Lathe leveling - do you do it with the lathe fully dressed or just the headstock and ways?

Lots of food for thought. Thanks for your help. Definitely gave me some ideas on how to proceed. I'm going to get it a little closer to level, and see how it goes for a bit. If it warrants, I'll make some improvements.
 
Fully dressed....well I don't generally work in the shop half naked!
 
I'm usually the one saying metal is the only way to go for a machine tool stand and there's no argument it's the best way to go.

Would a well fabricated metal stand built to triple duty specs be best, of course it would. But, could you do good work with something less? Many have....

Your attention to detail with the process of getting it down into your basement suggests you will do a good job no matter what materials are used.

John
 
jwmelvin said:
Honestly, in many instances they are just more expensive to design, not necessarily to manufacture.

Here's a sketch of what we've discussed:
View attachment 385700

Blue frame, gold feet, gray stand-offs, red foot-bars. Here's a section through the tailstock foot-bar:
View attachment 385701

I drew it with just one of the standoffs (of four) adjustable; that one's the twist knob. (In reality, I'd probably make them all the same but just think about adjusting twist with one.) Then the three frame feet are responsible for leveling overall (one extra adjustment!). There is some interaction between them, and unfortunately the way to deal with that is to adjust in a certain sequence. Adjust twist and then overall level. When adjusting level, if you first adjust about z-axis (the two feet under the headstock end of the frame), then adjust about x-axis (the one foot at the tailstock end of the frame), it will minimize interactions.

Looking at this section makes me think it'd be worth skinning the inside of the frame too, in the upper section, to remove the frame's tendency to twist. As with some other ideas, this may be going well beyond what the lathe requires.

I'm sure there are ways to make this even easier, but this doesn't seem too bad in the current state. The foot-bars could be sections of rectangular tube, which would give you more stiffness for a given weight, but takes up more room and may cost more; it also has a tendency to crush if a bolt tightens through it unless you sleeve the hole. I'd go with solid bar, like 4" wide and 3/4" or 1" thick.

The chip pan will prevent you from accessing the screws that connect the foot-bars to the standoffs, countersunk into the foot-bars, so I guess I'd do those only moderately tight so that the adjustment standoff can still turn. Alternatively, one could thread the hole in the foot-bar and run a long bolt the full length of the standoff from underneath, tightening into threads in the foot bar. That leaves the head accessible notwithstanding the chip tray. Only the adjustable standoff would have to be like that. The other three could get bolts from the top, tight and with threadlocker.
Click to expand...
I wouldn't recommend using the mounting scheme depicted above. The stand itself is flexible and and any flex in it would be telegraphed to the two plates. A rigid sub-plate which is floating with respect to the stand would be preferential. What is important is the relationship between the two cross plates; specifically, their angular relationship to each orher, as this is what will determine bed twist.
 
I would strongly recommend loosening the mounting bolts and running a test for taper. The old adage, "if it ain't broke, don't fix it " applies. If the test is successful. tighten the headstock bolt, and check again. Leave the tailstock bolt finger tight or loosely snug.

Leveling isn't necessary. It is a tool used to help with alignment but as has been pointed out many times, the ultimate test is whether you can turn a length without taper.
 
RJSakowski said:
I wouldn't recommend using the mounting scheme depicted above. The stand itself is flexible and and any flex in it would be telegraphed to the two plates. A rigid sub-plate which is floating with respect to the stand would be preferential. What is important is the relationship between the two cross plates; specifically, their angular relationship to each orher, as this is what will determine bed twist.
Click to expand...
I went back to read your thread on mounting/leveling your G0602. Found it informative, but a bit hazy (for me anyways) to understand your implementation. At the end of the thread, if I recall correctly, is a link, but it is a circular reference, meaning it just goes back to the same thread.

Do you have any pictures, sketches or drawings of what you ended up with? Did you just add sub plates on top of the channel to do the adjustment? Were the sub-plates tied to the channel, or were they just supported by the 3 jack screws? Are the sub-plates larger than the lathe feet? If not, how did you access the jack screws?
 
RJSakowski said:
I would strongly recommend loosening the mounting bolts and running a test for taper. The old adage, "if it ain't broke, don't fix it " applies. If the test is successful. tighten the headstock bolt, and check again. Leave the tailstock bolt finger tight or loosely snug.

Leveling isn't necessary. It is a tool used to help with alignment but as has been pointed out many times, the ultimate test is whether you can turn a length without taper.
Click to expand...
I will try this.
 
RJSakowski said:
I wouldn't recommend using the mounting scheme depicted above. The stand itself is flexible and and any flex in it would be telegraphed to the two plates. A rigid sub-plate which is floating with respect to the stand would be preferential. What is important is the relationship between the two cross plates; specifically, their angular relationship to each orher, as this is what will determine bed twist.
Click to expand...

A rigid sub plate is not less rigid when affixed to the stand. So the floating aspect is of no benefit other than avoiding how the feet may twist the stand. With three feet, that doesn’t happen because the loads don’t meaningfully change as the feet are adjusted. Not using the stand as part of the torsion structure is rather inefficient, in my view.

I think we agree that the angular relationship of the cross plates is what matters. The notion of a stiff connection between the two cross plates is the whole idea we’ve been discussing. The proposal has been to skin the frame with sheet metal or, less desirable, plywood, to increase torsional stiffness. I think mentioning a “plate” in this regard is counterproductive, as a plate shape will not have good torsional stiffness.

To the extent sheeting/skinning the OP’s frame would leave one wanting more stiffness, I’d suggest that adding diagonal bracing or sheeting on the top and bottom surfaces of the boxed section under the bed would be most efficient. The channel RJ uses is a relatively inexpensive shape of steel but tubing or a fabricated box structure would be torsionally stiffer, given equal mass.

The dual prongs of this discussion are amusing. One is “just try it you may need nothing” and the other is how to best achieve the ability to control bed twist. If your need to control bed twist is minimal, then your frame probably doesn’t need much in the way of modification. Yes, it will take a little longer to balance the adjustments while iterating toward the desired result, but overall time invested could be less (certainly money). In other words, you can achieve the same end point with very minor structural changes.
 
The Hardinge lathe three point mount comes to mind...
One pin, two ball in groove, all three spring clamped.

Sent from my SM-G892A using Tapatalk
 
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