Best plastic for milling parts ?

Hi Guys,

So i have a few cylindrical parts i want to mill for some of my kits. I've got a miniture lathe, nothing fancy but does the job just fine. This will be the first time ive tried to make model plastic parts with it.

I've been told that delrin is prooably the best to go with as its easy to shape and i can smooth it enough to make a mould of the finished part.

Is there anything else i should use instead or consider ?

Thank you all
T

PVC is good, but small diameter parts can be tricky because it is a softer plastic. I have also heard that you can mill standard casting resin, but I've never tried it myself.

TazMan2000

delrin takes a little time to get the right 'finish' on it IMHO...

its also a 'slippery' plastic.

but I have machined (lathe) it before.. and it works well.

Renshape may be a solution.

This is a pretty good Renshape primer on material, finish, and practical application.
[video]https://youtube.com/watch?v=9_7ymrcxiFo[/video]

i have machined via mill and lathe many plastic parts... my preferred plastic is PVC, but i have done smooth-on 325, smooth-on onyx and alumilite tan and white resins. do not try to machine acrylic. under the stress of a lathe, odds are more than 50/50 that it will shatter.,, more than probably when you are 95% done...

Delrin/acetal is beautiful free-machining wonder, but doesn't stick to much well. PVC machines ok, can be a little rough. Acrylic should only be done lightly under full soluble flood coolant. The best all-rounder for both machining and fitting afterwards is urethane resin. I collect my casting leftovers for that purpose, but obviously they tend to be a bit bubbly. If you can vacuum/pressure cast urethane tooling blanks, you'd be set. Grabbing a pint of Smooth-Cast 300 or Onyx and some PVC piping wouldn't be particularly beyond the prices of normal plastic stocks.

You should probably also look into grinding your own HSS tooling, if you haven't already. Carbide is kinda blunt for plastic.

I machine acrylic all the time and have never had much of a problem. The trick is to use nice sharp cutting tools and a non-solvent based cutting fluid. I like Relton's A-9 Aluminum cutting fluid which is a mineral oil and wax based lubricant. Jut a little bit of the cutting fluid as needed. Never had to use a full flood coolent on acrylic, which is messy and most small machines aren't set up for. A-9 Washes clean with soap and water. When machining any plastic you want to watch your feed rate and size of cut to keep heat down. Acrylic is most sensitive to melting if you work too fast, particularly when drilling down the center.

One thing I like especially about acrylic is that I can glue other styrene details to it with solvent cement, either for a pattern or final part.

Delrin machines beautifully and is fine for a pattern to be molded but not as a finished part as paint and glue doesn't stick well. Delrin is also lot more expensive than acrylic.