Broken centre drill recovery

[John S]

Bought some TiN coated 4.8mm stub drill bits in cobalt HSS.

I tried starting a hole edgeways through the teeth on an aluminium timing pulley and watched the bit bend like a banana

I went up and down a few times to see if it could straighten itself up but it didn't, then I reached for one of my trusty old Slocombe's which put me back on true instantly.

Did I buy the wrong thing? :confused:

Here's a spotting drill

http://cgi.ebay.co.uk/3MM-NC-SPOTTIN...mZ140320534140

No connection with the sale just came up in a search. Note the very short flute length to give rigidity.

John S.

[Robin Hewitt]

Here's a spotting drill

Hi John

I saw them, bought one in 8mm, seems okay but I was not instantly converted. Still like my Slocombes

Hi Gilly

I have tried that in the past with varying degrees of success. If the broken end starts to turn it usually prepared to drop out. If it flips and suddenly becames a lot taller, being edgeways on, it is goodbye carbide cutter. That's why I favour attacking them with a cheap masonary bit if I can't be fagged to set up and spark it out

best

Robin