[modeleng] Re: Broken tap and sulphuric acid

Many thanks, made a jig and bolted to casting and managed to drill out
broken tap, many thanks to everyone for all the ideas.=20

-----Original Message-----
From: modeleng-bounce@xxxxxxxxxxxxx
[mailto:modeleng-bounce@xxxxxxxxxxxxx] On Behalf Of Ron Head
Sent: 23 October 2007 20:45
To: modeleng@xxxxxxxxxxxxx
Subject: [modeleng] Re: Broken tap and sulphuric acid

Hi Kevin

You can always heat the casting to dull red and let it cool slowly.
This will have the effect of annealing the tap, and it can then be
drilled out.=20
To prevent the drill wandering off into the phosphor bronze, make a jig
plate and clamp this firmly over the hole.  With luck you will be able
to drill the core out, and the threads will just fall away.

The down side to this, of course, is the possibility of distortion to
the casting.

Regards
Ron

----- Original Message -----
From: <kevin.osborn@xxxxxxxxxxxxxxx>
To: <modeleng@xxxxxxxxxxxxx>
Sent: Tuesday, October 23, 2007 11:24 AM
Subject: [modeleng] Broken tap and sulphuric acid


>I have broken the end of tap in a phosphor bronze casting, and I have
> heard a rumour that a couple of drop of sulphuric acid will dissolve
the
> tap. Is this correct? And if so where can I buy / get a small
quantity.
> I have been offered 25 litres, but cannot get anything smaller.
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