New Lathe Twisted bed

[Silverbullet]

Out of a China lathe , what do you really expect , we all want a top notch part when we make them . But a lot of it is the machinist , not the machine.
If you get it level then what? If your tailstock or head stock is not aligned. Do you reset everything . I agree the lathe should be level but to what extent .007 in 40" . Should not stop the lathe from turning out good parts accurately. I'd Ck the alignment over the bit of level it's off. But I'm a hobbiest now not working for NASA so my tolerances aren't that critical. The others have also stated the weather , the earth are always moving . Good one day may not be better then yesterday. It will change not many places bolt them down , most concrete pads are tapered for water run off , my garage is sloped 2" in 20' , yet the apron is 2" in 10' . When my compressor wasn't piped outside it would run all the way to the street. How to help change just try totally loose the anchors and let the lathe regain its shape. It will move on its own , if you try forcing it I'd bet money it will crack or bust.

 

[benmychree]

Straining a lathe bed to straighten it out to level is not going to break it; we think of cast iron as being brittle and inflexible; brittle, it can be, but inflexible it is not; I had a lathe, a 14" Lodge & Shipley toolroom model that would not cut straight, and the bed proved to be twisted, likely from not being leveled for a long period of time; you could level the head end, then attempt to level the tail end and the rear leg would be off the ground and still not level; a heavy weight was placed in the pan behind the lathe to bring it down to level, then it would cut straight. The same effect can be had by bolting all four legs to the floor and shimming or adjusting leveling bolts until true level is had. A carpenter's level or even a .005" per foot millwright's level is not good enough for precision leveling, the normal precision level is .0005 per foot.
That said, one does not really need a precision level to get a lathe to cut straight; level the head end with an ordinary level and level the length of the bed to approximate level, then adjust the leveling of the tail end until the lathe cuts straight, using a test bar with 2 narrow bands at either end and chucked in the spindle; cut a fine cleanup cut on each and note the difference in diameter; if small on the tail end, shim up or adjust the rear leg until it cuts the same diameter at both ends; if anything leave it alone if the cuts are SLIGHTLY larger at the head end.
A good example of flexibility was a horizontal boring mill I bought about 30 years ago; when I first set it up, it cut out of square vertically with the head leaning inwards towards the table; I leveled the bed, but left the leveling screws of the column a little loose at the far end; over the years it sagged back to its level position and will now cut square with the table. I could have hastened the process by bolting it to the floor, but in the building I was in at the time the floor was thin and poor and I did not want to drill holes in the floor either; in its new home it just sits on leveling pads and is so heavy that movement is not a problem; I think I remember it being about 17,000 lbs.
If a lathe bed is leveled accurately and still cuts taper, my fix is to shim the headstock until the taper is removed; on a lathe with one prismatic way and one flat way, I insert a shim on the opposite sides at each end of the prismatic way until taper is removed; the proper way would be to re scrape the surfaces under the headstock, but for most purposes, the shimming is effective.
If one makes a test bar and finishes both bands to the same diameter, and dial indicator can be used to show inaccuracies in alignment, both laterally and vertically; if there is a difference in readings on top of the test bar, this can also effect cutting tapered, although not as much as the lateral difference. I have done this on several lathes that I have owned over the years and it makes it very much easier to do precision work without resort to (all to) much filing and polishing.

 

[fradish]

To further what benmychree said, even something as brittle as glass can flex quite a bit before breaking.
You can see this in large panes of glass when the pressure in a building changes, like when a door to the
outside is opened or closed.

I think the thing you have to worry about is the distance over which you are flexing the material. If you have
a piece of cast iron and attempt to flex it 1/8" over a distance of 1", you probably will crack it. But 1/8" over
a foot probably would not (just a guess.) I think if you shim up one part of your lathe, if you have your shim
stock around the bolt hole so that it is supported from the stress of tightening the bolt you'll probably be ok.
Now I'm not saying shim it 1/8", but .010" or 0.020" probably wouldn't be a problem.

 

[benmychree]

To further what benmychree said, even something as brittle as glass can flex quite a bit before breaking.
You can see this in large panes of glass when the pressure in a building changes, like when a door to the
outside is opened or closed.

I think the thing you have to worry about is the distance over which you are flexing the material. If you have
a piece of cast iron and attempt to flex it 1/8" over a distance of 1", you probably will crack it. But 1/8" over
a foot probably would not (just a guess.) I think if you shim up one part of your lathe, if you have your shim
stock around the bolt hole so that it is supported from the stress of tightening the bolt you'll probably be ok.
Now I'm not saying shim it 1/8", but .010" or 0.020" probably wouldn't be a problem.

And I would add that the likely shimming to achieve straightness in any case would be just several thousandths, that has been my experience.

 

[4GSR]

Don't get too carried away bending/twisting a bed. I've seen broken lathe beds in past lives.

Edit: I've also seen big lathe beds with unbalanced loads twist, rock and roll to the point of breaking. Yeah, cast iron does have a little elasticity to it's iron make up. Just depends on how much "alloying" is done the the iron in the melting stage. And when it hits that point of breaking, it will snap off with a bang!

 

[scwhite]

Your Clausing is in no risk of falling over unless you run into it with a car or fork lift or similar.

I didn't say it was going fall over
Or even thought it would turn over .
It is just tipsy and needs to be stable

 

[Mister Ed]

And when it hits that point of breaking, it will snap off with a bang!

That would actually be interesting to see in a video.
Anyone want to volunteer??

 

[4GSR]

That would actually be interesting to see in a video.
Anyone want to volunteer??

I have broken off cast iron components in testing under controlled conditions over the years, trying to get a good sound product. The industry I work in, we take cast iron, which is not allowed as pressure containing materials per ASME rules, and make it hold pressure. Of course in actual applications, it is planted down hole in the oilfield, where it is of no harm to anything living. Tensile testing of cast iron is interested, you don't get that sudden .2% drop in tension and go up the scale before its breaks. It go up the scale and boom, its over with.

EDIT: I correct myself, when cast iron breaks, it don't go boom, just goes "crunch" It's steel that goes "boom" when it breaks in tension. Sorry.

 

[Splat]

You did right by anchoring the stands to the floor. Hopefully you leveled them while anchoring to get them as level as you could. A lathe should be rigid. Anchoring it helps with that. I remember after securing my lathes to the floor what a difference it made. Also it prevents movement across the floor. After taking your precious time to carefully level your lathe that all disappears if the lathe moves across your floor and throws your level off.

So after anchoring and leveling the plinths it's time to sit the lathe on them, but don't bolt it down. Wait a few days to let the cast iron relax. I gave mine a week and then bolted it down to the stands. Put your machinist's level on the cross slide perpendicular to the ways and run the carriage to the headstock and note your level's bubble position. Now run the carriage down to the tailstock end and again note the bubble. Shim between lathe and plinth as needed to get the bubble in the same spot at both ends of the ways. How level the lathe is parallel to the ways doesn't mean much. I have my lathes sitting higher at the tailstock end for coolant purposes. Get your lathe ways level and then do the 2-collars test. Shim again as needed to get the 2 collars as close in diameter as possible. After a week check level again. I check mine once a month.

 

[MattM]

Last I heard ships at sea have machine shops and those machine shops have lathes and those ships are seldom if ever level.

Tell me why I should be concerned about my lathes being "level".

That being said my lathes and mill are level to the best that I and Starret can make them.