Atlas TH54 Lathe apron assembly

 Ronald Crowell

Since you are new to this group, I'll assume you might find some info useful as follows.

•1.a. The bearing stanchion has a shim under it so that its miter gear body will center on the lead screw for least drag. The 'U' shim (in the diagram, goes around the stanchion bolt) thickness must be determined for your new bearing stanchion. Note: It will not be necessary to repin the bearing stanchion to the apron with the original dowel pins, and in fact repinning it will likely locate it a small amount high or low causing it to drag on the screw. Leave the dowels out. •1b. So...first make sure your lead screw is straight and level (constant distance under and out) with the lathe bed ways and is the same distance its full length. Then, when the apron is bolted to the carriage and the bearing stanchion/miter gear assembly is loosely bolted to the back of the apron, move the carriage all the way to the left where the screw is least flexible and let the screw locate the bearing stanchion vertically and with a small gap from the apron. Try feeler gauges under the stanchion foot to see what shim thickness is needed before tightening down the bolt. Tighten the bolt while letting the screw locate the bearing stanchion/miter gear assembly. Check the feel of the drag.

•2.a. The gear case also is originally dowel pinned. Leave out the dowels for the same reason you left them out of the bearing stanchion. Before proceding its assembly on the apron, check that the handwheel shaft does not wobble in the apron bore since that shaft locates its gear that meshes precisely with the gears in the gear case.

•2.b. I'll assume you can figure out how to re-assemble the gears in the gear case. The shaft is swaged on the ends in the square holes in the gears to hold the gears, and it should be swaged nearly flush.

•2.c. The gear case's 3 mounting bolts (with square nuts) are through slots in the gear case to allow it to be adjusted. When installed, the lead screw goes through a pass-through hole in the gear case. It is possible in some instances that the screw will hit the gear case pass-through hole side when installed, so be aware of this. (If this happens upon final adjusted gear case location, you may need to dremel a small amount off the pass-thorough hole.)

•2.d. The gear case is adjusted along its slotted holes while the apron is mounted on the carriage and the lead screw is in place through its gear case pass-through hole. Adjustment is done by moving it so the one gear engages the gear rack under the lathe bed way with appropriate meshing backlash, and the other gear meshes with the handwheel shaft gear. Do this with the carriage movedall the way to the left, and lightly tighted the gear case bolts. Then carefully crank the carriage moving it down the lathe all the way to the right making sure the mesh to the gear rack does not get tighter and bind or gets too loose (which means the rack is not dead parallel to the ways). The rack is pinned along the lathe bed, so it is best to just ensure there is no rack mesh binding. (If it's really a large difference, you have other problems.)

•3.a. I post a picture of a mockup assembly here below for reference, mostly for showing items 2a to 2d, since item 1a-1b should be self explanatory: