Levelling my Colchester

[Tony]

Technically I think the student is a bench lathe, right? Its on a steel
stand, and I don't know if the stand is tough enough to level like
floor (engine?) lathe.

This little student is pretty darn stout. I'm sure it gets poked
fun at in school.

So the tailstock end has two large bolts coming in from the bottom
(through the coolant tray, accessed via the drawer). There are
two (non threaded) holes on the tailstock end, operator side. None
on the flip side. None visible at the headstock end of the casting either.

These wouldn't be the easiest holes in the world to thread.
(I'm thinking jack screws)

From my understanding, as it is, I'd have to shim one side or the
other, between the lathe casting and the stand.. but boy would
that be some tough iterations. (loosen, lift, shim, drop, tighten,
measure, repeat).

There's got to be a better way?

If I hear just winding up the rubber isolation feet on the stand
would do the trick I'd be a happy camper.

Thoughts?
Tony

[Stuart Br]

My Chipmaster manual says that no special leveling is required. Not sure if the same goes for the Student though ?

Regards

Stuart

[Tony]

my manual simply says
"level the lathe with a precision level longitudinally and traversly"
"do not grout in"

and thats about it.

-Tony

[Tony]

Maybe some pictures will spur some interest in my teensy thread?

Using the two collar method I thought "what the heck" and just shimmed
under the cabinet:



here's the results of the first pass.. dimensions are over 1" OD (eg 1.314")



put shims here:

[Tony]

and I kept adding shims



you can see I got it down to about 0.004" over 4". (0.013"/ft)

at this point any additional shims would pick the lathe up completely.. ie
it would start rocking.

i imagine I have to put anchors in to actually do some pulling?

or maybe my headstock isn't aligned to the ways. i could get a test
bar.. but I wouldn't know where to start.. how do I trust my test bar
if I dont know what the twist (or wear) is like?

any thoughts greatly appreciated.

Tony

[philbur]

So have you asked yourself if shimming is the correct solution for a taper that has multiple possible causes?

If you buy a precision level you can test for bed twist and bed wear separately and independent of spindle or part deflection issues. If you buy a test bar and a dial indicator you can trace spindle/part deflection issues.

Then you will have the basis for deciding on what compromises you will have to make to get the best precision out of your not new machine.

The two collar on its own only provides you with useful information to correct an error if you know where the error is.

Phil

or maybe my headstock isn't aligned to the ways. i could get a test
bar.. but I wouldn't know where to start.. how do I trust my test bar
if I dont know what the twist (or wear) is like?

any thoughts greatly appreciated.

Tony

[Tony]

how about a Machinists' plumb bob?

I've read that the R's D's Method obviates the need for a level.. but
apparently thats not the case.

a level it is.. off to do some shopping.

with a level, how do you isolate twist and wear? I can see the level
doing its thing on the tailstock end.. but at the headstock?


-Tony

[philbur]

There is a very high probability that the bed, hard up against the headstock, is unworn. You should compare a level reading at this location versus the tailstock end in order to differentiate between wear and twist. I think a reasonable procedure is as follows:

Place the level on the cross-slide (oriented across the bed) note the level reading for say every 5cm of carriage position along the bed, starting with the carriage all the way, hard up against the headstock. Plot a graph of the readings and you will see the twist and the wear separately.

Place the level on the cross-slide (oriented parallel to the bed) and repeat the above procedure. You will then clearly see any bow in the bed.

Don't forget that the graphs show the change in angle not the actual bed profile You need a bit a maths to obtain the actual profile.

Phil

how about a Machinists' plumb bob?

I've read that the R's D's Method obviates the need for a level.. but
apparently thats not the case.

a level it is.. off to do some shopping.

with a level, how do you isolate twist and wear? I can see the level
doing its thing on the tailstock end.. but at the headstock?


-Tony