History on the use of rough cast mags

[kevinT]

I'm trying to find data on Gibson's use of rough cast magnets and haven't found much info. What was the deal with these.

1. Why weren't they polished? Were they cheaper or did Gibson want them rough specifically for tonal reasons?

2. When were they used? Timeframes?

3. What pickup models were they used in?

4. Were there short rough cast mags used or were they all standard size bucker mags used for all models?

5. What were the general gauss strength for these? Same as polished?

Any other relevant info is appreciated.

[Possum]

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They were rough because they were sandcast. You find them up through late TTop era. There isn't any magic about them being rough surfaced, the difference was in the raw materials and methods used to make magnets. I think the last ones were probably from the early 80's. I and some others helped bring them back about 4 or 5 years ago, they just look cool

[JGundry]

1. The rough sand cast magnets are cheaper. The more surface to be ground the higher the price. A smooth magnet is ground on all sides and will cost more.

2+3. I'm pretty sure that just about every Kalamazoo made alnico bar magnet pickup uses rough cast magnets. They vary in look widely due to different supplies though.

4. Yes there are short rough cast alnico mags.

5.A rough cast pole edge will read a little lower because thee texture keeps the probe a little further away. I talked to an engineer at a US magnet maker once and when I asked about having the pole edges as cast and not ground down he said we can do that but be aware that it will change the properties of the magnet in your circuit a little bit. So yes it does have some effect. The oxidation is a non conductive coating and does effect the magnetic circuit. Personally I think you get just a little bit clearer low end with the oxidation.

[Possum]

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Unfortunately if you want GOOD sand cast magnets they will cost you more, because companies have to cast them individually, we're talking humbucker magnets. Modern companies just aren't set up to do rough cast but they are becoming more common than five years ago when magnet companies basically told me I was nuts to ask for such a thing :-) Magnet companies are set up to do rapid production, so cut and polished magnets are the norm, and pretty much the cutting also does the polish, probably using diamond blades which does this as it cuts. I don't really hear any difference, but the ones I get made do sound different because the old ones were much thicker than modern. The rough cast ones from Sensmag all sound real shrill, and oddly the A5 ones sound the best of the 2 they offer.

[Possum]

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I could see in theory that rough surface alnico might change the magnetics in theory, but I personally haven't heard this effect and if its real it might be opposite of you might think it does. The rough cast Sensmag magnets in alnico 2 are real shrill to my ears but the polish cut ones are alot better sounding. So who knows.... here are the ones I had made and love, looks real....