acrylic drill speed

[Geo in Winnipeg]

I searched to try and find what the best speed is for drilling acrylic. There's lots of info on finishing but I can't seem to find anything on drill speed. I know that heat is the enemy of plastics so chips should be cleared often and some people cool the bit with water.
I usually drill wood about 1400RPM (slower for larger bits). So should it be slower than 1200? Faster? Would it be the same for PR and celluloid?
One more important question - lathe speed??
I'm sure these questions must have been asked before but I can't find the answers.
Thank you for any help you can give me.

 

[alamocdc]

George, this has been a topic of much discussion here. Just not in the last few months. You'll get a variety of responses ranging from high speed, high feed rate hopefully keeping the heat down, to slow speed, slow feed rate and a variety of methods for keeping the bit cool. Some use a shop vac or DC close to the bit keeping the cuttings collected and cooling the bit in the process. Some use water to keep the bit cool. I've tried the shop vac method and didn't really notice a difference in bit temp. I haven't used water... yet, but I might. At the moment I drill everything on my slowest speed and I use a moderate feed rate, but I keep the cuttings cleared by withdrawing the bit often. I do use a slow feed rate when nearing the bottom of the blank to try and keep the blank from blowing up. If you speed through the bottom, you'll blow at least the bottom of the blank off and may blow up at least half of it. Once you find the method that works for you, stick with it.

 

[wayneis]

George I drill at about 1000 to 1200 and I use water to keep the blank cool and the vacume to keep the bit cool. With the vac you need to actually slide the hose so that the bit is in the hose while the bit is still turning. This will cool a bit down in short order, I also use a crevise tool on the hose as its easier to get the bit insode. I turn with the lathe at the highest speed and sand with it on the lowest.

Wayne

 

[DCBluesman]

1500-1800 (or faster). Clear the chips frequently with your shop vac. Cut your blanks long and dril to the right depth, then cut off the excess. Result: no blowouts in a year.

 

[Geo in Winnipeg]

Thanks for the replies. It looks like I have to be more careful with acrylic than most woods. I'll try implementing the advice given above and see what happens. Judging from the albums of those giving the advice (and what I've seen them post here) it doesn't look like I can go wrong.
When I do manage to get some done there will be pics[] Even if they're crummy.

 

[Rifleman1776]

90% of all my drilling is at about 600rpm. I do a lot of big (3/4") end grain boring into hard hardwoods, faster just burns things up. I just leave the drill press at that speed except in circumstances where high speed is required. Even though I do very-very little work with synthetics, I keep a large syringe (available at farm supply stores) on hand to squirt small amounts of water for cooling. And, for those blanks you postively, absolutely don't want to blow out at the bottom, I cut over length, do not drill all the way through, then cut to length on band saw after drilling.

 

[Skye]

Originally posted by Rifleman
And, for those blanks you postively, absolutely don't want to blow out at the bottom, I cut over length, do not drill all the way through, then cut to length on band saw after drilling.

QFT

 

[bloggstein]

I've never done anything with acrylics, but I've heard several times of the problems of them cracking from the heat.

Has anyone ever tried making a small water bath that clamps to the drill press table and has your blank holder & aligner inside of it? That way you could completely cover and surround the blank with water while still getting a straight hole and not have to have 4 arms to do it all with. It might be a little messy, especially after drilling a bunch of blanks, but I would think it would keep the heat down significantly. You could even toss a cold pack or some ice cubes in there.

Just an idea, as I've never dealt with them and may be completely talking out the wrong end. I'd like to work with them someday, though, and would be interested to hear if this might be a decent way to address the problems.

 

[woodbutcher]

I normally drill at 450 rpm and havent had any problems. I go slow. I have found a little heat actually helps soften the material and seems to actually help. Let me also say there is a somewhat fine line between warm enough and too warm.
Jim