Importance Of A Twist-free Lathe Bed: Leveling

[janvanruth]

Now why would you want to level a used and worn lathe?
Levelling isnt going to make it turn true.
A 2 inches wide 12 inches long alu bar and a micrometer is all you need to make the lathe run as true as it will be able to.
As for the levelling feet, save yourself $80.
Four bolts, 12 nuts, 16 washers is all you need and you will be able to adjust things just by turning two nuts.

 

[mws]

Wildo, I think you misread what I said about referencing the level. I meant getting repeatable reading of the lathe bed's level. A surface plate won't help with that. For getting the level trued that's a whole 'nother matter not for this thread.

I agree with what Janvanruth said about nuts and bolts. To get the twist or bow out of the bed you may need to push AND pull on the bed mounts to get things straight, level is just an easy reference to do that but nothing NEEDS to be level. To level the whole kit and kaboodle adjustable feet are convenient on the mounting frame or table. Just compensating for an uneven floor really requires adjustability. But I would never rely on gravity and machine weight alone to straighten the bed out. In fact, to eliminate the torquing of tables and benches, or reference plates, only three points of contact are recommended so only the machine and it's mounting surface are acting on each other, reducing if not eliminating the affect of other forces.

So, two things are being discussed here, as usual when this topic comes up, "level" and "straight". Even the title of the thread conjoins the two ideas, which clouds the discussion somewhat. They are not the same and not mutually exclusive. In addition, when talking about "leveling feet" I'm not sure where you are applying them, between machine and bench or bench and floor. For my purposes, and I think for most, rigidity and straightness of the bed are paramount. To achieve that things need to be bolted securely from moving up, as well as down and sideways. I'm not so sure leveling feet achieve that end. I've read several discussions on the topic and one common consensus is NEVER use cushioned feet on machine tools. Seems that put nuts and bolts well in the running for your application. I can buy a LOT of nuts and bolts for $83. Further, you have a lathe capable of turning all sorts of couplings, feet, points, whatever to achieve a secured machine.

Mine is but one opinion on a topic that I believe concurs with the majority but you can always find contrary opinions on any topic should it suit you. I hear they're relatively inexpensive. Maybe so, but I've found the better ones were obtained at greater expense.

Mark

 

[wildo]

Mark- I'll have to digest all you wrote here, but I did specifically state in the thread topic "a twist free bed." I'm aware that when we talk about leveling the lathe bed, we aren't talking about making sure it's "level." I thought this was understood. I'll reread your posts and see if I've missed something. Is not the machinist level the tool used to ensure the bed sits in one geometric plane- that it is twist free? Is not this process called "leveling the lathe"? Maybe I have missed something.

 

[4GSR]

Wildo,
I have a 9" SBL that was my dad's, bought new in 1949. To this day it has not been bolted down solid to any table top, stand, or whatever. Only the bolts on the headstock end of the bed are secured to the bench. The bolts on the tailstock end of the bed have always been loose, never tighten. I don't recall ever trying to level the bed. It stills cuts just as straight as the day it left the factory. At least I think it does. I haven't done any long turning on the lathe in many years. Just short stuff. It cuts with zero taper. I have put a machinists level across the bed to check for twist, again, same reading at both ends of the bed. Of course, I have larger lathes with longer capacity that have to be releveled from time to time, so it will cut reasonable straight. It's nearly impossible to get a lathe to cut perfectly straight from end to end, especially if the lathe has wear on the bed. You can level it all you want, but you cannot straighten out wear to get a lathe to cut straight.

 

[Bob Korves]

My old Logan 1957 has adjustment bolts, not quite as convenient as the southbend setup, but beats heck out of shims as far as convenience. Easy to check level every couple of months and adjust.

Bob, I'll have to ask you about level vs twist tests. I just try to make it cut straight regardless of twist or level.

Exactly, Jon! What we want is a lathe that cuts work accurately. Do whatever it takes to get there. Level or thereabouts is usually a good place to start.