triple ripple and rio grande drill bits breaking?

I've been having my drill bits break a lot recently while drilling holes in jewelry. I normally use the diamond coated 1.6 mm drill bits from Rio Grande and do obey the rules--drill slowly, in water, move drill bit in and out of the hole to let it cool off, don't press hard, etc. I'd been doing holes this way for about a year without that many problems but recently I've been having the drill bits break halfway up (or so). I thought maybe I'd just gotten a few weak bits, so in the mood of experimenting I ordered some l.4 mm triple ripples (which seems to be a top choice for a lot of people). Again, I get breakage in just about the same way and number of drillings. I even did only five holes at a time, and let it rest for half an hour inbetween. I use a dremel with a drill press and I noticed with the triple ripples the drill bit actually bends a bit when I'm drilling, with very little pressure so I moved the drill bit way up into the drill so as little of it was hanging out (real technical language here, eh?) but it still broke. Could my drill press be at a slight, but invisible angle and therefore putting pressure on the bit causing it to break? Could the drill bit be in the drill crooked because something's screwy with the little metal nubby that holds the drill bit in place? Has anyone else had this problem? Please excuse the length of the ditty but I wanted to be clear about what I've been doing. Thanks for any information! I can't afford too many more broken bits! AND I don't want to use glue for findings--I've got to have the holes......

* Something strange going on Kate. Bit breakage is the last thing I would expect. Check your bits for wobble just as the motor starts or just before it comes to a stop. About the only thing I can think of that would cause breakage is metal fatique from a constantly flexing drill bit.
There should be no wobble at all. It is possible the motor shaft is bent or the little collet that squeezes the bit in place is damaged.

* When you say you're going slow, are you referring to the speed of your hand, or the rpm of the drill? I used to break bits sometimes when I used a higher rpm. Now I stay at around 5000, which is usually the lowest setting on a dremel, and there are no breakage problems.

* It sounds like the dremel tool is a bit cocked in the drill press fixture... that'll put a bending load on the bits as you plunge them into the glass. Take the dremel out of the drill press and reassemble it. It might be easier to see if it's out of alignment by using a long piece of brass rod (from a hobby shop) in the collet. When you plunge the drill press, it should move inline with the rod.

* Also, when you put your bit in the chuck, make sure the bit shaft is sticking out of the chuck only as much as you need to drill the hole. This will help reduce the flex in the bit shaft when you're drilling.

* Thanks for the information, everyone! Today I replaced the collet (so that's what that thing is called, thanks Ron) on my drill, put in a new drill bit and drilled holes without using the press. No broken drill bits so I guess tomorrow I eyeball the press (thanks for the tips Tony). Doing the drilling while holding the drill made me really appreciate the press, so I hope I can get it straightened out. Yet another glass learning experience.
Thanks again for pointing me in the right direction!
Kate whose right arm is still vibrating from holding the drill too long

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