On 9/12/2019 4:45 AM, Jim Wilkins wrote:
"Bob La Londe" wrote in message
...
...
So what kind of "normal" cutting fores might cause those vises to
move. I put the word normal in quotes, not because I wanted only
include safe cuts that work every time, but also things that can
happen, but maybe shouldn't. I know a crash with a fly cutter could
do as much damage as a hammer. How abut a 1/2 inch mill entering a
piece of hard steel or a face mill banging on the edge of a work
piece.


It can be interesting and informative to read the vise with an
indicator in the spindle while tugging on the machine in various ways
with a strong spring scale. A 50 Lb fishing scale is enough to affect
my half century old Clausing. I've been positioning the vise near the
table ends where there is less dovetail wear and freeplay than in the
middle.

South Bend specifies 0.0007" to 0.001" vertical spindle deflection at
"about" 75 Lbs for the plain bearings adjusted with shim packs. That
doesn't equate to inaccuracy because the cutting force is nearly
orthogonal to the diameter of the part.

The drawing shows one hand lifting a lever of round stock in the
spindle bore.

https://www.academy.com/shop/pdp/gam...big-game-scale
I replaced the hooks with chain shackles so it's less likely to be
dropped while setting up.




This is an 18 month old machine, although it does have some intended
small backlash tolerance. I would sweep the vise jaw, back up and then
come into the jaw to zero. Then do the same with the other vise. They
might have not read the same each time, but their relative zero should
have been the same in relation to each other.

Well, I'm cutting parts on it now. I'll check it again after I run a
couple batches of parts that are really non-critical with 360 degree
machining.