Looking for thin walled, .188" id tubing...

[David King]

I have an idea for a bass pickup that involves insulating the alnico pole pieces by slipping short fiber tubes over them so that I can slide the magnets up and down inside the coils without damaging the insulation on the wire. I was hoping it would be easy to find thin wall tubing of forbon or mylar that I could super glue directly to the flatwork above and below to build a bobbin. So far I haven't been able to find anything, mostly because I don't know where to look for it. When I ask I get directed to Kynar heat-shink tubing but I don't want too tight a fit and I don't know if Kynar is a plastic that will glue to anything at all.

The Forbon tubing I've seen is probably too thick and might kill off too much high frequency but I don't know that for a fact yet.

Anyone care to help me?

Thanks, DK

[David Schwab]

I've seen phenolic tubing that would probably work... it was used as spacers for circuit boards. The question is getting the right inside diameter.

Let me see what I can find.

[Possum]

plastic bobbins...

why don't you just get some plastic bobbins like DiMarzio or cheap Fender bobbins, I think Andy C makes these as well. You can slide the magnets up and down all day......

[Joe Gwinn]

I have an idea for a bass pickup that involves insulating the alnico pole pieces by slipping short fiber tubes over them so that I can slide the magnets up and down inside the coils without damaging the insulation on the wire. I was hoping it would be easy to find thin wall tubing of forbon or mylar that I could super glue directly to the flatwork above and below to build a bobbin. So far I haven't been able to find anything, mostly because I don't know where to look for it.

You are in luck. ID=0.187" is a standard dimensions, as is 0.030" wall thickness. Try the following:

Electrical fiberglass: http://www1.mscdirect.com/CGI/NNSRIT?PMAKA=63409114

Canvas-phenolic: http://www1.mscdirect.com/CGI/NNSRIT?PMAKA=63412720

Paper-phenolic: http://www1.mscdirect.com/CGI/NNSRIT?PMAKA=63411458

The fiberglass is the strongest (and most expensive), and the paper is the weakest.

How will you keep the magnets from loosening and flying out?

When I ask I get directed to Kynar heat-shink tubing but I don't want too tight a fit and I don't know if Kynar is a plastic that will glue to anything at all.

Kynar isn't stiff enough for your purpose. It can be glued with epoxy, although it may require a surface treatment. But there are better choices.