Any magnet experts here? (determining how strong a custom magnet will be)

[peskywinnets]

I'm just wondering what the smallest rectangular bit of alnico that, when fully charged could yield 120 gauss along its edge?

I want to use an alnico blade in a custom pickup - there are none available in the small size I want/need , so need to arrange some custom magnets to be made for me....but I'm worried that any magnet I order may not be strong enough when it arrives.

Given that the blade length will be pretty much fixed (width of the strings)...say 55mm, the thickness of the blade I'd like to be about 1.2mm - I need to know the smallest final dimension I can get away with to allow that 120 gauss number (I'm hoping it can be as little as 5mm)

[salvarsan]

I'm just wondering what the smallest rectangular bit of alnico that, when fully charged could yield 120 gauss along its edge?

I want to use an alnico blade in a custom pickup - there are none available in the small size I want/need , so need to arrange some custom magnets to be made for me....but I'm worried that any magnet I order may not be strong enough when it arrives.

Given that the blade length will be pretty much fixed (width of the strings)...say 55mm, the thickness of the blade I'd like to be about 1.2mm - I need to know the smallest final dimension I can get away with to allow that 120 gauss number (I'm hoping it can be as little as 5mm)

All the simulations I've done put the field strength at 100-300 Gauss at the string 1/4" above the pickup. The surface of the magnet is usually much stronger and I suspect you would need to demagnetize the piece to get it down to 120 Gauss.

A 1.58mm thick by 9.5mm tall (1/16" x 3/8") A5 magnet models to a 150 and 100 Gauss field strengths at string heights of 4.7mm and 6.3mm (3/16" and 1/4").

[peskywinnets]

Oops...my bad - that 120 gauss reading was at the string about 3mm above the pickup! (just as well I never placed an order!!!)

I actually need about 430 gauss on the physical edge of the proposed blade - does anyone think this is possible with Alnico for dimensions of 55mm x 5mm x 1.2mm?

I got to say...ordering a custom magnet is a bit of a chicken/egg situation ...ie how do you know how strong it is (or can be) until you receive it? The one Chinese factory I've spoken to about ordering a custom magnet said something along the lines of "I think we have a gauss meter somewhere" !!!)