[gpraceman]

I'm looking to mill cutouts in plastic (ABS) electronic enclosures; DB9, jacks, switches, etc. What type of bit and size is good for that purpose?

I currently have a single speed RotoZip at my disposal, but might find another spindle or get a variable speed controller, if necessary.

[neilw20]

ABS plastic can be quite abrasive.
If you just have small quantity high speed steel is OK otherwise solid carbide cutters will last the distance.
You will get a better finish if you DON'T climb mill.
The rubbing action of the convention milling gives a nice burnished finish.
If you want to run fast coolant is a necessity to stop the ABS melting with the heat generated. It is bad conductor of heat so the cutter can get hot enough to melt the stuff.

[gpraceman]

The enclosures are only about 0.1" thick, so I thought I could just drill all the way through and then start the milling. I was not intending to use any coolant, certainly not any liquid coolant.

If I need to find a different spindle to do this, I certainly can or get a variable speed controller to throttle down the speed on the RotoZip.

[neilw20]

Often, although a little crude I use a drill right up near the end of the flute as a milling cutter.
Cheap and effective on plastic, and although no clearance on the land of the drill it worked ok for me.

[gpraceman]

I currently have a 6 piece set of HSS end mills from LMS (4 flute), ranging from 1/8" up to 1/2". I don't mind purchasing a solid carbide bit, as I may be doing a bunch of cutouts over time. I would just like to know what is the preferable type and size of bit to do these cutouts.

[stevespo]

Those HSS tools will cause you trouble. A single flute carbide cutter (straight flute or "O") style is a much better choice. Even these should be run at slower RPM and fairly fast feed rates. A Roto-zip at 30K RPM with a 4 flute bit will generate a lot of heat and melt that plastic in a heartbeat.

The "O" style in an upcut will clear chips fairly well to avoid welding. It tends to lift thin material and may cause some vibration unless it's fastened down really well. The straight cutters don't tend to lift, and do well with a steady stream of compressed air (and dust collection) to keep the tool clean and move chips out of the way. That has been my preference lately in acrylic, lexan, HDPE. Not sure how those compares to ABS.

Depending on your machine and your feedrates, I'd start cutting at 12K RPM and see how it goes from there. At .1" thickness, I'd probably go one (or maybe two) pass with a .125" cutter.

.125" single flute "O" at .005" chipload and 12K RPM = 60 IPM feedrate
http://www.onsrud.com/files/pdf/Chip...oftPlastic.pdf

Steve

[gpraceman]

I forgot that I had a couple of the single flute Onsrud bits, 1/8" and 1/4", "O" style in upcut. I got these expecting to use them for some light milling of aluminum, but it seems from what you are saying, they may also work for the enclosure cutouts. I can get a straight flute bit if that will work better.

[stevespo]

Those Onsrud "O" style will work great. They'll probably make cleaner cuts than the straight flute. Just make sure you have a good way to hold the sheet stock (double stick tape, screws, etc) to avoid lifting it up off your table. You may still want to slow down your spindle, but you're got more margin with the single flute.

Steve

[gpraceman]

These are relatively small electronics enclosures (about 3.5" x 5"). I'll make up a jig to hold the pieces.

I'll look at getting the variable speed router controller. I've seen them at Harbor Freight, Woodcraft and Rockler.

Thanks for the tips.

[andy88]

plastic mill cutout wont do any good in there
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plastic machines

[gpraceman]

plastic mill cutout wont do any good in there
------------
plastic machines

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