Lapping advice

An Ebay seller let me scrounge parts off his machine that didn't sell, and now I am trying to fit a new part from 1950? to his used part from about 1925. It is a 1/2 inch straight center into the holder. My new center is about .0002 larger than the original center. Probably Barber Colman did selective assembly on original assembly.

McMaster sells these spiral ball hones and laps.

McMaster-Carr

The center holder is hard to the extent a file won't touch it. Any advice on the best method to remove the 0.0002 from the center holder, or is there better way to reduce the diameter of the center, which is also hard?

Thanks

first thing that comes to mind grind it to size.

Forget the dingleberry "hone". It will make a mess of a minor problem. If the hole is cylindrical, hone it. With REAL hone. If taped make lap with proper taper and lap to size. .0002 is not a lot to remove either way so be careful and go slow.

Obviously I know more about gear hobbers than grinding...

Gary: How do I grind it accurately?

TD: Thanks for the recommendation. What is a REAL hone? Is it the type that McMaster is selling? The center is straight shaft 1/2 inch.

John

These are common cylinder hones.
cylinder hone - Bing

A round stock with a hack saw cut also makes a decent hone. The length of the abrasive paper makes the bore very close. RE: each full wrap might equal .006 .010 ..so a certain fraction of that equals what you might need.

Make lBrass Lap

bll230 said:

An Ebay seller let me scrounge parts off his machine that didn't sell, and now I am trying to fit a new part from 1950? to his used part from about 1925. It is a 1/2 inch straight center into the holder. My new center is about .0002 larger than the original center. Probably Barber Colman did selective assembly on original assembly.

McMaster sells these spiral ball hones and laps.

McMaster-Carr

The center holder is hard to the extent a file won't touch it. Any advice on the best method to remove the 0.0002 from the center holder, or is there better way to reduce the diameter of the center, which is also hard?

Thanks

Click to expand...

If I understand your post!
Make a lap from brass One inch long. First ream the hole in the lap with a #2 taper pin reamer and turn the outside diameter of the brass lap to work in the bore. Then turn a tapered arbor to match the tapered hole in the lap. With a hack saw cut through the 1" length of the lap on one side. Cut a few slight groves around the lap with a file for a place for the lapping compound. To adjust the lap, drive taper pin arbor into the lap with a small hammer. Clover Leaf Lapping Compound from McMaster-Carr or MSC. Lap the bore using the drill press 350 to 500 RPM and fit the mating part to the bore. Clean the hole with solvent and rag. Try the fit a little at a time. Use oil when fitting the components.

Roger