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?

[SeanB]

Ceramic tile back and waterpaper............. Or for a coarse initial work use 2 cheap chinese whetstones with the stock between them, well lubricated with oil.

[aghp]

One DIY wink

Last time I have repaired (to condition what is like new) these HP front panels I made some springs my self:

I just buy this (look image) and use one strip (not  remember exactly thickness)  and cut exatly right size piece with normal (really good) scissors (it need some exercise to make exatly specially this lenght of spring what is very important (also there may need do some compensation in dimensions if there is some wear in plastic parts) .
(this tool was not expensive and I need only some springs so I use this for material source)

Result: as new original. (it depends of course this metal sheet quality, so do not buy crap)

Also these keyboards cleaning (inside switch) is fun work.
 

[mamalala]

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.

Search for "Alucorex". It's made by Bungard, a German company:

http://www.bungard.de/index.php?option=com_content&view=article&id=26%3Aalucorex&catid=3%3Abungard-produkte&Itemid=77&lang=english

It's rather simple to use, very similar to presensitized photopositive PCB material.

Greetings,

Chris

[TerraHertz]

Update: OK, so the stainless steel shim I purchased first didn't work. It bends to a 'S' shape, ie too ductile.

Then McMaster-Carr (USA) refused to ship a small roll of what looks like the right stuff (1095 Spring Steel - Full Hard Temper, polished) to Australia, quoting 'export rules.'

Next I found an Australian supplier (smallparts.com.au) with full hard, cold rolled, low carbon steel shim, 0.002".
That arrived a while ago, coming in a box that shows it's originally from http://www.precisionbrand.com (in USA.)
I got around to cutting a sample spring yesterday.
It doesn't work. Immediately bends to an 'S' shape, even worse than the stainless.
The HP springs obviously are the 1095 spring steel material, or something similar.

It turns out that  http://www.precisionbrand.com also has the right stuff:
High carbon 1095 hardened spring steel, Blue Tempered Shim Stock Rolls
http://www.precisionbrand.com/ProductsCatalog/PBPCategoryDetails.aspx#l1=14&l2=79&l3=112&lcd=112&l4=0
including:
23110  .002"  .051mm  3" 23C2    0.18

But smallparts.com.au doesn't stock any.
A USA distributor does: http://www.applied.com/apps/commerce/catalog/catalog.do?e=10&s=5534686

I'm about to try them. Will be interesting to see if they have the same attitude about shipping to Australia as McMaster-Carr. It won't surprise me at all if they refuse.

Edit: Thanks Chris, that's an interesting option. But, I'm seeking a way to incorporate multiple colours during anodizing of already machined panels. Some of which I already have, just waiting for surface finish.
Hah... it's taking longer than expected to get around to trying the idea I have for that. What a surprise. 

[mamalala]

Edit: Thanks Chris, that's an interesting option. But, I'm seeking a way to incorporate multiple colours during anodizing of already machined panels. Some of which I already have, just waiting for surface finish.
Hah... it's taking longer than expected to get around to trying the idea I have for that. What a surprise. 

I guess you could laminate the panels with Tenting resist, expose & develop, then anodize. Strip it off, and repeat for the next color.

Greetings,

Chris

[robrenz]

AFIK Anodizing is a 3 step process. First is the actual anodic process that grows a pourous aluminum oxide layer on the surface of the aluminum. Second is the color infusion into the porous aluminum oxide skin. Third is sealing of the pores locking in the color. You could get your parts commercially anodized but tell them not to seal the the anodizing but leave it open pore because you are going to print on it.  HERE is one example of how it is done.  Google "printing on anodized aluminum" and you will get lots of examples.

[TerraHertz]

AFIK Anodizing is a 3 step process. First is the actual anodic process that grows a pourous aluminum oxide layer on the surface of the aluminum. Second is the color infusion into the porous aluminum oxide skin. Third is sealing of the pores locking in the color. You could get your parts commercially anodized but tell them not to seal the the anodizing but leave it open pore because you are going to print on it.  HERE is one example of how it is done.  Google "printing on anodized aluminum" and you will get lots of examples.

Yeah, I've been looking into this for a while, discussed on an anodizing forum, bought a book on it, and also most of the gear and chemicals needed for a hobby anodizing setup. And funnily enough, the method you linked to is almost exactly what I'm going to try. It has to be something I can do at home, with bonus points for posting the complete recipee on the anodizing forum so others can do it too. I'm pretty good at coming up with methods that work, but I've not done anodizing before. Currently it's on hold till I finish a side-track project.

The problem with the DuraJet system is it requires a specialized inkjet printer. What I'm planning on trying is using a standard printer, onto high quality photo (glossy) paper, then contact-transfering the dyes to the unsealed aluminium surface. Various potential means for doing that, we'll see which works best.
Fingers crossed that standard inkjet dyes will work, ie survive the sealing process.
The objective is to produce instrument fascias for my projects, that are as pretty, hi-res and durable as the old Tektronix 7000 series fascias. The primary project this is for needs a lot of different panels with system block diagrams mixed with the controls and indicators. There's a reason why 'looking impressive and professional' is highly advantageous to the whole exercise. And no I don't want to go virtual and have it all on monitor screens. Reasons for that too, to do with needing guaranteed control system function.

Using the paper-transfer method means it's easy to solve the problem of aligning the text to the machining of the panels. Not so easy with direct printing, even if I had a printer that could feed thick aluminium sheets.
The image reversal required is of course just a photoshop step.

[SeanB]

Best inks to use are the photo archival inks from a printer that can handle photo paper. If you have a printer that can do a CD/DVD in a carrier then you can make panels that size and print direct. Otherwise I would try a PCB transfer film that dissolves to act as an ink carrier, with a damp aluminium panel supplying the moisture to mobilise the ink and a roller to provide pressure and keep the ink from diffusing too far. If you are going to do a lot it might pay to take a printer and modify it to have an open back and arrange the paper feed to pick up the anodised sheet to print direct.

[TerraHertz]

I'm planning to try a vacuum system to achieve even contact pressure of the paper on the aluminium. Then add heat and/or solvent vapor and/or electric diffusion to encourage dye migration.

I want something that's fine for one-offs up to medium volume, needs no special printer, and can be copied by anyone.

[SeanB]

Then probably best is photo paper and archival quality ink cartridges.  Vacuum holdown to a damp aluminium panel with open pores will do the transfer if left in contact for a few hours.

[robrenz]

The vacuum may cause bleeding and migration in the carrier sheet and the porous anodize layer.  Just thinking out loud

[yangshen]

so many stuff wanted

[TerraHertz]

The vacuum may cause bleeding and migration in the carrier sheet and the porous anodize layer.  Just thinking out loud

By 'vacuum', I mean pressing the paper against the aluminium by having another sheet of plastic behind the paper (around the entire al-paper sandwich) and evacuating that enough for air pressure to press the paper to the aluminium. But yeah, I know what you mean. The air molecules between the paper and metal have to get out by traveling sideways. Doing so, they may force the ink to blur too. It's going to be a series of experiments, I expect.
The 'porous layer' of anodizing is actually an array of vertical hole structures if done right, so there's little horizontal travel of the dyes possible inside the aluminium.

Anyway, you're just making me feel bad about being too tied up with other stuff atm to proceed with the anodizing experiments. Happy new year to you!

[robrenz]

Sorry, just trying to be helpfull   have a great new year also.

contains how I do graphics for instruments. it works very well and the cover film is very durable. I know you have a lot invested in the anodize process but this can do what you want now up to 11 x 17 "

[SeanB]

Digging this back from the grave..........

Here is a suggestion from a good source about a material for the springs.

http://www.ko4bb.com/dokuwiki/doku.php?do=show&id=test_equipment%3Areplacing_leaf_springs_on_hp_equipment

If you are looking for the tags mentioned contact your local Meto agent or a store using the labels, they might have a roll of them they will give you.

[free_electron]

Oh no... This completely slipped my mind. I have those things ready to be sent. Monday first work...

[robrenz]

Get a quote from these guys for a whole sheet of them, you could sell the extras.  They are in Australia, a photechemical machining job shop they would supply the material.  The quote won't cost anything.

[SeanB]

The tags are available worldwide. If you want free ones go buy a Transcend flash drive, they have them built into the package for loss control use in retail.

[TerraHertz]

Hey thanks, those are some really good ideas!  I definitely will pursue the photochemical machining suggestion. Scrounging shop tags one by one - not so great.

I want to publicly thank Jay_Diddy_B for sending me a bunch of the springs over Christmas. That's taken care of the HP 3497A that was my immediate problem. Free_electron - I'd assumed you decided not to send those, since I PM'd you a couple of times asking for your mail address for the exchange, but got no reply. No urgent need now, so thanks for the thought but save yourself the trouble.

I've been sidetracked by new-year-ism, camping trips,  and some recent acquisitions that are hogging all my bench space. Will be getting back to the 'bulk source of those springs' hunt soon.

[SeanB]

Shop tags are easy, just ask one of the shelf stackers for a roll. Or use the local yellow pages and look for retail security solutions.

[scopeman]

Ahh. The Bill West switch.

Here is the patent. Very interesting.

http://www.google.com/patents/US4017700.pdf

[TerraHertz]

Ahh. The Bill West switch.

Here is the patent. Very interesting.

http://www.google.com/patents/US4017700.pdf

Hey, thanks for that.
I like this: "... a leaf spring ... may be made of a high carbon steel for optimum spring qualities..."
Ha ha... 'may be.' As if anything else works.

These switches really do work nicely. Except for one flaw - if the plunger is depressed very rapidly, like by flicking it with your finger from thumb-tension, the spring end that is buckling upwards has enough momentum to pull its end free of the tiny bottom-stop lip. So then it's a case of SPROIIING, it's gone!

Ah. And reading back a bit I realize that the 'mystery gift' of 30 springs I got in the mail a while ago was probably from free_electron. Sorry I didn't get back to you, I didn't think you'd sent them. The packet had no information from who it was from (eevblog tag-wise.)
But I kept the return address, will find some Australiana for you.