Broken tap

[Jon Page]

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I would laboriously route a slot in the top with a Dremel Tool and carbide
bit 
for a screw driver to remove the tap.

Second plan of attack would be to drill a hole with the carbide bit and 
attempt an easy out.  Or perhaps consult a machinist first.

As a final endeavor, I would use the carbide bit and drill out as much of the
tap as possible and try to remove the loose pieces or drill them out with a
larger bit.  Don't drill all the way through, you want to preserve the threads
on the bottom if possible.

Once the tap is removed and the hole is clean, the threads can be rebuilt with
MarineTex Epoxy or maybe a helicoil.

The repair I made with epoxy a while back used a drill bit shank which was the
same diameter as the inner diameter of the threads on the lower portion of
the hole.  I applied a mould release to the shank and inserted it up through
the
bottom.

Apply epoxy first to the walls of the top section and then insert the shank so
that it sticks up above the plate enough to swab the shank with more epoxy
and pull it down into the hole so as to fill it as much as possible and still
have
a little protruding above the plate.

Once cured, remove the shank and start you tap from the bottom through the
good
remaining threads. That will chase the tap tight up the center.

Make sure you have the right threads per inch . . .

Then insert a new agraffe and fit it precisely, don't stress the threads by
overturning.

Good Luck, take you time, it's a long, tedious drilling operation.

Jon Page

At 11:25 AM 5/29/99 -0400, you wrote:
>A customer was referred to me by a very good technician who had the miss 
>fortune of breaking a tap while retapping agraffe threads.  The tap broke
off 
>nearly flush with the plate.  This is a S & S S? circa 1920's.  It is the 
>fourth agraffe in the tenor section.  The tap is firmly imbedded into the 
>plate.  It will not turn.  I made a tool with two rods to fit into two of
the 
>four flutes to attempt turning it out.  The rods broke.  Is there a 
>commercially available broken tap removing tool?
>
>I attempted to drill the tap out.  My titanium bits did little.  Though the 
>grinding bits I used to flatten out the top seemed effective in removing 
>material.  Is there a solution here?
>
>The customer does not have enough money for rebuilding the piano (which it 
>could use) so removing the plate and coming in from the bottom is out.
>
>My last idea (which I don't care for) is to drill a new agraffe hole infront 
>of the old.  There is plenty of room in the plate.  Will this cause any
undue 
>weakening in the plate, and how badly will the tone on the now 1/2 - 3/4
inch 
>shorter be affected?
>
>I know this is not your everyday type of repair, but any input would be 
>greatly appreciated.
>
>Andrew Remillard
> 

Jon Page,  Harwich Port,  Cape Cod,  Mass.  mailto:jpage@capecod.net
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