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Alum as metal remover.

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bricky18/12/2018 21:53:13
342 forum posts
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I have nearly finished the body of a small carburetor.I was drilling and tapping a 8BA hole when the tap broke.I can't make a core cutter to cut round the tap as there isn't room.I recall reading of alum to remove broken taps but can't remember how it is used.I have a small tub of alum crystals,could someone enlighten me please as how to proceed.

Frank

Vic18/12/2018 22:43:05
1878 forum posts
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I think it depends on the type of tap. I think Alum works with carbon steel taps but I’m not sure if it works with HSS. You may need to get some Nitric Acid instead?

Neil Wyatt18/12/2018 22:44:00
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Assuming the carb body is aluminium, dissolve a heaped spoon of alum in a glass of warm water, leave the part in it for a few days, every day poking the remains of the tap with a needle until it falls out.

Neil

bricky18/12/2018 22:47:38
342 forum posts
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The body of the carb is brass ,will this be a problem.

Frank

vintage engineer18/12/2018 22:49:20
39 forum posts

What material is carb?

Fowlers Fury18/12/2018 23:03:51
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Don't use alum if the carb is aluminum, if it's brass (or a bronze) then try it.
You may find it of interest to read this article if the carb is aluminium: "How to dissolve steel without affecting aluminium alloy" :-
**LINK**

8BA is a bit small but I've had success with a diamond bur in a hi-speed mini drill. Ask your dentist for a used narrow, cone type; it will rapidly remove the bulk of the tap even if HSS. The remains can be picked out then with a needle. However with an 8BA tap you'll need a steady hand & good eyesight !

Mick Berrisford19/12/2018 00:06:56
113 forum posts

Posted by Fowlers Fury on 18/12/2018 23:03:51:

Don't use alum if the carb is aluminum, if it's brass (or a bronze) then try it.
You may find it of interest to read this article if the carb is aluminium: "How to dissolve steel without affecting aluminium alloy" :-
**LINK**

I've used alum in aluminium alloy bike bits for broken taps in the past with no problem. I can't see where in your link it says don't, in fact alum is recommended by a couple of posters.

Edited By Mick Berrisford on 19/12/2018 00:09:35

bricky19/12/2018 07:01:11
342 forum posts
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Thanks to all for your input.I am proceeding as Ian suggested.

Frank

RichardS19/12/2018 09:19:41
27 forum posts
1. Yes it works on HSS
2. Keep it warm (think coffee cup heater)
3. Replenish with water each day to make up for evaporation
4. Have the opening at the top
5. At 8BA you will need to initially encourage circulation in the hole (syringe?)
6. Clear debris from hole daily
7. Use a glass jar so you can see the bubble stream.

You should get a fine stream of bubbles rising from the hole (might be very fine or intermittant at 8BA). When that slows clear the debris. If clearing the debris does not result in a stream of bubbles after a couple of hours then replace the solution. If replacing the solution does not result in a stream of bubbles then it is probably done.
bricky07/01/2019 12:13:38
342 forum posts
41 photos

My first attempt was with some alum that I had in stock,nothing was happening but my son pointed out that it was 20 years out of date.I sourced some of amazon and within a week the tao has gone .I did as Niel suggested and piggled about with a needle and today to my delight and suprise a full depth 8 BA tap is gone.I have recharged the cup to make sure the threads are clear.I thank everyone for their help in this matter.

Frank

SillyOldDuffer07/01/2019 12:41:44
3621 forum posts
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Posted by bricky on 07/01/2019 12:13:38:

My first attempt was with some alum that I had in stock,nothing was happening but my son pointed out that it was 20 years out of date.

...

Or perhaps caught out by the name 'Alum' being used for at least six different chemicals, only one of which is suitable. You want Potassium Aluminium Sulphate, also called Potash Alum or Potassium Alum.

Of the true Alums, Sodium Alum might work as a substitute tap remover, but maybe not Chrome Alum or Ammonium Alum.

Some chemicals called 'Alum' aren't Alum at all: Aluminium Hydroxide and Aluminium Sulphate. These are useless for removing taps.

The confusing nomenclature is historical. Once a common name has caught on in a trade it's difficult to change it.

Dave

Chris Trice07/01/2019 13:06:47
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1135 forum posts
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I'm glad you posted that. I bought some "alum" online specifically to try it out and over a period of several weeks, absolutely nothing happened to the metal. Obviously not the alum I wanted.

Chris Trice07/01/2019 13:08:09
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1135 forum posts
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If anyone knows of a source for the right stuff, I'd be much obliged.

paul rushmer07/01/2019 13:22:05
71 forum posts
10 photos

Try eBay I bought some from a chemical company (south Essex I believe ) last year to remove a 10 BA from Dads new copper boiler. It worked well but took a week.

Paul

paul rushmer07/01/2019 13:51:49
71 forum posts
10 photos

Just looked at my eBay history, Minerals-water Ltd 800g £12 inc postage.

Hope this helps Paul

RichardS07/01/2019 14:11:13
27 forum posts
A rummage in my bookmarks leads here:

https://www.trustleaf.co.uk/aluminium-sulphate---iron-free-503-p.asp

Aluminium Sulphate 17% AL2O3 Iron Free

Tge concentration I used: 2 table spoons (30 ml) in a 720gm Branston Pickle jar ('cos it's "pickling").

Remember to keep it warm.
Chris Trice07/01/2019 19:50:35
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Posted by paul rushmer on 07/01/2019 13:51:49:

Just looked at my eBay history, Minerals-water Ltd 800g £12 inc postage.

Hope this helps Paul

Thank you very much Paul. thumbs up

Chris Trice08/01/2019 11:37:47
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1135 forum posts
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For anyone interested: https://www.ebay.co.uk/itm/500g-Potassium-aluminium-sulphate-Alum-Potash-Alum-Kalinite/140897858272?hash=item20ce2ab2e0:g:j3cAAOSw6EhUR4rw

Rik Shaw08/01/2019 13:13:32
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1193 forum posts
327 photos

You can buy alum rock chrystal from lots of outlets. I have used it on my pits for years now after developing an allergy to deodrants. I expect someone will tell me its the wrong sort of alum though. sad

Rik

Neil Wyatt08/01/2019 14:07:13
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Posted by Rik Shaw on 08/01/2019 13:13:32:

You can buy alum rock chrystal from lots of outlets. I have used it on my pits for years now after developing an allergy to deodrants. I expect someone will tell me its the wrong sort of alum though. sad

They work well though!

Alum is dirt cheap from Arabian food suppliers.

Neil

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