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Re: [TCML] Secondary Coil Form



On 9/12/12 6:24 PM, mddeming@xxxxxxx wrote:

It comes down to this:

White pipe -- always OK
Grey pipe -- usually OK
Black pipe -- Occasionally OK



Leaving aside green pipe (SDR, used for sewers and such) and the pinkish stuff that has UV inhibitor used for landscape watering.

White pipe is NOT always OK. It is white on the surface,but might be grungy and full of particles under the surface. I learned this when turning a piece of white PVC down on a lathe to cut threads in it.

Grey pipe (as in electrical conduit) has, by specification, some electrical properties at DC/50/60 Hz kinds of frequencies, but not at, say, 100 kHz.


The problem is that plastic pipe is made by extruding shredded plastic, and that shredded plastic is chosen to be cheap and meet the *structural* requirements (e.g. burst strength) and chemical properties (solvent welding).

When you get to large diameter sizes, the problem is worse: since the wall thickness is greater, the maximum "grunge" particle size can be bigger without the mfr worrying about it sticking through the wall.

So ANY pipe is a take your chances, unless you're buying something specifically characterized for the application (expensive! in most cases)


YOu couldn't even depend on cutting off a 1" slice from the end and testing it, because for all you know, that thin metal ribbon scrap is in the next inch.

So, what do you do: Most folks just hope for the best. If you're winding a big coil, and are investing a substantial amount of time and money in the wire and winding, you might want to test your form before you start winding.
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