garycurtis

I'm planning to make a few jigs using plexiglass. The bit can be any modest straight bit. My first few attempts ended with the plastic shattering. Even with relatively shallow cuts.

What am I doing wrong?

Gary Curtis
Northern California

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bobj3

Hi Gary

It maybe the bit you are trying to use, most straight bits are Not made to plunge in... they have a blank spot right in the center of the bit .

Try one like below
http://www.mlcswoodworking.com/shops.../bt_plung.html
Or
http://www.mlcswoodworking.com/shops.../bt_solid.html

Note.. the picture below, this is the one you should use in a router (upcut) down cut in a plunge router..


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fibertech

Bob, Where can you get Plexiglass? I am hoping to make a couple of router bases and want clear. Thanks in advance. -Derek

bobj3

Hi Derek

I'm not a big fan of Plexiglass ,it's great if you need to replace some glass but for jigs I don't like it ,, it's almost always under size and it is almost always comes with clear or blue film on it that's are to draw on...and like the name it will flex easy..HD/Lowes/Ace has it on hand.

But I do like acrylic ,it almost always comes with a paper cover that I can draw on and it comes in a true size, if you ask for 1/4" it will be 1/4" thick unlike Plexiglass ,if you ask for 1/4" you will get 9/32" thick the norm...

I sometimes get the acrylic from HD or Ace but you must look hard for it..
and take a your ruler with you...

When I have the time I also get some from the plastic companys in town out of the cut off box,,they just about all have one...some great deals, 50 to 75 cents ea....the stuff I like best is the scratch resistance to a point ,it's a flim that they put on the plastic,I think .......


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RustyW

Plexiglas is acrylic. It's just one of many brand names for an acrylic sheet product. The reason the stuff at home centers is undersized and with plastic rather than paper masked, is because they get the cheapest available product. I prefer polycarbonate (Lexan,Hyzoid are common brands) which can be worked like wood with common woodworking tools. Acrylic I treat more like mdf, if you drill it eventually it will crack out from the hole. Luckily for me, I work at a glass shop near lots of gravel plants. At least once a week I cut and install scratch resistant polycarbonate windshields in their equipment. So I have tons of cut offs and scraps.

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fibertech

Thanks guys. I have a couple of Tap Plastics in the Seattle area that I can check. We are currently trying to sell our house and move further north. That would put me 25 miles from the Grizzly headquarters. My shop will be more than twice what it is now. I want to devote much more time to this hobby. -Derek

kp91

Rusty,

If you're having trouble drilling plexi, you can try a trick that works about 85% of the time for me. Deliberately dull the drill at the point where the grind angle transitions to the outside diameter of the bit. By dulling these 'ears', it will prevent the bit from catching as you drill.

You can also pilot drill your holes with a propane torch and a nail.

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Lee Brubaker

For jigs I prefer polycarbonate. It wont shatter & stands up to hard use. As BJ says, take your ruler with you because often in plastics the thickness's are in mm's instead of inches.

Lee

cbsjoez1935

Gary

I noticed that you did not respond to the suggestions on bit speed for plexiglass. I am not sure what problem you are having. If it is using the bit as a drill bit, you are going to need the plunge cut type, as suggested by BobJ. If you are attempting to use a staraight cutting bit as a "planing bit" on the edges that is something else. Could you please clarify your usage? Too high a speed with too low a feed speed could cause melting.

Joe Z.

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garycurtis

I am the OP on this thread. I'll be making jigs, so there will be a few holes bored straight in, but the breakage has been primarily on cutting and shaping edges.

I got all of my Plexiglass and Polycarbonate (known as Lexan) from Hastings Plastic in Santa Monica, Calif. Behind their store, they have several dumpsters. A treasure trove.

Again my question. What speeds do I use for drilling (I have end mills) and for edge shaping?

Gary Curtis