drilling perspex.

I read in another thread that when drilling through perspex you should "put negative rake on the drill's cutting edges". Can someone explain what this means. Cheers.

This link probably explains it better than I could (has a pic too), go down to the section on dubbed drills.
http://www.mmsonline.com/articles/068901.html#fig5

Fantastic link, Dan, a really good analysis of the topic. Thanks :2tsup:

Thanks for the link Dan. Have filed that one away.:2tsup:

:google2:

Having just blown out the bottoms of two acrylic pen blanks, despite having a brand-new sharp bit, and drilling slowly, and clearing the bit frequently, I googled "drilling acrylic".

Seems much like what you're looking for:
http://www.bertram31.com/proj/tips/drill_acrylic.htm
http://www.hawkfish.org/snailman/acrdrill.htm
http://www.sdplastics.com/acrylic.html

http://www.ultimatehandyman.co.uk/AC..._MACHINING.htm

I also wondered about using a masonry bit, as they seem to have zero rake...
Anyone tried that?

Cheers,
Andrew

Enjoyed reading the Drill Point Geometry article linked to above, here is another link to a longer version of the article, for others interested loike moi. :D


Cheers.................Sean