[modeleng] Re: Broken tap and sulphuric acid

How many flutes does the tap have?  How deep is it
inside the hole?  Is it a Carbon Steel or HHS tap?

Al Messer


--- Ron Head <ron.head@xxxxxxxxxxxxx> wrote:

> 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. 
> 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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