more on broken taps

Hi Jon:
Have you had trouble with the drills breaking?
I always found them far trickier to use than home made drills because the
flutes in CB drills are ground so deep.
The most painful part of making your own is shelling out for a diamond
wheel.(150 bucks CDN)
I use broken off Garr cutter shanks as my source for really top grade
carbide.
I make 2 flute stubbies; the flutes and relief are ground freehand on the
corner of the wheel, just long enough to penetrate 3 diameters or so.
I put on split points at 120 deg or thereabouts.
These drills are really robust; you can chuck them up short and push hard to
keep them cutting.
I flood the work with cutting oil, and usually drill right through the tap.
Works really well and it is fast. (useful if you're expexting the boss to
show up any moment!!)

Cheers

Marcus


Jon wrote:

>If you need to remove taps, one other trick that works in some cases
>is to use a fairly hefty solid carbide circuit board drill, about .040"
>or so. If there is a relatively flat spot on the top of the broken tap,
>let the drill bit down until it just barely touches the tap, and let it
>chatter around there for a while, lowering the drill just a hair at a
>time. Eventually, it will make a fairly good dimple in the tap, and then
>you can apply a little more pressure and start drilling into the tap.
>Once you have a hole .050" deep in a small tap, or maybe .1"
>deep in a larger one, you can put a center punch in the hole and
>shatter the tap with one whack. Then, you can usually pick the
>fragments out without excessive damage to the hole.
>