Broken drill bit in hole

Hi, I have just broken a 1.6 mm drill bit in hole that was to be one of the two threaded holes for the fire door hinge in my copper boiler. The first hole was all good. But the second hole was going alright, then snap. I was taking it very slowly as I know that copper can be a bit grabby.

Can anyone give me some ideas please on how to get round this problem. I've snapped the odd drill or tap over the years, but never this small. I've googled the problem, but they all seem to be about much larger bits.

Thanks

Garry

Try soaking in an Alum solution. This will not dissolve the steel quickly by it will reduce the diameter to the point where it will fall out.

The solution works best with moderate heat and will not affect the copper.

Brian

Thanks for the reply Brian.

I saw someone using Alum, but that was on a steel part. I was not sure about using it on copper.

Garry

The alum will only work on steel or cast iron and will not affect the copper.

Brian

My experience. I recently dissolved a 5mm or 6mm tap from what was to be a repaired brass feed screw nut. The old nut had been bored out and plugged with a solid brass plug before boring and threading and I was going to securely pin the parts together with a brass threaded screw as well as loctiting the assembly.

The tap was about 20mm, perhaps more, through the hole before breaking, and total thickness was around 25mm. Took some time to dissolve, needed as concentrated a solution as practical and required to be kept very close or at boiling point for any decent reaction rate. Afterwards I wished I had stuffed the reaction vessel in an old pressure cooker, to raise the temperature a lot more!

At one point I experimented a bit and used some small pieces of pure copper - to ensure as free a flow as possible of solution past the broken tap - to support the nut away from the vessel. Solution turned decidedly blue, so the copper chips were removed. Eventually the tap was dissolved virtually completely from the brass . Slow but effective.

So, it definitely works for dissolving steel from brass items. I would use it again, so am keeping an eye out for a sensibly priced alum supply. Small quantities on epay are expensive (used by hobbyist dyers, in particular). It is not aluminium sulphate (as reported on one thread). It is the double salt potassium aluminium sulphate (usually) - with an awful lot of water of crystallisation.

You can get alum from middle eastern food suppliers really cheaply in 500g bags.

Neil

Are there not two different Alums? One being useless

Ah NDIT got there first !

Edited By Dave Halford on 10/12/2019 20:57:17

Garry,

As you are making a boiler, and therefore have pickle for cleaning it up, just put your boiler in the pickle and leave it overnight. You will likely find your drill will have disintegrated, or can readily be removed the next morning.

I first tried this with a similarly sized broken drill in brass and, much to my surprise, found the drill was broken up the next day and basically dropped out of the hole. I used clean citric acid (i.e. which had not had copper in it) as I didn't want a layer of copper depositing on my brass.

Regards Tom

There are many 'Alums'! In chemistry Alums are a family of related compounds. They have different chemical properties, as unlike as cast-iron is from mild-steel, tool-steel, or stainless.

The word is also used loosely by various historic trades. The 'Alum' in tanning, may not be the 'Alum' used in Dyeing, nor is it the 'Alum' used in cookery, or as a fertilizer. Or perhaps they are! Alum might be the most misleading name in common use, only slightly more precise than 'thingy'.

The Alum needed for removing broken taps and drills is NDIY's Potassium Aluminium Sulphate. Although other Alum's are likely to have some corrosive effect on steel, so does water given long enough. My advice: accept no substitutes! Potassium Aluminium Sulphate is widely available, for example from Amazon.

Dave

I've just come to this thread for obvious reasons!

I was drilling a 2mm hole through the ali hopper into the CI liner for my Economy Engine when the drill broke just as it was breaking through into the bore of the liner, there is about 20mm stuck in there. The hole is for the oil drip feed for the piston.

So, as I can't get at either end of the broken drill easily I thought I check to see what others have done here. I've never used Potassium Aluminium Sulphate so I plan to give it a try being careful to mask the bore to protect it as best I can, fortunately it has still to be honed. My question is how much Alum will I need, will 100g be enough? I'm assuming it is diluted in water but what ratio for dilution.

Thanks in anticipation for any help or suggestions...

Just 5 posts above yours?

Took some time to dissolve, needed as concentrated a solution as practical and required to be kept very close or at boiling point for any decent reaction rate.

georgeweil.com lists Alum Mordant (Alumimium Potassium Sulphate) - 500g

£8.60

" Synonyms: Potash Alum, Aluminium Ammonium Sulphate. "

They are out of stock as their supplier is closed.

Rob

Using pickling acid will certainly do the job without harming the copper. Heat it up to speed the process.

I once made some earrings from 1.5mm OD gold tube. The tube was made with a core of 1mm iron wire to support it when it was coiled to make the helix required for the earring design. The iron core was removed by immersing the helix in 10% H2SO4. I had to heat the acid, but it still took about 2 days to remove all the iron.

Gary,

I am more interested in how they made the gold tube. Was it simply iron wire dipped in melted gold - a bit like making candles?

We reclaimed 3.6kg of Au from, I think, over a tonne of turbine scrap by dissolving away the base metals, before dissolving the gold and recovering by sulphiting the solution. Holding a 3.6kg cone of 99.99% gold and flattening the point by (quite gently) dropping the cone, on a flat surface, was quite satisfying after months of time spent on the job.

NDIY.

I made the tube from 0.5mm sheet, which I first rolled down to 0.25mm and cut a strip just a little wider than the circumference of the required tube. I cut one end of the strip into a 'V' and then used a swage block, and a series of suitably sized rods, to bend the strip lengthways into a 'U' shape. The end of the 'V' was then poked through a suitably sized hole in a draw-plate, and then pulled through to start closing the 'U' shape into a circle. Smaller and smaller holes were then used until I had a hollow tube - albeit too large an OD - which I then soldered along the seam. I then used smaller and smaller holes in the draw-plate until I reckoned it was just right for inserting the iron wire. With the wire inserted I could then continue using smaller and smaller holes until it got to the required OD. After a final annealing I could then coil the tube around a former to make the required helix.

Acid then got rid of the iron core.

Clever chap, making your own tube at that size! I thought it might be a product available to the trade - from someone like JM - for these purposes,

Sorry to disappoint. Making small tube is not difficult, just time consuming.