jcm71
Member
Some time ago I bought some circuit board blanks from a vendor who will remain unnamed. I finally got around to turning the purple ones last week, with disastrous results. These blanks are cast in a very brittle and unforgiving poly resin, are a bear to turn, being very prone to a blow out. I don't know who casted these, however, the vendor suspects they were casted in China. The picture shows an unturned blank with the inferior casting, a completed bank that cracked on pressing (thick end), and a completed pen just to show it can be done. My recommendation is to stay away from these. If you do decide to turn one of these I recommend the following:
a. Square the blank using a disk sander. Do not use a barrel trimmer.
b sand off the corners using a disk or belt sander. Turning a square blank invites a blowout.
c. Turn one blank at a time, using TBC bushings or a mandrel saver.
d. Turn as fast as you can, using a negative rake carbide with a fresh edge.
e. Use an extremely light touch when turning. Plan on taking twice as long to turn as an acrylic or rhino plastic blank.
f. Stop turning when 1/16 inch or more proud of the bushings. Wet sand the rest of the way.
g. Ream out the barrels until your components slip fit, and then use loctite to secure.
h. Keep in mind turning these are not fun.
As background I have been turning pens for over 12 years and have made and sold over 30 circuit board pens.
a. Square the blank using a disk sander. Do not use a barrel trimmer.
b sand off the corners using a disk or belt sander. Turning a square blank invites a blowout.
c. Turn one blank at a time, using TBC bushings or a mandrel saver.
d. Turn as fast as you can, using a negative rake carbide with a fresh edge.
e. Use an extremely light touch when turning. Plan on taking twice as long to turn as an acrylic or rhino plastic blank.
f. Stop turning when 1/16 inch or more proud of the bushings. Wet sand the rest of the way.
g. Ream out the barrels until your components slip fit, and then use loctite to secure.
h. Keep in mind turning these are not fun.
As background I have been turning pens for over 12 years and have made and sold over 30 circuit board pens.