ben carter wrote:
Got a late 60's BP in great shape but needs a tweak to tighten up the
table backlash. My friend the veteran machinist says it has plenty of
adjustment left but hasn't done it himself yet for this model of
machine. I can't find anything online that resembles instructions and
the manual I have doesn't really address it specifically. Anybody been
there, done that?

thanks

Ben
The Y axis is pretty easy, the X is a bit messier. There is a big,
wide-head screw that holds the bronze nut in a bore in the yoke. For
the Y, remove 4 SHCS on the Y-axis bracket. Unscrew the leadscrew
completely from the nut. Reach in with a long screwdriver, and remove
the clamp screw that locks the wide-head screw. Now, remove the wide
head screw. You can now reengage the leadscrew with the nut and pull it
out of the yoke. Saw it in half with a bandsaw. It is the toughest
bronze I've ever seen, cuts like tool steel. You cut it to form two
complete rings. Use the leadscrew to reinsert it to the yoke, and
remove the screw. Now, you can put the two screws back into the yoke,
but leave the wide-head screw quite loose. Put the leadscrew back in
until it engages both nut halves. If the saddle is pulled forward,
there's enough room to get the screwdriver between the leadscrew and the
knee casting at this point. Adjust the wide head screw until the
leadscrew binds. Then, back off a hair, and clamp in place with the
smaller screw.

The procedure is about the same for the X, but the access is different.
You have to take the right end bracket off, and then remove the screw
from the left side, with it's bracket. Note that differential wear
of the leadscrews will make for more backlash in the middle of the
screws. If you set for minimum backlash in the middle, it will bind at
the ends of travel.

Jon