Spring material advice needed

[old martParticipant @oldmart]

The turret indexing spring on a microscope is on it’s last legs and I am considering either 0.5 x 4mm steel or 0.8 x 4 berillium copper or a bronze alloy of some sort. With steel, I would have to anneal and re heat treat after shaping but I’m not sure about the copper alloy requirements.

[Michael GilliganParticipant @michaelgilligan61133]

Depending on your source, you may find the cuprous alloys are already ‘springy’ enough … If not, they usually respond well to hammer-hardening.

MichaelG.

.

Edit: __ From one of my go-to reference sites:

https://www.copper.org/publications/pub_list/pdf/a1360.pdf

 

[Paul LousickParticipant @paullousick59116]

If it’s just a little flat spring, making it from a piece of “Band-it” strapping may be suitable.

[DiogenesParticipant @diogenes]

With small bits of thin brass often the forming will ‘fix’ it sufficiently, if you feel it’s still ‘lacking’, a bit of planishing or even a couple of well-placed taps with a broad punch will often do..

 

[John HinkleyParticipant @johnhinkley26699]

There was a short thread on here a little while ago, asking for a suggestion for the use of the stainless steel flat spring to be found in windscreen wipers.  This might be a source of suitable material for you, if the design of the spring lends itself to it.  The size that you quote in your original question looks to be close to those of the sample that I’ve kept “for a rainy day”  (Quite apt, as it happens, since it came from a windscreen wiper!)

John

 

[Andrew CrowParticipant @andrewcrow91475]

Broken mechanical clocks or wind up toys are a good source of light springs ( if anyone can remember what they are).

I generally take apart broken or discarded items so always have a supply of assorted springs.

If you can find the right one of course!!!

Andy.

[old martParticipant @oldmart]

Thanks, John for reminding me about the windsceen wiper spring which had completely slipped my mind. Now I will be searching the garage for one I think is there to add another possible metal. I have started making a little press tool which will make a stretched W in the centre of the spring which is supported at each end by 10BA screws about 2″ apart. The tool is made from two short lengths of 1/2″ key steel pinned together by 4mm dowels which keep them in alignment as they are pressed together. I have not milled out the W shapes yet.

[Russell EberhardtParticipant @russelleberhardt48058]

If you are considering beryllium copper alloy you need to be very careful when working it.  Beryllium is toxic and carcinogenic Fine particles from sawing, filing, and polishing can get into the pores of your skin and can be inhaled with severe consequences.  When I worked at the Philips research labs it was strictly controlled and had to be processed by appropriately trained technicians in a special area.  At least it’s not as bad as the beryllium oxide used as an insulator in microwave transistors those transistors had to be disposed of very carefully if they failed!

Personally I would stick to hammered brass or heat treated steel depending on the required force.

Russell

[old martParticipant @oldmart]

Don’t worry, I started working with beryllium copper back in the sixties and will be showing it respect should I try it for making a spring. I’m not sure just how prone to cracking it would be compared to the other options.

[Nigel Graham 2Participant @nigelgraham2]

I think you would find it difficult or impossible to obtain beryllium-copper these days, short of salvaging some from a scrapped electrical item of suitable age. It was phased out (except perhaps for very special duty??) simply because it is so toxic and safer alternatives exist.

The windscreen-wiper spring thread is still here in this Materials section.

[NimbleParticipant @nimble]

Hi Oldmart,

You could look at a Lucas contact breaker spring, 7.63 x .39-.42mm. you should be able to get a 40mm length out of one.

Best of luck.

NimbleNeil.

[old martParticipant @oldmart]

The strips of spring steel arrived yesterday, it is CS95 grade. It won’t bend enough as is without cracking and has to be red hot to get the desired bend. After cooling it seems just as springy as before heating over a short distance, so has potential. The press tools used probably quench the steel almost as fast as water would and letting the steel cool by itself before shaping was not a great success.

I bought a pair of Bosch wipers for the car and took the old Bosch ones to bits and salvaged two strips of spring steel from each blade, 0.79mm x 7.13mm which is too wide and would have to be reduced for making my small spring. The wipers had been on the car for about 4 years and the springs which were lacquered black showed very little corrosion.

Beryllium copper is easy to get hold of, on ebay there is a good choice, mostly from China, for small jobs it is not too expensive.

[old martParticipant @oldmart]

The result of several attempts to get the tools to use in the fly press right with steel spring strip is ready to use, but I will also have a go with the beryllium copper when it arrives. The steel has had to be thinned down somewhat because it was too stiff and getting the 1/16″ holes each end exactly spaced needed the mill and drilling 20.5mm each side of the centre for the 10BA screws.

Assembling with about 120 x 1/8″ ball bearings will need some car brake grease to hold them.

 

 

 

[Ian PParticipant @ianp]

If the 41mm distance is between the two end drillings in the spring, and its also 41mm between the fixed mounting points then the spring will be restrained and effectively be stiffer.

The 10BA screws are not visible in the photographs but one of the 1/16″ holes in the end of the spring should be oversize or better still slotted?

Ian P

[old martParticipant @oldmart]

I had thought of that and there is just room for cheese heads rather than the original countersunk. The clearance is about 1.5mm. My choice of spring is slightly stronger than the original which is why I have thinned it, but not enough, yet.

[old martParticipant @oldmart]

Update: I assembled the turret fully and the spring force seems better with the ball bearings and I have started using the microscope with Leitz 4X 0.12,   GS 10X 0.28,   GS 20X 0.50,  Nikon 40X 0.65 sprung,  Watson para 60X 0.85 sprung, and a Swift 100X 1.25 oil. The 4,10 and 20 are parfocal and I will need 11mm added to the 40 and 7mm added to the 60, the 100 can wait till later.

[Author]

Posts