This one's come up a couple times recently and I ran across some pictures, so here's my lathe test tube cutting method. It's possible to cut tubes accurately like this.
The tube is gripped lightly in a collet (if it doesn't fit a handy collet, wrap some tape around it to fit a larger size-- all the forces are and must be very low for any of this to work). You could probably chuck it as well with appropriate tape padding.
A Dremel with standard cutoff disk is placed in the toolpost (I use a handpiece extension since it's much easier to clamp up in a QC holder). Protect the lathe from grinding and glass dust with some paper towels.
Run the lathe at a fairly slow speed and turn on the Dremel (I spin them opposite directions, but it probably doesn't matter much). Feed in very very slowly, trying to keep some oil in and around the cut as you go.
The drill bit down the center of the tube is a long 'aircraft' drill held in the tailstock to catch the cut off piece and prevent it from running amuck or getting lost in the chip pan. Deburr the glass lightly on a diamond hone.
The tube is gripped lightly in a collet (if it doesn't fit a handy collet, wrap some tape around it to fit a larger size-- all the forces are and must be very low for any of this to work). You could probably chuck it as well with appropriate tape padding.
A Dremel with standard cutoff disk is placed in the toolpost (I use a handpiece extension since it's much easier to clamp up in a QC holder). Protect the lathe from grinding and glass dust with some paper towels.
Run the lathe at a fairly slow speed and turn on the Dremel (I spin them opposite directions, but it probably doesn't matter much). Feed in very very slowly, trying to keep some oil in and around the cut as you go.
The drill bit down the center of the tube is a long 'aircraft' drill held in the tailstock to catch the cut off piece and prevent it from running amuck or getting lost in the chip pan. Deburr the glass lightly on a diamond hone.
oh:
