Re: [EE] Small electromagnet cores?

https://en.wikipedia.org/wiki/Carbon_steel#Low-carbon_steel

> Low carbon steel. >0.5% carbon,

Should be "less than" 0.5% ?

-----Original Message-----
From: Microcontroller discussion list - Public. <[email protected]>
Sent: Jun 5, 2025 8:25 AM
To: Microcontroller discussion list - Public. <[email protected]>
Subject: Re: [EE] Small electromagnet cores?

Low carbon steel. >0.5% carbon, commonly called 'mild steel', is used
extensively for screws, nails and low cost ironwork that holds stuff
together, especially in wood. Exceptions being deck screws and fasteners
with a grade rating, i.e., grade 8 bolts. A quick test with a file will
give you its approx class., soft iron files or cuts easily. Test the
filings with a magnet for attractive response.

On Tue, Jun 3, 2025, 4:54 AM Spehro Pefhany wrote:

> At 01:51 PM 2025-06-02, you wrote:
>
> Hi, Mike:-
>
> There's sellers for 3mm diameter 'soft iron' and for 1J50 permalloy
> rod on Aliexpress.
> The latter is stupidly expensive compared to the domestic price in
> China- it's just that
> nobody is bothering to sell it for a reasonable price overseas. There
> you can get
> a couple meters of 3mm diameter permalloy for a few dollars delivered
> overnight.
>
> If you happen to have a friend in Shenzhen getting them to chop it up
> into short
> lengths and put it in a package for shipment might be an option if you
> want a
> material that's got a _datasheet_ and is characterized for magnetic
> properties.
>
> Soft iron:
> https://s.click.aliexpress.com/e/_oE8kZe0
>
> Permalloy:
> https://s.click.aliexpress.com/e/_okGhroo
>
> The latter type 1J50 is a about a 50:50 Ni-Fe alloy that is hydrogen
> annealed
> to improve the magnetic characteristics such as permeability.
>
> You can get similar material to the 1J50 off the shelf at electrical
> steel suppliers
> in the US such as Carpenter and Fry (with different numbers) but they
> don't generally
> carry small diameters-- 3/16" is about the smallest and IME they
> don't tend to be
> enthusiastic about tiny orders even for exotic materials.
>
> But I'd give a cheap steel screw, nail or threaded rod a try first
> and see if it's
> good enough. In the US, McMaster sells 3mm threaded steel rod cheaply:
>
> https://www.mcmaster.com/98861A040/
>
> Best regards,
> Spehro Pefhany
>
>
> >Hey all-
> >
> >I'm trying to make a flip-dot display like this one:
> >https://hackaday.com/2021/05/29/3d-printed-flip-dots/
> >
> >I'm having a hard time with the electromagnet component of the project. OP
> >used 3mm threaded rod, and it seemed to work okay per his videos, but it's
> >not working for me at all.
> >
> >I'm relatively sure the problem is in the permeability of the core.
> >Stainless steel is not a great magnetic field conductor. I'm looking for
> >something better.
> >
> >Lots of searching has led me nowhere. I'm thinking of trying a nail next;
> >I'm wondering if anyone has any better ideas for a core? NB- I've seen the
> >"soft iron core" that Amazon sells; it's a bit expensive for my taste ($16
> >for 200mm; I would need four of those rods to complete the project).
> >
> >Mike
> >--
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