Another 'drilling acrylics' question

[lago]

I have drilled several with the 7mm bit and not problem. I messed up 2 blanks today when trying to drill with a 1/2" bit.

I did a search and it looks like some of you drill almost to the end but not all the way thru. That won't work for me since I am trying to get 2 pens out of one blank. I have some blanks that are about 5 1/4" long and trying to get a Gatsby and the PSI Lipstick pen. The blanks come out long enough for each tube if I cut with a Chinese flush-cut saw, which has a very small kerf. It just doesn't leave me with a blank long enough to stop before I get to the end.

I was using a brand new DeWalt 1/2 bradpoint bit at 200rpm and had a piece of wood under it.

Any suggestions other than using just over 1/2 of a blank for the Lipstick pen and toss the rest of the blank.

Thanks
Lago

 

[IPD_Mr]

Have you tried spraying it with Pam cooking spray as you drill? Spray inside the hole you are creating and the drill bit. Clear often and don't let it get hot.

 

[D.Oliver]

Also use a sacrifice piece (like plywood) to give some support the blank where the drill bit exits. Some centering vise have this incorporated into them but some don't.

 

[ed4copies]

Another possibility--if you are using a brad point, drill just until the brad point marks the bottom of your blank, then turn it over and drill from the bottom.

 

[Drstrangefart]

What I do is use an infant syringe to add water to eht hole as the bit goes deeper. Once you exit the bottom, you WILL lose all that water instantly, things WILL heat up and you need to get to the shutoff switch fast. That being said, if I'm careful, I can drill out the bottom without having the massive shatter-out. I do back it up by setting it on a small sacrificial plank just to be sure.

 

[firewhatfire]

Buy colt drill bits

 

[jbswearingen]

I've found that regular drill bits blow out less than brad point bits for me.

 

[snyiper]

I use a spray bottle of water to cool and lubricate...Must lift the bit all the way out and clear debris off.

 

[DennisM]

Drill on the lathe, keep the bit cool and lubed, make small passes, clearing the bit. Never had a problem, would cool and lube the bit with plastic polish as I drilled. Would glue a scrap piece on the end of any blanks that I couldnt afford to lose and drill into it..

 

[ToddMR]

One thing that has worked for me is to start drilling on one end, then flip the blank over and drill the other end. If you have a good vise for securing the blank this works nice and normally helps prevent blow out and cracking on the blank. You can mark both sides' center if it helps you. If you hear chattering or a chirping sound while drilling, STOP, let the bit cool down. Like I said I have done MANY blanks this way and it worked out well for me.

The other suggestions are are good as well. Can't tell you the number of blanks I lost because I kept trying to drill straight through, especially on the bigger pens that have caps.

 

[Justturnin]

I am a bit new to this and have only drilled 2 pieces of Corain (50% success rate) at 7mm but could you use a pilot bit, 1/8" and step up to the 1/2" slowly?

 

[ToddMR]

Yes and no. One thing I personally have found is doing that causes a lot more stress in the blank, which can cause a crack down the side, than to just straight drill the correct size first. That is my experience though.

 

[AlanZ]

If your blank is too short to drill short of the end... consider making the blank longer, at least temporarily.

Use some CA glue to attach a short scrap to the end of the blank, making the blank longer. Then you can either stop short of coming out the end of the blank, or go ahead and let there be some blowout at the scrap end.

Would this work for you?

 

[lago]

Good idea. I will try that next time.

Lago

 

[RSidetrack]

I have had the horrific blow outs myself and the method I have used and seems to work every time is I simply drill very slowly - I let the bit do the work, so very minimal pressure. I also add some water in as it drills. I take a piece of scrap wood or even acrylic and place under where the bit will come out - this helps prevent the week part at the end from pushing out.

If it squeaks give it a break.
If it is smoking give it a break.

Acrylic blows out so easily if heated - or as I have had a couple times, it actually warps the hole. So a blow out may not occur but then you are trying to figure out how to fill in around the blank because the hole becomes an oval.

It takes some getting used to - I have gone through my share of ruined blanks.