Removing broken drill bit

[Deleted]

Hello folks. 1/4" deep no 47 (1.99mm) hole in a gm casting but the tip of the bit broke in the bottom of the hole - there is about 1/8" depth to the back of the bit. I've tried poking around with a pin and also with a smaller drill bit but no success. I need to tap the hole when the bit is removed. Any thoughts would be appreciated. Thanks, Dave

[AndrewP]

Pickle for a day or so, or alum solution if you have it lying around.
Then fresh hot pickle to remove the copper plating from your gm casting.

Cheers, Andy

[Deleted]

Thanks for that. I don't think I have any alum solution lying around, just plenty of the usual household solvents. Unless of course one of these is fiendishly alum solution in disguise. Also, I have to be careful not to remove too much of the casting as I need to tap it; the broken bit is for a tight thread anyway so I do have a little to play with. Dave

[redmog]

Dave.

The alum solution attacks the ferrous metal, thus deteriorating the steel without harming the non-ferrous. So they say!
Have a look at this -
etsymetal.blogspot.com/2009/01/tip-broken-drill-bit-removal.html

Chris

[jackrae]

If you go to e-bay and look up the item number 290309587180 you'll find a product listed as BTR-10 (broken tap remover) which is sold for around £8.00

No connection, just a satisfied buyer of some of the same
Jack

[redmog]

That's the stuff!
Ever 'Model Engineer' should have some and hope never to use it.

Tel - Any photos of Shawki's birthday.

Chris

[Deleted]

Thanks chaps, I'll be off to get this as soon as possible. Dave

[Deleted]

Thanks to everyone, the offending bit end is removed, hole threaded and all is sublime (!). It was so encouraging to see little bubbles coming out of the hole as the bit oxidised (although it may not actually be oxidisation, but you know what I mean).

Ta again,
Dave