View Full Version : Leveling Lathe and/or Mill

03-15-2005, 01:36 PM
OK, I have read alot of posts about leveling your lathe.
My question is what "exactly" is ment by leveling and why is it important?
I believe that you would want each foot/corner of the machine to have a solid base. This would eliminate the machine from flexing during heavy cuts.
As for having it level. How accurate is necessary? I believe if its within a few degrees (which is actually alot) it would not have an affect on accuracy Unless your looking for the cutting fluid to flow downhill!!
Finally is this "leveling" used on milling machines also?


otto luck
03-15-2005, 01:46 PM
Leveling a BP is not all that critical because it does not flex like a lathe, but it should be close. A lathe on the other hand requires that it be accurately leveled, not in degrees but in thousandths!. A lathe can twist and warp. If it is not totally level you will not be able to do accurate work!, and a lathe is supposed to be able to do highly accurate work!. I level my lathes to be within .001" any were along the bed and to .0005 or less across the ways!. I am sure there will be a bunch of feedbacks--- Stay Tuned For Further Details!!!.....

03-15-2005, 02:00 PM
The bed could be straight and true without necessarily being level.

otto luck
03-15-2005, 02:26 PM
YES it could be!!. I quess as long as the ways are absolutely parrallel and on the same angle from end to end your OK!. But make sure they are, unless you have a level that is can read to .005/ft., you will not be certain!!. You'll get more response!!

03-15-2005, 03:15 PM
We see this discussion come by regularly. I think we are confusing 'level' with 'straight. Neighter a mill nor a lathe needs to be level. The lathe on the a ship is the usual example.
However, a precision level provides a roundabout way of achieving 'straight'. As long as you have the working length of the bed level to itself, it will also be pretty straight.
Best advice I've seen is to tighten the head end of the lathe down, then let the tailstock end 'float' except was neccessary to remove bed twitst.

03-15-2005, 04:17 PM
The lathe should be level in the same plane...You could have your lathe set up at 45 degrees and it would still cut as accurate as if it was set to perfectly level....

So long as the bed is free of twist it will be right...

Forrest Addy
03-15-2005, 09:32 PM
Let's cut to it.

Knee mills and similarly constructed machine tools are compact and stiff. They don't really need leveling. They're stiff enough that they hold their own alignments. That said its convenient for them to be accurately leveled so work can be more simply made parallel with the table and saddle axes.

Engine lathes, bed mills, and planers feature long beds that are somewhat flexible. Their beds have to be brought into accurate alignment so the saddles/tables/whatever are fully supported and run in a true plane.

While leveling isn't absolutely necessary to make the machine function correctly, in most cases it is convenient to use a level to acheive the degree of alignment necessary for proper function. For this reason machine manufacturers provide bed surfaces that when used as leveling references will ensure the bed lies in a plane true enough for proper function and guarantees machine accuracy is attained.

Smaller bench lathes often have pedistals having set-screw adjustment for tilt. The machine can be plunked on a bench, bolted down, and the tailstock end pedistal setscrews backed off to allow the tailstock end to acheive their natural alignment. Then the setscrews are brought up just barely finger tight and snugged equally and simultaneously. Thus the machine will be in adequate alignment.

Larger home shop lathes and production lathes are not only more sensitive but more accurately made. Their installation instructions specify the leveling sequence (read bed alignment as represented by leveling) and the accuracy of the level required - most often levels calibrated in 10 arc seconds (0.0005" per foot) per graduation. Many installations manuals I've read threaten dire performance degradation and void warranty if the leveling isn't accomplished to factory specs.

So don't get huffy about leveling per se but be real picky about ensuring the alighment of any machine in your inventory. If it takes a precision level to attain this alighment then that's what you have to do.

03-16-2005, 12:03 AM
To answer Hidley's question - if your lathe isn't level it won't cut straight. In every step of construction on a new lathe it is repeatedly checked to be sure it is level and the alignments are all made with it level. After it is moved and properly releveled it should be back in as built alignment. If lathes were built out of level you wouldn't know which out of level condition to put it in to make it like it was built. There are a lot of out of levels but only one level.
Actually the last step in a lathe leveling job is a test cut. It may be as level as you can measure it and cut tapered. If it does you have to tweek the leveling screws to get it to cut straight.
Home shop machines probably aren't all that critical for level but large machine with a vertical column need to be earth level because a heavy headstock going up the column would try to bend the leaning column more at the top than at the bottom making the axis move in an small arc.


03-16-2005, 02:40 PM
Well after filling my garage with water and mounting everything on a raft I think I have it figured out!!

Thanks for all the replys everybody....

Now if I cut a test piece and it is tapered how do I know if the tailstock is missaligned-front to rear, the tailstock is missaligned up and down, the ways are twisted or the ways are arched up or down.
I really cant justify buying a level of that accuracy to use one time...

What happens if the moon is pulling at the time i cut my test piece, thus changing the gravational pull?

p.s. After learning that the garage filled with water was a bad idea due to electrical issues. I have turned the lathe upside down and mounted it to the ceiling. This helps in the clean up of chips as they fall away from the ways onto the floor. Easy to sweep up. You dont have to sweep around anything.

[This message has been edited by ahidley (edited 03-16-2005).]

J Tiers
03-16-2005, 05:56 PM
<font face="Verdana, Arial" size="2">Originally posted by ahidley:

Now if I cut a test piece and it is tapered how do I know if the tailstock is missaligned-front to rear, the tailstock is missaligned up and down, the ways are twisted or the ways are arched up or down.

I really cant justify buying a level of that accuracy to use one time...

[This message has been edited by ahidley (edited 03-16-2005).]</font>

yeah, that's why I never progressed past my $10 (estate sale) 0.005 per foot Starrett level.....

I'd say that you would level the machine as best you can with the levels you have, which is to say that you take out all the twist you can detect that way. Then you can do the "two rings" test, with a piece of pipe etc in a chuck and sticking out maybe 6 or 8 inches. Undercut the middle of the pipe leaving a narrow ring near chuck and at end

If machine cuts same diameter using very light cuts and not moving the crosslide, near chuck and out at the end, your ways are not twisted. Any taper between centers is then likely due to T/S alinement, which is easy to fix.

Been there, did it, didn't buy the fancy level.

No doubt the level would be nice, but.....

Actually I did buy one from Grizzley, but it was poorly made and I sent it back. Maybe someday I'll find another super deal at a sale.

BTW, after leveling, "Rollies Dad's method" will also work to final tweak, although I prefer the two rings test.

[This message has been edited by J Tiers (edited 03-16-2005).]

03-16-2005, 08:53 PM
JTiers said: "If machine cuts same diameter using very light cuts and not moving the crosslide, near chuck and out at the end, your ways are not twisted. Any taper between centers is then likely due to T/S alinement, which is easy to fix"

This first test on pipe does not use centers so to check tailstock alignment, you need to make a 2nd test bar, solid rod, held between chuck and tailstock center. Again, cut two rings, one at each end. You can adjust the tailstock and re-cut until the two rings are equal OR, cut one ring, reverse the bar end for end, cut a 2nd ring without moving the cross slide setting. Now both rings should be about identical and you can use a dial test indicator, mounted on the cross slide or compound, and indicate the ring at the chuck end and then the one at the tailstock end. The tailstock can now be adjusted and the steps repeated until both readings are the same. This latter method avoids a bunch of re-cutting.

JTiers: I think we covered both ends of the question but it's been a long day so I can't be sure http://bbs.homeshopmachinist.net//wink.gif

This board should have a good FAQ section for stuff like this. It does take a few words to say it right each time http://bbs.homeshopmachinist.net//wink.gif

03-17-2005, 07:40 AM
Ahhhh. Hummmm
If I have 3 foot ways and I use the "two ring" method WITHOUT a tailstock and its off .0001-.0002. That is fine for anything that I want. But thats only 6-8 inches in length. By the time I get 3 feet out it could be .005 But I can't do that without using the tailstock for the full length.
So back to the orig question. Which is off, the ways or the tailstock?

J Tiers
03-17-2005, 09:52 AM
Past 6 or 8 inches, you DON'T care......because you can't hang out work much farther than that.

At 20 inches, you will be using centers, or steady rest (I hope). So at that point the remedy is obvious.............

If you level the best you can, then shim for best on the two rings, you are doing the same as any lathe manufacturer.

Could you do better? Maybe....but if that is an S-B, the slop (lube space) in the headstock nose bearing is at least 0.0007 and if adjusted right, no more than 0.0014, probably. Figure that out at 20 inches............and quit worrying so much

03-17-2005, 10:11 AM
Here's the most recent thread on tailstock alignment:

BillB 02-23-2005 General