Adjusting Bridgeport backlash?

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?
Reply to
ben carter
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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.
Reply to
Jon Elson

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