Help with drilling resins

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vick

vick

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I have never done any resin pens before so I got a couple crushed velvet blanks to try. I managed to break both drilling the tube holes. Is their a trick to drilling the holes? I am worried because I have a couple of celluloid blanks on the way and do not want to ruin them.
 
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Mike - Although I sure am no expert, you might try drilling a small pilot hole first, then go up in progression of size until you reach the right size for your tubes. I'm sure it's a little time consuming, but it beats busting out blanks. - Just an idea
 
Vick...it's easy to do this right. First, make sure your bit is <b>sharp</b> or else get a new one. Second, drill <u>very</u> slowly and keep your flutes <u>cleared</u>...backing your bit out after every 1/4-3/8" is not too frequent. Third, backfill the hole you are creating with cool water <u>frequently</u> to keep both the blank and the bit from overheating. If you follow this path, grasshopper, you will succeed! [8D]
 
Lou is spot on. Another thing that can easily break the blanks is if the blank is able to move when it's drilled. It takes a steady vise and drill press, or something of equal rigidity. Clear those chips and use a spray bottle with water, water with a little soap, or coolant.
 
Not to rock the boat, But I cut allot of resins and since I changed to Brea's parabolic bits, I haven't lost one. It drills at a high RPM, clears the chips, bores straight & fast. My secound choice would be the DeWalt pilot point, the tit breaks thru first and less breakage.

Ken, scratch the pilot hole, I tried that once, and that's ALL, just once. When you go to expand the hole with the next bit, it justs sucks the bit right down and will probablly crack a resin. Anthony
 
I keep a 30cc syringe by the drill press and each time that I pull the bit up to clear I fill the hole with water, I've never melted or broke a blank doing this.

And I agree with Anthony on the pilot hole, it does not work with acrylic and even with some woods it can be problematic because like Anthony said it draws the bit down.

Wayne.
 
I have done quite a few resin pens and never used any cooling liquids. That sounds like a real mess.

I agree with many of the other sugestions though. Keep the flutes cleared, drilling slowly, making sure that the blank cannot move during drilling and using the DeWalt Pilot point bits. I would also add to this list putting a block of sacraficial wood under the blank to support the end of the blank as you drill through the end. This is when most blowouts have occured for me.
 
I do pretty much what Tony and Wayne recommended:
* parabolic flute bit (important, it clears out the chips well)
* high drilling speed ( I do over 1000 rpm)
* do not intend to go through too fast, clear out often the chips, or better the long shavings that wrap around the bit and chuck
* use water as coolant (I use a wet paint brush that soaked in water and hold against the bit and drop also some into the hole when I clear the bits out

With this I never broke plastic anymore, one important thing is that you not intend to drill through too fast.
No idea about coolant, but some are oil containing that might interfere with later gluing of tubes into the blanks.

Rudy
 
One item I haven't seen mentioned is rigidity.... due to the brittleness it’s especially critical for the plastic blanks. I have the good fortune to have a 800lb mill-drill that I use to drill all my blanks and have never had a problem with anything other than those damn sunflower seed blanks! [xx(] So…. Figure out some way to fasten that sucker down solid!

In regards to using a liquid coolant, if your tools are sharp, you keep the flutes cleaned and you use reasonable feeds and speeds all should be good without the need to create that kind of mess. Your ear is also your best friend when you’re doing any machine work. It’s gonna let ya know if something is getting warm, dull or whatever.

Don’t give up on the acrylics… they can make for some really pretty pens!

Vern

oops.. looks like Bruce covered the rigidity issue
 
I use coolant. I use ValCool, which is essentially slippery blue stuff in a water base. I did about 15 of the plastic pens this week and didn't have any issues. The coolant does help keep the chips cool and you usually get a cleaner hole. I use a milling machine at around 2200 rpms, which is a bit fast unless you really cool the drill and have a rigid setup. Another thing that works well is WD-40. It is one of the few slippery spray type things that won't hurt most plastics. I used to design plastic parts and we did a lot of experimentation with WD-40 to see if it would affect the plastic, and the ones we were working with that are normally affected by solvents like acrylics and polycarbonates were not affected by WD-40.
 
Mike, I have done several resins, acrylic, acrylester, etc. I pretty much do it the same way that Lou does. My main bits are carbide. I even turn off the drill periodically to let the bit cool. I just take more time to drill than wood. This is one of the reasons I charge more for the resins. Kirk [8D]
 
I've turned many Accrylic and Celluoid and Corian. Key is speed and I use A B&D Bullet Tip. Must be Sharp and you can't hurry. Also you can't clear the bit too often. Trying to drill all the way through is a Recipe for Disaster. Cut like 3/8" longer, drill to within 1/8" of bottom. Cut extra bottom material off. [:)]
 
I go along with every one else execpt I got tired of the water coolant thing. So I now use a spray coat of the teflon type stuff I get from Woodcraft. Used for saw blades snd such for preventing pitch build up.
 
this is a littel bit of the subject but not by far enough that it doesn't belong here.
I have a drill speed chart I got off the net when I first started turning pens.
If anyone knows the location of that chart or any other chart please put a link to it here. or in the links section.
now for my diversion. in my opinion (notice that is a disclaimer) but an opinion backed by plenty of research. drilling speed combined with feed speed,(how fast you push the drill through) are very important. I don't think there is enough information shared on this group about this.
A drill bit is engineered to work in a certain way. If you do not use the tool the way it was designed to work you will not get the results it was intended to give.
the harder a material is the slower speed you need to use. this does not mean slow it means slower. the larger the bit the slower you need as well, and the two work together. a half inch bit in steel requires a much slower speed than a quarter inch bit through the same steel.
now having said that. i will also ad that slowing down is not usually the answer for the average penturner. speeding up either the R.P.M. or the feed rate usually is expecially for the beginner.
here is my rule of thumb. if the shavings are not fountaining out of the top of the blank. I am not getting something right. in the case of plastics it is more like the stream of plastic is snaking it's way out.
keep in mind that a drill bit is designed to only clear chips for 4 times its diameter. this means that a 7mm bit is made to only clear chips from a 1 inch deep hole. you can get a little more with a faster feed rate but it takes really slamming the bit through and this would not work for plastic. this is the reason for needing to back out the bit and allowing the flutes to shovel out the chips. this is probably the reason parabolic flutes work better. an auger bit also works better as it is designed to carry out the chips from a deeper hole.
drilling from the hoizontal position would also help. but that is pretty much out of the range for most of us.
in short find a drill chart and follow it. I have made a rack for my 100 plus drill bits with the speed for each bit color coded on it. I think I have four different materials listed for each bit. soft wood, hard wood, plastic and metal. it makes it real simple when I grab the bit to check the speed. what is a pain is changing the belts on my drill press. anyone got a variable speed drill press for sale cheap?
from this chart and experimenting with feed rates. I drill a 7mm hole through a 3 inch blank of soft to med wood in about one second. no blow outs. going slower I blow them for about 1 in 10-20 blanks. hard wood takes more like 4-5 seconds for the same hole as I have to clear the bit once or twice. plastic is very slow as the chips will not clear after the first inch or so no matter what I do and the palstic will not withstand the pressure of haveing the bit rammed through like that.
very slow one quarter inch at a time using water and a slow drill speed.
and by the way using oil in plastics will give you a very smooth cut. it is the way to drill through clear plastic and still be able to see through it. not sure how well that would hold the tube afterwards.
 
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