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acrylic blanks stuck on drill bit

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Forum topic by csnyderdvm posted 10-06-2015 07:34 PM 705 views 0 times favorited 5 replies Add to Favorites Watch
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csnyderdvm

20 posts in 1200 days


10-06-2015 07:34 PM

Topic tags/keywords: lathe turning tip

So I’ve trashed 2 acrylic blanks so far after the bit became stuck when drilling the hole. I tried chilling the stuck acrylic/bit in the freezer- couldn’t get it out. Both times I had to score the acrylic and split it with a chisel to get it out. Am I trying to bore too deep a hole before backing out to clear shavings? Am I taking too long to drill the hole and creating too much heat that results in getting stuck? I’m looking for some advice?
Thanks in advance!
Chris


5 replies so far

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Picken5

224 posts in 2153 days


#1 posted 10-06-2015 07:41 PM

I’ve never worked with acrylics, but I’d suggest the following: Slowing down the speed of your drill and backing out the bit more frequently to clear chips. Sounds like the chips aren’t being cleared quickly enough and the chips may be melting a bit while your bit is still turning inside the blank — which I imagine would be similar to “hot gluing” your bit into the blank.

-- Howard - "Time spent making sawdust is not deducted from one's lifetime." - old Scottish proverb

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CharleyL

197 posts in 2826 days


#2 posted 10-10-2015 01:37 AM

Plastic materials require much slower drill speed and a bit that more scrapes the hole than cuts it. If you take a regular twist drill and grind small flats where the sharp cutting edge is and make these flats in line with the shank, the cutting edges will become scrappers while the twisted flutes will still remove the cuttings. Slow down the speed to keep heat build-up below the melting point of the plastic, and you should be able to drill holes without the melting and sticking problems that you are having. A tiny bit of water dropped into the hole as it’s being drilled should help minimize the heating problem too, but it makes a mess.

Don’t forget to properly re-sharpen the bit before returning it to the drill index DAMIKT.

Charley

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waho6o9

7171 posts in 2038 days


#3 posted 10-10-2015 01:48 AM

Drill bits for plastic ^

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Vince

1111 posts in 2890 days


#4 posted 10-10-2015 01:07 PM

I use an air gun to keep the bit cool while drilling, haven’t had a problem since.

-- Vince

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gwilki

121 posts in 935 days


#5 posted 10-11-2015 01:20 AM

I use brad point bits with good success. The key, as already mentioned, is to drill slowly. Back out every 1/4” or so. I use a mix of water, alcohol and dish soap in a squeeze bottle to keep the hole cool and lubed. Also, cut your blank a bit long so that you don’t need to drill out the end. It will prevent blow out.

-- Grant Wilkinson, Ottawa ON

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