Drilling clear acrylic

[Penultimate]

I'm trying to make a pen body from clear extruded acrylic and it cracked while drilling. I had 0.5 inch diameter rod in my collet chuck drilled progressively larger holes with lube to .360 ID. I got a bunch of stress cracks.

Any advice on drilling? Do I need a different material?

Thanks.

 

[Mortalis]

I saw this post

How to drill acrylic rods?

Sirs, I am new to working with acrylic and facing lot of problems trying to drill acrylic rods on lathe-the material is melting like jelly at the drill head and sticking to the flute of the drill. I have tried to reduce speed even down to 100 rpm to reduce heat- but no improvement. I was using...

www.penturners.org

while reading yours.

 

[jalbert]

I would use cast acrylic. Extruded has a higher propensity for cracking. Also make sure you are using lubricant and appropriate drilling speeds. Clear Acrylic will develop crazing, which appears as cracks, if the above 2 variables aren't addressed.

 

[Joebobber]

Sounds like you went a little fast and hot. Try a pilot hole.

 

[duncsuss]

It is unwise to lubricate with alcohol or an alcohol-based) product, this is known to trigger cracking in Plexiglass and other acrylic acetates. Google "pmma alcohol crack" if you'd like corroboration of this.

Why does this happen? LINK to an organic chemistry forum that discusses it.

I use tap water with a drop of dish detergent to cool and lubricate when I'm drilling resin blanks; I protect the lathe ways using magnetic floor vent covers (the ones designed to cover up AC floor vents in winter - LINK to Home Depot)

 

[TonyL]

Duncan...what do you think about using PAM as a drilling lubricant?

 

[duncsuss]

Duncan...what do you think about using PAM as a drilling lubricant?

Tony - I've tried it and found it's a great lubricant, but I don't think it cools either the bit or the workpiece as effectively as water. (Plus it's a bit messy to clean up afterwards!)

edit to add: I've also used Tap Magic and "pink" automatic transmission fluid, both of which are great lubricants but don't do much to cool things off, so I tend to keep them for when I'm cutting threads.

 

[PatrickR]

It is unwise to lubricate with alcohol or an alcohol-based) product, this is known to trigger cracking in Plexiglass and other acrylic acetates. Google "pmma alcohol crack" if you'd like corroboration of this.

Why does this happen? LINK to an organic chemistry forum that discusses it.

I use tap water with a drop of dish detergent to cool and lubricate when I'm drilling resin blanks; I protect the lathe ways using magnetic floor vent covers (the ones designed to cover up AC floor vents in winter - LINK to Home Depot)

I have seen polished plexiglass craze simply by being exposed to VOC fumes.

 

[Penultimate]

Hi
Thanks for the great suggestions. I used PAM as a lube but I didn't let the bit cool enough. I'm going to get cast acrylic and use water.

 

[TonyL]

Tony - I've tried it and found it's a great lubricant, but I don't think it cools either the bit or the workpiece as effectively as water. (Plus it's a bit messy to clean up afterwards!)

edit to add: I've also used Tap Magic and "pink" automatic transmission fluid, both of which are great lubricants but don't do much to cool things off, so I tend to keep them for when I'm cutting threads.

Thank you. I may try my Bostik Blade and Drill bit lubricant the next time I drill clear.

 

[jalbert]

I've found mineral oil to work quite well, and it doesn't get gummy on the bits and tools

 

[Woodchipper]

Tried to drill an acrylic blank. Got in a hurry and the blank glued itself to the bit! Now I consider the time it took to remove the blank from the bit!

 

[Joebobber]

Tried to drill an acrylic blank. Got in a hurry and the blank glued itself to the bit! Now I consider the time it took to remove the blank from the bit!

Definitely been there done that!

 

[PatrickR]

For truly effective cooling, flushing with fluid or air would be required. Oils applied to the bit or in the hole will help with cutting but very quickly reach the same temp as what is being cut. I plan on adding a nozzle to blow air into the hole on my set up to keep both hands free.