drilling through acrylic

[mdwilliams999]

I just started turning wood pens and have turned about 20-25 at this point. I have used my drill press (low speed - I believe 1100 rpm). I'm doing slimline so I'm using a 7mm carbide bit tip. I am also using a self-made jig to hold the wood and drill it center. I take my time and will make multiple passes to avoid to much heat or any build up that might cause the hole to go out of shape. Up to this point I haven't had any problems.

Tonight, I tried my first acrylic pen blank and had a bit of a nightmare. on a 2 1/4 piece of the acrylic I get about half way through and my drill bit starts to wobble and starts to screw up the hole. I pulled it up immediately, everything looked fine, and I tried again. Same problem. I made it through but with less than desirable results. I tried the other half and had the same problem. I checked by drill bit and press out everything seemed fine.

I decided to try wood again, and was able to run 3 more blanks through with absolutely no problem. I tried another piece of acrylic and had the same problems again. The acrylic is perfectly straight.

Does anyone know what is going on? Is a standard 7mm carbide tip bit not good enough (it's new off of Woodturningz), Do I need to drill at a higher or slower speed? A little lost right now.

Mike

 

[fireangels]

I personally do not use a carbide tipped bit and have never had that problem and ive done my share of 50 to 80 acrylics I have had a few blowout because of bad casting. I would definately try a faster speed I think mine is in the 2000 range then try a new bit if it is still a problem

 

[Manny]

I find it odd that the drill bit itself starts to wobble on acrylic but not on wood. That doesn't make sense. I have had out of round drillings before but they were usually associated with the bit not seated correctly in the chuck or the bit bending.
are you apply too much pressure when drilling. Perhaps you are bowing the bit.

I use a drill dr. And can not recommend it highly enough.

Have you tried drilling on the lathe?

Manny

 

[Akula]

need to clear the bit more...I clear acrylics about every 1/4 inch...back it all the way out to remove the soft warm cuttings

 

[Manny]

That seems a bit excessive to me. As long as the shavings are being ejected through the flutes you should be ok to progress forward. Once the slow down you need to back off. Also lubricate when you pull put.

Just my opinion

Manny

 

[workinforwood]

I used to have this issue yrs ago all the time. Solution was drill speed. 1100 is too fast I drill 600

 

[1080Wayne]

Almost certainly , the acrylic is melting because of frictional heat . Don`t use a pilot hole - start full size . Slowest drill speed , backing out every 1/4 inch or so to clear cuttings . In and out fast . Water in hole each time . Stop drilling before bit exits the blank so it won`t blow out (blank needs to be 1/4 inch or more longer than the tube to do this) . Blank must be rigidly held .

Following all of those steps should allow you to drill any plastic material except a very low melting point one . Some plastics are easy to drill and don`t require all of the steps . I`m assuming you have acrylic acetate . The water may not be necessary , but it won`t hurt .

Carbide bits aren`t required . I prefer a high quality brad point because it reduces the chance of blow-out when the bit exits the blank .

 

[rherrell]

I agree with Jeff, 1100 is not slow. I drill at 500 and don't have any problems.
I use regular HSS drill bits, there's really no need for carbide when drilling wood and plastic.

 

[snyiper]

I drill on the second pully on my press not sure of the speed but it isnt the slowest. I will use pilot bits as well as non with equal results. I use a spray bottle of water to keep the hole filled and back out and clear every 1/4 in or so. This is just how I do it.

 

[IPD_Mr]

The acrylic is most definitely getting hot and melting or becoming soft as you are drilling. I played around with a piece of Lucite because so many were having problems. I got it hot and soft enough that I actually watched the blank come out of round as it was being drilled on the lathe. This is also a good thing to see as some of your woods that are known for cracking such as ebony and amboyna will most definitely be effected by this kind of heat. The solution is slow way down when drilling, clear often and drill a little at a time. If you find the blank is getting warm, stop and go do something else for 15 minutes and come back to it. Remember it is the tortoise that wins the race.

 

[BKelley]

Hi,
I'll put in my two cents worth. Do away with the carbide drill. I use Colt drills and they are great. Colt makes several type drills, but the Colt 5 Star Pen Makers bit does a wonderful job. They are on the expensive side, but well worth it. CSUSA and Woodcraft carry them.

 

[G1Pens]

I know nothing, but I drill at the slowest speed on my lathe, around 500 and have never had an issue

 

[Chasper]

Are worms coming out of the drilled hole? Worms are melted shreds of resin that melt together into long strings. They have a tendency to "worm" their way around a small diameter bit and make it wobble.

Sharper bit, slower speed, pull out more often, and use some water to cool it off; that should take care of the worms.

 

[nativewooder]

I must be a lot older than I thought 'cause the only carbide bits I'm aware of are carbide bits for drilling stone and masonry. There are too many better steel bits out there that will be less expensive and do a better job. I also use the Colt 5 Star pen drilling bits.

 

[workinforwood]

I must be a lot older than I thought 'cause the only carbide bits I'm aware of are carbide bits for drilling stone and masonry. There are too many better steel bits out there that will be less expensive and do a better job. I also use the Colt 5 Star pen drilling bits.

Nah..those types of bits are totally different. These bits he's using are no different than any other bit in their shape, it's just the metal has a high quantity of carbine in it, so it can be sharper and harder. I have lots of them and they work great. For plastic..they are not better or worse than anything else, but for certain metals they have a real advantage. I personally would use something like a colt 5 star, but not because the metal is better or worse, it's just that the 5 star has a nice lead point on it, and the bigger the bit, the better the lead you will need to guide the bit straight into the hole, unless you are going to pilot the hole first...but for acrylics I'd be too lazy to do that.

 

[Dudley Young]

I agree with most. I drill at 600, use brad point drill and no water. You're over heating the acrylic and when it gums up down in the hole it will wobble. I agree also, get rid of the carbide unless you want to drill some rifle casings. Welcome to the madness. Have fun.

 

[Katsin]

This has been working very well for me:

• I use a self centering jig.
• I drill everything super slow. 240 I think.
• I always stop short of the bottom of the acrylic blank and trim the end.
• I clear the bit every 1/4" too like the other gentleman suggested.
• I check on how hot the bit is getting and let it cool if needed.

 

[arw01]

Silly me, I knew about this thread and did not write down which speed I drilled two acrylic blanks with. One that I've turned down to sanding size has some BAD crazing and will have to become a around the house pen. I'm hoping the other ones is in better shape!

The drill press I use would allow you to count the revolutions on the bottom end of the speed dial, but I drilled one of these around 1500 and the other at 1200.

Alan

 

[joefyffe]

Katsin and IPD Mr. hit it on the head for me. Slow speed (my Jet 1220 allow 200 r's, that's where I go, round turned blank, between center bits and then placed in a collet chuck at 200 rpm) On acrylics, or wood, the bit can still become hot to the touch, "WALK AWAY" When cool, drill another half inch or so till it get warm/hot to the touch and "WALK AWAY"! LOW SPEED, COOL BIT, FREQUENT PULL OUTS!!!! "WALK AWAY"