broken calipers

[Anthony KnightsParticipant @anthonyknights16741]

On another thread I described how the spring on some outside calipers self destructed when I was cleaning them in hydrochloric acid. I believe this was due to a pre existing start of a crack which the acid stimulated. To make a new spring I need a piece of 20mmx70mm x1.8mm springy stuff. Suggestions please. I have had the calipers for at least 40 years. They are stamped ALFRID SHEFFIELD MADE.

[Anthony KnightsParticipant @anthonyknights16741]

spring material

[Andrew TinsleyParticipant @andrewtinsley63637]

I have the same problem with a pair of my grandfathers calipers (must be a genuine antique by now!). I too have had difficulty in locating suitable spring steel for a repair. I shall watch this topic in hope!

Andrew.

[egaParticipant @ega]

What about a spring from an old rim lock eg from Victorian door?

[BazParticipant @baz89810]

Why not buy a pair of best quality Chinese callipers and use the spring from them?

[Jonathan GarsideParticipant @jonathangarside40968]

M Machine Metals list 3/4" x 16 swg which is 1.6 mm spring steel strip at £3 per 300 mm.

Jonathan

[Anthony KnightsParticipant @anthonyknights16741]

Hi ega, I've looked in several old locks which I've kept because "they might come in handy" but nothing seems the right size.

Jonathan. your suggestion appears to be what I'm looking for. Thank you. I'll give them a call.

I just need now, is info on how to heat treat the item once I've made it.

Edited By Anthony Knights on 03/04/2019 17:30:07

[Peter TuckerParticipant @petertucker86088]

Hi Antony,

When the spring on my caliper broke I used some high tensile steel tube to make a replacement. I skimmed the tube on the outside and inside on the lath, then cut a piece off and shaped it by hand, after which I hardened it and tempered it down to blue. As a replacement spring it seems to work fine.

Hope this helps.

Peter.

[Brian OldfordParticipant @brianoldford70365]

There might some pearls of wisdom on the degree of temper here.

**LINK**

[duncan webster 1Participant @duncanwebster1]

Modern throwaway saws must be made out of decent stuff, but perhaps a bit too thin? I've got one stached away waiting for me to experiment on it. It might be waiting a long time!

[John ReeseParticipant @johnreese12848]

I like Peter Tucker's method. If tubing were not available it could be turned from solid stock.

[Tony Pratt 1Participant @tonypratt1]

Posted by John Reese on 04/04/2019 01:47:46:

I like Peter Tucker's method. If tubing were not available it could be turned from solid stock.

Sounds like a nice solution!!

Tony

[Anthony KnightsParticipant @anthonyknights16741]

Hi Duncan-great idea! I happen to have one of the saws you mention. The teeth are knackered but I've kept it because "it might come in handy" and now it will. I will use a cutting disc in the angle grinder to hack a piece off. I will then anneal it and see if I can cut, file and bend it to the correct shape. Then re harden and temper.

[Neil WyattModerator @neilwyatt]

I tried and failed at making a spring several times, I failed to get a combination of thickness and tempert that was both springy enough and not too brittle.

The 'use on off a cheap pair' solution is probably a good one.

Neil

[Ian S CParticipant @iansc]

Hi Neil, wondered how you got on with your spring.

I'v got 2 pair dividers, 2 pair inside and 1 pair outside calipers, fingers crossed they are all OK, I don't think any of them are less than 50 years old.

Ian S C

[Glyn DaviesParticipant @glyndavies49417]

I would turn and file it from solid silver steel bar, hardened and tempered to blue.

I did a search on cheap calipers to see how much it would cost to buy one for the spring and came across this one from RS:

la-603828824872&s_kwcid=AL!7457!3!243856879586!!!g!603828824872!&gclid=Cj0KCQjw1pblBRDSARIsACfUG13cJU_Wihtr7RdSiBs2-A6i65aSn2ELPLDXqsf9zVUKNZhQjNuqO7UaAlgREALw_wcB&gclsrc=aw.ds”>LINK

I'm not sure why it's listed as being metric!

[CirclipParticipant @circlip]

Problem with using a piece of tube or bar stock bored and turned is that the grain flow runs in the wrong direction. Flat strip is the better choice.

Regards Ian.

[Russ BParticipant @russb]

This spring disintegrating reminds me of changing brake fluid types on my trails bike, technically both compatible as per the manufacturers recommendation, however the change in PH caused the spring to disintegrate.

[Howard LewisParticipant @howardlewis46836]

Hydrogen embrittlement?

Howard

[Anthony KnightsParticipant @anthonyknights16741]

Well, I managed to find the old saw and cut a piece off. It's only 1mm thick but I'll give it a try.

[Anthony KnightsParticipant @anthonyknights16741]

Now into the firery furnace to see if it will anneal wthout oxidising away.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Neil Wyatt on 04/04/2019 10:43:15:

I tried and failed at making a spring several times, I failed to get a combination of thickness and tempert that was both springy enough and not too brittle.

The 'use on off a cheap pair' solution is probably a good one.

Neil

Glad it's not just me. This week's failures included a go at a small coil spring.

I made two springs from the wire from a broken knitting machine. It's very difficult to bend cold and won't stay in shape even when forced into position. Heating the wire softens it, but nothing I've tried in the way of heat-treatment gets the spring back again. Give it a pull and it unwinds as in the lower example. Hopeless.

The two springs on the right are more successful. Made from piano wire, they can be bent cold and still work as a not-quite-so good spring. Heat treatment doesn't help. Pretty sure I have Tubal Cain on Springs somewhere in the mess. Funny thing about books and tools, they're never where I left them…

Dave

[Ian S CParticipant @iansc]

I was looking at a moderately large Bulldog paper clip, the type with two lugs sticking out the top, and a large cylindrical spring. I think that maybe the spring could be cut to get two springs that could be pushed together to make one, this just might be strong enough.

Ian S C

[Brian OldfordParticipant @brianoldford70365]

You could use something removed from these perhaps? **LINK** 

 

Edited By Brian Oldford on 14/04/2019 11:30:50

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