# Leveling the lathe for twist



## PWF (Jun 4, 2019)

Looking at the pics.    What is the correct way to level the lathe for twist?

A,b or c?


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## Technical Ted (Jun 4, 2019)

I use method B because typically the tops of the V ways are not worn (as the flat ways might be) and should be close to as built condition. I would touch them lightly with a hone to remove any possible burrs. 

Ted


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## benmychree (Jun 4, 2019)

I would use A, the tailstock ways would not be worn at the headstock end, or the very tail end of the bed, and yes, stone the surfaces to eliminate any burrs.  On some lathes, the tops of the prismatic ways may not be at the same height.


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## Cadillac (Jun 4, 2019)

The V’s are not the same height at least on all the ones I’ve seen. You will need to use 123 blocks or parallels to get you off the the V,s. You can do like C but you need to remember any variance can be within saddle or cross slide fitment. Check your blocks or parallels for errors so you know what your dealing with.


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## Technical Ted (Jun 4, 2019)

Well, I guess it depends on what lathe you have. On my South Bend lathes, I only have one flat way with 3 V ways (which are all at the same height).

Level it with whatever method you choose, but then check/verify by a two collar test. 

Ted


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## rogerl (Jun 4, 2019)

What is a "two collar test"?

Roger L


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## benmychree (Jun 4, 2019)

You chuck up a piece of stock of large enough diameter to be stiff, say an inch or more, and 6" plus long, you want to end up with a piece that is relieved on the diameter, leaving a short distance of full size at each end, say 1/4 - 3/8  long, then with a sharp tool, light cuts and fine feed, take a light cut on the full size ends without adjusting the cross feed; measure the resulting diameters to determine whether or not the lathe is cutting a taper; if, say it is cutting taper large at the head end, lower the tail end leg in the front or raise the head end in the back.  I would tend to truly level the headstock end, and make adjustments at the tail end.


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## darkzero (Jun 4, 2019)

I also use method A. Not that it matters but I lay my 123 blocks flat instead of standing up like in the photo.


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## Technical Ted (Jun 4, 2019)

There's a lot of discussions on this list and others about leveling lathes. The only reason I level my lathe is to get it in the ball park for cutting true as benmyhree described. Things will move over time and if I find my lathe is cutting a taper while only holding a piece in the chuck/collet (not using the tail stock) I will tweak the tail stock end lathe leg levelers to make my lathe so it cuts true.

I don't really care if my lathe is level (within reason of course). I want it to turn and bore true.

Ted


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## PWF (Jun 4, 2019)

THANKS to all.

I have found that A and B are essentially equal just a bit offset.

Meaning that they measure the same tilt on both ends, but absolute value of A and B are different.


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## Cadillac (Jun 4, 2019)

B will not give you a reference for "leveling"the lathe. You can compare readings down the lathe but not for level just twist. Those two V surfaces are different heights measure them to the flat surface. 
A would give you two surfaces on the same plane. Keep you blocks on the same side down the whole length of bed do not mix during reading trying to position in the same spots to take variables out.


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## mikey (Jun 4, 2019)

I use method C myself. I prefer to level the lathe using the surface upon which the tool post rides. This reduces the influence of wear, mismatched blocks or whatever. I remove the compound and put the level on the chuck side of the cross slide where the tool will be located. Using this method, I can usually finalize my level with a few cuts in a 2-collar test.


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## Richard King 2 (Jun 4, 2019)

I would use C as it is spanning the bed ways and the saddle can be cranked and you need not move the level by picking it up and not setting it back down in the exact place of the ways on the other end.   I would put an equal amount of pressure on al the leveling screws and hopefully the screw in ontop of a leveling plate that has a counter-sunk hole in it.  Then zero the level bubble on the head stock end and  move to the tail-stock end.  Then crank it back to the headstock end and read it again....then move to the tail stock end and only adjust down there.   The head end will change a little so you can re-check the pressure on the plates by tapping on them with a hammer.   This way you are aligning the bed using a level and your saddle will be following the same path your tool bit follows.   Then you can get the final tweek doing the 2 collor method as Ben said.


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## Dan_S (Jun 6, 2019)

I've always used C.


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## Tom1948 (Jun 6, 2019)

My lathe ways are different heights and I considered using method C . It seems the most obvious and makes the most sense. But I never seen anything that said so. Now, I respect what mikey says because he has always given good advice here and seems to be quit knowledgeable. So, could you please elaborate a bit further on it. Dan S, feel free to jump in here as well as you seem to concur. Now, most of my work is within 6 inches of the chuck. My lathe is a PM1020.  Two mounting bolts at the chuck end and one at the tailstock.


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## mikey (Jun 6, 2019)

Tom, thanks for the kind words. Many lathes have front and rear ways that are not level with each other, my Emco Super 11 and your lathe included. Even if my ways were level I would still use the cross slide as a platform for the following reasons:

My cross slide is flat along its full length and is accurately machined.
It is the reference surface that I use to support my tool post.
It more accurately reflects and magnifies the geometry of each way in relation to the other.
It is quick and easy to do, and it is, for me, accurate. My level is sensitive to 0.02mm/M and sitting the level on a surface that accommodates its entire length adds to the stability and accuracy of whatever it is reading. Plus, once I put the level on the cross slide, it doesn't move until I am done with the leveling process; this eliminates any error induced by moving the level around to different spots.
Typically, this allows me to more quickly level the lathe. I admit that some days God smiles and I'm done in a few minutes; some days he doesn't smile and I can be at it for several hours. In the vast majority of cases I can level the lathe quickly and take a few quick cuts with my 2-collar bar to finalize things and I'm done. I guess what I'm saying is that this works for me and that I'm not guessing that it works; I've proven to myself that this is the best way for me.


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## darkzero (Jun 6, 2019)

While I have used method C (well like only twice that I can remember), I like to use method A cause it's quicker. Leveling for twist can sometimes be a time consuming chore. I only have a 36" between center bed but cranking the carriage back & forth gets old really quick. Especially if you have a big lathe, say like 60" between centers, I'd hate to crank the carriage back and forth from end to end multiple times.

Method A saves me a lot of time & gives me equally good results. Just pick up the level, move it over, wait till it settles. Test cuts are a part of my leveling process. After leveling I'll tweak the leveling feet with test cuts. I usually get down to 2 tenths over 10" & stop, anything less than 3 tenths is good enough for me & cause it may not last long.

I relevel my lathe once a year no matter what as part of my maintenance routine but sometimes more often. I live in earth shake country & the ground likes to move here. Anytime there's a quake big enough where I can feel it I'll relevel. Anything that helps me get the process done quicker I'll do as I hate doing it as it is.


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## Tozguy (Jun 7, 2019)

Just an academic question;
 once a two collar test has been done and the results are acceptable, can we not use that piece as a test bar with a tenths DTI on the cross slide for future twist checks?


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## mikey (Jun 7, 2019)

If you mean to use a 2-collar test in lieu of using a level, yes, you can certainly do that. In order for that test to produce acceptable results the lathe must be level.


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## Technical Ted (Jun 7, 2019)

Tozguy said:


> Just an academic question;
> once a two collar test has been done and the results are acceptable, can we not use that piece as a test bar with a tenths DTI on the cross slide for future twist checks?



I have done this before, but sometimes it's quicker and easier to take a light cut, after getting the test bar indicated close, rather than taking the time and care to indicate it in perfectly and just use the DTI alone (without taking a cut). Getting that test bar indicated in within a few tenths can be an arduous task. But if you did, then checking between the two collars with said DTI could help you get things true without taking a cut. 

Ted


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## Technical Ted (Jun 7, 2019)

Further, what I have done that helps speed up the process is take a light cut and then use a tenths DTI to tweak things in before taking another light cut to verify by going back and forth between the two surfaces with the DTI and adjusting accordingly. 

I'll also do this if I'm actually machining on a work piece and I find I'm getting a taper and want to tweak it out prior to my finish pass. So, I'll have one longer machined surface rather than two small ones and just check the entire length with the DTI and tweak it in. 

Ted


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## Tozguy (Jun 8, 2019)

Thanks for the response.
I took great care in setting up my lathe using the two collar test. As a newbie I was more adept at using a micrometer but was not so certain how much deflection was occurring so I took several 'spring' passes. I found it to be delicate work at the time and the lathe (a 12x36) not always responsive to the tweaking. Fortunately the lathe is sitting on a very stable cement slab in a controlled atmosphere far from tectonic faults so all I do now is keep an eye on the work in progress for any signs of twist in the ways. 

PWF, how is it going?


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## Richard King 2 (Jun 8, 2019)

If you don't own a precision ground test bar you put in the spindle taper, you can turn the 2 collars different diameters from a worn lathe.  Just mike them until they mike the same size.   Then you can twist and  indicate the bar so it reads zero zero or plus a few tenths + on the tailstock end to compensate for push away.  This way is faster then taking multiple cuts.   Or if your moving the head if it is one a pin like the Asian ones and Colchester have.   Another test you can make is to chuck up a 4 to 6 inch x 1 to 2" thick, round bar stock of aluminum and face it.   Then indicate the face.  It will read zero zero from the outside to the center where you just cut.  But then continue cranking past the center and indicate the back side of the aluminum bar, this will show the error of the cross-slide doubled.   How about one of you do that test and take some photos for us to see.


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## Firstgear (Jun 13, 2019)

Don’t forget to calibrate your level before you start..l...


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