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Jeff Belany
07-02-2011, 5:03 PM
Even though I've been laser engraving for many years, my experience with plastic is somewhat limited. I did a quick search but didn't find anything on drilling acrylic. Anyone have some hints on what type of bit works best? How about speed? It seems whenever I drill close to an edge I get a fine crack to the edge. Doesn't cause any strength issues, just looks bad. I should add this is not making holes with the laser, that I can do. It's when I drill holes on the adge of a piece, as when you hang a sign. I have a new store sign for my window and I need to get it installed. Any help from you guys who do a lot of plastic.

Jeff in northern Wisconsin

Tony Lenkic
07-02-2011, 5:12 PM
Jeff - If the piece you're drilling can fit in your laser cut the holes with it.
Otherwise check out Quality 1 engravers (Q1 dot com). Fred sells bits specially shaped for acrylics.

Bruce Volden
07-02-2011, 5:13 PM
Jeff,

I guess I never "drilled" acrylic without it cracking either. My best luck has been with a dull drill bit at a higher speed and more or less melting through it. A sharp bit wants to "grab" the material and force itself through it. Also, I use a drill press instead of a hand held drill---way more control. I'm sure others will chime in here and offer up more help--for US.

Bruce

Ken Shea
07-02-2011, 5:40 PM
Jeff,
Agreed, if you need to drill plastics you will need a drill specially engineered for that.
Onsrud also makes fine drill and end mills for plastic.

http://www.onsrud.com/xlink/xlProductDetail&xlProductDetail_xcrit1=70-502&xtdlksearchprodlst_xcrit1=C1DRILL&xtdlksearchclassesprodlst_cn=Drills&xtdlksearchclassesprodlst_xcrit1=&xtdSpecialPageName=&xtdSpecialPageLinkName=&xtdSpecialClassPageName=&xtdSpecialPageLinkName=&xlProductDetail_PN=HSS%20Upcut%20Plastic%20Drill

Ken

Joe Pelonio
07-02-2011, 5:56 PM
With regular bits the edge grabs into it and tears it apart. Tap Plastics, Delvie's and the rest sell the bits made for it.

Bob Davis
07-02-2011, 10:02 PM
Something that will help is to have another piece of acylic (or wood) under the piece you're drilling. The added support and avoidance of the shock when the bit breaks through should give a good result. Best drill speed to use is where the swarf comes out as a continuous spiral. If you need it to be immaculate make sure you have transfer tape on both sides.

russell dietrich
07-03-2011, 12:42 AM
You might try a brad point bit. Can be ordered from pen making catalogs for drilling acrylic blanks. Most hardware stores will carry some. Can be ordered in sets from 1/8" to 1/2" in 1/64" increments. Since the point comes through first the piece can be turned over to finish with a clean hole. If backed properly it will cut through cleanly.

Michael Simpson Virgina
07-03-2011, 3:57 AM
You just need a bit with the correct angle on the tip. The bits I find that work the best are Bad Dog Carbide tipped bits. The carbide is on the tip and its at the correct angle to sheer the hole. I can drill a 1" diameter hole without any lifting (Thats what cracks the acrylic).

Before I got hold of those bits there are some things you can do. First the piece must be held ridgid. Next the piece must be fuly supported with a piece of scrap, so that when you drill through the acrylic you will also drill through the scrap. When I would drill the hole I would use my fingers or scrap to support the top side of piece being drilled.

Mike Null
07-03-2011, 6:39 AM
I just use my standard bits at a slow drill press speed (500-700 rpm). Don't force the bit through the material and use a sharp bit.

Doug Griffith
07-03-2011, 11:58 AM
I use downward spiral bits from Onsrud. Usually in a CNC but they also work in a drill press. The downward spiral loads the hole up with chips but the part doesn't lift and cause stress cracks.

Mark Giese
07-03-2011, 1:33 PM
Onsrud carries a great line of industrial quality bits for drilling plastics/acrylic you can order direct, or try Connecticut Tool and Saw as they sell Onsrud products at 30% off list, may have to order but can be drop shipped

Craftics in Albuquerque also carries a line of plastic drill bits

Check your local Plastics Distributor, they may carry tooling.

No doubt plenty of other places you could order from, check grainger, mcmaster-carr, MSCDirect, etc...

Can you drill acrylic with standard twist drill bits..... yes, is there a huge difference and reduction in breakout/material failure when using bits designed for drilling plastic, YES!

Plastic bits have a tip ground to a higher degree angle, and flutes ground differently to minimize the tendency to pull the bit through at breakthrough.

These are generally sold by the bit, and can add up fast when trying to complete a full set,

The thing I have found is to let the bit do the cutting, not too much down force, particularly at breakthrough. I also prefer to cut with a slower speed, whether in a drill press or a hand drill, and if it is thicker than 3/8, i often peck drill, heat and plastic is not your friend, you want to clear the debris to minimize heat

Hope this helps,

Richard Rumancik
07-03-2011, 6:24 PM
You can get some technicical info on the Evonic/Cyro site for Acrylite FF. It is probably applicable to other extruded grades. You want to locate Acrylite FF Tech Brief "#4 Drilling".

Start here

http://www.acrylite.net/product/acrylite/en/application-areas/fabrication/pages/default.aspx

then click "download documents" and hunt for Tech Brief - 4 - Drilling. I think it is on the third page. There are some other ones that might be of use as well.

Seth Dolcourt
07-03-2011, 10:02 PM
Tap Plastics carries drill bits for acrylic, about $7 for the 3/16". It made a very clean hole in both acrylic and polycarbonate, no fuss or muss.

Jeff Belany
07-04-2011, 11:24 AM
Thanks for all the replies. I will order a special bit but for now I'll try some of your tips and see how it works. I need to put the sign up fairly soon but it's just for my store so if I crack it no one can get mad at me.

Jeff in northern Wisconsin