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broken calipers

spring material

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Anthony Knights03/04/2019 14:13:09
271 forum posts
87 photos

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 ALFRIDname.jpg SHEFFIELD MADE.

Andrew Tinsley03/04/2019 14:39:42
919 forum posts

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.

ega03/04/2019 15:00:26
1265 forum posts
108 photos

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

Baz03/04/2019 15:13:18
259 forum posts

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

Jonathan Garside03/04/2019 15:21:27
40 forum posts
3 photos

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

Jonathan

Anthony Knights03/04/2019 17:29:17
271 forum posts
87 photos

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 Tucker03/04/2019 17:33:36
179 forum posts

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 Oldford03/04/2019 17:35:01
avatar
566 forum posts
4 photos

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

**LINK**

duncan webster04/04/2019 00:09:56
avatar
2232 forum posts
32 photos

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 Reese04/04/2019 01:47:46
784 forum posts

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

Tony Pratt 104/04/2019 06:48:44
904 forum posts
3 photos
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 Knights04/04/2019 07:21:07
271 forum posts
87 photos

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 Wyatt04/04/2019 10:43:15
avatar
Moderator
16578 forum posts
687 photos
75 articles

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 C04/04/2019 10:58:13
avatar
7447 forum posts
230 photos

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 Davies04/04/2019 11:08:10
113 forum posts
21 photos

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!

Circlip04/04/2019 11:20:44
978 forum posts

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 B04/04/2019 11:29:40
547 forum posts
21 photos

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 Lewis04/04/2019 14:33:11
2341 forum posts
2 photos

Hydrogen embrittlement?

Howard

Anthony Knights04/04/2019 17:54:06
271 forum posts
87 photos

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.offcut.jpg

Anthony Knights04/04/2019 17:57:15
271 forum posts
87 photos

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

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