As I have recently stared doing my homework on pick up building I wanted to start with the types of magnets used well as I can see this topic will take a lot of time so I thought I would try to save lots of hours of study and start this topic on here well lets start with rod magnets ok I see there is a few types of grades to choose 2,3,5 etc I have found some info on using different types I still need more info like the best one to get that swampy delta blues sound and for the next page of my studies I am very lost on what diameter and length to use well I will stop here and see what feed back I can get for now and then move to the next page of my studies thank you for reading this.
There are two main magnet diameters when discussing rod style magnets: .187" and .195". The .195" have beveled tops (our's do but not all .195" are beveled). The beveling has an impact on tone. (I don't understand the physics but I do know from experience that it has a positive effect on tone) There are also .250" diameter rod magnets. (we carry them) We stock AL2, AL3, AL5, AL8, & neodymium rod magnets and AL2, AL5, and AL8 in bar magnets as well as AL5 in humbucker blade magnets.
One thing to keep in mind when building pickups with rod magnets is that not all of the rod magnets have to be the same in terms of type of alnico magnet.
I had a customer come into my shop a few years ago that wanted a Strat set handwound but he said that he hated how "ice-picky" the B and E strings were. We built a Strat set with AL5's in the E, A, D, & G positions and AL2's in the B & E positions and he loved them.
A few rules when pickup building: #1) the taller the coil, the brighter the pickup, #2) the more overwound the coil, the less highs, #3) if you underwind a pickup (based, loosely on vintage values), it will sound brighter but will also have less "body", #4) larger diameter magnets will give you a larger magnetic field and might increase the power a slight bit but doesn't automatically give you a better tone, #5) the shorter the coil (a la humbucker type coil), the less highs and more mids/lows.
Magnetize the pickup LAST... even after you wax pot it. Striking a magnet with a hammer (pounding it into a pickup bobbin, for instance) that is already magnetized can cause it to lose some of it's magnetic properties. So does heat. Soaking a pickup in 156 degree hot wax for 20 minutes after you have magnetized it is a bad idea.
There are a zillion other little things but those will get you started!
Assuming you're making three or four pole pickups, as a starting point, try some .195 diameter magnets, A5 strength.
The Strat sets have staggered magnets of different heights to match the curvature of the strings and emphasize or de-emphasize certain strings. Cigar box guitars typically have no curvature, so my suggestion would be to use magnets of all the same height.
Any height available will work, just pick one and go with it.
That's partially but not entirely accurate. Strat pickups do have staggered magnet heights but they do not match the curvature of the strings, Strat magnet heights are as follows: E, A, & E = .671" D & G = .710" B = .650" The height of the B string magnet is retarded because the output frequency of that string would drown out the tone of the pickup.
Also, if you are building a 4-string pickup, you might want to go with the larger .250" magnets. It depends on what you're building. If it's a cigar box guitar that's going to be played with a slide and the strings are farther away from the pickups, a larger magnetic field would be better. If what you're building is going to be fretted, the .195" or .187" would work fine. And, if you want to accentuate a certain string, make that magnet taller (closer to the string).