Vacuum chuck for irregular shaped plastic part

So, mount a similar mold to a lathe faceplate, apply pressure on the workpiece center with the tailstock, and face off the outer rim of the gizmo. Then apply clamps, retract the tailstock, and complete the cut.

Fly cutting something that I can't hold in a vise makes me nervous.

Yeah I'm not so keen on the fly cutting myself. Actually I may have misled you. As you've probably guessed I am not a machinist.

Facing would be done using a tool like this but with only 4 cutting inserts.

It cannot be machined in a lath chuck as the cast part has a long cable attached to it.

Cheers.

I've been doing a lot with vacuum work holding lately. It sounds like your plan is pretty good. If you have a reasonably close fit around the sides, y ou are safe from the part flying out of the fixture.

What I would do is machine slots for the vacuum to spread around and also m achine a groove around the periphery of the bottom to place a seal. I use 1 /8" neoprene round cord from McMaster. Make the groove about 3/32 deep and

1/8 wide and the neoprene will just sit in there and make a very good seal. If you have irregularities larger than that will absorb, go to a thicker s eal - I also have 1/4" material, but haven't had the need to try it yet.

If you are using a refrigeration pump and you have a good seal, you are goi ng to get a LOT better than 1/2 atm, much closer to 1 atm.

A face mill.

Is there any reason you can't put the face mill in the lathe chuck and fasten the piece to the cross slide? Perhaps held tightly in stiff foam rubber?

Paul

What would be the advantage to that over doing the same in a mill?

Perry - do all as you describe but skip the vacuum and use two hold down clamps on the surface you're cutting. Use the clamp on the left while you surface the right side and the opposite. If too costly timewise, you'll at least get a look at the finished appeareance.

Hul

Perry wrote:

I'm worried about holding the work piece. The sloped sides make holding it difficult.

Thats not a bad idea Hul. Maybe some of those toggle type clamps would make it easy to do. Thanks.

Thanks. I was thinking of buying an eBay refrigeration vacuum pump. I can get a 6 or 12 CFM unit for a couple of hundred dollars. I've got a fridge compressor pump but its small and pumps a low volume.

Thanks for the info on the sealing bead.

Mine pulls 26".