metalresearcher - 27-2-2011 at 12:58
After failed earlier attempts, today I finally got it: drilling a hole for glass tubing into a silicone stopper.
I used a lathe (can also with a drill + vise) and a brass tube and a drill bit.
For those interested, here the description.
[Edited on 2011-2-27 by metalresearcher]
Drilling softer plastics
ciscosdad - 27-2-2011 at 20:50
Try putting the rubbery material in a freezer for a while.
Most of these materials stiffen considerably at low temperatures and behave quite well in turning or drilling.
You need to be quick though: only get one out at a time if you're doing a batch.
Never tried anything lower than -20 deg C.
Also helps to make a custom clamp of some description so the clamping load is evenly distributed around the circumference. Drill a hole just smaller
than the rubber stopper in something stiff (either square or round outer shape depending on whether you're turning or drilling). Then cut the mandrel
in half across the hole.
Makes a good secure clamp. To increase clamping force, shave the cut surfaces or make the initial hole smaller.
Oops. Just read the link. You covered that.
How embarrassing
[Edited on 28-2-2011 by ciscosdad]
Panache - 7-3-2011 at 18:10
hole saws, in this case the cheap shitty complete set of like 10hole saws (from china) you can buy for $5 are the best because they are very thin, use
lube like a petroleum jelly. for clamping you need to have the stopper in something that replicates it's taper, like an broken ground glass joint, or
simply tap out a 1/10 taper in a 2inch or so piece of softwood, this can be then used almost universally,