Winding coils on lathes, preparing coil forms on lathes.
I've tried all sorts of methods of winding coils on the lathe, some were
disasters, and others brilliant. Most were 4.5", 6.625", or 10.75" in
diameters. (I've probably wound 4 or 5 dozen coils on the lathe in the past
But all in all, I think I found the only way to fly!
In fact, I have a more difficult time winding primaries than secondaries!
I take the whole idea of using a lathe to a new level for TCs-- that
involves using the lathe for it's original purpose! And this involves a
time-consuming, but well-worth-it procedure to prepare the coil form before
laying the wire on.
Above all, ANY turning of PVC pipe requires the lathe's center.
A PVC end cap with a perfectly centered hole works great.
Pipe spinning in the lathe without a center is a receipe for disaster.
First, I've noticed that PVC is rarely clean or perfectly round!!
To remedy this, I take several thin passes on the PVC to remove any dirt or
grime, and also to make the pipe spin as true as possible.
After several passes of the cutting tool, the PVC will spin almost perfect.
A true spinning coil will accept wire much better than one wobbling.
I usually do this at a slow speed, with a medium-slow feed rate.
Care must be taken not to take too deep a cut, or else the PVC will tangle
itself everywhere. The last place you want PVC turnings is wrapped around
the lead screw! And that's exactly where they like to gather if you don't
keep an eye on them. No need to rush anyways.
Now that I've figured out it's not impossible I always make threaded coil
forms. 22 gage wire close winds at 33 TPI. A lathe will cut 32 threads per
inch. This is close enough for me! The lathe MUST be in back gear for
cutting threads, and VERY fine passes are essential. I've take on average
4-6 passes, in the lowest speed possible.
If all goes well, you end up with a really large plastic bolt!
Now I have a perfect threaded-form, bright white [or gray]. This can be
well varnished, and is ready to accept wire. I also wind the wire onto the
form on the lathe, also in the slowest speed, back gear, and in reverse. To
keep tension on the wire at all times, I have a cloth loop bolted to floor
that it passes through on it's way to the pipe.
I always leave 1/4" of threads on either end of the pipe, to show that the
form was in fact threaded. This adds a certain elegance and appeal to the
coil, totally disguising the former sewer pipe. Even the snobbiest of
machinists will have to take a double look at the form!
The finished coil is also well varnished.
I plan on adding a step-by-step "how-to" section with photos on my website
of the exact procedures.
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