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From where I might be able to source some 1300 micron (1.3mm) mild steel sheet?

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John Smith 4719/10/2021 21:16:50
271 forum posts
11 photos
Posted by peak4 on 19/10/2021 19:41:56:
Posted by John Smith 47 on 19/10/2021 19:20:17

It would be fine to be high carbon/spring steel, but like I say stainless steel is best avoided.
Either way I can't find any "steel shim stock" of any sort that is 1.3mm thick (i.e. 50, 51, 52 thou)

...........

Ah, so it doesn't really need to be 1.3mm
18 Gauge equates to 50 thou I think See Wiki
https://en.wikipedia.org/wiki/Sheet_metal

Be wary though as other sources list it as 48 thou, so those that say 50 might just have rounded it up..

Obviously this is more than you need, but maybe food for thought.
https://www.ebay.co.uk/itm/402689752952?hash=item5dc22dff78:m:mCP8WeBThOlx1fV-SzLwLVg

Bill

Edited By peak4 on 19/10/2021 19:57:16

Well, within reason it need to be as close as possible to 1.3mm. But if 0.1mm out I suppose that web be fine, but not ideal.

Strangely enough, from what I can see for Sheet Steel, "Gauge 17" 0.0538in (1.37mm) would be closer than Gauge 18 - 0.0478in (1.21mm) - if that is you can find any!

...Though in this modern age, why the heck manufacturers continue to make it so darned complicated is totally beyond me. Also those tolerances are jaw-droppingly imprecise. For 18 gauge steel sheet it appears to be +/- over 8%! You have to wonder how the heck does anybody in manufacturing industry manages fabricate any useful products out of that mess! Bonkers.

John Haine19/10/2021 21:22:12
4259 forum posts
251 photos
Posted by John Smith 47 on 19/10/2021 21:16:50:
.....


...Though in this modern age, why the heck manufacturers continue to make it so darned complicated is totally beyond me. Also those tolerances are jaw-droppingly imprecise. For 18 gauge steel sheet it appears to be +/- over 8%! You have to wonder how the heck does anybody in manufacturing industry manages fabricate any useful products out of that mess! Bonkers.

It's called "engineering" John. Designing within the constraints of materials and components that can be sourced at an appropriate price.

speelwerk19/10/2021 21:30:19
424 forum posts
2 photos

The closest I can find has a thickness (starke) of 1.25 mm, dimensions you can select from 50x50 mm minimum. Hope your German is up to date but they write that it is magnetic and do deliver to the UK. **LINK** https://www.metallparadies.de/stahlblech-glatt-0-75-6-0-mm-staerke-bis-2x1m.html Niko.

John Smith 4719/10/2021 21:30:23
271 forum posts
11 photos
Posted by Michael Gilligan on 19/10/2021 21:00:34:
Posted by peak4 on 19/10/2021 19:21:27:

If you're cutting it down and can get by with ½" wide, you could try HERE
https://www.repco-tech.co.uk/shims

Bill

.

That looks a useful Supplier, thanks Bill yes

[ noting that the minimum order value might encourage ‘strategic’ purchases ]

MichaelG.

.
[quote]

We have a £35 minimum order policy. Any orders under this value will incur an additional fee to adjust it to the minimum.

[/quote]

These sort of unfriendly barriers are actually pretty much out of date. I have talked to a few small-scale manufacturers and they seem to be quite irritated by this sort of thing.

It seems to me that to a quite a large extent the whole world is just thundering onto the likes of Amazon and the old tidy structures of wholesaler / distributor / retailer etc are just being crushed.

 

Edited By John Smith 47 on 19/10/2021 21:37:02

Michael Gilligan19/10/2021 22:32:57
avatar
19258 forum posts
959 photos

Strangely enough, John … it didn’t seem particularly unreasonable to me:

I was simply observing that purchases would be more economical if ‘strategically planned’ rather than treating the Supplier as one’s Stores and calling-off ‘as required’.

They don’t owe the small consumer any favours.

MichaelG.

duncan webster19/10/2021 22:45:39
3581 forum posts
65 photos

Most thin sheet will be CR4, very low carbon, high ductility for pressing. As to why it has a large tolerance, well if you make things to a tight tolerance it costs more, so if it doesn't matter, you don't, and for most applications it doesn't. As others have said, design around what is available, or pay the cost of grinding it to size

chris bale 119/10/2021 23:25:39
10 forum posts
9 photos

Best just find 1 10thou sheet and cut it 5 times! Or 2 .020s and a .010 if it really has to be 051 add a .001 too, by the time you have stacked them to .050 you will possible have too remove 1 of the 10s and swap for a 5-6thou.

Cromwell tools list .8 and .5mm at 30£ each for a roll or imperial mixed various from .001 to .015 6x12 sheets for 56£

Pete.20/10/2021 00:44:57
avatar
703 forum posts
181 photos
Posted by John Smith 47 on 19/10/2021 21:30:23:
Posted by Michael Gilligan on 19/10/2021 21:00:34:
Posted by peak4 on 19/10/2021 19:21:27:

If you're cutting it down and can get by with ½" wide, you could try HERE
https://www.repco-tech.co.uk/shims

Bill

.

That looks a useful Supplier, thanks Bill yes

[ noting that the minimum order value might encourage ‘strategic’ purchases ]

MichaelG.

.
[quote]

We have a £35 minimum order policy. Any orders under this value will incur an additional fee to adjust it to the minimum.

[/quote]

These sort of unfriendly barriers are actually pretty much out of date. I have talked to a few small-scale manufacturers and they seem to be quite irritated by this sort of thing.

It seems to me that to a quite a large extent the whole world is just thundering onto the likes of Amazon and the old tidy structures of wholesaler / distributor / retailer etc are just being crushed.

Edited By John Smith 47 on 19/10/2021 21:37:02

£35 isn't much, what would you expect their profit from a £35 sale is? it probably helps them avoid the time wasters.

Dave S20/10/2021 10:08:49
256 forum posts
56 photos

[quote]

We have a £35 minimum order policy. Any orders under this value will incur an additional fee to adjust it to the minimum.

[/quote]

These sort of unfriendly barriers are actually pretty much out of date. I have talked to a few small-scale manufacturers and they seem to be quite irritated by this sort of thing.

It seems to me that to a quite a large extent the whole world is just thundering onto the likes of Amazon and the old tidy structures of wholesaler / distributor / retailer etc are just being crushed.

Edited By John Smith 47 on 19/10/2021 21:37:02

Seems reasonable to me.
It costs money to stock a thing, pick it, pack it, arrange postage and deal with any customer enquiries. I would be surprised if they actually make more than a couple of quid (end profit after all costs and taxes) on a minimum price order.

It also helps to keep time wasters away, the sort who as a load of questions and then buy a tiny amount never to be seen again.
Whilst it may seem an impediment to small businesses actually if a business can’t afford a £35 order it really isn’t much of a business.

Machining is a hobby for me, but I will buy from trade suppliers by making sure I order a good selection of both the things I need now and the stuff I’m likely to need before I can make another order upto the minimum amounts. That way I can access stuff the hobby supplier doesn’t stock, and often at a better price.

Dave

Nigel Graham 220/10/2021 22:38:52
1767 forum posts
22 photos

If I recall correctly, the sheet material used in motor and transformer laminations is not steel.

It is pure iron, which allows the magnetism induced in it to rise and fall closely with the current cycles.

I do not know if or how this will affect your design but it may be a point to consider.

noel shelley21/10/2021 09:41:20
847 forum posts
19 photos

Nigel is correct ! If magnetism is important to your design then you want lamination steel/ iron not mild steel. Noel.

John Haine21/10/2021 09:48:17
4259 forum posts
251 photos

If you look at the earlier part of the thread the magnetic properties are pretty irrelevant as long as it is magnetic enough to work as some sort of latch.  And lamination iron even at 50 Hz is well under 1mm thick.

Edited By John Haine on 21/10/2021 09:49:25

not done it yet21/10/2021 10:45:50
6430 forum posts
20 photos
Posted by John Haine on 21/10/2021 09:48:17:

If you look at the earlier part of the thread the magnetic properties are pretty irrelevant as long as it is magnetic enough to work as some sort of latch. And lamination iron even at 50 Hz is well under 1mm thick.

Edited By John Haine on 21/10/2021 09:49:25

I would expect laminations to be thin to reduce eddy currents within the assembly?

SillyOldDuffer21/10/2021 10:51:40
Moderator
7675 forum posts
1693 photos
Posted by Nigel Graham 2 on 20/10/2021 22:38:52:

If I recall correctly, the sheet material used in motor and transformer laminations is not steel.

It is pure iron, which allows the magnetism induced in it to rise and fall closely with the current cycles.

Pedant alert. Though Iron was the original material you have to go back well over a century to find it in transformers. It was discovered early on that Silicon Steel is magnetically superior to Iron because it stores less residual magnetism when the AC field reverses.

Interestingly, Silicon Steel isn't much use for anything other than electromagnets because it's mechanical properties are poor.

Anyhow, the exact type of steel doesn't matter here because John is making a latch, where the exact magnetic performance of the steel won't make much difference.

In John's place, I'd try to avoid the problem of sourcing 1.3mm steel at the design stage by not depending on hard-to-get materials and odd sizes. Not easy - design is hard work, especially when you don't know what materials are available, how much they costs, or where to get them! John's difficulties are multiplied because he's short of space and money.

Faced with the problem of reducing a steel sheet to 1.3mm, I'd probably roll it - dead mild-steel is quite soft. Otherwise, glue the plate to a flat surface and sand it down with coarse Emery Paper. Takes time and effort but it will get the desired result at minimum cost.

John's goal being secret makes it difficult for the forum to suggest alternatives. This is unfortunate because there's more than one way of skinning a cat, especially in engineering! Rather than finding 1.3mm strip, how about padding out a thinner metal plate to fit with paper backing or epoxy?

Dave

peak421/10/2021 11:29:36
avatar
1537 forum posts
165 photos
Posted by SillyOldDuffer on 21/10/2021 10:51:40:
................................

John's goal being secret makes it difficult for the forum to suggest alternatives. This is unfortunate because there's more than one way of skinning a cat, especially in engineering! Rather than finding 1.3mm strip, how about padding out a thinner metal plate to fit with paper backing or epoxy?

Dave

My initial thoughts were to use 1.2mm steel and hold it in place with double sided tape before fixing with screws, but that wasn't what was required in the material spec.

Bill

Tony Pratt 121/10/2021 11:38:04
1752 forum posts
8 photos

You need to come up with a 'design' which uses obtainable materials.

Tony

John Haine21/10/2021 11:41:39
4259 forum posts
251 photos
Posted by not done it yet on 21/10/2021 10:45:50:
Posted by John Haine on 21/10/2021 09:48:17:

If you look at the earlier part of the thread the magnetic properties are pretty irrelevant as long as it is magnetic enough to work as some sort of latch. And lamination iron even at 50 Hz is well under 1mm thick.

Edited By John Haine on 21/10/2021 09:49:25

I would expect laminations to be thin to reduce eddy currents within the assembly?

Again, if you look back, he's using a neodymium magnet so there are no eddy currents except transient when the latch closes or opens.

speelwerk21/10/2021 12:28:18
424 forum posts
2 photos

This one sells 1.30 mm C75 springsteel of 25 mm width **LINK** but no indication of minimum order quantity.

Howard Lewis22/10/2021 12:07:43
5528 forum posts
13 photos

If you want an easy release from the permanent magnet a shim of copper may do what you want. I believe that the pole, piece of a solenoid had a thin copper coating to prevent the armature sticking to the pole piece.after the current had been removed

Shim brass might do the same job..

Howard

John Smith 4726/10/2021 18:40:31
271 forum posts
11 photos

[I just lost a rather long reply]

In my experience everyone thinks that they understand magnetics but is an extremely hard subject.

It turns out that in practice (magnetic) "Permeability" is almost irrelevant and the only number that really matters for magnetic latches using permanent magnets is the (magnetic) "Saturation Flux Density".

Nobody will tell you this, but my understanding is that (roughly speaking) Permeability is how easily a material can start to be magnetised by a weak magnetic field, but Saturation Flux Density is how much you can magnetise a material... and it's the latter that matters most in practice!

Cheap mild steel (AKA Low Carbon Steel) seems to be be remarkably 'magnetic' in the sense of having a high Saturation Flux Density.

Despite being rather hard to machine, mild steel become incredibly easy to bend permanently when 1mm thick strips become long and narrow. For this reason I could always use spring steel and temper it, even though I am told that this would add "c. 20%" to manufacturing costs.

Of course the other problem with mild steel is that it does RUST very easily with fingerprints and would presumably need to be electroplated. I might consider some kind of 'magnetic' (i.e. Ferritic or Martensitic) surgical steel but from what I can see they will create about half the magnetic pull of mild steel. Also one would need to be careful as most grades seem to be about as soft as mild steel.

Tricky stuff, eh?


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