Magnets & Copper Wire: A Pickup Building Thread

[slowburnaz]

Thanks, Bruce!

As always, I appreciate your informative replies.

The holes on the covers I may try making molds for have odd sizes.. like .265" dia for the pole screw holes, and also some .12" dia holes.

If I do go this route, maybe I'll commission you to make me some pins.

 

[Bruce Johnson]

Thanks, Bruce!

As always, I appreciate your informative replies.

The holes on the covers I may try making molds for have odd sizes.. like .265" dia for the pole screw holes, and also some .12" dia holes.

If I do go this route, maybe I'll commission you to make me some pins.

You can buy O-1 Tool Steel rod stock in a whole list of diameters. That should cover any size you need. It's in annealed form, so you can easily saw it and file it, etc.

McMaster-Carr

 

[dwizum]

A follow up from the ponoko material selection discussion a few pages ago, in case anyone else goes down that road. If you use acrylic for flatwork, and you plan on wax potting the pickups, you need to either leave big tolerances, or... don't wax pot them. Tolerances tight enough to allow a nice press fit of the slugs will result in the flatwork cracking at wax potting temps once the slugs heat up. I'm potting these with shellac since I have it on the bench already and it doesn't require an extra step of mixing epoxy. Just eye-dropper a few drops of shellac on the finished coils, prop them up so it doesn't run towards the front (don't want to ruin the nice shiny surface of the top flatwork), and move on with life.

On to a new subject. I'm considering doing a custom pickup for my Ibanez ATK bass. It doesn't seem like anyone makes them. Bassculture apparently did, but since the owner passed earlier this year I'm not sure if the company will exist any more, which leaves zero options. It's a weird shape with three coils but it seems like only two have magnets in them. At any rate, it's a gigantic case, so there's a ton of room, which opens up possibilities. The case is 4" x 1 7/8" with mounting screws in the ends, so the useful inside size is probably 3 3/8 x 1 5/8" I don't really have any plans except I want to try something different. I'd like a much bigger and thicker tone than anything I'm building now. I may try to do two really short fat coils around short blades, with a ceramic magnet on the bottom. Or directly on magnets if I can find the right size.

 

[dwizum]

@Bruce Johnson - a question out of curiosity. I see you cast your bobbins with polyurethane resin, but then you pot/cast the finished pickups in west system epoxy. Any reason for the difference? Your coils look pretty small, it makes me nervous to think about casting a big MM-style pickup as a solid block of west system, even with the slow hardener I'd be worried about the heat it would give off. I was thinking about getting some polyurethane resin to use instead.

 

[Bruce Johnson]

@Bruce Johnson - a question out of curiosity. I see you cast your bobbins with polyurethane resin, but then you pot/cast the finished pickups in west system epoxy. Any reason for the difference? Your coils look pretty small, it makes me nervous to think about casting a big MM-style pickup as a solid block of west system, even with the slow hardener I'd be worried about the heat it would give off. I was thinking about getting some polyurethane resin to use instead.

Hey dwizum;

I use three resin materials in my process: I cast the bobbins from polyurethane casting resin. Then I pot the wound coils with CPES, the super-thin penetrating epoxy. Then I cast the whole works into an outer shell of West Systems 105/206.

I like using West Systems epoxy for the outer shell because of its adhesive strength. On my pickups, the outer surface is made up of perforated brass sheet on the side walls and an ebony cap on the top. The epoxy fills the space behind those parts and holds them all together. I want to make sure the parts stay together.

Polyurethane resin, cast against parts, doesn't make a strong bond to them. Particularly metal. After the polyurethane resin has cured, you can use epoxy to bond metal to it. But the polyurethane resin isn't a very good glue.

Now, if you are casting the pickup into a plain block of resin in a mold, polyurethane resin can work well for that. It may give you better surface finish and color choice than epoxy. I don't think I've ever cast a whole pickup in polyurethane, but I have cast many other types of parts.

For many of my early basses, I was buying Seymour Duncan coils and casting them into my own housings of West Systems. I used the 105/206 mix with black pigment, and it worked well. I never had any problems with it overheating or damaging the coils.

 

[dwizum]

That all makes sense, thanks for explaining.

When you were doing the seymour duncan coils, how was the surface finish of the epoxy? Good enough for a finished part? Or were you still gluing on the ebony tops on for those pickups as well?

West system recommends casting in 1/4" thick layers for thicker parts as far as I remember.

I don't expect I'll make many of this pickup, but I would like to just cast the wound and potted coils in a mold and end up with a finished part, all in one step. I need some west system epoxy for another project so I may just try tinting it black and casting this design with it. I'd rather not buy another product just for casting these if I can avoid it.

 

[Bruce Johnson]

That all makes sense, thanks for explaining.

When you were doing the seymour duncan coils, how was the surface finish of the epoxy? Good enough for a finished part? Or were you still gluing on the ebony tops on for those pickups as well?

West system recommends casting in 1/4" thick layers for thicker parts as far as I remember.

I don't expect I'll make many of this pickup, but I would like to just cast the wound and potted coils in a mold and end up with a finished part, all in one step. I need some west system epoxy for another project so I may just try tinting it black and casting this design with it. I'd rather not buy another product just for casting these if I can avoid it.

Black-tinted West Systems comes out of the mold as a semi-gloss shine, and you may have trouble with some little bubbles in it. But, the good thing about epoxy is that it can be patched and polished. You can fill in bubbles or flaws with more epoxy, file them level, and polish them to a nearly invisible repair.

Here's an example of a pair of 7-string bass pickups I made a long time ago, that are pure cast West Systems outer housings. They are right out of the mold; I didn't do any finishing operations to them. My first real attempt at an epoxy cast pickups! They have some little flaws and marks, but they aren't bad.

Here are some of my circa 2003 Series III model pickups. Those are Seymour Duncan QP P-bass coils in there. They have thin ebony top caps, but the ends and sides are cast black West Systems. They have been sanded and lightly polished to a semi-gloss.

Here are some of my early SSB pickups. More SD QP P-bass coils, cast into West Systems. I made these molds from wood masters, so the wood grain is transferred into the epoxy. They almost look like ebony. Minimal finish work after they came out of the molds.

 

[Simon_Blanch]

Hi all,

new to this thread, but appreciate the enormous amount of knowledge here

Apologies if it's already mentioned here, but would it be possible to fit ~10,000 winds of 42 on a 9,5mm X 14,5mm slug and use it as a bobbin. The intention would be to build a Wal style 8-coil pick-up and fit it into a (4-string) MM pickup cover.

Appreciate the replies!

Kind regards,

Simon

 

[Bruce Johnson]

Hi all,

new to this thread, but appreciate the enormous amount of knowledge here

Apologies if it's already mentioned here, but would it be possible to fit ~10,000 winds of 42 on a 9,5mm X 14,5mm slug and use it as a bobbin. The intention would be to build a Wal style 8-coil pick-up and fit it into a (4-string) MM pickup cover.

Appreciate the replies!

Kind regards,

Simon

Welcome, Simon!

You'd have to do some layouts and test samples to find out, but I doubt that's going to work. Trying to fit 8 coils inside a MM cover would be tough enough, of any size. Using a 3/8" (9.5mm) center slug makes a bigger coil, and 10K turns of #42 is a lot of wire!

Marko (MPU) and Chris (Slowburnaz) have done multi-coil pickups with 8 round coils on this thread. Take a look at the size and geometry of the coils they made.

 

[Freekmagnet]

Hi all,

new to this thread, but appreciate the enormous amount of knowledge here

Apologies if it's already mentioned here, but would it be possible to fit ~10,000 winds of 42 on a 9,5mm X 14,5mm slug and use it as a bobbin. The intention would be to build a Wal style 8-coil pick-up and fit it into a (4-string) MM pickup cover.

Appreciate the replies!

Kind regards,

Simon

You could try plugging your info into this handy-dandy online coil estimator:

Coil Estimator

It’s not 100% accurate, but it will give you a general idea.

 

[Simon_Blanch]

Hi all,

Welcome, Simon!

You'd have to do some layouts and test samples to find out, but I doubt that's going to work. Trying to fit 8 coils inside a MM cover would be tough enough, of any size. Using a 3/8" (9.5mm) center slug makes a bigger coil, and 10K turns of #42 is a lot of wire!

Marko (MPU) and Chris (Slowburnaz) have done multi-coil pickups with 8 round coils on this thread. Take a look at the size and geometry of the coils they made.

Thanks for the reply, Bruce. I contacted Marko (MPU) on his neat 8-coil pickup design and he told me that he actually used MM covers, but with taller steel pieces. So in the end, his pick-up will be much taller than the typical MM pickups, but at least he was able to fit it all into the MM pickup cover. So indeed, I think i'll have to go with narrower slugs (5mm) and extend the height of the slugs as well. Does anyone know whether the size of the slugs have a big impact on the sound?

You could try plugging your info into this handy-dandy online coil estimator:

Coil Estimator

It’s not 100% accurate, but it will give you a general idea.

Wow, that's pretty handy indeed. Thanks a lot for sharing!

 

[Freekmagnet]

Does anyone know whether the size of the slugs have a big impact on the sound?

The size of the slugs will change the sound, but the height of your coil will have a far greater effect on your overall sound. Almost every variable has an effect, some more than others. Unless you’re trying to replicate a specific pickup or you have a certain sound in mind, I wouldn’t worry about the pole size too much. Your pickup won’t sound exactly like a Wal or a Stingray - it will sound like your pickup. Just make your multi-coil, drop it in that pre-cut MM route and rock out!

 

[Simon_Blanch]

The size of the slugs will change the sound, but the height of your coil will have a far greater effect on your overall sound. Almost every variable has an effect, some more than others. Unless you’re trying to replicate a specific pickup or you have a certain sound in mind, I wouldn’t worry about the pole size too much. Your pickup won’t sound exactly like a Wal or a Stingray - it will sound like your pickup. Just make your multi-coil, drop it in that pre-cut MM route and rock out!

Many thanks for the advice, Freekmagnet! I fully agree that pickups are unique in sound (too much variables), so no bother trying to replicate. However, I like the 'overall' sound of a 8-coil pickup, so will pursue in making one. Would you have any preference of having magnetic pole pieces vs steel rods with bar magnets underneath? Any idea how the sound will be impacted by this variable?

 

[Freekmagnet]

Would you have any preference of having magnetic pole pieces vs steel rods with bar magnets underneath? Any idea how the sound will be impacted by this variable?

I don’t have any preference. Here you’re getting into the realm of subjectivity. Ultimately, you’re going to have to make the pickup yourself and decide which approach works better for you. In a lot ways, pickup making is straight super-science and engineering in its approach, but finding the "best" building process and the end results are matters of opinion.

Building a multi-coil is a challenge or a PITA depending on how you look at it. My advice is to make a drawing based on the space you have available inside the MM cover and your string spacing. Then find out what materials you can easily access and decide which are most cost-effective. Weigh that information against what you think would be the least resistant way to build the pickup. With this in mind, refine your drawing, figure out how you’re going to make your parts and assemble the piece and then go for it. I think by the time you finish finding your materials, that will largely determine whether or not you’ll use magnets or steel rods. I’m sure you’ll be happy with the results either way.

 

[MPU]

Many thanks for the advice, Freekmagnet! I fully agree that pickups are unique in sound (too much variables), so no bother trying to replicate. However, I like the 'overall' sound of a 8-coil pickup, so will pursue in making one. Would you have any preference of having magnetic pole pieces vs steel rods with bar magnets underneath? Any idea how the sound will be impacted by this variable?

Both A5 pole and steelpole/ceramic have that 8-coil sound. A5 magnets inside coils versions are easier (and faster) to make. Adjustable steel poles need threaded keeper bars and that takes some time to make.

 

[slowburnaz]

Both A5 pole and steelpole/ceramic have that 8-coil sound. A5 magnets inside coils versions are easier (and faster) to make. Adjustable steel poles need threaded keeper bars and that takes some time to make.

Agreed.

For the ones I make, I use steel "keeper" bars, but they're not threaded. I actually put threads in the brass baseplate for the big set screws (brass is so much easier to tap than mild steel, and easier on your taps, too ). There are holes sized just right in the keepers so that the set screws still make contact with the steel bars, and the ceramic magnet charges them nicely.

 

[slowburnaz]

Been messing around with another cover design for my multicoils, so I figured I'd share:

I like being able to use different inserts. Black, silver, and copper are shown here, but there are many options. I figure black, silver (chrome), and gold can be used to match hardware, or wood veneers could be used, painted inserts to match a body, etc.

Might try casting the covers with this kind of design next.

 

[dwizum]

That's a really nice design and overall a very clean looking assembly. So cool!

 

[dwizum]

I've been playing with more new materials at ponoko for flatwork. The vulcanized fiberboard they have can get really pricey - even some of my simple blade designs are more than $3 a piece for quantities under 50. For a pair of humbuckers that's $24 just in flatwork. Recently I tried their white taskboard which was more like 80 cents for the same design. Only $6.40 for a pair, more reasonable.

The taskboard came recently and it's much softer than I expected. It's a paperboard style product but it feels almost like kinda-stiff foam. Too easy to bend or crease it. So I soaked it in thin CA and it stiffened right up. I'm going to keep working with this as a material now that I figured that out but I might try a few others. Their bamboo plywood looks attractive.

Here's the taskboard coated in CA and assembled into bobbins:

 

[Freekmagnet]

I've been playing with more new materials at ponoko for flatwork. The vulcanized fiberboard they have can get really pricey - even some of my simple blade designs are more than $3 a piece for quantities under 50. For a pair of humbuckers that's $24 just in flatwork. Recently I tried their white taskboard which was more like 80 cents for the same design. Only $6.40 for a pair, more reasonable.

The taskboard came recently and it's much softer than I expected. It's a paperboard style product but it feels almost like kinda-stiff foam. Too easy to bend or crease it. So I soaked it in thin CA and it stiffened right up. I'm going to keep working with this as a material now that I figured that out but I might try a few others. Their bamboo plywood looks attractive.

Here's the taskboard coated in CA and assembled into bobbins:

View attachment 4343571

Dude, I'm digging your blue tape solution! I've been meaning to get some white paper tape to do that, but it's hard to find. They have it at Blick's. I just haven't gone down there to get some yet.

$3 each seems kind of expensive for Ponoko. Are your getting the thin fiberboard or the thick? I usually order the thin stuff and gang 30-40 pieces on one sheet. If you order more than one item, they usually give you a pretty substantial discount. Last week I had some MDF templates cut and it was $40 for one and $20 for the second one.

The cheapest thing I've used on Ponoko was the .02" cardboard. It came out to like 30¢ apiece. I was able to glue together a pretty nice paper bobbin with it. By themselves, they weren't very strong, but I made a little holder for my winder that sandwiched them on there for support. It helped a lot against flaring.