Broken drill in Aluminium - - how to remove it?

[AndyBoyd]

I'm making a telescope mount from Aluminium, and have just broken a drill. I was drilling 3.2mm holes tapping for 4mm screws into 10mm thick aluminium plate and the drill broke, leaving a bit in the half drilled hole, with nothing sticking out.

Is there a simple way to remove small drills when they break like this?

I was using metal lubricating fluid and had drilled 8 of the 12 needed holes in this plate so somehwat annoying I must admit, but c'est la vie I guess

Any tips on roads to recover this situation would be useful as I do really need a screw in this location and don't fancy sourcing another piece of aluminium plate shaping etc

thanks in advance

 

[ro]

I had the same thing happen when I was making a steam engine from brass. I managed to drill out the hss drill that broke with a larger cobalt tip drill and then put an insert into the hole and drill the insert to the right size.

 

[AndyBoyd]

Thanks Ro - I'll try and source a large cobalt tipped drill then fill the hole somehow

Cheers

 

[Oryxdesign]

If it isn't going to be blind tapped sometimes you can drill in from the other side and tap it out with a punch.

Simon

 

[Modernist]

I have seen them removed by tacking a welding rod onto the end, bending it over and pulling it out! Mind you that was at Cosworth's in the 70's

 

[jasonB]

You can melt them out with Alum in nonferrous metals though not tried it with Alloy.

As Simon said punch it out from the other side if possible

Also if you want to avoid snapping your taps then your holes should be 3.3mm for M4 coarse not 3.2.

Jason

 

[AndyBoyd]

I'm afraid the aluminium plate is 200mm x 180mm so I cannot drill and push from the other side.

I haven't got any welding kit so I'll have to try and drill it out

3.3mm hey Jason, my book says 3.2mm for aluminium, so far the tapping has gone well so I'll stick to that

cheers everyone - excellent advice as ever

 

[Oryxdesign]

M4 X 0.7 tapping size would be diameter minus pitch or 4-0.7=3.3mm
Simon