Pole Piece Screw in High Tensile Steel, gonna work?

[jop120]

Hi Everyone, I'm searching for pole screws for some custom bass pickups. It seems screws made of regular mild steel no longer exist in the non-guitar world. The nearest thing I can find is High Tensile Steel 10.9 grade, from what I can find it's mostly a low-carbon steel, but then with a little bit of Nickel and maybe a little Phosphorous and Boron mixed in.
Has anyone ever tried using these as polepieces? would appreciate any knowledge/experience, as I'll have to have them Nickel Plated so don't wanna spend the money on that if they're not gonna work.

cheers
Josh

[David King]

A standard hardware store fastener is a grade 2 bolt made from low carbon steel, next up is a stronger grade 5, then grade 8.8, followed up by grades 10.9 and 12.9. All of those are medium carbon steel that's been quenched and tempered to increase the tensile strength:
https://www.boltdepot.com/fastener-i...ade-chart.aspx
Nickel, phosphorus and boron would be more likely to be found in a stainless steel along with chromium.
I'd give them a try as is and then after the nickel plating which may change the sound somewhat as nickel is magnetic. I suspect the big pickup makers either custom order exactly the formulation they want or they buy the off-the shelf parts and have them annealed to make them more permeable (less likely to hold a magnetic charge on their own) and possibly to burn some of the carbon out of the steel (at least near the surface). There's a place down the road from me that does annealing http://www.stackmet.com but there must be similar companies all over the world.

[Helmholtz]

A standard hardware store fastener is a grade 2 bolt made from low carbon steel, next up is a stronger grade 5, then grade 8.8, followed up by grades 10.9 and 12.9. All of those are medium carbon steel that's been quenched and tempered to increase the tensile strength:
https://www.boltdepot.com/fastener-i...ade-chart.aspx
Nickel, phosphorus and boron would be more likely to be found in a stainless steel along with chromium.
I'd give them a try as is and then after the nickel plating which may change the sound somewhat as nickel is magnetic. I suspect the big pickup makers either custom order exactly the formulation they want or they buy the off-the shelf parts and have them annealed to make them more permeable (less likely to hold a magnetic charge on their own) and possibly to burn some of the carbon out of the steel (at least near the surface). There's a place down the road from me that does annealing http://www.stackmet.com but there must be similar companies all over the world.

For PU poles you want high (DC and AC) permeability. Permeability decreases with higher carbon content. Annealing increases permeability. Higher permeability means better magnetic field focussing, higher sensitivity and increased inductance.
I don't think that a nickel layer of some µ (microns) thickness can noticeably change the magnetic properties of the poles . (Nickel is less permeable than iron.)

[epizootics]

Hi Everyone, I'm searching for pole screws for some custom bass pickups. It seems screws made of regular mild steel no longer exist in the non-guitar world. The nearest thing I can find is High Tensile Steel 10.9 grade, from what I can find it's mostly a low-carbon steel, but then with a little bit of Nickel and maybe a little Phosphorous and Boron mixed in.
Has anyone ever tried using these as polepieces? would appreciate any knowledge/experience, as I'll have to have them Nickel Plated so don't wanna spend the money on that if they're not gonna work.

cheers
Josh

I have made a bunch of pickups with those, as well as 8.8 and 12.9, and they all work as pole pieces. There isn't much differences between 8.8, 10.9 and 12.9; however, they do sound a tad (and I mean a TAD) brighter than your low-carbon steel screws. When you're fiddling with the alloys of your screws, bear in mind the difference is going to be very subtle, unless you switch to something dramatic like a barely-magnetic grade of stainless steel. You can however tap into the wide array of high tensile machine screws to chose a screw with a bigger/smaller/wider head if you want.

One last thing - I found that some cheap Chinese screws of Aliexpress seem to have just the right alloy, I wouldn't use them in any type of construction but they work great as pickup pole screws, especially if you want to boost the mids some (once again - subtle...)

[jop120]

Hi All, thanks for the info. The screws should turn up today or tomorrow, I also got some M3 screws of the same type, so I think I'll wind up a quick p90 that I can use to A/B with regular 1018 polepiece screws before I send them off to be plated. Then if they don't sound too good I can look into having them annealed, but hopefully they'll be fine, the bass pickups will be a mixture between a Ricky pu and a P90, going into an all maple bass, so if they're a tad bright, should balance well with the overall tone.

Will let you know the outcome after I A/B the screws.

cheers
Josh

[jop120]

Hey, so I just did the A/B test with regular 1018 pole screws and the 10.9 in a P90. reckon it'll be a no go. They work but don't sound too great. There's a notable lack of low-end (not so good for using in a bass pu), there's also quite a big peak in the upper-midrange which makes them sound harsh as well as a notable lack of presence/harmonic detail.
Does anyone think having them annealed will make a substantial difference to this? It'll probably cost around £70 ($100) to get them done, as these kinds of places tend to have a minimum fee of around that much. Alternatively I've read a bodge way of annealing is to throw the screws into a hot coal fire, then let the coals gradually cool down throughout the night, anyone know if this actually works?

If anyone knows a source of low-carbon screws, approx M4 or 8-32 that would work for bass, I'd be glad of the help. I can buy either in Europe or the States.

cheers
Josh

[big_teee]

Could you give the screw size, and a picture would help.
Also if you will update your country in your profile, that will also help those in different places know what you have available?
Thanks,
T

[Helmholtz]

Hey, so I just did the A/B test with regular 1018 pole screws and the 10.9 in a P90. reckon it'll be a no go. They work but don't sound too great. There's a notable lack of low-end (not so good for using in a bass pu), there's also quite a big peak in the upper-midrange which makes them sound harsh as well as a notable lack of presence/harmonic detail.

I noticed a similar sound difference between 1010 and 1022 pole screws in guitar PUs.

Alternatively I've read a bodge way of annealing is to throw the screws into a hot coal fire, then let the coals gradually cool down throughout the night, anyone know if this actually works?

I am no steel expert, but to me this seems like a method for case-hardening, increasing outer carbon content. That might be counterproductive.
But even real annealing probably won't change much.

[rjb]

I am no steel expert, but to me this seems like a method for case-hardening, increasing outer carbon content. That might be counterproductive.
But even real annealing probably won't change much.

Joe Gwinn says annealing small carbon steel parts is easy.
https://music-electronics-forum.com/...ll=1#post46624
https://music-electronics-forum.com/...l=1#post123694
https://music-electronics-forum.com/...ll=1#post50792

But R.G. says "it depends"....
https://music-electronics-forum.com/showthread.php?t=6172&page=2&p=50841&viewfull=1#post5084 1

[jop120]

Ah right, didn't realise you needed a vacuum for the annealing, thought it was about controlling how slowly the steel cools down. Will have to do some more reading on ways of doing it on the cheap.

Terry - cheers, the screws i got are M4 x16mm, though a 8-32 thread would also work, and length could be anywhere between 16-20mm 5/8"-3/4" (not including head height), the ones I got were a button head socket screw as they were the closest thing I could find to the shape of an old Rickenbacker rivet. I'm not overly concerned on the type of head as long as it's about the right size and will sound good.

Here's a pic of the screws i've got and how I'm making the pickups

[Bloomfield]

If you simply heat the screws to dull red with a torch and allow to cool slowly, they will be at least partially annealed as a file will confirm. Whether this will make any difference to their magnetic permeability I have no idea; I am just speaking in a general metalworking sense. Simple enough to test.

[David King]

You don't necessarily need a vacuum either since that's mostly just want to get rid of oxygen to reduce oxidation of the metal which you hardly care about. You can buy stainless steel foil to wrap them in (it's made precisely for this purpose.) Having the steel laying in the hot coals will induce some carbon to glom onto the surface so probably not ideal but heating them with a gas torch and then letting them cool as slowly as possible is your best bet, easier said than done with small parts that tend to cool quickly in air. moving the torch away slowly is the only way i know of and i couldn't tell you how slowly but a stack annealer usually runs for 24 hours. Perhaps you know a potter with a kiln who could help.

If Rickenb-ker used rivets than that's where I'd look too. Wrought iron rivets are usually nearly pure iron and very soft so that they can be peened with a hammer without work-hardening. Do you really need them to be threaded? Of course you could thread them by hand if you absolutely had to but what a royal pain in the ass that would be.
Here's a place you might call for info: https://maccmodels.co.uk/other-fastn...on-rivets.html

Wooden step ladders is a good source of low carbon steel, usually 1005. Ladder bolts are thus to prevent them from work-hardening and failing over time. I found a source in the states but the wire came in thousand pound spools -very cost effective.

[big_teee]

Not what the OP requested, but would a 10-32 threaded A5 magnet work, in place of steel rods, and magnets on the bottom.
Magnetic hold sells them.
Should make pickup building simpler!
See small screenshot.
They get cheaper with quantities.

[jop120]

Dave - Brilliant those rivets are exactly what I was originally looking for. I gave myself a good slap on the forehead when I read your post. Like an absolute plonker, I'd spent ages searching for 'steel rivets' only to find stainless ones, I have no idea why it didn't occur to me to search for Iron ones. Will be ordering them today and having them sent straight to the platers.

Terry - Threaded A5 rods? ohh they sound pretty awesome, not for this bass, but would be a helluva useful thing to have laying around. Didn't know you could thread Alnico, thought it was too brittle. Can't seem to find them on the Magnetic Hold website, are they on a pdf catalogue? do those guys supply small orders of will it be a 200pc min order?

cheers lads

[big_teee]

Can't seem to find them on the Magnetic Hold website, are they on a pdf catalogue? do those guys supply small orders of will it be a 200pc min order?

Shea with MH was keeping them in stock.
I think all the info is on the pdf below.
I imagine the threads are cast into the magnet when they are made?
Quanity pricing is on the pricelist pdf.
https://music-electronics-forum.com/...1&d=1419985272

T