Armortek

No, not plumbing, but something rather more useful

One of the perks of attending the Armortek Open Day is that there are usually a couple boxes of odds and ends of parts - usually over-stocks and mishaps.

I had managed to pick up a Sherman bogie frame with an M3 tap broken off in one of the bogie keep retaining holes.

Received wisdom was that it should be fairly easy to use a chemical etchant to remove the broken tap.

Yesterday, I managed to devote some time to the problem.

This was the part, with an M3 tap stuck in the middle hole. It appears this was to have been the last operation on this piece, as is always the way:
You can just see the pointy end of the tap poking through at the end of the slot:
With the aid of a £2.50 aluminium pan from Asda and a solution of BTR-10 Tap Removal Powder, I set it simmering yesterday afternoon.
Once it was up to temp, you could clearly see the bubbles emanating from the reaction with the tap:
It took several hours, but then I did keep removing to check on progress. One worrying factor was that parts of the aluminium also appeared to be fizzling but it doesn't appear to have affected the part.

Once washed and dried, I was able to complete the thread in the hole. The end is a bit bashed around from previous attempts to drive the tap out, but I think it will be perfectly serviceable.

Adrian.

Hi Adrian,

Nice tutorial and a good bit of information for those that haven't tried it before

Paul.

Hi Adrian,

Very nice and interesting tip.

It might be useful to point out that this powder only works when the tap is lodged in non-ferrous materials - i.e. bronze, brass, gun metal and aluminium and the tap is iron/steel not tungsten carbide.

Where did you buy this powder - a link would be useful.

Cheers,

Per

Hi Per.

Thanks for pointing out the limitations with non-ferrous metals.

I was banned from doing this indoors in case the fumes attacked our oven or extractor fan, hence the camping stove setup

The chemicals came from a company called TransLunar Technology back in 2009, but they don't seem to be in business any more.

Adrian.