Leveling the lathe - not sure if I'm "doing it right"

Yeah I did, the level is calibrated as best as I could get it. The bubble is only a smidge off.

You are correct in what you said earlier, if the lathe is not level, it's fine. You're looking for relative changes.

If your level is not calibrated in any way, it doesn't matter "much". If you can get the bubble close to centered, (and NEVER rotate the level...), you'll be guaranteed to be in the "accurate range" of the bubble. (Although the one you're using might be beyond that issue).

I think I know what I'm doing wrong here though. I'm shimming the headstock side and it seems that you should avoid doing that at all costs unless you're trying to get rid of nod in the headstock. You should always shim the tailstock side first.

I'll agree with that, but it's not because it's not equally effective at the stage you're at. There are several mechanical reasons why it's "better" not to shim the headstock end. If you're in a position to start over from the tailstock end, you should do it, but there's still more to sort out here.

I think you have a combination of "V" ways and flat ways. That's gonna make it tricky to get a dead nutz level reading anyhow. The flat ways are going to show wear, where the very tip top of the V ways are not going to show wear. That'll be down on the sides.

My suggestion is to A, use your level (even out of level) to establish a flat plane across the ways as close as you can. Level is cool, but if you didn't want to calibrate the level, it doesn't matter. What you NEED is to find a flat plane. Level is only a convenience. If you've got two V ways (I think you've got one V for the saddle, and another for the tailstock? If I'm off, you can still use the principal here.... Put the level (on a parallel if needed) across the tip top of the two V ways, where it's unworn. Do as you're doing, and make the reading the same up and down the lathe bed. That's a baseline. A jumping off point. Then you know where the lathe bed is to start. That is important, as you DO want to use the "twist" measurement to get it to a minum, but if there's any wear, you're actually, in the end, going to probably "dial out" some wear....
Once that's done, put the level on the carriage. At that point, you can use the level (calibrated or not) to track -deviations- from the original "plane". That would be (typically) closest to the headstock, but it won't be consistent across the whole bed. That will need to be accounted for on a judgement basis, to get the most repeatable results over the longest possible distance.
After that's as good as it can (reasonably) be, your final adjustment (shims and otherwise) will be based not on "level", but on actual cuts. And this can be a process, but setting your stuff up "close to" being in plane will make that process of identifying errors go a lot better.

For your lathe, which has a foot on each end- You are going to "dial in" enough twist to make it cut right, that the level you have is more than you'll ever need. Folks calling out a half thou resolution, they're not wrong. If you were SETTING the lathe with the level, you'd want at least that. Your lathe is not heavy enough to "sag", its not long enough to have six, eight, ten (or more) sets of feet along it's length, that ALL need to be set to the same height and same level. Accurate levels are almost required to set these up, because "absolute level" is a datum, a reference, a concret thing that you can pick up and carry from one place to the next, and the next, and the next... You've got a foot at each end. You don't need to carry "level" to any place except across the ways. "Bubble not moving" is plenty level enough to get that baseline adjustment done, the secondary "accounting for wear" adjustment done (IF that's an issue- I have no idea), and move on to taking cuts, doing math, tearing your hair out and sorting out a crooked headstock from a shifted tailstock, while not blaming either of those possibilities for what might just be deflection in the test bar... That's where you want to put your headaches. The leveling is really just as simple as you have described. "planar" in your case is every bit as good as level. I only would add the extra step of "baselining" the machine from unworn areas to know an actual "start point" so that you know where you're at to begin with, and help with keeping track of overall changes.
 
I have nothing constructive to add. But I have a question, once you have the bed level or planer, if you are still cutting a taper how do you know the headstock is not the problem?
 
I was leveling my lathe and the wife was helping, I finally said it looks like we are about 0.0003 off now and she stood up and says how much is 0.0003? I gets my feeler gauge out, find the 0.001 tooth and said see this? if you could divide the thickness up into 10 pieces it would equal 3 of them over 10".... she told me my parents were not married in one word then called me a bunch of ugly names...:face slap:..
Someone gave me some beer cans to chop up for rough shims they left them under my car as i was out the neighbor trying to be helpful threw them away and of course it was rubbish day so i couldn't fish them back out the bin. Mentioned this to the neighbor and said i was going to use them as shims for leveling the lathe he promptly said i have some you can have and went and got 10mm builders shims.
 
I have nothing constructive to add. But I have a question, once you have the bed level or planer, if you are still cutting a taper how do you know the headstock is not the problem?
I have tried to figure that out too. In my internet research, for whatever it is worth, I came across some comments that a facing operation may tell you. Whether this is accurate or not, I don't know. But here goes. If you do a facing operation and the cut leaves a convex surface (higher at the center) the issue may be the headstock alignment. Hopefully someone will chime in with their opinion on this.
 
I have nothing constructive to add. But I have a question, once you have the bed level or planer, if you are still cutting a taper how do you know the headstock is not the problem?


Facing a large disc and checking it for flatness across the whole diameter is the easiest way. But that depends on the accuracy of the cross slide as well....

You can also put a (known) round bar in the chuck, tightly, and use an averaging method to measure at several points. That'll pick up twist and nod, RELATIVE TO the motion of the carriage. Very "down to earth" versus trying to precision measure things we're not qualified to measure, let alone get a handle on all the variables, which in the end are (usually) out the window with used stuff with small amounts of wear anyhow... That bar doesn't have to be in the chuck "dead nutz", just tight. It could even have a bend in it, it's just gotta be "round". Was (and sometimes still is) called "Rolly's Dad's Method", or "RDM" if you want to look for it, but honestly, it's so old that the forums are lost, and the three million results that you find just say "search for it", but it isn't there....

If you find it, great. If not, maybe I'll write it out, but it won't be right now...
 
If the machine is a Machine you are unfamiliar with or even new there are a number of things which can be off that will affect the test bar from issues with the carriage to a misaligned head stock (all solvable issues) but you have to have a reference plane you know to be true before fixing those. The bed being level/twist free is that reference plane; so, if your leveling your bed ways by checking a test bar in the chuck or head stock you may be dealing with compounded errors.
 
this is what i am struggling to get my head around. if i get the lathe bed level to a plane and the headstock is out i have to shim the headstock but by doing so i am altering (spoiling) the level plane of the bed.

the second thing is where does one draw a line for arguments sake lets say i get 0.001 over 12" im never going to be turning anything of that length as my interest lies in making model hot air engines (maybe steam if i progress enough) i only have 10" swing so most parts i make are going to be less than an inch long
 
Firstly, South Bend’s standard level for lathe leveling back in the day was a Starrett No. 98. No, it’s not as precise as the Master Precision Level, but leveling the bed is a means to an end, not the primary objective. The primary objective is the ability to machine straight cylinders without tapers and flat faces without dish. Chasing level beyond our technique may cause insanity. :)

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The two-collar test in all its forms can certainly start with the level achieved using a Starrett 98, especially if one is reading the level with good technique. If the lines on a 98 represent .005” per foot, then it’s not hard to interpolate that down to 0.001” per foot or even .0005” per foot. (Of course, the markings on a 199 can also be interpolated.)

Here’s South Bend’s instructions for leveling:


Their standard is the ability to detect a 0.003” shim under one tailstock leg. If the legs are 24” apart (a guess based on my own South Bend lathe), that’s 0.0015” per foot, which is detectable in a Starrett 98.

Let’s think about this. Let’s say I am turning a 12” cylinder. And let’s say my bed has a twist of .001”/ft—the smallest difference between head and tail I can easily measure with a 98. With a 10” lathe, the center will be about 5” above the bed rails, or a bit less. Let’s say it’s 6” because that simplifies the math. In 6”, .001”/ft difference between the tailstock and the headstock will move the tailstock center laterally by 0.0005”. That can be measured right at the headstock and right at the tail of the lathe, maybe 4 feet separated on a lathe that is 36” between centers. The twist in any one foot will therefore move the tool or tailstock center laterally by 0.00013”. A two-collar test with that 12” between collars will show a diameter at the tailstock 0.00025” smaller than at the headstock.

That is well into fantasyland for most hobbyists who are making small parts. Any slight lapse in technique will make a bigger difference, it seems to me. But we can still throw another .001” shim under one leg and dial that out, assuming our technique is careful enough to be repeatable at that level of precision.

So, use a level that won’t make you crazy with as much care as possible, and then switch to a two-collar test.

Rick “judge lathe adjustment by the parts it makes” Denney
 
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