>> I've never tried to make jacks, but reading John Barnes' "Making a spinet by
>> traditional methods" it seemed not impossible, even for an amateur builder.
>> How the jigs you tell about are done? (pictures, decriptions...)
To which David Jensen wrote a lengthy and thoughtful answer ending:
>I've gone on too long once again...<
Not really,in particular the emphasis on tolerances is very worthwhile.
I my days as shop foreman of a middle-sized organbuilding company I
got to a point where jigs became an obsession, an art in their own right. I
visited training courses and newest industrial techniques and read the
newest books, obtained the data sheets from the pneumatic people. This
carried over into my self-employment. I have more than one shelf of jigs in
the attic, mostly unused now. I have with practice reduced the number of
machine jigs for making jacks to exactly two, both for the drill press: one
for drilling the bristle hole and one for the axle hole which is adjustable
for axle height for the 4' jacks. Everything else has been relegated to the
attic. I have learned to do it better and faster without these. I even
think I can or could almost compete with Swainson in the meantime, though I
have absolutely no intention of this. I also have the usual bench-planing
jigs but these are not necessarily single-purpose jigs. I use beech, mill
the sheets to almost jack thickness and cut off lengths for the particular
instrument (slightly too long, of course). These are planed square across
the top with one of these bench jigs and a red pencil line across the
endgrain of the bottom. Then, the blanks are cut off, slightly too wide.
These are planed to width and slightly conical (less than a mm) with
another of these bench jigs. The slots are cut with a 4.5mm milling machine
cutter and the damper slots with the bandsaw, no special jigs required,
just depth stops. Admittedly, the machines at hand will dictate how this
can be done best. I have the good fortune to have very small but extremely
good patternmaker's tablesaw, long since disappeared, as has the company
itself, from the market.
Now jig No.1: the bristle holes are drilled; this jig uses the bottom of
the tongue slot as a stop, so jacks of any length, top or bottom, can be
drilled with the same setup. The finished blanks are fitted - planed with
the trusty No.4 with Hock blade - into their requisite mortices of the
registers and numbered. Now jig No. 2; the jacks are drilled with the
tongues in place .7mm through the thin tine and the tongue but not into the
thick side. I use Rose .6mm English Brass as axle. Stick together,
The tongues are made from holly on the above saw without any
special jigs by making cross-grain profiles and cutting them off like
sausage. Such parts have always been made that way. I use milling machine
saws here, too.
I don't deceive myself into thinking this to be in any way "earthshaking" -
far from it. I have learned from experience that straightest way is the
easiest and fastest. I now make the jacks for each instrument individually,
making only the tongues in larger batches.
I've gone on far too long. too.
Keyboard Instrument Maker