[How do I?] Cut Down A Drill Bushing

[JimDawson]

This is a bit of a mental excersize in machining operations problem solving.

I'm working on a drill fixture for a customer. I need to install four 31/64 drill bushings, one in each corner of the fixture. The body OD of the bushings is 0.751

The Problem: The fixture material is 1/4 inch thick and the flange to end length of the drill bushings is about 1/2 inch, so they will protrude through the fixture by about 1/4 inch. This is not acceptable, they need to be flush. The bushing material is heat treated and file hard, probably around a RC62 or so. Thus carbide won't cut it.

The Question: How would you cut these bushings down to size? Assume you have access to most common equipment one might find in a well equipped tool & die and fab shop.

 

[Franko]

I'd make new bushings to size and temper them, if I had a tempering oven.

 

[NightWing]

If you could figure a way to hold them, Snag the ends off with a bench grinder and then have them finished to size on a surface grinder. You will have to deal with a sharp edge or tiny burr on both the ID and OD after grinding.

 

[Billh50]

It would depend on the fixture. If you can press them in flush with one side of plate then put the plate on a surface grinder and grind the bushing down to the plate. Otherwise you would need to either grind close to size by hand on bench grinder. Dipping in water often to keep from loosing hardness. Then block them up on surface grinder and grind to size needed.

 

[Ebel440]

Use a cutoff disk in a tool grinder cut to length chamfer edge and press them in

 

[NightWing]

It would depend on the fixture. If you can press them in flush with one side of plate then put the plate on a surface grinder and grind the bushing down to the plate. Otherwise you would need to either grind close to size by hand on bench grinder. Dipping in water often to keep from loosing hardness. Then block them up on surface grinder and grind to size needed.

He can't press them in flush on one side because they are flanged bushings.

 

[Billh50]

sorry...missed that.
If the fixture is a flat plate he can also lay the flanged side down on parallels and block the plate in to grind bushings flush.
It is really hard to know exactly what to do without seeing the fixture and bushings.

 

[RJSakowski]

The bushings will have to be ground. Make a fixture to hold the bushing with a light press fit and slightly thinner than your customer's fixture. Depending on your method of grinding, either a flat plate for a surface grinder or a cylinder for the lathe.

If using the lathe, I would cut the bushings with a Dremel mounted cutoff wheel. and finish with light grinding (can be a Dremel wheel).

It would also be a good idea to break the sharp inside edge to avoid damaging the customer's drills and chamfer the outer edge to facilitate pressing into the customer's fixture. A small cone point in the Dremel should do nicely.

As always, if grinding on the lathe, protect your precision surfaces from grinding dust and clean up thoroughly afterward.

 

[JimDawson]

All good ideas gentlemen!

If I had my tool & cutter grinder powered up, it would be pretty easy. Just put the bushing in a collet and use a cut-off wheel. But I don't, so an alternate method will be used.

So what I am going to do is cobble together a quick expanding arbor that will go in my battery drill to cut the rough length to a scribed line using a bench grinder with a cut-off wheel. I'll just hold the drill by hand.

Next I'll put them on the surface grinder to finish. Then chamfer with a die grinder and press into place.

I'll post pictures of the process.

 

[w9jbc]

v block and a surface grinder comes to mind here