical ~1” diameter section on the other. Insert into the head stock socket, indicate along the cylindrical length. Boom, done. You have eliminated the chuck, related mounting, material deflection properties, cutting forces, surface finish and probably some other things I forgot. If your head stock taper is MT5 you will require the converter socket which hopefully came with your lathe. It does introduce some teeny fit-to-fit tolerance but now we are hair splitting. Either bars can be used for tail stock alignment which is the next very important thing. I kind of prefer the MT style for this reason if you don't already own one of either.

I don’t know but I suspect the suggested cutting methods are related to bigger lathes where they just don’t have access to an inexpensive test tool, so this is the legitimate way to do it. But for hobby machines especially with common MT sockets, it’s a waste of material & time IMO. The cutting method also tells you nothing about an upward or downward pointing spindle or tailstock axis. Yes this form of misalignment has a muted effect on actual taper cutting runout, but again I would prefer to measure it rather than wonder.
Yes, so thats something I learned when we were doing the test cuts. The test was hard to do because of the amount of chatter and overhang of the stock material. So if that is happening during the test you would know dang well it is happening during the alignment process as well.

So that is another plus side to the way we did it. There was no deflection because we were not cutting and pushing on the part.
 

Dabbler

Well-Known Member
#31
The dog bone method of holding between centres is for fine tuning only on a well set up lathe.

PeterT has it nailed. The carriage and the headstock have to be aligned first and accurately - like TheLocalDrunk did it. Then the tailstock has to be indicated in until it is just as accurate. Only then the 'dog bone' or 'barbell' method can be used to fine tune and map out the carriage movement.

On my small lathe, we had a lot of problems with rough surfaces and very coarse alignment screws so we didn't do quite as well. I'm looking forward to checking the alignment on my new lathe - when it is back together!
 

RobinHood

Active Member
Premium Member
#32
@TheLocalDrunk : i am following your process very closely, as aligning the headstock will be next on my list of important things to do on the Cholchester.

I like all the input from @PeterT , @Dabbler , et.al. Excellent discussion.

All my previous lathes did not come with adjustable heads as they were scraped in at the factory and are sitting on a V on one side and a flat on the other. The best i could do is shim if required.
 

PeterT

Ultra Member
Premium Member
#33
The only other thing I can offer (in my case) is just breathing on those jack screws is enough to get them in & out alignment. They are quite sensitive. That's another advantage of having a DTI in direct contact with a pre-mounted test bar. You get immediate & direct visual feedback as to how the head has moved after adjustment. I barely cracked the screws on one side & got lucky. Taht was very close to perfect alignment just by sequentially snugging the screws to final torque. Kind of 4 jaw chuck principle.
 

John Conroy

Well-Known Member
Premium Member
#34
Peter, did you buy a test bar For your lathe? If so, where did you get it? There are lots of inexpensive ones on eBay that are made in India so i wonder about accuracy.
 

PeterT

Ultra Member
Premium Member
#35
Yes John, of Indian origin & Ebay. I could find the seller for you but I recall he had other bars as opposed to machinist items & household goods.
I really figured it was going to be a doorstop because other things I gambled on from India were low quality fails. But this was decent, some niche they have put a bit of effort into for some reason. I have a hunch that is what you are getting with brand name versions like KBC & Travers unless they explicitly say made in Europe or elsewhere. The only way I could measure it was with my good Mitutoyo down the length in different orientations then DTI at different quadrants. So not 100% validation because I don't have access to real metrology level or even granite plate. But I think its decent value for intended purpose. It came in a simple bubble wrap & cardboard box & in a plastic DHL bag. Not awesome from that perspective.

USA & Europe are 2-5X that & not as common with integrated MT & long bar. I came close to getting USA all cylindrical bar with centers but I'm always leary if I cant see how they are ground. Centerless are very nice OD dimensionally but you cant trust the centers.
 

John Conroy

Well-Known Member
Premium Member
#36

PeterT

Ultra Member
Premium Member
#37
For some reason I cant go back more than a few years in my Ebay history. ATOZ name rings a bell though & .I remember they had more extensive selection.
https://www.ebay.ca/str/atoztoolstore/Lathe-Test-Bars/_i.html?_storecat=18372947012

double ended taper, hmmm... dont know what I'd use it for, but interesting
https://www.ebay.ca/itm/ATOZ-2-in-1...518120?hash=item3d7f1b9128:g:GEsAAOSwa0VZ8Mdh

The diameter was as accurate as my mic could measure. I rotated in V blocks with some finger preload & DTI was flat so seemed good in that cursory way. If its anywhere close to 0.0001 - .00002 we are laughing. I think its worth getting a long one for lathe work. The more extended, the pronounced any DTI deflection shows yaw presuming also co-axial. I checked my tailstok against my Edge setting & both read same so I'm confident for grade of work I do. You may want a shorty for standup mill work though where too long is impractical

I cant speak for any of their other tooling. I suspect sketchy.
 
#38
That setup looks awesome, well done. I like the idea of the tool cabinet underneath, thinking I might do something similar when I'm finished making new larger pedestal pads for mine.