High carbon or low carbon?

[David Schwab]

Low compression mp3 is still compressed. You should save your files in the flac format.

Since he's on a Mac he can use Apple Lossless.

You wont hear the effects of compression on a high bit rate MP3 file with guitar clips anyway. I keep my test clips in MP3 format.

[Joe Gwinn]

I found Joe's comment interesting, and i'd be interested to see if he had any science behind it. the last piece of my humbucker equation was the screws, and i had high hopes for the mojotone vintage pole piecs (advertised as 1010 but are actually 1022 verified with xray spectroscopy) but they were muddy and dark. I also tried low carbon screws and they were much better, and livelier. Though the screw i finally settled was mid carbon (somewhere around 0.20), it had a higher manganese content - I think that was what did it for me.

There is some science behind it. Carbon content (as well as other ingredients) and degree of hardening both matter.

The general rule is that physically softer ferrous metal alloys are both softer magnetically (meaning higher magnetic permeability) and have lower bulk electrical resistivity.

Both permeability and resistivity affect the level of eddy currents one will get for a given variation in magnetic field. Specifically, the higher the permeability (and/or the lower the resistivity) the greater the eddy currents.

So for example, let us consider slugs made of carbon steel, say 1030 (commonly used in mechanical hardware because it can be hardened to be very tough). When annealed soft, the permeability is high and the resistivity is low, so the eddy currents are maximum, which will result in a warmer sound. If we take these same slugs and harden them (by heating to red heat and dropping into brine), the permeability will be reduced and the resistivity will be increased, so eddy currents will be reduced by comparison, and so the sound will become brighter.

This is an experiment one can easily do, but there is one thing to be aware of: The lower the carbon content the less the steel can be hardened, so the less effect annealing and hardening will have on eddy currents and on tone.

So, 1005 will show little effect, while W-1 (which is roughly 1095) will show a large effect, and intermediate alloys (like 1030) will show intermediate effects. W1 is cheap and widely available in all manner of shapes, so I would use it for the initial experiments. I would not use hardware store metal, because you have no idea what it is today, or will be tomorrow.

[RedHouse]

There is some science behind it. Carbon content (as well as other ingredients) and degree of hardening both matter.

The general rule is that physically softer ferrous metal alloys are both softer magnetically (meaning higher magnetic permeability) and have lower bulk electrical resistivity.

Both permeability and resistivity affect the level of eddy currents one will get for a given variation in magnetic field. Specifically, the higher the permeability (and/or the lower the resistivity) the greater the eddy currents.

So for example, let us consider slugs made of carbon steel, say 1030 (commonly used in mechanical hardware because it can be hardened to be very tough). When annealed soft, the permeability is high and the resistivity is low, so the eddy currents are maximum, which will result in a warmer sound. If we take these same slugs and harden them (by heating to red heat and dropping into brine), the permeability will be reduced and the resistivity will be increased, so eddy currents will be reduced by comparison, and so the sound will become brighter.

This is an experiment one can easily do, but there is one thing to be aware of: The lower the carbon content the less the steel can be hardened, so the less effect annealing and hardening will have on eddy currents and on tone.

So, 1005 will show little effect, while W-1 (which is roughly 1095) will show a large effect, and intermediate alloys (like 1030) will show intermediate effects. W1 is cheap and widely available in all manner of shapes, so I would use it for the initial experiments. I would not use hardware store metal, because you have no idea what it is today, or will be tomorrow.

(in my best Elmer Fudd...)

Shhhhh! be vewwy vewwy qwyet, I think he just said eddy currents.

[ShannonH]

many thanks and an added question

So, 1005 will show little effect, while W-1 (which is roughly 1095) will show a large effect, and intermediate alloys (like 1030) will show intermediate effects. W1 is cheap and widely available in all manner of shapes, so I would use it for the initial experiments. I would not use hardware store metal, because you have no idea what it is today, or will be tomorrow.

That made complete sense! This is probably why 1018 is favored by many, because it can only be hardened so much.

So does it stand to reason that "grade 8" set screws don't sound good because they've been hardened to the highest degree for a high carbon alloy? If you knew the actual steel, you could temper the screw to a point in between, although that seems impractical in the long term.

[Joe Gwinn]

This is probably why 1018 is favored by many, because it can only be hardened so much.

Well, I think you give them too much credit. More likely, they use 1018 because it is widely available, and cheap. People mostly use 1018 as is, without heat treatment.

So does it stand to reason that "grade 8" set screws don't sound good because they've been hardened to the highest degree for a high carbon alloy?

Grade 8 screws likely have lower eddy currents than Grade 3 bolts. As for "sound good", that is a matter of opinion and intent.

If you knew the actual steel, you could temper the screw to a point in between, although that seems impractical in the long term.

It would probably be too complex to figure out. And, one is making a pickup, not just some poles, so too bright in one place can be compensated for by too warm somewhere else, the usual team members being the magnets, the slugs, the baseplate, and the cover. It all has to balance and yield the desired tone.

[Possum]

......

I think its a mistake to assume manganese is doing anything to the tone. I've been working with an magnetics alloy steel specialist for the past 3 years and had all my vintage Gibson steels analyzed, from very early P90s to late TTops. Manganese is used and combines with sulfer to make manganese sulfides which are there to make machining easier. Manganese in old PAF keepers and modern 1018 stock are about identical and often the modern is higher in manganese than the old stuff is. I've never been able to put a finger on piles of lab work and say WHY vintage steel sounds different, but it sure does. Comparing my new PAF screw order with near identical PAF screw analysis, nothing really stands out blatantly, there is noticeably more sulfur in the PAF screw, but I wouldn't necesserily point a finger at that.

[David King]

Possum,
Just for fun you should try cryogenically "aging" your new screws to see what happens. For a while there everybody was cryogenically treating everything from strings to tubas and claiming fabulous results. I don't know if anyone still bothers anymore but it is supposed to realign the crystalline structures of materials and relax the stresses left from manufacturing.

Notice how I like spending other peoples' money...

[Possum]

....

I had an offer from a cryogenic services guy to treat some pickups, but my specialty is the PAF thing and there's really nothing vintage about dunking pickups into liquid nitrogen or whatever they're using. Duncan was cryogenically treating magnet wire for awhile but doesn't anymore. The guy told me it improved factory single coils etc. well cool, I don't make factory pickups so doubt I will ever try it. There are infinite enough possibilities just in the materials we already work with, would rather keep it stupid simple as possible.

[David King]

I agree stupid simple is the best approach but I was wondering if the difference you are hearing between old steel and new steel is entirely related to formulation or possible related to age as well. Here is a simple, cheap way to speed up the aging process and see if it makes any difference. I'm not suggesting that you change your approach or start mass producing pickups, it was all in the interests of science but apparently it's of no value since Duncan has already tread there.

[Possum]

....

It does have value in industry but in pickups, yeah probably not.

[RedHouse]

...stupid simple is the best approach but...

Modus Operandi hmmm

[defaced]

Has anyone ever had their steel metallographically analyzed? Looking at composition in only half of a materials properties.

[David King]

You mean sawn through the middle, polished, acid etched and stuck under the microscope? I think that's pretty standard procedure. It should tell you if your crystalline structure goes through and through or just skin deep.

[defaced]

Yes, that's what I'm talking about, but if you're just getting chem work done, the lab won't look at your sample under a scope and report phases present or their amount. They'll just shove it in their OES machine (or whatever they're using) and wait for the print out. I ask because I've never heard anyone here discuss things like volume percent pearlite, or more specifically cementite (iron-carbide), which from the conversations about carbon, is really what you're after.

Manganese does alot of different things to steels. Is a substitutional element for Iron, which increases it's mechanical strength. It is a stronger deoxidizer than Iron. It also combines with Sulfur which helps with high temperature workability properties.

One other thing to think about, the amount of cold work done could maybe, possibly, affect its magnetic properties as compared to vintage steel. It would be interesting to compare hot rolled that's been milled to thickness, hot rolled that's been ground to thickness, and cold rolled steels of equivalent compositions.

And what about rolling direction and grain orientation relative to the magnetic field?

[TGD]

Greetings,

Interesting discussion. I'm no pickup expert, just a hobby, as someone once said "you're just an old eccentric musician working on his sound".

When a permanent magnet is used to induce magnetic field in steel, you are dealing with the B/H curve. That characterizes the resultant magnetic field strength eminating from the steel. It is not linear, and there is a saturation point, i.e., increasing the strength of the permanent magnet will not increase more magnetic field in the steel beyound a certain point. The B/H relationship is affected by carbon content. Lower carbon yields slightly stronger fields. You have the option; either you need a bigger field or a weaker one.

Google "Magnetic properties of low carbon steel" for interesting tidbits on this topic including the issue of Eddy current losses and the use of Silicon steel that may be useful when making blades for pickups.

Regards.

JBF.

Absolutely correct!