countersink drill bit question

[Alex Franke]

I have some of those tapered countersink drill bits where you use hex set screws to set the depth of the countersink and the depth of the hole. (Because it's tapered, it should be the same length as the screw.)

The problem is that twice now the bit has snapped where the set screws are holding it in place when I'm drilling for short screws (1") -- I can only assume because the set screws are against the twist and not the solid shaft.

Any advice?

[LCHIEN]

My comments are this:
Cutting tool steels are always brittle - that's the character that makes them hold an edge.
Drill bits have not a whole lot of cross section left after you cut the flutes in them.
If you are working way down the end (in the last inch) of tapered bits then you are working in the thinner part of the bit, even weaker.

Given the above points, I am always very careful when tightening the set screws.
I'd rotate the stop so that the set screw lands on the flat, not in a flute and especially not on a undercut part above a flute. I then teighten only the supportred screw, no both screws (if there are two). And just tight enough to do the job.
Perhaps if the stop is so far down a slim bit maybe you should go to a smaller sized bit or a fatter screw, if possible.

[cabinetman]

I've encountered the same problem, and just switched to a regular drill bit. I don't extend the bit the length of the pilot drill. I like to have some solid wood for the screw to bite.
.

[bthere]

I have done that more than once, also. Like cabinetman, I have just converted to a standard bit and I take a little bit more time and use a counter sink for the head.

[walter_lars]

sears use to have a set of conter sink drills that were flat like a spade bit and had a stop that was held in notches with a spring I recall that they had a very small one like for size 4 x 1" I rcall useing them for 1/2" thick wood Iwas useing to make boxes a quick search of sears.com didn't turn any up I am going to keep googleing around and see if I can find any if I do I will post the link here

[Alex Franke]

Thanks for all the input -- I ended up just switching to a regular drill bit.

I can never seem to get the set screws lined up just right...

[drillman88]

I don't know if this will help but as you drill into the work piece be sure to back your bit out to let the flutes clear and then go back into the work piece.
The flutes can get full and bind with the applied torque to snap small bits.
The regular bits do seem to hold up better as well.