Machineability of Plastics

Have never done much machining of plastics, but I need to make up some small parts that will be used in gasoline environment. Looking at the softer plastics, such as nylon, delrin, teflon etc. Turning, milling, tapping, possibly some external threading.

Do these plastics machine equally, or somewhat so? Any special requirements as to clearance or rake angles, lubricants or speeds?

John Martin

Reply to
John Martin
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Not enough difference in the machinability of those three to override other desirable properties. Delrin is probably the most versatile, nicest to machine, and falls between nylon and teflon in cost.

They're also all pretty forgiving of tool geometry, but I'd suggest sharp high speed tools with generous nose radius and relatively high rake and clearance angles. No lube; high speeds as long as good chip removal can be maintained in order to limit heat buildup.

I know you're somewhere close by. I've got a good sized bin of cutoff rounds if you want some samples of each to play with.

Ned Simmons

Reply to
Ned Simmons

Can't really tell you which will machine the easiest, but if color has no bearing on your project, I suggest getting a few different colors to play with. We have found that the pigmentation in some plastics actually makes them easier or harder to drill. On one particular part, the white material drills easily and does not "grab" the bit. The dark gray or black material, on the other hand is muc harder to drill. The bits grab at the beginning of the hole regardless of polit hole or not and "spiral" through with a VERY heavy and unintentional cut when used on manualy fed machines.

It might or might not make a difference for what you want to do, but it might so... It's worth the $0.00 you paid for the info, right?

Reply to
Joe AutoDrill

It greatly depends on the plastics. Delrin machines well with standard HSS tooling if you are only doing a few. In production environments Carbide tooling is needed. It taps, threads and finishes well.

Nylon..well..it makes good spacers, but is poreous and tends to suck up liquids. Teflon is soft. machines well..taps about as poorly as nylon..the holes tend to close up somewhat...

Razor sharp tooling. A bit of positive angle. Best tool Ive found for boring most..not all..but most..is a 2 flute, sharp pointed endmill held in your tool holder. Has good positive angle, and chip removal is excellent..well...it directs the long assed strings out of the way pretty well. Lefthanded ones work marvelously for turning.

My personal choice..take it as you will...for most things is delrin. I dont know much about gasoline handling abilities of plastics though..not something Ive needed to inquire about. Delrin is hard and tends to be a smidge brittle..so impact parts should be something else. The one time I made a delrin face for a soft hammer..it lasted about 3 good blows. I now use HDDP for such.

Gunner

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Reply to
Gunner

Use polypropylene or polyethylene if it will be exposed to gasoline.

Reply to
daniel peterman

Ned:

You're in the Brunswick/Harpswell area if I recall correctly? I'm in Cumberland. I'd like to take you up on that offer, and I'll send an email off-list.

Thanks to all who have answered,

John Martin

Reply to
John Martin

Delryn will absorb gasoline and swell over time. I think teflon is pretty inert but it's kinda gummy to machine.

Reply to
Don Foreman

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