Harrison M300 Taper Attachment

[trevj]

You are no fun Trev....

I suppose we won't be able to do more than agree to disagree then.

I'll make a bigger one like @Upnorth and report back later.

Oh, I am too fun! LOL!

I just want to (in this case) be a voice of reason, in that I propose to solve problems that occur, rather than seeing a problem that likely isn't actually one.

My nickel sez, that even if you get ham-handed, and start FORCING things, You are more like to cause either the anchor block, or the rod pinch point, to slide, than you are to effect a compressive collapse of the rod as provided.

It seems to my eye, that the rod will be well aligned, and have a very limited ability to begin flexing, until a very UN-sympathetic amount of force is applied to it in compression.
And, a 1/4 inch piece of rod, is a lot cheaper to replace than anything further up the train of parts!

 

[mbond]

I was wondering if you would show up here.....

Basically, it's a long rod about 22" long that is locked to a bed anchor bracket at one end and the taper base plate at the other. It's purpose is to stop the plate from moving as the cross slide traverses back and forth on the taper attachment way.

The taper base plate basically hangs from a rear extension of the crosslide and the cross slide moves front to rear following a taper guide on the plate.

My rod is about 1/4" in diameter and @Upnorth's is about 3/4 inches in diameter.

Mine is prolly adequate but its a weak link in the system. I can see no reason not to upgrade it to a 3/4 inch bar.

I have not done a buckling analysis. But my guts tell me that there will be a huge difference between 3/4 and 1/4, and further that shearing of the anchor screws is a non-issue. Here is a rendering of the parts:

View attachment 49339

The large beige block screws to the back of the saddle. The bottom plate is fixed in relation to the ways by the anchor bracket and the subject bar at the bottom left of the photo. Internally, there is a follow-block inside the large block that follows the smaller adjustable taper plate to move the rear anchor of the cross-slide leadscrew in and out.

To visualize the concern, I already suggested substituting the rod with a piano wire. Doing so allows anyone to see the problem. As the slenderness ratio improves with fatter rods, the assembly gets stiffer and stiffer.

Doing the math wouldn't be difficult if we knew the loads. I don't. That would require testing. Therefore about all I can say for now is that piano wire would surely buckle, a 1/4 rod might or might not be a problem depending on your definition of a peoblem, and a 3/4 inch rod would be a safe bet.

The OP @S.Heron really just wanted to know what size of rod to use, and I suggested making it bigger than mine because the one on mine looked too small to me. When I saw how much fatter and shorter @Upnorth's was for roughly the same size lathe, it somewhat vindicated my concerns.

Normally, I wouldn't get overly concerned about such things, but I'm particularly sensitive to the design and manufacturing issues of the taper attachment I just bought. It's VERY disappointing so far.

Post in thread 'Is Taper Attachment worth it?' https://canadianhobbymetalworkers.com/threads/is-taper-attachment-worth-it.8860/post-156856

You have written a book and only showed some bad photos. I suppose I'm guilty of worse

we are making tapers. It is hard to move the headstock, so we must be moving the tail by some amount. How much? well that's what this tool will help us with. And specifically without changing the standard tailstock

If I read the pictures right, we fasten this the to lathe bed, and then adjust

Is the rod you are worried about the one on the top or the one on the bottom? Based on this picture, the top one might be threaded? and the bottom one straight?

 

[trevj]

You have written a book and only showed some bad photos. I suppose I'm guilty of worse

we are making tapers. It is hard to move the headstock, so we must be moving the tail by some amount. How much? well that's what this tool will help us with. And specifically without changing the standard tailstock

If I read the pictures right, we fasten this the to lathe bed, and then adjust

Is the rod you are worried about the one on the top or the one on the bottom? Based on this picture, the top one might be threaded? and the bottom one straight?

Put a basic boring head in the tailstock taper. In our hobby sizes, a basic, Morse Taper, boring head is pretty cheap. Prolly should NOT have to mention, but will, to put the adjustment range so it runs horizontally, not vertically... Can't fix stupid, and not allowed to hit it with sticks any more...

Mount a ball end center (super easy too make, silver solder a ball bearing on the end of a suitably turned body) in said Boring Head.

Now, you have an adjustable offset, without having to dick about at ALL (not like its really all that onerous, but see also, "Fear of Four Jaw Chucks" and other similar subjects), with the tailstock offset adjustment. AND, it comes, generally, with a scale to allow you to know, at the least, how much you moved the head.

Add some basic measurements, and some Trig, and you can get VERY close to what offset you need, to get a particular taper over the length of that part!

I will add, that there have been any number of offsetting tailstock accessories published, though none that I can recall, that had as easy a way to add or subtract a given amount to or from!

 

[Susquatch]

Now, you have an adjustable offset, without having to dick about at ALL

Many alternatives were thoroughly discussed in my own thread......

Thread 'Is Taper Attachment worth it?' https://canadianhobbymetalworkers.com/threads/is-taper-attachment-worth-it.8860/

Want me to move this post there Trev?

 

[Susquatch]

You have written a book and only showed some bad photos. I suppose I'm guilty of worse

My apologies. That, and I still failed to convey the functionality. I contemplated a drawing, but the book was just easier... LOL!

we are making tapers. It is hard to move the headstock, so we must be moving the tail by some amount. How much? well that's what this tool will help us with. And specifically without changing the standard tailstock

If I read the pictures right, we fasten this the to lathe bed, and then adjust

Actually, it is fastened to the saddle and essentially becomes another function added to it. The rod and bed anchor bracket are the only parts that attach to the bed thereby providing the position input for the taper

Is the rod you are worried about the one on the top or the one on the bottom? Based on this picture, the top one might be threaded? and the bottom one straight?

The top one is the replacement cross slide leade screw - so yes, it is threaded. The bottom left is the subject unthreaded rod.

I'm really glad you ask that question. If I scale off of the rendering, the two look to be about the same size. But the leade screw is at least 3/4 inch and maybe bigger. That also suggests that the reference rod should be bigger than it is.

This is yet another sign to me that my under sized rod is simply a manufacturing error - another artifact of transferring manufacturing to China.

 

[trevj]

My apologies. That, and I still failed to convey the functionality. I contemplated a drawing, but the book was just easier... LOL!



Actually, it is fastened to the saddle and essentially becomes another function added to it. The rod and bed anchor bracket are the only parts that attach to the bed thereby providing the position input for the taper



The top one is the replacement cross slide leade screw - so yes, it is threaded. The bottom left is the subject unthreaded rod.

I'm really glad you ask that question. If I scale off of the rendering, the two look to be about the same size. But the leade screw is at least 3/4 inch and maybe bigger. That also suggests that the reference rod should be bigger than it is.

This is yet another sign to me that my under sized rod is simply a manufacturing error - another artifact of transferring manufacturing to China.

Don't much care if you do or don't move the post, but given that it started out in this thread, it may as well stay in this thread, no?

Why do you think that the size of the operating rod should scale to the lead screw? FWIW, to my eye, the lead screw looks very close to the same diameter of the rod, if you consider that the root diameter of the thread, is the effective column being put under compression, no? Nobody gives a second though about loading up the cross slide screw with loads like knurling applies.

I have bent a lead screw on a cross slide, but it took a ten pound or so part, coming out of the chuck at considerable revs, banging in to the tool post, to do it. Said incident also blew the mount screws and bearing housing at the dial. And left me pondering yet another poor life decision...

 

[Susquatch]

Don't much care if you do or don't move the post, but given that it started out in this thread, it may as well stay in this thread, no?

OK, I'll leave it unless the OP suggests otherwise.

Why do you think that the size of the operating rod should scale to the lead screw? FWIW, to my eye, the lead screw looks very close to the same diameter of the rod

Sometimes I think I speak a different language than everyone else.....

But exactly Trev. I only meant that if you lay a scale on the photo, they are similar diameters. But MY leade screw is 3/4" and my anchor rod is 1/4". So both the rendering and the data from @Upnorth show a significantly fatter anchor rod than mine. This concerns me. In fact, my skinny rod concerned me BEFORE I knew others were fatter.

A 3/4 inch rod has roughly 9x the cross sectional area of a 1/4 inch rod. In my mind that's a very significant difference.

Nobody gives a second thought about loading up the cross slide screw with loads like knurling applies.

I was NEVER particularly concerned about compression or stuff like lead screw load. My concern is buckling (bending of the anchor rod itself). Not permanent buckling, just temporary load related buckling. Think of it like a long skinny piano wire with a compressive load at both ends. As you push the ends together it will bend outwards like an archery bow.

But just so you know, I don't like loading up my lead screw to do pressure knurling and I know that I am not alone in that regard. I much prefer pinch knurling or cut knurling over pressure knurling. It's simply not true that "nobody gives a second thought".

I have bent a lead screw on a cross slide, but it took a ten pound or so part, coming out of the chuck at considerable revs, banging in to the tool post, to do it. Said incident also blew the mount screws and bearing housing at the dial. And left me pondering yet another poor life decision...

There is a big difference between a yielded permanently bent leade screw and temporary load induced stress/strain. You overloaded your leade screw and it bent permanently.

But ANY load, no matter how small, will cause stress and strain in the part. This is where my concern lies. The smaller the rod, the more it will bend under a given load.

Any bending affects the precision of the lathe. Is it enough to worry about? That's debatable. I'd rather just eliminate the possibility. Especially given that other lathes with a similar taper attachment are so much beefier than mine.

 

[mbond]

It should be mentioned that there is a much bigger difference than just the cross sectional area.



a basic bar in compression looks like this. With a perfectly straight bar made of some hypothetical ideal material, the width is irrelevant and it can carry infinite load. With a real material that's obviously not true. An isentropic material (material properties are the same in every direction) that is perfectly straight will eventually fail in sheer. Yes sheer. The sheer plane will develop at 45 degrees and initiate at either a stress concentration of a material defect, and the ultimate capacity is a function of the yield strength times the cross sectional area over the whole sheer plane (which is larger than the cross section because of the angle).

No real bar can ever be made that is perfectly straight, and so a real bar won't fail in this way. Inevitably, the bar will buckle long before it gets to this point.

so a real bar looks more like this. The lateral force is the component of the axial force that isn't perfectly aligned and I show one here for simplicity. It has to be resisted some how, and that produces a moment (or torque) on the other end of the bar. Like this



That means that the different sides of that end of the bar are under different loads (which amplifies the eccentricity - omitted here for simplicity). The further apart those edges are, the smaller those forces have to be - because moment is force * distance.

The ultimate capacity can be calculated using a formula for slenderness ratio and what is called radius of gyration (a measure of the likely eccentricity), but for the purpose of machine tools, the ultimate capacity is not really a problem. If you ever get there, you have broken your lathe / mill / etc. or at least the work piece.

Within the working range of the tool, the deflection for a given load is reduced for a larger rod _both_ by it having a larger cross section _and_ by virtu that the metal that is in that cross section is farther away from other metal in that cross section. Think about why I beams and wide flange beams are shaped the way that they are.

The technical term is moment of inertia and no it has nothing to do with inertia

 

[trevj]

OK, I'll leave it unless the OP suggests otherwise.



Sometimes I think I speak a different language than everyone else.....

But exactly Trev. I only meant that if you lay a scale on the photo, they are similar diameters. But MY leade screw is 3/4" and my anchor rod is 1/4". So both the rendering and the data from @Upnorth show a significantly fatter anchor rod than mine. This concerns me. In fact, my skinny rod concerned me BEFORE I knew others were fatter.

A 3/4 inch rod has roughly 9x the cross sectional area of a 1/4 inch rod. In my mind that's a very significant difference.



I was NEVER particularly concerned about compression or stuff like lead screw load. My concern is buckling (bending of the anchor rod itself). Not permanent buckling, just temporary load related buckling. Think of it like a long skinny piano wire with a compressive load at both ends. As you push the ends together it will bend outwards like an archery bow.

But just so you know, I don't like loading up my lead screw to do pressure knurling and I know that I am not alone in that regard. I much prefer pinch knurling or cut knurling over pressure knurling. It's simply not true that "nobody gives a second thought".



There is a big difference between a yielded permanently bent leade screw and temporary load induced stress/strain. You overloaded your leade screw and it bent permanently.

But ANY load, no matter how small, will cause stress and strain in the part. This is where my concern lies. The smaller the rod, the more it will bend under a given load.

Any bending affects the precision of the lathe. Is it enough to worry about? That's debatable. I'd rather just eliminate the possibility. Especially given that other lathes with a similar taper attachment are so much beefier than mine.

I think the math on the difference between 1/4 and 3/4 inch is EXACTLY 9 times, no? In my farmer irrigation math, if I make the pipe square cross section, a 3 inch pipe will supply 9, 1 inch pipes.The ratio remains the same, without getting all misty eyed about the value of Pi! LOL!

I raised my experience with a bent leadscrew,, as a point of reference only, mainly because I had a VERY personal experience with it, and a very painful and long lasting bruise(not to mention 'death by process', with the accident paperwork!), from said part striking me AFTER it had expended the needful energy to wreak havoc with the cross slide feed of a fifteen inch swing lathe. Just sayin' that I have a pretty good idea what it takes to actually destroy one without resorting to abusive wear!

And I remain mystified, how, other than in a crash type or BAD user error situation, you might put enough strain on the rod to have to worry about it even flexing, let alone buckling. You would pretty much destroy the lead screw, no matter it's size, by the time you got a big enough lever on to it to make the sliding, low angle system of the Taper attachment, apply any real force against the rod, I think. The sheer mechanical advantage of the usually low angle of the taper attachment seems to counter the need for a big beefy rod, and as I stated before, like as not, you might just 'want' that rod to go, in a bad case, rather than destroying something much more expensive. Like, the bed clamp, chunks out of your bed, if the gears in the power feed don't fail first, as a couple examples.
Not gonna say that I don't think a larger rod would work, hells, you could make the rod out of four inch stock! Think of how many times more rigid that would be! But will it actually provide a value for the effort? That I think, is questionable.

I would, in your position, likely install it as is, push it as hard as I dared, in the most demanding circumstances I could put it to, and be honest in my criticism, while deciding if it worked adequately for the need, or if it really DID need 'improvement'. Given the other conditions that already cause a fella to have some doubts as to the overall build quality of that particular Taper Attachment, I'm just gonna say that the rod being too small is probably not the failure point that will bite you in the posterior! At a guess, I'd suggest that worrying about one of the castings, deciding to become TWO cast parts, is a higher possibility. Just my guess.

 

[Susquatch]

I think the math on the difference between 1/4 and 3/4 inch is EXACTLY 9 times, no?

No, not EXACTLY. but close enough.

But I only raised the cross sectional area to point out how much bigger a 3/4 inch rod is. It's really the slenderness ratio that matters.

I remain mystified, how, other than in a crash type or BAD user error situation, you might put enough strain on the rod to have to worry about it even flexing, let alone buckling.

Buckling is flexing. It's a term that means flexing in a direction perpendicular to the force. It doesn't necessarily mean collapse.

You would pretty much destroy the lead screw, no matter it's size, by the time you got a big enough lever on to it to make the sliding, low angle system of the Taper attachment, apply any real force against the rod, I think.

Any force no matter how small results in deformation and might reduce precision. I am not concerned about breaking anything.

I would, in your position, likely install it as is,........ deciding if it worked adequately

I intend to.

 

[trevj]

No, not EXACTLY. but close enough.

But I only raised the cross sectional area to point out how much bigger a 3/4 inch rod is. It's really the slenderness ratio that matters.


Buckling is flexing. It's a term that means flexing in a direction perpendicular to the force. It doesn't necessarily mean collapse.



Any force no matter how small results in deformation and might reduce precision. I am not concerned about breaking anything.



I intend to.

What got deleted?

The phrase that it might bite you in the buttocks?

Not trying to stir anything, but, as I have said before, I would not mind a detailed explanation about what I said that supposedly caused offense!

To my eye, if a three by three array of squares will fit a three by three array of the original size pipe, then a three by three array of round pipes is gonna equal the same number of round pipes, no?

Show math! Thanks!

(serious request) Not seeing how it could NOT be and exact Ratio.