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Datum for Lathe Leveling

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ddickey

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#1
What is the preferred datum for checking twist. Rest the level on the top of the V's, on the carriage or on 1-2-3 blocks on the flat ways?
 

Technical Ted

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#2
When I level my SB lathes I go off the top of the V ways. I have a 12" level that spans them. I mark where I'm going to repeatedly place the level with a marker and then very lightly hone the flats on the V way tops in this location to verify there are no high spots. The tops of the V ways should not have any wear at all since they shouldn't come in contact with the mating surfaces (there's a clearance there). Just make sure there are no bangs, burrs or git there.

I would never use the carriage and the flat ways can have a lot of wear on them.

My two cents,
Ted
 

ddickey

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#3
Thanks. Is it known that the Vee's are on the same plane? In other words, is it an industry standard?
 

Technical Ted

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#4
I've never read any spec that states that they are, but lathes being the machines that they are it only makes sense to me that they would be. Maybe some of the guys here that do way truing and scraping can offer some input in any written industry standards that may exist.

I would find it hard to believe that they wouldn't be.

Ted
 

mikey

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#5
Not all lathes have level front and rear V-ways. My Emco Super 11 doesn't so I use the carriage and it works just fine.
 

Technical Ted

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#6
Looks like I should have limited my answer to SB lathes... I also know that some lathes like Atlas have flat ways and if I remember correctly the LeBlond lathes we had at work had flat ways at an angle. Below is what I use for SB lathes. What brand lathe are you going to level? Per Mickey sounds likes some lathes with multiple V ways don't, by design, have them at the same height or at least I hope it was by design! :)

Ted

SB Leveling.jpg
 

ddickey

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#7
It's a 2000 Acra-Turn. One vee each side. One for the carriage and the other side the TS.
 

ddickey

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#8
I went out and put the level on the V's. I measured the distance to the flat way and the difference was significant.
 

Chuck K

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#9
I went out and put the level on the V's. I measured the distance to the flat way and the difference was significant.
As long as you use the same position on each end it shouldn't matter. You're just making a comparison to determine bed twist....or maybe I'm not understanding what you're asking.
 

ddickey

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#10
No that's correct. You make a good point though.
I have a few issues. One is any adjustment I make to the leveling feet have little or no affect on cutting a taper. I've found I need to shim under the lathe feet.
The other issue is I'm trying to start that process with a level bed, then take some test cuts. I find I am only adjusting two feet exactly diagonal or opposite of each other. What's happening is I end up with only 2 feet on the floor. I don't know if that makes sense.
 

Chuck K

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#11
That would make sense if you had a lot of twist in your bed. Until gravity worked on it you would have 2 feet off the ground.
 

Bob Korves

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#13
The lathe bed was ground lengthwise on all surfaces in one setup at the factory. All the ground surfaces are parallel after grinding. Find areas that do not have wear from use on them and you can use those for reference surfaces after cleaning and deburring them.
 

RJSakowski

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#14
By using the top if the ways, you make the assumption that they are in the same plane and parallel with the ways. Since those surfaces only function is to provide clearance for the carriage and tailstock, that is a bit of a stretch. It may be ground but that may just be to look pretty. To be useful as a datum when using a machinist level, the tolerance should be sub-thousandth.
As has been pointed out by others on this forum, an uncalibrated surface plate, square, or straight edge is of diminished value. Before using those surfaces as datums, I would want verification that they are true.
Those surfaces on a G602 are definitely not in the same plane. The tailstock vee ways are smaller than the carriage vee ways. I use a pair of 1-2-3 blocks as risers on the flat ways and my measuring points are close to the headstock and the far right of the bed where there is no wear.
 

Chuck K

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#15
I think what I'm going to do try to get all six feet to bare load. Take some cuts and see where I'm at.
That sounds like a good plan. In the end its all about making a a straight cut. If the machine has wear in the bed, the level might not get you where you need to be anyway.
 

Janderso

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#16
I decided to level my Sb 13 today.
I don’t have a precision level. I do have an accurate construction level.
The way I approach this is, it’s better than nothing.
I observed something interesting. Cast iron moves. I watched several YouTube videos on how to do it.
After about an hour of doing my best, my construction level showed a decent days work.
I checked later, the day is warming up, all four bolts are touching and the level is right on.
I used the best surfaces I could find, ways at several points proved my level is just not sensitive enough.
I will continue to look for a real level, they are expensive. I see the imports run about $125-$175 for a 12”.
I do feel better though, I have been reading through, Machine Tool Reconditioning, the section on leveling does mention, permanent damage can occur if a precision tool is left too long un balanced/leveled. I’m paraphrasing here.
I have been chasing a taper, maybe this will help.
 

NortonDommi

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#17
Have a look at 'Build something cool' on the you tube. has a simple pendulum level very simple and accurate. Then,(opening can of worms), try Rollie's dads method to check alignment.
 

Cadillac

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#21
Shars has a 12” precision level in their monthly sales flyer for 85.00. Sign up for their email list u get 10% off.
 

Janderso

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#22
I like the 10% off. Good advice.
I'm a Shars owner, 12" precision level!!!!!
Maybe I can detect my twist now.
Thank you very much.
 

epanzella

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#23
I use the Shars prec lvl on the flats with 1-2-3 blocks. When I first set up my lathe every time I raised a foot off the concrete I had to wait a day for it to come down. I also have an MT5 test bar that plugs right into my spindle bore. Very handy.
 

rgray

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#24
Have a look at 'Build something cool' on the you tube. has a simple pendulum level very simple and accurate. Then,(opening can of worms), try Rollie's dads method to check alignment.
Definitely try the "Rollie's dads method" if your trying to stop cutting a taper. Amazed me how little change to an adjustment on the feet changes the twist on the lathe bed.
Leveling is not necessary but nice.
 

ddickey

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#25
I have all six feet bearing load now. I was able to get the HS side level with small adjustment to the outside. Then to get the TS in line I ended up with .005" Shim directly under the two lathe feet (outermost or backside). Took a test cut with no TS support and cut .0005" taper in about 7 inches. Larger on the TS end. I'll let it sit and try again in a few weeks.
 

Chuck K

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#26
What was the diameter of your test bar. You could easily deflect 0.0005.
 

Chuck K

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#28
Thats a beefy bar, but I would still wonder about deflection. I guess it would depend on the tool and depth of cut.
 

ddickey

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#29
It was also Aluminum I think 7075. Still pretty beefy.
 

Richard King 2

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#30
I answered this same question a few weeks back on another forum. I set the level on the top of the saddle and use it as a sled to check the path of the tool after I level the bed long ways. I usually leave the bed slightly higher on headstock end so the coolant in the bed flows toward the tail-stock end where generally the coolant pump is at. Just last week I did a repair on a Sharp 1440 lathe and the saddle inverted V and Tailstock inverted V ways were not the same height, so setting the level on top of the cross-slide flat worked perfect.

On many of the old American Iron like Lodge and Shipley the manuals told you to set a parallel on the saddle wings and put a level on there so you follow the path. Look at figure 8 -- http://vintagemachinery.org/pubs/2104/3558.pdf

Has anyone here ever leveled a slant bed lathe?
 
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