Lathe leveling

[curtis cutter]

I finally got around to checking the trueness of my old lathe. When I start at the chuck, with the level on the carriage, I have the level adjusted (by using feeler gauges) under one end until it is level. I then take the carriage to the far end of the lathe and added shims under the far end base until I saw the same level indication. I believe it does not tell me the carriage is necessarily level but that any tilt of the ways is consistent at both ends.

About 12-18" from the chuck I drop at the operators side about 6 ten thousandths (six marks on the vial & the level is accurate to 2/10000 in 10"). My assumption is I am looking at wear of the way, on the operators side, in the most common working area of the bed and not much I can do about it. Is that a fair assumption?

[pete]

Yep. Have you got a 10ths reading dti? If so remove the tail stock then run the carriage all the way to that end as far as you can. That will be the most unworn area on your lathe bed with most lathes and how there generally used.Set up your dti on it's magnetic base so the indicators tip is maybe 6" in front of the carriage towards the head stock on the way surface. Zero the indicator then slowly run the carriage up to the head stock. For V way's you'd need to do it twice so both sides are checked of course. But the indicators tip and carriage are then starting on those almost unworn areas and the wear can be quite closely measured in the area it was most used. Your actual wear amount will be a combination of both the bed ways and bottom ways on the carriage. It wouldn't hurt to do both the front and rear way surfaces on your lathe as a comparison for how much the front way is worn compared to the rear. Once the carriage does start moving over the worn area then accurate and dependable measurements aren't possible of course.

The vertical wear amount unless it's really excessive has very little effect on the part diameter since the tool tip is only moving slightly up or down on the parts radius. It's the bed twist that rolls the tool tip into or out of the cut that can cause a tapered cut in either direction depending on which way the bed is twisted. It's effect is also greatly magnified because of the height of the tool tip above the way surfaces. For an example let's say the bed was twisted by .001" Because of that magnification at the tool tip it's going to move far more out at that tool tip than what the twist happens to be.

[curtis cutter]

Yep. Have you got a 10ths reading dti? If so remove the tail stock then run the carriage all the way to that end as far as you can. That will be the most unworn area on your lathe bed with most lathes and how there generally used.Set up your dti on it's magnetic base so the indicators tip is maybe 6" in front of the carriage towards the head stock on the way surface. Zero the indicator then slowly run the carriage up to the head stock. For V way's you'd need to do it twice so both sides are checked of course. But the indicators tip and carriage are then starting on those almost unworn areas and the wear can be quite closely measured in the area it was most used. Your actual wear amount will be a combination of both the bed ways and bottom ways on the carriage. It wouldn't hurt to do both the front and rear way surfaces on your lathe as a comparison for how much the front way is worn compared to the rear. Once the carriage does start moving over the worn area then accurate and dependable measurements aren't possible of course.

The vertical wear amount unless it's really excessive has very little effect on the part diameter since the tool tip is only moving slightly up or down on the parts radius. It's the bed twist that rolls the tool tip into or out of the cut that can cause a tapered cut in either direction depending on which way the bed is twisted. It's effect is also greatly magnified because of the height of the tool tip above the way surfaces. For an example let's say the bed was twisted by .001" Because of that magnification at the tool tip it's going to move far more out at that tool tip than what the twist happens to be.

Makes total sense that the actual tool in relation to the work piece would amplify any small changes seen on the bed. I will run the carriage with the the indicator and see what it looks like.

Thanks

[10KPete]

Remember to take in to account the wear on the bottom of the saddle. On most lathes it will be 4 or 5 times more than is what is seen on the bed. The saddle is short compared to the bed and travels the bed, so.... And the left operator side will have the most wear.

I will long remember when that discovery hit me in the face. A bunch of shimming I hadn't seen coming.

Good luck!

Pete

[pete]

Maybe with large heavy duty industrial sized lathes getting a proper level condition works fine and nothing further is needed. I wouldn't know since I've never set one of those up. For the lighter weight lathes most of us might be using it still took me making very small adjustments after running a few cutting tests Gregg. What your then doing is compensating a bit past that exact level condition to adjust for the machines deflections under those cutting loads. Only a few 10ths of adjustments were needed, but they make a measurable difference.

And I'd sure agree with Pete's point. Even on lathes with hardened beds the bottom way surfaces on the carriage are still soft on any lathe I know about. It makes me cringe when I see people on YouTube polishing parts, turning rusty metal or cast iron without covering the bed. That harder material will get under and embed into the softer metal and work just like a lap from then on. Usually the tail stock runs on different way surfaces than the bed does. Because of that there usually not cleaned or lubed like the carriage ways might be. Unless the lathes tail stock has felt wipers and they were maintained it's also usual to see the tail stock quill pointing down hill by quite a bit on lathes with a fair number of hrs on them.

[liveaboard]

it's also usual to see the tail stock quill pointing down hill by quite a bit on lathes with a fair number of hrs on them.

When my lathe was made, dinosaurs still roamed the earth.
The tailstock ways are banana shaped. The lead screw is rounded.
Attempts at accuracy are futile.

Interestingly, the main ways are fairly straight.

[curtis cutter]

There is much to know about tooling and turning. It is becoming increasingly clear to me that my choice of getting old iron was fortunate as my lack of understanding of how one properly cares for a machine could potentially have cost me a great deal.

I believe I will continue to learn on this cheap machine with the most critical lessons to be on how to keep a nice machine nice. One day perhaps I will move up in the world.

[earlgo]

A big help would be scraping in the bottom of the carriage using the unworn end of the bed as the place to match.
My old Atlas carriage had a lot of tilt on the operator front left, as mentioned above. Scraping helped a great deal.
Couldn't do much with the .005 wear on the ways, though.
--earlgo

[LIALLEGHENY]

At one point I owned a WWII vintage Lodge & Shipley Lathe , 1943 to be exact. It was a 23" swing x 72" between centers lathe, and had considerable wear in the middle of the bed. I cranked down more heavily on the center pedestal leveling bolts and was able to bring the center of the bed up to compensate for the wear. I did a job turning some 5" diameter 4140 , 54" long bars, that needed to be turned to 4-3/4" diameter. I was able to hold .0015 over the entire length.
Where there's a will there is a way .

As for a tailstock that is dipping, you can try shimming between the 2 halves of the tailstock and bring up the nose.

Nyle