Newbie question on steel (a bit long post)

[David Schwab]

I have a box of black finish 10-24 allen set screws I got from McMaster-Carr, which look exactly like what you'd see in a DiMarzio pickup.

The box lists them only as "alloy socket screws, cup pt" so 1045 makes sense.

The O1 bar I have certainly seems as magnetic as the rest of the blades I've been using. I have no idea what they are, and they are also plated with something shiny.

I'll be working on the pickup in the next few days, so I'm curious to see how the new steel sounds.

[kevinT]

Both 1018 and 1022 steel is readily available to fastener manufacturers if you're having some fillisters made.

[David Schwab]

Still the big question is what does carbon content do to the tone, and why?

[Possum]

...carbon

Carbon affects permeability right? If you have iron with alot of carbon in it, it can be magnetized and will stay that way and will resist being demagnetized by an opposing force. Pure iron on the other hand is really permeable and won't hold a magnetic charge and changes polarity really easily. How this affects tone I can't quite get a grasp on, maybe Joe can explain it.

[salvarsan]

Carbon affects permeability right? If you have iron with alot of carbon in it, it can be magnetized and will stay that way and will resist being demagnetized by an opposing force. Pure iron on the other hand is really permeable and won't hold a magnetic charge and changes polarity really easily. How this affects tone I can't quite get a grasp on, maybe Joe can explain it.

Permeability is how well something conducts magnetism.
Higher permeability in a coil core means more inductance in the coil.

Coercivity is how well something resists demagnetization.
If something can hold a magnetic charge, it has enough coercivity to be useful.
Permanent magnets have high coercivity and 'soft' steels don't.

-drh

[Joe Gwinn]

Carbon affects permeability right? If you have iron with a lot of carbon in it, it can be magnetized and will stay that way and will resist being demagnetized by an opposing force. Pure iron on the other hand is really permeable and won't hold a magnetic charge and changes polarity really easily. How this affects tone I can't quite get a grasp on, maybe Joe can explain it.

Qualitatively, anyway. The harder (physically) the steel, the lower the incremental permeability and the higher the bulk resistivity, both tendencies causing eddy currents to be reduced. So I would expect the harder steel to make brighter pickups, because the eddy current loading is reduced.

The more carbon in the steel, the harder it can be made.

I don't know how much of the effect on sound is due to the carbon percentage alone (regardless of physical hardness achieved) and how much is due the the degree of physical hardness achieved (regardless of how achieved, the extremes being medium carbon, severe quench, and no tempering versus high carbon, ordinary quench, and medium tempering).

[David Schwab]

Qualitatively, anyway. The harder (physically) the steel, the lower the incremental permeability and the higher the bulk resistivity, both tendencies causing eddy currents to be reduced. So I would expect the harder steel to make brighter pickups, because the eddy current loading is reduced.

Very interesting!

Bill Lawrence is always saying his blades are stainless steel, and his pickups are very bright. I don't know what kind of stainless he's using, but he must have picked it for a reason.

[Joe Gwinn]

Bill Lawrence is always saying his blades are stainless steel, and his pickups are very bright. I don't know what kind of stainless he's using, but he must have picked it for a reason.

Most kinds of stainless steel are non-magnetic, but a few are magnetic. We ought to be able to figure out which one he uses. One common magnetic stainless steel alloy (widely used in knives) is 440C. Small quantities may be bought from sellers of knifemaking supplies.

Stainless steels as a class have relatively high bulk resistivities, which greatly reduce eddy currents.

Use of stainless steel would eliminate the need to plate or otherwise finish the blades to prevent rusting.

[David Schwab]

Stich always talkes about eddy currents, so I'd bet that's the reason he uses that type of steel.

I have a few of his pickups with the blades, and they don't appear to be plated. They look like stainless steel.

One pickup is non working, so I could take it apart to access the blade.

[dpm]

there's some good info on ferritic stainless alloys here - http://www.cartech.com/ssalloys.aspx


Seems 430F and 430FR could be interesting to experiment with

[Joe Gwinn]

Stich always talkes about eddy currents, so I'd bet that's the reason he uses that type of steel.

I have a few of his pickups with the blades, and they don't appear to be plated. They look like stainless steel.

One pickup is non working, so I could take it apart to access the blade.

If you do, consider having the blade composition analyzed by a steel supplier.

[defaced]

An independent lab should be able to do chem analysis if they do metallurgy work. OES (optical emission spectroscopy) is a good technique to get chem results for most steels. This technique will not pick up trace elements but it will get all of the big players. Where I get my stuff done for work, a full workup costs ~100 bucks for steel.

Use of stainless steel would eliminate the need to plate or otherwise finish the blades to prevent rusting.

Some martensitic and ferritic stainlesses will rust on the surface if the Cr content is low enough (~12-14 wt%). If you want a ferritic stainless that will not rust, look for one with a Cr content above 16-18 wt%.

[Possum]

......

Did anyone try the stainless steel slugs SK sells?

[salvarsan]

Some martensitic and ferritic stainlesses will rust on the surface if the Cr content is low enough (~12-14 wt%). If you want a ferritic stainless that will not rust, look for one with a Cr content above 16-18 wt%.

At the low magnetic field strengths in pickups, magnetic permeabilities
of soft steels and type 400 stainless are in the same ball park.

The means that type 400 slugs and blades will work okay in a pickup
and that they will sound different enough from type 1000 steels to be
worth exploring.

Type 413 and 416 are commonly available and take a very high polish -- nickel plating is unnecessary.

Many machinists provide type 413 parts at reasonable cost.

-drh