What bobbin materials are safe for machine sanding?

[Stealth]

Suppose you had a pre-cut piece of plastic the size of a regular bobbin, but it's rectangular and needs the corners rounded so it'd fit properly into the pickup cover. FR4 is a bad choice because it fragments into fiberglass dust, which is bad mojo for the lungs. What other bobbin materials can be used instead that can be machined easily (i.e. so they're not a health hazard)?

On a semi-related note, is there any material available for making your own bobbins, like making a template out of modelling/polymer clay and making the actual bobbins with epoxy?

[David King]

You can sand just about any plastic but some will melt right away and leave a gobby mess behind like acrylic, polystyrene and ABS. I'd say the toughest sand would be glass-filled nylon. Your best bets would probably be delrin (acetyl) followed by lexan (polycarbonate). Skip PVC.

Why not get a polyurethane casting kit from jgreer.com?

[Jim Shine]

Garolite from McMaster Carr. I suggest using the paper type (I believe it is prefixed XX). If you get black, it looks very much like vulcanized fiber, but is much more rigid and stronger.

[Joe Gwinn]

Suppose you had a pre-cut piece of plastic the size of a regular bobbin, but it's rectangular and needs the corners rounded so it'd fit properly into the pickup cover. FR4 is a bad choice because it fragments into fiberglass dust, which is bad mojo for the lungs. What other bobbin materials can be used instead that can be machined easily (i.e. so they're not a health hazard)?

There are lots of different kinds of circuit board material available that contain no glass fiber. It's kind of a Chinese Menu:

Resins = {epoxy, polyester, melamine, bakelite, ...}

Reinforcement = {paper, linen canvas, cotton canvas, various synthetics, fiberglass, ...}

Garolite (see McMaster-Carr), mentioned by another poster, is a brand name for one family of such products. There are many others.

[Stealth]

Thanks for the input. I'll check out the local store where I got the FR4. It was easy enough to cut and drill but tough to finely machine, maybe they have something similar.

[David King]

I have some 1/16" linen with bakelite/phenolic resin that's not very stiff, hopefully the Garolite XX black paper is stiffer. It's cheap enough, a 12" x 24" of the 1/16th thickness is just over $8, that's a fraction of what forbon sells for.

[Bruce Johnson]

I've worked with Garolite XX and it's a very nice material for many non-conducting structural parts for electronics projects. It can be sawn, drilled and filed to shape easily, and the edges can be polished up. The surfaces of the sheets are a smooth semi-gloss black. It's towards the brittle end of plastics; that is, if you bend it too far it will snap, or if you try to press a part into it with too much force, it will crack. But it's reasonable, not excessively brittle. I'd say that it's less brittle than Plexiglas. It's quite a bit stiffer and stronger than an equal thickness of styrene or urethane. I think it would be an excellent material for the style of pickup construction that usually uses Forbon.

[Jim Shine]

It is a very friendly material to work with. I have used it for making many items including pickguards, cavity covers, jackplates, string nuts, trim rings, bobbins, and inlays. Keep a sheet around. You too will find it a great multi purpose material.

[David Schwab]

Here's another use for xx garolite. I use it for fingerboards.

[Jim Shine]

What a great use! Do you have to radius it, or is it bent and glued to a radius surface?

[David Schwab]

What a great use! Do you have to radius it, or is it bent and glued to a radius surface?

It's actually an old use, and commonly called "ebonol". Kramer and Steinberger used it for years.

It has a radius. I think it's 16", but it may be 14". It's not just a layer, the entire fingerboard is xx black paper phenolic. I think it's 1/4" thick. It's fair;y easy to machine, but I used sanding blocks to radius it, and that was grueling!

My fretted bass also use phenolic boards. It makes a nice sounding neck too.

When you put a radius in it, the layers of paper look like wood grain lines.
(don't mind the unpolished frets!)

[Jim Shine]

I didn't know ebanol was phenolic. That is very useful info! Love the laminate design of your basses. I wish that look caught on a larger scale with guitars.