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Discussion Starter #1
I'm on the first step of building my 3 axis Lindberg skull from kit from Graveyard Skulls. I'm using a 3/32 bit and got one hole drilled in the plexiglass plate. The next hole the bit gets stuck and breaks off in the plexiglass. I filed it down and started another hole and the same thing happens. Is it bad bits, wrong type of bits or is there a trick? Will these bits embedded in the plexiglass affect anything?
 

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Funeral Crasher
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That must be some pretty thick/strong plexiglass to break a drill bit!
Maybe you need a higher speed drill. I know the battery powered one I have now isn't as fast and doesn't have as much torque as my old plug-in electric one!
Or maybe start the hole with a smaller drill bit. Then work your way up to the 3/32 bit? Just a thought.
Maybe experiment on a scrap piece (if you have one).
 

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Discussion Starter #4
DateintheGrave, thanks for the reply. I'm using an 18 v cordless drill, and the skull plate that came with the kit. This is the same plexiglass plate that everyone else who got the kit has used but I didn't find where anyone else had a problem. After the 3/32 bit broke off, I did use a smaller bit for the next attempt but that one also broke off.
 

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Blaberus craniifer
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Odds are you are having a tough time keeping the drill straight if you're using a hand drill. Doesn't take much effort (slight change in the angle) to snap these small bits. A drill press would be much better for this if you have access to one. Also, don't try to push it too fast, just let the bit slowly cut/scrape through the plexiglass.
 

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Discussion Starter #7
OK, no access to drill press. I see that they make special bits for plexiglass so I guess I'll get that since I need bits anyway.
Pod: The bit didn't snap off, it got stuck inside the plexiglass to where the drill would no longer turn it forward or reverse so I had to break it off.
 

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You actually probably need to slow the drill down. The higher speed heats the plexi up and melts it which can blow out your hole in that small of an area. Get the plexiglass bits, go slow, and use dish soap & water to lubricate & cool the process.
 

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Blaberus craniifer
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If the bit got stuck, you melted it to the plexiglass. Drill speed too quick causes it to melt vs. cut. use he soap and water like hedg12 suggested to help keep from heating up.
 

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Discussion Starter #10
Thanks for all the suggestions everyone. Tomorrow I'll try to find the plexiglass drill bit. The melting must be what happened so I'll try really slow. How is the soap and water used? Is it mixed and sprayed on the plexiglass, or is a little soap put on first and then spray with water?
 

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slow and cool and steady. I used to drill holes in acrylic for fish tanks. The heat build up stresses the acrylic till it cracks. I let the drill do the work without adding too much weight, then use a water sprayer to cool things off then dry the acrylic and continue. It's a slow process but doable. If you do crack it and it won't be under pressure or need to keep a perfect seal then it's easily repairable with acrylic cement (I use DAP) It's a chemical cement so the two sides are chemically welded together. If you do get the cement read the warnings, they're pretty funny....you get the feeling of 'in case on ingestion, consult a mortician' Good luck!
 

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Bête noire
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I agree with the previous posts - feed and speed are critical when drilling any low melting temp plastic. Using a coolant is a good idea, but don't use any type of solvent, even alcohols, on acrylic. You'll get stress cracking in no time. A press is really the way to go, that way you can touch off the bit repeatedly until the hole is drilled. Also, keep in mind that when drilling plastics the hole may be significantly smaller than the bit due to material contraction after drilling.
 

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Discussion Starter #13
Thanks to all for the advice. I ended up getting the holes drilled and tapped by just going very slowly and reversing it out and then resuming. I did end up breaking off a screw in the plexiglass also. Now there's 2 drill bits and a screw embedded all in a row in that one section. Alrighty then, at least I now know that all drilling is not equal.
 

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Drilling plastics is not for the faint hearted...

It takes a special 60 degree angle drill bit to properly drill through Plexiglas, Lucite, Acrylite, or Perspex acrylics. They have specially ground flukes with a 90° point for drilling holes in acrylic plastics including, Plexiglas, Lucite and Acrylite materials.

Metal drill bits will not work as they are made to bite into the metal as they are pushed into it. If they are used on acrylics they will chip and cause other damage to the plastic. As you create excessive heat by drilling into plastic with a metal bit, some of the plastic melts. As it cools and resolidifies, it may seize the bit and snap it...

When drilling holes for screws, you must make the hole larger than the screw itself to allow for expansion and contraction of the material. If not you will cause stress cracks at the hole and they will spread!
 
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