Using the agraffe cutter

[Overs Pianos]

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List,

I got a private email requesting further information on the use of 
the agraffe cutter, so I thought I'd post my reply to the list also 
for those who are interested.

>. . . .  Do you use it in a drill press or in a handle manually?

We use two methods.

The first and oldest;

The drill is fixed to a bench vise to face the operator with the axis 
of the drill in a horizontal position and at about waist height, 
using an adapter I made for mounting the drill to the tool post of 
the lathe.

A stop will need to be fitted to the shank of the cutter, to ensure 
that the cutter enters the string hole to the correct depth. Too 
little depth will not give the donut shape the correct profile (the 
string contact with the brass will be too wide). Too much depth will 
result in a sharpened inner string hole profile which will not allow 
the brass to withstand the string up bearing pressure.

The drill is run at low speed only, since very little material is 
removed, and the faster the drill, the shorter the tool life of the 
cutter.

We use a brass handle for holding the agraffes up to the cutter. This 
is made from a piece of 15 mm hex, free machining brass say 150 mm 
long. A threaded hole is cut in each end for a different kind of 
agraffe thread, eg. we have one with a 1/4 x 36 tpi in one end and a 
7/32 x 36 tpi in the other. The body of the holder is tapered at each 
end to provide good operator vision, and the threaded holes are free 
bored such that the agraffe will only be held by a couple of threads. 
This allows for fast insertion and removal of the agraffes from the 
holder (This holder is also handy for polishing agraffes).

With the agraffe in the holder, it is moved towards the cutter being 
careful to hold the agraffe such that the axis of the string hole 
lines up with the axis of the cutter. The holes are cut from both 
sides. After cutting the second side of agraffe holes, it is turned 
and the first three holes cut are just lightly cut again to ensure 
that no burr remains in the string hole.

The second and most recent method.

We now own a small three axis mill/drill with tilting head (which we 
purchased for making action models, but it's also very useful for 
other piano type small engineering jobs).

The cutter is held in the mill which has accurate depth stop control. 
A small flat surface is mounted on the mill table, and set up as a 
backing for the flat of the agraffe. The agraffe is held with the 
holder as described above for the first method. The depth stop of the 
mill is adjusted to allow for the correct insertion of the cutter.

The second method is by far the best. A small drill press could be 
used instead of the mill, but accurate depth control is more 
difficult to achieve with a standard drill press.

Ron O





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Website:  http://www.overspianos.com.au
Email:      mailto:ron@overspianos.com.au
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