Delrin 2nd op Pulling out of vise

mhajicek · Jan 22, 2021

Are there any special tricks to keep a Delrin second op from pulling out of the vise? It's a partially hollow rectangular box, so I can't tighten it much without distorting it. I've heard of putting sandpaper on the jaws, but I'm worried about marring the finish; should I not be? I suppose I could make a filler block to put inside, but it's a moderately complicated shape. I only have 12 parts to do. This is a bit outside my wheelhouse, I'm used to 17-4 and Ti.

Thanks

Milland · Jan 22, 2021

mhajicek said:
Are there any special tricks to keep a Delrin second op from pulling out of the vise? It's a partially hollow rectangular box, so I can't tighten it much without distorting it. I've heard of putting sandpaper on the jaws, but I'm worried about marring the finish; should I not be? I suppose I could make a filler block to put inside, but it's a moderately complicated shape. I only have 12 parts to do. This is a bit outside my wheelhouse, I'm used to 17-4 and Ti.

Thanks

Low helix endmills meant for plastics. Check out Onsrud cutters.

Plastics - Solid Surface - Foam

Depending on the cuts, you may even benefit from downcut helices, which they also offer.

mhajicek · Jan 22, 2021

Milland said:
Low helix endmills meant for plastics. Check out Onsrud cutters.

Plastics - Solid Surface - Foam

Depending on the cuts, you may even benefit from downcut helices, which they also offer.

Thanks, I'll check that out for next time. For now I seem to be having some luck just making shallower passes.

woodchuckNJ · Jan 22, 2021

Milland said:
Low helix endmills meant for plastics. Check out Onsrud cutters.

Plastics - Solid Surface - Foam

Depending on the cuts, you may even benefit from downcut helices, which they also offer.

yep, as a woodworker I use upcut and downcut bits to control tearout. This is a perfect application.

FYI They also have compression bits that cut toward the center so they are up and down cut.. very useful in certain situations.

one more thing, it's always a good idea to make a plug to fill a hollow plastic to machine it.
I do that when machining PVC. i have a bunch of different plugs I've made up for making certain pvc connectors (mostly for vacum adapters).

mhajicek · Jan 22, 2021

woodchuckNJ said:
one more thing, it's always a good idea to make a plug to fill a hollow plastic to machine it.
I do that when machining PVC. i have a bunch of different plugs I've made up for making certain pvc connectors (mostly for vacum adapters).

Yep, looks like I'm going to have to do that. With the lighter cuts it isn't pulling out, but even the lightest vise pressure and it's warping.

sirAIG · Jan 22, 2021

100% I'd be making a plug to clamp on. It works very well!

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Scruffy887 · Jan 22, 2021

Peel and stick fine sandpaper. 180 grit.

AJA · Jan 23, 2021

How about filling with plaster of paris?

mhajicek · Jan 23, 2021

As I said, above, I only had 12 parts to do. I bit the bullet and made a snug fitting delrin plug. That allowed me to clamp harder without distorting the part, and I got them run off yesterday.

Thanks for those who helped!

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