Drilling Acrylics???

[bca1313]

I purchased some of the Italian Acrylics recently and attempted to drill one of them last night. It did not go very well so I am hoping to get some ideas so I can make it work next time.

Right away when I was drilling the plastic started to melt and it pretty gooey when it came out. I slowed the drill press down and tried again, but it blew out. The hole was not clean the second time because of the melting during the first part.

My question is what speed do I need to be drilling these at and are there any other tricks to this?

I am drilling with pretty tight tolerances also.

Ben

 

[Skye]

Sharp drill bit? Normal point, not brad?

I have been pretty lucky drilling mine. I just go at a medium speed, a little at a time. I try and let it cool a little between pulses incase it starts to melt. I've had one that's just flat stuck in a blank, yet to be retrieved though.

Make sure you dont drill all the way through. Cut the blank a little long, almost reach the end, then use a little box saw to cut off the undrilled end, exposing the hole.

 

[vick]

Heat is the enemy of acrylic. I usually drill on the slowest speed on by lathe (not sure what it is off hand). I would guess that your bit is not sharp and. If that is not the case make sure to back the bit out often, on some materials I will back it out every 3/8 inches or so. If you bit is getting warm let it sit and cool before you start drilling again.

Skye's advice on not drilling all the way through is good advice, I do the same except use a table saw sled to cut off the undrilled end.

 

[alamocdc]

What works for me: 1) SHARP bits, 2) slow speed with deep cuts (3/8" - 1/2") through the first half of the blank, 3) let the bit cool until it is comfortable to handle (this will also cool the blank, if you quit getting clean cuttings stop and let cool), 4) leave the blanks long and don't drill completely through (just make sure you go far enough), 5) no cuts larger than 1/8" for bottom half of blank.

 

[Rudy Vey]

The best way (at least for me - others may differ)is to drill at medium speed, and dribble water onto the drill bit to cool it. Very important is not to force the bit, back out often to clear out the chips. Take your time to drill the blank. Careful when you reach the bottom, make sure that you have a backer board under the blank in good contact with it, or, like some do make the blank longer, don't drill through all the way and cut later to size. Very often the acrylic and other plastics break when the bit comes through the lower end. I think, pilot drill bits help here tremendously. I use a small dropper bottle one can find in the cosmetic supply shops for the water I dribble onto the drill bit.

 

[btboone]

I use coolant, and lots of it. It makes all the difference.

 

[redfishsc]

I drill on the lowest speed the shopsmith can handle, 750 rpm, which seems good.

Second, I make SURE that the blank isn't sitting directly on the plywood base--- I make sure there's a 1/4 inch or so under the blank so the drill bit doesn't have something to grab once it exits the blank (I do drill all the way through).

Third, my bits are sharp and non-brad point.

Fourth, and perhaps most importantly, I use mineral spirits in a squirt bottle (like the yellow and red restaurant condiment bottles) to spurt on the drill bit to lubricate and cool. This works fantastic.

The mineral spirits will evaporate (I rinse it out with lacquer thinner which evaporates immediately) so it won't interfere with the glue, but it's oily enough to lubricate well.

 

[ctEaglesc]

From your post I came up with a couple of things.Too fast a speed on the DP and a dull or dirty drill bit.If the flutes don't extract the waste , it will harden andor compact while the bit is still turning.That's why blow outs happen.

I don't know if there is any difference in acrylic versus the plexiglass I make my blanks out of, but always sharpen my bit before Drilling(Drill Dr. and I make all my bits split bits).I do drill all my plexi-blanks on the lathe.There wouldn't be any difference than with a drill press other than I drill on the lathe at 500 rpm, I have no idea what the DP is set at, it works.
With the lathe there is no way to use a back up block and I drill them all the way through with no problem.

 

[herper62]

would starting with a smaller bit then increasing bit size help???
Herper

 

[emackrell]

Why are brad point bits no good for drilling acrylics? Just curious.

cheers Eileen [8D]

 

[Pipes]

I guess iam just lucky BUt I have used all kina bits at all kina speeds and as long as there SHARP and I take my time drill a little nd pull it out and go really slow ! I never had one blank blow out of a well 100's now ..
IMHO its a sharp bit any kind key being sharp and go SLOW and pull it out to clean itself a LOT just my 2 cents !





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[Thumbs]

Drilling speed seems to be a problem for many of us. I used to run my drill press as slow as I could around 250RPM and had considerable problems with blowout, splitting, etc. It didn't matter what kind of bit I was using either! Brad point, bullet tip, normal twist or split point bits.

I raised the speed up to around 800-900RPM (per my good friend, Knotty Harry)while drilling rifle brass and have left it there with no problems with any material I have drilled since. I don't know why everything seems to work much better at a more moderate speed but it does...for me.... I always thought because of drilling steel that slower was better. Sometimes, it isn't, I guess.

Of course, this still doesn't allow you to bore in without pulling the bit to let things cool down every 1/4" or so as many others here can attest, also.[}]

That kinda reminds me of when I was showing off my new Paul Huffman vise and blew a nice afzelia blank --- You can't always blame the tools![B)][]

 

[thewishman]

I usually wrap the bottom of the blank with electrical tape before drilling on the lathe. No blowouts when using that extra support. I drill all the way through the bottom at 500 rpm, back out the bit every 1/4 to 3/8 inch.

Chris

 

[bca1313]

Thanks everyone. I just drilled a couple at around 750 speed, backed out a lot and let the bit cool down a couple times. Worked great...now just have to wait for the glue to cure and I am ready to turn them.

Ben

 

[Pipes]

Originally posted by bca1313
<br />Thanks everyone. I just drilled a couple at around 750 speed, backed out a lot and let the bit cool down a couple times. Worked great...now just have to wait for the glue to cure and I am ready to turn them.

Ben

[]





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[Justin_F]

I agree with all the above - whatever works for you, but would like to add my 2c. I use compressed air during drilling at very low speed (350rpm) and when half way through extract the bit completely and bathe in compressed air until cool to the touch. Also blow air into the drill hole to cool it completely.[]

 

[Kaspar]

... Oops. 2x post.

 

[Kaspar]

Originally posted by btboone
<br />I use coolant, and lots of it. It makes all the difference.

Ditto. On acrylics, I use a moist, but not sopping, sponge to cool the bit. I have a syringe or eyedropper with soapy water for lubrication. I deep bore through the first half while the material clears easily, then use successively shorter bores as more of the bit is buried, the bit can't clear away the chips as easily, and heat by friction increases exponentially. Keep the blank long to avoid tear out at the end, use your depth gauge to know when you're deep enough, and then cut to length.

BB's Norseman bits do a fine job, btw.

 

[Blind_Squirrel]

My number one rule on almost all of pen turning is SLOW DOWN! I make pens for enjoyment, so why would I want to rush through any part of it? Clear the blank often; I only take 1/8" - 1/4" passes when drilling any blank. Let the bit do the work.