Drilling Acrylic fail!

[edstreet]

I can say with 100% proof fact that regardless of where or how you drill this type problem can happen. The causes are diverse and the problem is fairly simple when you get down to the nuts/bolts of what is going on when you drill.

When you have a rotating cone impacting a block that is secured on the opposite end the block tends to twist like the drill bit does. The torsion strength (like tensile strength) of the block comes into play. The support column of the blank that is needed to overcome this is directly related to the pressure of the drill bit, the RPM of the drill bit, the size of the drill bit and the wall thickness of the post drilled blank. After that magic point the blank, regardless of material WILL crack.

Softer fragile blanks will do this more often than harder and stronger blanks, simply due to tensile strength.

There is a large gap of information to accurately say with any degree of certainty which area the problem is coming from.

 

[seamus7227]

I can say with 100% proof fact that regardless of where or how you drill this type problem can happen. The causes are diverse and the problem is fairly simple when you get down to the nuts/bolts of what is going on when you drill.

When you have a rotating cone impacting a block that is secured on the opposite end the block tends to twist like the drill bit does. The torsion strength (like tensile strength) of the block comes into play. The support column of the blank that is needed to overcome this is directly related to the pressure of the drill bit, the RPM of the drill bit, the size of the drill bit and the wall thickness of the post drilled blank. After that magic point the blank, regardless of material WILL crack.

Softer fragile blanks will do this more often than harder and stronger blanks, simply due to tensile strength.

There is a large gap of information to accurately say with any degree of certainty which area the problem is coming from.

I concur, what he said!!:biggrin::tongue:

 

[nates02gt]

Another option

I am still a newbie but I read about another way to help prevent blowouts that I did not see mentioned in the thread so far. It has worked well for me on my acrylic blanks. I drill about .25" into one end of the blank and then turn it around and drill all the way through from the other end. I am drilling on my lathe and would definitely agree with everyone else that drilling on the lathe is the way to to if at all possible. I use the pin jaws with my Baracuda chuck and it seems to work great.

 

[BayouPenturner]

t tried many things but a sharp bit and using the nova pen jaws is working fantastic.

 

[WriteON]

I'm using a lathe. Blanks were cut in half(2.5) I drilled slightly past tube length and stopped. Sawed the end off. Worked out fine. This was first my drilling experience. I was warned about drilling entirely through. 3/8 camo blanks for Bolts.

 

[hazmat74]

Ugh..ignore this. Should have read further into the thread. Question answered. Thanks!

 

[CrimsonKeel]

I notice when i near the end i have to go much slower and also its much more important to clean out built up chips or plastic in this case. this puts outward pressure on the blank and will blow them out much easier.