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re: beginners question



Original poster: jdwarshui@xxxxxxxxx

Making a primary:

You can get perfect spirals by winding the copper tubing  between two
very stiff disks of plywood spaced apart with oversized fender washers
and secured across with a bolt. Arrange so the tube is a bit tight
between the disks. Slip the tube next to the washer (tangentially) and
run a wood screw through the plywood into the tube to secure it for
winding.

The tube will unwind a bit when it is removed from the form (spring
back). The spacing will be around 1/8 inch between winds for 1/4 inch
O.D. tube. You can wind two pieces of tube side by side if greater
spacing is required or you can carefully open up a single spiral by
hand.

Must emphasize using stiff plywood. Glue two sheets of 3/4 inch
plywood together for each disk. As you wind any misalignment of the
tube faces will cause the plywood to spread apart, then you can get a
submerged tubing  mess. If I had to make an unusually large pancake
primary, (like a few feet across) I would use metal plates instead of
plywood and keep a few deep reaching C clamps handy to prevent form
spread.

Leave yourself some elbow room and add a few extra winds, you will
want to tap for the correct inductance then trim away excess before
mounting to a board or support blocks.

You can also space out winds by weaving nylon rope between the tubes
(starting from the center). When finalized saturate the rope with
polyester resin or watery epoxy (tropical epoxy)


Working plastics:

 You can get spiral down cut router bits and this should help with
many difficult materials that tend to bounce or chatter. Feed rate is
everything with many thermoplastics, if you go to fast you get a rough
cut, go to slow and heat starts gumming up the saw kerf and you get
galling.

A negative rake blade with a high tooth count is what you will
probably want for cutting most plastics with a table saw.

The classic finger loosing maneuver is to cut P.V.C. tubing on a table
saw or chop saw without making absolutely sure that the stuff cannot
start spinning. A tiny C clamp on the end of the pipe or between two
pipes will save fingers (and nerves!)


Working Stainless steel:

If you ever need to drill  stainless steel clamp the stuff down like
it was a wild horse and stay out of the line of fire. Stainless can
cool off and shrink down around a rotating cobalt drill bit, then you
get a Metal Frisbees Of Death.

Good luck from Jared Dwarshuis