straight and narrow

[pussaw]

is there anyway to set up my lathe (bench) to make it run true for the full length. if i put a center in the tail stock an one in the head they look like they line up point 2 point but when i turn things round and go to flip it :eek: around and return the other end its not one the same cente :confused: r . so i think my lathe is getting twisted further away from the headstock. there has to b an easy way to fix this without alot of fancy tools and trail and error shimming. how did they build the pyrmaids with just a stick and a string :D .

[RollaJohn]

Pussaw:

Even big, heavy metal lathes will twist. The machinist uses a sensitive bubble level to measure this twist. This level is like the common carpenters level except the vial has a flatter curve so it the bubble moves farther with a small difference of twist.

First thing to do is to find, buy, or borrow one from someone. Place the level across the bed at the headstock end and take note of where the bubble is located. Then place the level at the tailstock end, keeping the level pointed the same end to the front, and compare the bubbles position. If different than before, place shims under the level to correct. Then place this shim stack under the foot of the lathe, twisting the tailstock end parallel to the headstock.

The ends of the lathe don't have to be level, just leaning the same on both ends. :)

Edit: Buy :eek:
How much accuracy do you need? Here are two levels to see why I suggest borrowing:
http://www.use-enco.com/CGI/INSRIT?PMAKA=240-0347&PMPXNO=4822318&PARTPG=INLMK3
and if you have way more money than I do, look at this:
http://www.use-enco.com/CGI/INSRIT?PMAKA=240-0352&PMPXNO=4822332&PARTPG=INLMK3

. :D :D

[GrayBeard Phil]

Hey Rolla:

This special level you mentioned, is it one of the ones on this page?

http://www.mcmaster.com/nav/enter.asp?pagenum=2210

Thanks for letting me learn something new today (correcting the twist in a lathe bed.)

Phil

[RollaJohn]

Phil, yup those are the ones.
While I was looking up examples from a different source, then editing, you beat me .

Realistically for woodworking this level has enough accuracy, just needs to rest on a flat bar across the ways due to its length:
http://www.use-enco.com/CGI/INSRIT?PMAKA=990-2997&PMPXNO=3012569P

[RollaJohn]

how did they build the pyrmaids with just a stick and a string :D .

Who said the sides weren't supposed to be vertical???? :D

[pussaw]

thanks 4 answers i'll give it try. if water seeks its own lever how come the world is not flooded. u dont have to answer this just ponder on it. and how come a plumb bob dont work next to mountains. and how come air weighs so much. i quess its not a perfect world :D

[RollaJohn]

:rolleyes: . Just a note to bring the sensitivity of that $600 level in Phil and my posts into simpler terms. If you place the level with one end on a piece of newspaper and then remove the paper, you will see the bubble move!!!

[pops-shop]

I think that type of accuracy would drive me absolutely crazy trying to get someting "level". :eek: I live a block from the train tracks and everytime one comes through everything level will probably not be. Besides, in my 100-year old house, nothing is "level".

[RollaJohn]

My brother is a machinist and even he didn't go for the high price model. He settled for a Starrett Precission Machinist's Level model 98Z-18, a $300 version. The Master level may be needed for the aero-space shops but not for the average machine shop. The $30 or $90 versions are plenty good enough for setting up our wood working machines.

The tool is called a level, and indicates that condition, but in use for our purpose it is an accurate tilt indicator. Which is what we need, the level condition is not necessary. The same amount of tilt across a machine is what we are after.

Shop floors are very seldom flat, they all seem to have dips and high spots. So we either make the legs fit the floor or we raise the low spots up to the legs with shims. A machine tool, a table or a chair will drive you nuts if its tippy. The lathe will twist in an attempt to sit solidly on the surface, even more so when it is bolted down.

The Oneway lathes, I think, are probably the least likely to suffer from this torsional displacement. I haven't worked with one but I like their looks. :)