Accompanying dimensioned sketches show the dimensioned end
drawings of both the wooden "core" and the 1/4" plywood "end-caps" of this
spool. Common "allthread" is used as an axle as shown. This not only holds
the end-caps on the core ends, it provides hardware to attach in the lathe
chuck, and to the live-center. But before the axle is bolted in, four tacks
should be driven in as shown to secure that the end-caps will remain indexed
with the core. That is, the allthread's two nuts and washers will not prevent
rotary slippage.
In the event a spool will be used for several identical transformer
coils, it is a good idea to glue on the end-cap on the left (chuck end),
and still use the four brads shown. But on the center end, (the end you
see above), instead of brads, use #6-3/4" pan head SM screws to hold that
end-cap, so it can be removed and put back easily and securely.
Dimensioned End View of Spool Core
Notes: This is to indicate that the dims of this core are to be
1% greater than the actual laminate stack, to insure it will fit thereover,
once wound, taped, soaked, and properly dried. If you intend to spirally-tape
around the winding, allow more space! Say, 5%! The notches on all four
sides are to provide space for string so you can temporarily tie the winding
before you slip it off the core, before Formvar soaking. You may determine,
with your own experience and habits, these are unnecessary. The 0.2" depth
of these grooves is a suggestion only.
Jan
Rowland