WTB: Tiny leaf springs from HP front panel buttons

[TerraHertz]

I need about 40 of the tiny steel foil springs for old HP equipment front panel press buttons, as used in 3497A, 8350B, 8901A, 3456A, 3253A, etc.

Some of the gear I bought on ebay from the USA had the springs missing from  the buttons. I think someone must have tried blowing dust out with an air gun and blew the little springs out too. I found a few loose in the equipment, but many are gone. Without the springs the buttons have no 'click', and can make contact intermittently by themselves.

A photo of one here: http://everist.org/HP_notes/HP_switch_springs.jpg
The springs are small flat strips of spring steel, probably nickel plated.
Dimensions are: 3.58mm wide, 14.20mm long, 0.05mm thick.

There is virtually zero 2nd hand test equipment market here in Australia, so my only hope of finding these is if someone in the US has some unwanted dead HP front panel PCBs that use these switches, and will charge me more or less just the postage. Or has a stock of the bare springs, in which case the postage would be very little since they'll fit in a standard letter envelope. Happy to pay for them.

There's some other things I need, listed here: http://everist.org/HP_notes/HP_hard_to_get.txt
if anyone's interested.

[jeroen74]

Maybe you could ask a local machine shop if they have or can get hold of this material? Then cut individual pieces from a long piece.

[TerraHertz]

Maybe you could ask a local machine shop if they have or can get hold of this material? Then cut individual pieces from a long piece.

I've been trying. I could cut it myself - have a small industrial guillotine. Actually the material is so thin it would cut easily in a paper guillotine, which I also have.
But so far no luck at all finding a supply. An engineering shop I showed one to, thought it must be spring steel, tempered then nickel plated.

They're the smallest incarnation of unobtainium I've ever encountered.

It's quite easy to remove and insert them from the plastic push-button bodies. Just needs fine tweezers. Also if they get any small kink they don't work properly. It's easy to see how a careless person could blow a whole lot of them out with compressed air. So you'd think there'd be a need for replacements for these, in all that old but excellent HP gear still being used. But no... nothing I've found. I also asked on a HP historical forum, no luck there either.

Another bit of lost technology I'm hunting, is a technique for making something like those beautiful photo-anodized aluminum instrument facias that Tektronix used for the 7000 series scopes.

[bradleytron]

Maybe you could acquire an old mechanical wind up toy or clock. They usually contain a coil of spring steel that you could then cut to size. Otherwise a metal supplier with spring steel shim stock.

Brad

[TerraHertz]

Maybe you could acquire an old mechanical wind up toy or clock. They usually contain a coil of spring steel that you could then cut to size. Otherwise a metal supplier with spring steel shim stock.

It's the thinness that is the problem. Measured with micrometer - that 0.05mm is not a guess. It's not much different from aluminum foil, except spring steel. I simply can't find. Yet. Still looking, currently on hold while busy with other things.
I'm also told that when you buy spring steel shim, it isn't heat tempered. Plus it will be bare steel not plated, so will rust. More problems.

Clock/toy windup springs are *much* thicker. Speaking as someone who started pulling toys apart at around age 3 or 4, got a clock back together and working around age 6, and never really stopped dissecting stuff for curiosity.

[dandare1948]

You might try ppshim.com.au for shim stock. I suggest 316 stainless but I don't know if it would be sufficiently "springy".  They might be able to suggest something better suited for this application. 

Alternatively, how about cutting up feeler gauges from your local car spares shop, might get pricey for 40 pieces though

[free_electron]

let me see how many i have. mybe not 40... but at least more than 25 ...
it's a start ... send me a PM with your address

[grenert]

I've successfully cut SS shim stock to replace these springs.  At that thickness (thinness?), it's easy to do, even with scissors.

[TerraHertz]

let me see how many i have. mybe not 40... but at least more than 25 ...
it's a start ... send me a PM with your address

Fantastic! Even 15 would solve my immediate problem - that 3497A in the bottom of the black rack (see 'my workshop' thread) has some missing and I'm trying to get it set up now.

Edit:

I've successfully cut SS shim stock to replace these springs.  At that thickness (thinness?), it's easy to do, even with scissors.

Is it springy enough, and doesn't stay bent? I tried the HP springs with a magnet and they are magnetic. So I assumed it isn't stainless steel. Plus they get bent to a fairly small radius in normal use, which also made me think stainless wouldn't work.
I realized that whatever it is it would be easy to cut (if I could find some.) The chief difficulty being to get the length exactly right. But that's nothing a cutting jig won't fix.

[free_electron]

15 i have for sure... send me pm with your address. will ship saturday. if i get around to it... been very busy last week and this week

[TerraHertz]

15 i have for sure... send me pm with your address. will ship saturday. if i get around to it... been very busy last week and this week

Done. And thanks!
I'm still going to keep looking for a way to make these, and if I can do them in quantity, put a note online about it for search engines. I'm sure a lot of users of old HP gear must have this problem. It's so stupid to have a big piece of nice equipment unworkable due to such tiny, simple, easily replaced things missing or broken.

[TerraHertz]

You might try ppshim.com.au for shim stock. I suggest 316 stainless but I don't know if it would be sufficiently "springy".  They might be able to suggest something better suited for this application.

My apologies, I somehow missed seeing your post till now.
Thanks! They turn out to be in easy driving distance from my home, so I'll definitely go visit them next week. Will take a sample spring and see what they think. Heh. I have one in a little ziplock bag, together with a tiny surgical clamp to make it possible to handle the spring without losing it.

I notice that's your first post here! I've only been here a couple of days myself. Didn't realize at first it's an Australian site - which is good to see.

Alternatively, how about cutting up feeler gauges from your local car spares shop, might get pricey for 40 pieces though

<shudder> I don't think I could make myself do that anyway. Would be in direct conflict with my 'care for tools' fetish (or whatever you want to call it.)

[SeanB]

Buy cheap Chinese ones then, no worry about them being tools then.

[TerraHertz]

Buy cheap Chinese ones then, no worry about them being tools then.

 
On the other hand, if I wanted to stick cheese in the buttons of my beloved HP instruments, I'd use actual cheese.

[G7PSK]

Are they steel or bronze springs, I have made leaf springs in the past from bronze drought excluder strip. If steel try a clock and watch repair shop as they often have stocks of such material.

[TerraHertz]

So, I've visited ppshim.com.au  warehouse in Smeaton Grange (near Narellan). They have a huge range of thin sheet metals, brass, steel, stainless, aluminum. The closest we could find to the HP springs was 0.05mm 316 stainless. Bought some, cut a sample spring.... and it doesn't work. It immediately bends to a permanent S shape in the HP switches the first time you press the button.

On closer inspection of another HP front panel PCB, the springs they use do seem to be developing some light rust spots, so they are not stainless, nor plated. Probably just plain spring steel.

Which ppshim do not stock, sadly.

The hardness rating system for metal shim goes "half hard", "three-quarters hard", and "full hard".
Ppshim only stock half and 3/4 hardness. The HP springs are probably "full hard". And there's little suggestion of where I might find some, apart from maybe a company in Melbourne.

Still hunting...

Free_electron, did you have a chance to post those? Cost?

[classicTEK]

Hello All,

McMaster-Carr is your answer for this:

http://www.mcmaster.com/#spring-steel-shim-stock/=kh2odn

.002 thickness is what you may be looking for.

Cheers

[robrenz]

Just a note to those making springs from spring steel.  Spring steel has a grain direction just like wood has a grain. It is parallel to the direction it was rolled to thickness.  It typically is parallel to the longer dimension of the material. Just like you would not make a wooden diving board with the grain of the wood perpendicular to the bending direction, don't cut your spring steel springs with the grain perpendicular to the bend direction.  If you take a piece of .002" blue tempered spring steel and try to fold it in half like a piece of paper perpendicular to the grain it will break in two very quickly with a relatively straight break right down the grain.  Try the same thing bending in line with the grain and it will almost fold flat before it breaks.  A very lightly loaded spring made improperly may seem to work fine but its fatigue life (cycles to failure) will be greatly reduced.

[lowimpedance]

 If you can track down some Starrett No. 667 thickness gauge stock in 2 thou, (I checked a spring from a scrap switch in my junk and it is 2 thou thick), you can cut this up and it should do the trick (maybe try 2.5 thou). The No.667 comes in a variety of thickness so make sure you check for the correct size first. Where I work I have used this for leaf springs etc and works quite well, allthough nothing as small as the HP springs, (but I reckon it should be okay for this too). Engineering supplies should be able to help you out, if not 'Epay' perhaps!.
 Good luck

[TerraHertz]

Thanks for all that help, ClassicTEK, robrenz and lowimpedance.

I've ordered a roll of the 0.002" 1095 Spring Steel—Full Hard Temper from McMaster-Carr. That's a useful supplier to know about, thanks. Unfortunately they don't seem to be set up well for overseas orders, and I couldn't get any other shipping method but 'surface'. And unknown cost while placing the order to boot. Hopefully, their shipping cost will be reasonable, but I hate being in that position of having to click 'place order' without knowing.
Plus, it will likely take months to get here, if by surface they really mean surface.

And thanks, for apparently registering on this forum to tell me that. 1st post - welcome to the forum!

Robrenz - I didn't know spring steel had grain. Thank you for that.

[TerraHertz]

Oh well, so much for McMaster-Carr.

Hi <name>,
Due to the complexity of U.S. export regulations, McMaster-Carr accepts international orders only from our established customers. This decision also applies to orders shipping within the United States, because it is based on the final destination of the items. We cannot accept this order or future orders.
Aaron

Talking about a small roll of steel shim, fits in one hand, costing $18 plus postage. Sheesh. 'Complexity of export restrictions' my arse. So, they should remove all non-US destinations from their online creditcard orders page then. As it is, it would seem to be false advertising. I like the implied threat that they'll check for attempts to place the same order via an intermediary in the US.

It's really sad, watching the USA corp/govt gradually turn into some kind of insane nightmare. Well, not so gradually.

At least I now know a specific product description, to search for in other markets.

[tjw]

Hi TerraHertz,
                       I am wondering whether you have looked at this supplier http://www.smallparts.com.au/store/categories/shim/all/pics/

They appear to have a large range of hard to find equipment and supplies.

Regards.

[robrenz]

What about the emi shield strips that are in old Tek mainframes and plugins. that is very close to the right thickness and already has a bow in it and is spring tempered. I don't know if you can get the shape you need from it but if you can it should work great.

[G7PSK]

Have you looked at this sort of material, clock pendulum suspension spring.

http://www.ebay.co.uk/itm/NEW-CLOCK-SUSPENSION-STEEL-SPRING-WIRE-STRIP-SPARES-REPAIRS-PARTS-/360512363997?pt=UK_Clocks&hash=item53f0361ddd

May be a bit thick but could be rubbed down to required thickness or watch springs might be better.

http://www.ebay.co.uk/itm/Watch-Flat-Wire-Springs-Assortment-100pcs-Approx-/390497960606?pt=UK_Jewellery_Watches_WatchAccessories_SpareParts_SM&hash=item5aeb7e029e

[TerraHertz]

Tjw, thanks for that link! Definitely a source that will be very useful. Sadly they don't seem to have any 1095 spring steel shim, only 1010 low carbon steel, full hard. I've ordered some of that anyway to try it, and asked them about the other. See how we go. Great to find a place with so much neat stuff, in Aus.

Robrenz, that's not a bad idea, except there's no way I'm pulling the EMI shield strips off my dearly beloved old Tek scopes, and anyway I need literally dozens of these little springs. Oh, and the required springs are flat, not curved.

An interesting thing happened while I had a sample HP front panel on the desk to try a spring made from the stainless shim I bought at ppshim. While pressing the buttons (just the bare switch stubs), on all the buttons in the matrix to get an idea (again) for the range of 'feel' the buttons have, one of the little springs in a switch went 'sproing' and flew out across the bench. Looking at the switches, and thinking about how that could happen, I think I see it. I've never observed it happen directly like that before, but maybe the missing springs on my old HP gear are _not_ all due to people dusting out machines with compressed air guns. It seems that in rare cases, the springs can just decide to depart.
It's a dynamic motion/inertia thing, hard to explain.  It may only happen if the switch hasn't been used for a while, and a part of the spring has developed a bit of stiction with the plastic switch body behind it. Or if someone whacks the button very hard and fast.

G7PSK  - Hmm. Close. But I kind of want something I can be sure of getting more of in future. Not just for myself, since I'm sure this 'old HP gear missing switch springs' must be a fairly common syndrome.
The bit about 'rubbing down to required thickness' makes me shudder. With copper or brass shim yeah I guess, but spring steel? How?