# Drilling plastic/acrylic pen blanks Problems.



## Indiana_Parrothead (Oct 5, 2009)

I need some help figuring out how to drill plastic/acrylic pen blanks without cracking them. I use the Rockler Pen Press/Drilling jig (http://www.rockler.com/product.cfm?page=18062&filter=pen%20vise) wirh a new sacrificial wood blank in it. I have tried both brad point bits and regular bits, both very sharp. I have tried drilling a small hole and working up to the size that I need. I have tried drilling slow and drilling fast.

The problem is when I get to the bottom where the bit is about to come thru, the bit catches and cracks or breaks of the bottom of the blank. I have thought about leaving the blank long drilling to the depth that I need and then cutting off the bottom to expose the hole but have not tried that yet.

What/how are other drilling plastic/acrylic blanks for pens?


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## rwyoung (Nov 22, 2008)

Your idea of leaving the blank long and not drilling through is 100% spot-on.


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## bendisplays (Feb 2, 2009)

You have the solution right there by drilling and cutting of the end. You can also have a sacrificial peice at the bottom. If you drill through acrylic and you have noting supporting it at the bottom it will "crack through".

One other thing to note is that there are special acrylic drill bits. Most drill bits will "corkscrew" through plastics like acrylic. Even if you dont crack through, regular drill bits will give a bad looking finish. Plastic drill bits need to have a 0 degree hook. You can grind a metal drill bit on grinder or better yet buy a plastic drill bit at a local plastic distributer or I have another source:

http://www.thefabricatorssource.com/products/06drills.htm

Cheers,

Ben


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## a1Jim (Aug 9, 2008)

Sounds like you hav it handeled


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## jchamb01 (Nov 3, 2009)

1. Put the blank in the freezer for a minimum of 6 hours, better overnight or longer if tou wish.

2. Use minimum pressure while drilling (be patient).

3. No more than three short stabs at one attempt, stop, feel the drill bit. If it is warm or hot, cool it off with cold water in a jar.

4. Set your drill press accurately and when nearing the end, slow down and use even less pressure.

5. Make sure that your starting point is absolutely in the middle of the blank.

6. Heat build up and drill bit wandering from excessive downward pressure are the enemies. Avoid them and you will avoid frustration.


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## fixitallman (Nov 4, 2011)

When drilling plastic, particularly acrylics you need a zero degree rake on the drill - just offer the drill up to the grindstone and carefully make the cutting edge parallel to the centre of the drill so that is acts as a scraper rather than a cutter. This way the drill will not try and pull itself into the material. It is also possible to make a perfectly concentric and straight hole down the centre by using what is called a D bit made from silver steel. Like the name suggests, the cross section is half the circle or at least it is for about 12mm or half an inch. The tip is cut back at an angle of about 30 degrees. Start with a conventional drill for half an inch then use the same diameter D bit introducing and removing to clear swarf at 1/4 inch at a time until you exit. You can use the hole for a threded mandrel to put it on the lathe for turning. D bits are used on woodwind instruments to make the long hole down the centre of the ebony shafts.

fixitallman


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## KenBry (Sep 13, 2011)

I honestly have had my bottoms crack out too. As you know you NEVER use the entire length of the blank. So make them 1/4" long when you drill YES, go slow at the bottom. When you glue in your brass tubes make sure you have the room to face the chipped out area.

Yes, buy a facing tool. These things give a great 90 degree face to your tube and clean up rough ends very nicely. 
Most of my pens that I make are acrylic and I mass produce. I never have the time to take the bit out and cool it or freeze my blanks over night.


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## charlesdicrus (Feb 26, 2016)

Thank you fixitallman, your reply is really informative.


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