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Saracen
26-07-2015, 02:09 PM
Further to my recent RFQ on removal of a tap from a machined aluminium part, I received a couple of PMs suggesting using 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:

http://i169.photobucket.com/albums/u216/sherman_tank/Tap%20Removal/DSCN7505-reduced_zpsqbd6lqa3.jpg

You can just see the pointy end of the tap poking through at the end of the slot:

http://i169.photobucket.com/albums/u216/sherman_tank/Tap%20Removal/DSCN7508-reduced_zps0tjk2voz.jpg

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.

http://i169.photobucket.com/albums/u216/sherman_tank/Tap%20Removal/DSCN7510-reduced_zpsbzbifho5.jpg

Once it was up to temp, you could clearly see the bubbles emanating from the reaction with the tap:

http://i169.photobucket.com/albums/u216/sherman_tank/Tap%20Removal/DSCN7515-reduced_zps2l1kau0o.jpg

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.

magicniner
26-07-2015, 03:38 PM
Good to hear you've got it sorted, and excellent to see you share the solution to help any future machinists searching for a similar solution,
Regards,
Nick

njhussey
27-07-2015, 09:25 AM
Glad you got it sorted, do you have a link to the powder used?

I'm sure that I'll be in the same situation in the near future..... My solution when I broke a tap in the top plate of my gantry, was to drive the broken tap through and use a bolt instead of tapping as I could get to the underside and the nut isn't in the way.

Gotty101
27-07-2015, 09:37 AM
Thats really cool, never knew such thing existed. Hopefully ill remember when i have the same problem.

mekanik
27-07-2015, 10:46 AM
Couldn't find the product mentioned but try this link
http://www.tap-die.com/contents/en-uk/d296_Tip_Remove_Broken_Tap_Drill_Reamer_Tap_and_Di e_Co.html
Mike

Saracen
30-07-2015, 09:12 AM
The powder I used was purchased from a company called TransLunar Technologies, back in 2009, but they don't seem to exist any more :(

Adrian.

mekanik
30-07-2015, 09:41 AM
Nice find Adrian
I have been in Engineering for 50 years and never come across that one,good news is Alum should be pretty easy to get hold of.
Regards
Mike

Crazy L
31-08-2015, 05:43 PM
Wow, Awesome, I've never heard of that one and I've worked in some right old school shitholes in my time. Normally it's the old boys who share this stuff.

Robin Hewitt
01-09-2015, 04:28 PM
Amazing, I typed into google, "Alum dissolves" and "steel" popped up on the drop down menu :beer:

I never knew that.

Then I tried typing "dissolves steel" and "alum" was the only real suggestion.

routercnc
01-09-2015, 09:13 PM
Not seen that one before. Only seen spark erosion for removing taps (from steel I think).