Drilling the hard stuff

Hi Peter,

Is this still about your liquid fueled rocket motor ? How's progress been recently ? I'd be interested to hear an update and I'm sure lots of other people here woulf be too.

Cheers,

If you can get hold of some Diagrit Hardcut drills they'll make short work of it - they are designed for drilliing out HSS taps, etc. using normal workshop equipment.

I've not seen any advertised for years but I'm sure one of the tool manufacturers must do something similar.............

I have used carbide drills in fairly hard (blued high carbon) steel but I don't know how it compares on the Rockwell scale. Eternal Tools are good for both carbide and diamond drills.

If you haven't used carbide drills before I suggest you buy two or three of them. They are extremely brittle and will shatter at the slightest hint of mis-alignment, wobble, or side load, and yet they need to be pushed into the work firmly to cut well.

Cliff Coggin.

Greetings Peter, Carbide will indeed work. The drill should have straight flutes and a split point. Use lots of high steady pressure. The chips will exit red hot and almost molten. A rigid setup is a must. If the hole is a through hole then you will need to back up the part with steel that's as hard as the part. Softer steel risks breaking the drill. Cheers, Eric

I've used the "drill anything" bits with success. They look like masonary bits. The technique is to use lots of speed and lots of pressure. The friction heats the metal which goes soft and the drill then cuts it. I've seen files and hacksaw blades drilled like this. Mind the swarf though, it can be white hot.

John

you could try a stellite drill, such as

cheap at list price, but they are usually discountable, and other sizes available.

Dave

oops, just notice they are out of stock. must be available elsewhere, or direct from delloro Dave

" you could try a stellite drill, such as

not cheap at list price, but they are usually discountable, and other sizes available.

Dave "

I have some 4mm carbide tig electrodes - they grind much like stellite, would a 'drill' fashioned from that do?