9-string blade bobbins

[Zhangliqun]

Got a request for a customer so anybody know if there's a source for these, about 90mm spacing? Given that the answer is very likely no, on to the real question:

Best way to fabricate some? Particularly the top without having to make it two pieces glued together that would show a seam.

[Helmholtz]

Regarding desirable magnetic properties (high µ, low Eddy current losses) transformer lamination steel seems to be a very good choice. The material is soft and easy to cut and shape. But would require coating (or black annealing) to prevent corrosion.

[Zhangliqun]

Not blades, bobbins. How do I fabricate the plastic bobbins?

[Helmholtz]

Not blades, bobbins. How do I fabricate the plastic bobbins?

Sorry, I misread.

[StarryNight]

Does it have to be plastic? I made this one out of forbon.

[jop120]

Depends on what kind of tooling you have available as to how easy it will be to make and how tidy it'll look when finished.
If you've got a CNC or a pin router then you'll be able to make them pretty easily with tidy results, if you don't you're gonna have to cut them out by hand and they'll take a long time and probably won't likely look that great.

Basically you want to make the top and bottom pieces of the bobbin out of some thin pickguard material or some fibreboard. They will have the shape of the blade cut out. Then make a centre piece that is the dimensions of the core with the shape of the blade cut out, you could make this out of plastic or wood(something dense and stable like hard maple). When you come to glueing them together, you can choose your glue based on the type of material used. If the glue won't stick to the blades, you can use a blade to line everything up, if the glue will stick to the blade then cut a piece of Teflon up to the same dimensions as your blade and use that to line it up. Also if you make some spacers the same as you'd use when assembling a fender style bobbin, again out of a material that won't adhere to the glue. This will help to make sure your top and bottom parts are parallel.

Don't forget when designing your core dimensions, you need to leave some room for screws that will attach it to the baseplate & magnet(s), look at a normal blade bobbin to see how that'll work.

If you don't have machining capabilities and have to cut them out by hand, use black plastic for the bobbin tops, then when you're gluing them together, use a glue that has been dyed black and will work well as a filler. This will fill the sloppy edges against the blade in. Then you can scrape and sand them back and finish using abrasive paper and wire wool, you can give it a matte/brushed finish that will help to hide the imperfections.

Here's a quick sketch of the individual pieces

[Zhangliqun]

I'm mainly concerned about cutting the long rectangular hole in the top and bottom pieces so I don't have to have a seam showing -- just one piece.

While we're at it, what plastic is good for holding up under heat in the wax pot? The pickguard material I've used before tends to warp.

[jop120]

If you're cutting it out by hand, you'll have to cut it out with a piercing saw and then tidy with a file, then fill any gaps as mentioned above.

I've made quite a few custom pickups like this and not had any problems with distortion due to wax potting, what temperature are you potting at? do you make sure not to let the pickup touch the walls or bottom of the wax pot?. How long are you potting a pickup for?
most pickguard material is made of PVC which is the same material as most humbucker bobbins and shouldn't distort. Ideally you'd want to be potting at around 58-62C.

If for some reason you want to pot at a higher temperature or for a very long time, then you could try using Bakelite pickguard material as this is a thermo-setting plastic and won't distort. Or use vulcanised fibre.

[Zhangliqun]

150F for just 4 to 6 minutes.

On the piercing saw, how do you make the initial hole to get in there? Drill a small hole?

[jop120]

I believe pvc will start to distort at around 65C (150F = 65.5C) so try bringing your pot temp down to 140F and put in a scrap of pvc pickguard material in for 15mins or so. If it comes out fine, then you're all good.

[basscu]

Got a request for a customer so anybody know if there's a source for these, about 90mm spacing? Given that the answer is very likely no, on to the real question:

Best way to fabricate some? Particularly the top without having to make it two pieces glued together that would show a seam.

hi zhangliqun,
there's a bobbin on aliexpress for 86mm bars, originally to be used with emg-style covers.
if that's no option you may send a P.M. to me, maybe I can help.
chr. aka basscu