OT: drilling plastic enclose

I have a small prototype circuit that's going to a client, that I'm putting in a repurposed acrylic plastic enclosure which I have several of. Due to the geometry involved, several of the 1/4th inch jacks have to sit right next to the joint where the main part of the case connects to the lid. I've been drilling the practice enclosure with hand tools, and I guess due to the type of acrylic, each time the drill bit cuts through to the other side of the material, the little lip of material between the hole and the box edge cracks or shatters. It's pretty annoying.

Is there a way to avoid this?

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Reply to
bitrex
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Use a soldering iron?

Maybe use a 4-flute end mill?

Cheers

Phil Hobbs

Reply to
Phil Hobbs

Den torsdag den 12. maj 2016 kl. 23.00.44 UTC+2 skrev bitrex:

look for drill with a geometry made for acrylic

-Lasse

Reply to
Lasse Langwadt Christensen

Smaller hole then enlarge with a tapered ream.

Reply to
amdx

Den torsdag den 12. maj 2016 kl. 23.15.01 UTC+2 skrev Phil Hobbs:

I think that is going the wrong way, you'd want something with ~0 rake angle so it doesn't grab and a low tip angle so is more gradual

-Lasse

Reply to
Lasse Langwadt Christensen

I have a small prototype circuit that's going to a client, that I'm putting in a repurposed acrylic plastic enclosure which I have several of. Due to the geometry involved, several of the

1/4th inch jacks have to sit right next to the joint where the main part of the case connects to the lid. I've been drilling the practice enclosure with hand tools, and I guess due to the type of acrylic, each time the drill bit cuts through to the other side of the material, the little lip of material between the hole and the box edge cracks or shatters. It's pretty annoying.

Is there a way to avoid this? ================================================

I suggest posting this in rec.crafts.metalworking, should just be a combination of the correct angle on the end of the bit, and perhaps some lubricant while drilling to keep the heat down.

----- Regards, Carl Ijames

Reply to
Carl Ijames

Ahh, I think i do have a ream sitting around here!

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Reply to
bitrex

Acrylic **is** brittle.

Consider the fastest spindle RPM you can muster with water coolant.

--sp

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Spehro Pefhany 
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Reply to
Spehro Pefhany

Have a drill press? Clamp the work in a vise, and feed very carefully, letting up on the feed just before it breaks through. That will generally keep it from jumping in and taking a big bite just as it breaks through. You need a drill press that has minimal backlash in the feed rack.

A milling machine will do even better, of course.

Jon

Reply to
Jon Elson

and try modifying the drill,

formatting link

-Lasse

Reply to
Lasse Langwadt Christensen

Unfortunately I don't have one available here, unless there is one hiding in the condo maintenence shed...

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Reply to
bitrex

Very sharp drill bit? Perhaps a brad point bit?

Reply to
krw

It's the cutting angles, not the sharpness.

Every material cuts best with specific cutting angles, and it's best to learn how to re-grind universal drill bits to suit the material you're working. Wood != steel != cast iron != brass != plastics

Reply to
Clifford Heath

It's both. The bit has to cut.

Reply to
krw

  1. "How to and not to drill through acrylic plastic tutorial" Basically start with a small drill and increase the dill size. The smaller hold gives the chips from later larger holes a place to go. If they're trapped between the drill and the plastic, the rotary motion of the drill will push the chips outward, creating radial pressure which is what cracks the plastic.
  2. The larger the hole, the slower the drill speed. Too slow is always better than too fast. If this is thick plastic, clear the chips out of the hole often.
  3. Use a drill press, not a hand held electric drill.
  4. Don't bother trying a step drill. The first step will work splendidly, but the other steps will crack the plasic.
  5. Use an end mill instead of a drill. You can do the 3/8" hole in one shot, but you'll need to clamp the plastic to keep it from moving. Also, make sure the plastic and drill are perpendicular.
  6. There are some tricks to melting your way through the plastic. I use this for odd shaped holes, but it will also work with a 3/8" round hole. Basically, make a pattern for what you want to "drill". I this case, it will be a 5/16" OD cylinder of copper or aluminum. Look at some old brass spent ammunition casings for something close. Get it hot with your soldering iron. Push it through the plastic. Deburr and enlarge to 3/8" with a reamer. You'll need to first practice this with some scrap plastic.

Good luck.

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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

Well, I tried it with a starter hole and a stepper bit, and it seems to be working a lot better than trying to punch directly through if I'm careful. I'm going to practice a few more times to make sure I get it right consistently...

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Reply to
bitrex

Why is this OT? I'm not sure of your material, but there are two types of plexiglas, extruded and (?) something else, One you can machine and the other shatters.

But it sounds like you have more of a break out problem. some sacrificial material held tight to the hole bottom may help.

George H.

Reply to
George Herold

If all else fails, you can drill the right size hole in a piece of metal. Clamp the plastic between and a piece of wood. This will provide pressure from both sides. Then your plastic shouldn't crack. You might want to use a fresh spot on the wood each time, or if you are good, you can use two pieces of metal with holes and align them so you are drilling through the two holes.

I can't say for sure this will stop plastic from splitting, but I use it to keep wood from splintering out the back. The worst thing I ever worked with was a piece of compressed wood that came in a shipping container as edge rails. It was hard against compression, but not so strong if you tried to split it. I was trying to notch it as shelf supports using a router. It loved to split out at the very end of the cut where the blade angle was exactly wrong. I ruined two or three pieces before I got the notches done properly.

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Rick C
Reply to
rickman

I use a small drill to start, then a grinding tool, hand file or very sharp knife to approach final dims. One-off or very low volume only.

RL

Reply to
legg

Get an acrylic drill bit. Has a different rake angle, it scrapes more than cuts.

TAP Plastic Amazon SkyGeek Home Depot or Lowes may have them

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Chisolm 
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Reply to
Joe Chisolm

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