Re: Extracting sheared bolts

"Roger Martin" <[email protected]> wrote in message
news:[email protected]...
> I've heard of spark erosion machines used on very old and rare equipment
> which cannot be replaced or will cost squillions to have re cast if
damaged
> beyond repair. Interesting process - like a spark plug I suppose. There
was
> a UK based model magasine - Model Engineer's Workshop that had plans.
>
>
> --
>
http://cgi6.ebay.com.au/ws/eBayISAP...land4x4hire&include=0&since=-1&sort=3&rows=50
>
>
Not quite like a sparkplug more of a copper tube which has current passed
through it whilst pumping a cooling fluid through the centre, the whole
thing the vibrates to break the "weld" that occurs. This method is widely
used across the engineering industry and will even remove solid tungsten
carbide (broken easyouts are no problem) The drawback is the part needs to
be removed from the vehicle first and that if too much current is applied
the parent metal gets eroded as well If the part has to be removed from the
vehicle then its easier to set up on a machining centre and drill the
stud/bolt out.
Al


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alan wrote:

> Not quite like a sparkplug more of a copper tube which has current passed
> through it whilst pumping a cooling fluid through the centre, the whole
> thing the vibrates to break the "weld" that occurs.

Not quite how it works, the electrode doesn't touch the work.

> The drawback is the part needs to be removed from the vehicle first
and that if too much current is applied
> the parent metal gets eroded as well If the part has to be removed from the
> vehicle then its easier to set up on a machining centre and drill the
> stud/bolt out.

Some tap disintegrators will actually work in the vehicle - like the
Gingery machine I mentioned.

Steve