On 2008-05-01, Jon Elson wrote:
Joseph Gwinn wrote:
I think I've figured out a big piece of the mystery of what I
generically called chatter in the "Clausing 5914 Chatter ..." threads.
Tightening the lathe dovetails up helped a great deal, and is a good
idea in general, but didn't really solve the problem.
It came to me in the shower Wednesday morning - self-feeding would
explain just about everything seen, and that if one reverses something,
the sign of the mechanical feedback loop can be reversed.
[ ... ]
I had some real problems doing these types of operations on
Atlas/Craftsman lathes. The 5914 is a MUCH sturdier lathe with
a much heavier bed casting, so I'm surprised you were having
this sort of trouble.
As am I. I've got the 5418 (similar bed profile, but manual
change belts), and have very little chatter.
I finally traded up to a Sheldon R15-6,
which is an even heavier lathe, in the 3000 - 3500 Lb class.
You can stand on the bed with no measurable deflection (and I
have precision electronic levels that are REALLY sensitive).
It is amazing what a difference stiffness of the lathe makes.
Now, another comment is that you may have a poor "fit up"
between your carriage and bed.
You know -- there is one other possibility which occurs to me.
I presume that your lathe, like mine, has the hollow level adjusting
screws in the feet of the bed through which pass the bolts to lock it
down to the stand. If you have something like the near side bolt loose
and the level adjusting screw a little clear of the stand, the bed would
wind up under torque, which could give you similar behavior.
Did you get a proper sensitive level and adjust the bed to
proper level at both headstock and tailstock end? (I did.) After that,
did you make sure that the hold-down bolts were tight (and didn't
disturb the leveling)? *This* may be where your flex is -- especially
since you have a longer bed than I do (I believe), and thus more total
flex possibility.
Get it chattering and feel each foot with the adjacent finger on
the stand so you can detect relative motion between them. If you find
any, you'll need to tighten the hold-down bolts, and probably re-level
the bed.
Good Luck,
DoN.
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