Broken drill bits

[Melanie De Castro Pugh]

Hi chaps, I have yet another problem and would welcome any advice!

I am making a bangle from 2mm copper sheet and want 1mm holes drilled every half centimetre or so around the edge. I have got a fair few done using my Dremel as a pillar drill but when the inevitable happens and a bit breaks, I'm having a heck of a job getting the broken tip out of the semi drilled hole. Some I've managed to retrieve by using a centre punch on the reverse and bashing it back through but this only works when the hole is deep enough that I can see a dimple forming on the other side.

I've been using HSS bits and also carbide microdrills, I seem to get the same levels of breakage with both so go with the cheaper HSS ones in a multichuck rather than the expensive ones on a 3.2mm shank. I've tried drilling speeds of 5000-15000 rpm.

So if anyone has any solutions, I'd be so grateful! Thank you x


Melanie

http://www.spinysharklythings.com

[Kwant]

I have used with remarkable success, alum dissolved in hot water to remove broken drill bits in silver, they just dissolve away, I am unsure what the effect on copper would be so you would have to try it first on some scrap to make sure it did not dissolve the copper too.

I used a saturated solution of alum and kept it warm in a hot water bath, the last time it happened it took about a half hour for the drill bit to be gone, with a bit of occasional stirring and poking. You can get alum at the chemists.

I also use burr saver when drilling and that drastically reduces the number of breakages in the first place.


A quick check on google would suggest the copper will be safe and unaffected.

[ps_bond]

Dissolve the bit out either with an overnight soak in some pickle and then a jaunt in an ultrasonic or use alum. You're bound to have some copper dissolve, but it shouldn't be too bad. Test first, As Kwant suggests!

As to why you're getting breakage, run the Dremel as slow as possible (slower than they can manage is better - you want the same linear speed as larger bits, but the small diameter means you get that at lower rpms if that makes sense), have the minimum amount of bit protruding (but don't grip the flutes in the chuck), don't put too much pressure on the bit and do not side load it. The bog standard jobber HSS 1mm bits I use will cope with that job, but I do run them slow. And yes, do use burr life, beeswax or a drop of oil as a cutting lubricant.

[Melanie De Castro Pugh]

Thank you both, why didn't I think of dissolving them in pickle.... Duh! I'll do that at the end as it's flat at the moment and won't fit in my bath, but after I've curved it should do the trick. I can finish the offending holes by hand then.

I have beeswax, so will give it a whirl (quite literally!) with that :-)


Melanie

http://www.spinysharklythings.com

[ps_bond]

I've always used old pickle to do it and not put it back in the main pot, BTW.

[Wallace]

I use wd40 instead of beeswax now (it comes in a pen type applicator too) I dab a little on a small lid and dip the drill and burrs into it. Very slowly, as Peter mentions, is indeed the key to reducing the breakages.

[Dennis]

For years I drilled happily with hardly a breakage, using Busch mounted drills on 2.35 shanks (Cooksons 972040-150) . Then I tried the HSS version and had repeated problems until I gave them up. I think you will find HSS just too brittle below about 1.5mm. There also seems to be more of a problem with copper which feels sticky to drill. Dennis.

[Melanie De Castro Pugh]

Sticky... That describes it perfectly! Well thanks to all your tips and help I drilled the last third of the holes on just one bit! It needed fresh beeswax for each hole, and sometimes two or three applications. While I had a bit of a grumpy five minutes that it made for a very staccato work flow, it saved more time than repeatedly changing drills! The pickle method worked a treat too, just need to give it a blast in the ultrasonic now :-)


Melanie

http://www.spinysharklythings.com