Repairing dividers

I have a pair of M&W dividers, but the 1" OD spring has cracked right across where the handle fits. I could transplant the spring from my el-cheapo Indian pair (which seems to have been properly tempered...) but it won't fit quite right and I would still only have one pair.

I've realised I could make a suitable spring from 1" diameter silver steel, but I'm not sure wh\at would be the right thickness. The M&W spring was very thick, about 1/16" or more, which may be why it cracked, but the Indian one is much thinner.

I don't know how 'springy' the silver steel will be even if tempered to a deep blue and I don't want to have to make several prototypes if I can avoid doing so. Can anyone suggest what might be a suitable thickness for a silver steel spring? These are 6" dividers by the way.

Neil

Hi Neil

If it's any use to you I have a spare 3" draughtsmans divider set it opens to give you a 2" radius so you can get 4" dia max, send me a pm with your address if you're interested, maybe you could return favour in the future

Always willing to help when /where I can

Cheers

George

Edited By mechman48 on 20/04/2013 13:51:06

I wonder if M&W supply replacement springs, although they may cost more than your Indian ones. If you were here the local second hand shop has about a dozen pairs of dividers, and calipers (inside and outside), mostly M&W for around $NZ6 each.

I'v always though of the hole in the spring as a weakness, even though none of my calipers have broken. Ian S C

Neil,

Silver steel is no good for springs, I make quite a lot of flat and V springs, use EN45 harden in oil and temper to a dark blue in daylight --not in artificial light the colour will be wrong. There are a few trick for tempering if you need them PM me

John

Thanks George,

I already have a pair of draughtsman's dividers; the broken pair are the heavy duty sort with ground ends for marking out metal.Perhaps they could be of use to someone else?

I've dropped an email to M&W, they only list spares for the more expensive tools. I caontacted them once about a 1/4" collar for my inside micrometer, it was scary expensive!

Neil

Parts from places like that seem expensive, they should be available at reasonable costs, the postage is proberbly the most expensive bit of the deal, and some firms supply parts like that gratis. Ian S C

I got an email from M&W asking where I was, which seemed promising.

I replied and got a second email that said they only supply the complete items.

So back to original question - is it worth trying a spring from silver steel?

Google not very helpful: Not sure if "Pair SILVER STEEL SPRING-LOADED CBR CAPTIVE EAR LOBE PLUG LARGE GAUGE RINGS 2g" will work.

Neil

Edited By Stub Mandrel on 24/04/2013 22:27:45

Hi Neil,
Have you tried to find a supplier of spring steel strip ? I have just done a Google search for spring steel strip and came up with this supplier that claims to sell small quantities. I wonder if their idea of "small" is the same as ours ? Another possiblity an old wood saw which could be softened to enable it to be cut and bent before re heat treating it. Even one of the disposable hard point saws may do if it could be softened and re hardened.

Les.

Neil,

I suspect that his idea of "small quantity" might differ from ours ... but this site is worth a look.

... and you never know; he might have some offcuts, or samples.

MichaelG.

.

Edit .... Les beat me to it !

Edited By Michael Gilligan on 24/04/2013 22:49:36

Neil,

Beyllium copper would do it. Easy to form and then a couple of hours at 300C to harden ( if you have the facilites I think I've got the material - need to check my spring making box).

Rod

As I see it the shape, a split tube, is to stabilise it. However you could make a tube part out of anything and then add the springiness with a springy loop like a key ring.

Would it be possible/practical to roll the spring, then for heat treatment place it in a fitted size hole in a tube to keep the form, it would also give more bulk, that would make temperature control easier. I'd almost consider forgetting the handle, unless it could be attached without drilling a hole. Ian S C

Try the silversteel, use the broken one as a guide for the dimensions, make the part for the hole little thickerr by turning it excentric, cut it with a separating disc after tempering at blue. Niko.

> make the part for the hole little thickerr by turning it excentric,

Excellent tip Niko. I've decided to give it a try at the weekend, even though other tasks (gear cutting - my favourite!) beckon.

Neil

Well folks, I carefully bored out my spring, filed it to a good facsimile of the original M&W one. hetaed it up and got it glass hard and then tempered it down to purple, to be on the safe side.

Yes, it worked fin right up until the dividers were almost closed when 'ping' cracked right across through the hole, straight as a a die.

I don't think silver steel of that thickness  - 0.060" - is really up to working as a spring

Neil

Edited By Stub Mandrel on 27/04/2013 19:38:08

Well if you not try you cannot win, perhaps roling one from an (old) clock spring is the way to go. Niko.

An interesting idea, Graham. I had noticed that the unhardened silver steel appeared to work as a spring already, once bored out, but assumed it would rapidly 'take a set'. I still have enough of the silver steel tube to make a 'wonky' spring. It won't do for keeps, but it does give me an opportunity to try your idea. If it works, I can try a second spring, perhaps a little thicker.

I will also keep my eyes open for a wee bit of proper spring steel.

Another option is to anneal the spring from the Indian pair, close it up using your jubilee clip technique, and then (after smartening up the finish) re-harden and temper it (with my fingers crossed, of course).

Neil

Hello Neil,

You might do OK with a cut down strip from a knackered hard point saw, if you can roll it up to the right diameter. They are in high carbon steel but not over hardened back from the teeth. I save mine for hard flat stock in thin section, having sheared the induction hardened teeth off.

Failing that I have a section of gramophone spring about 1 inch wide and would be happy to post 4 inches of it to you; it is already in blue temper. Send me a PM if that helps you

Brian

Hi Neil,>>

I have a pair of dividers with a broken spring, they have been in the "to be fixed" pile for years now your efforts have inspired me to have a go. I have some high tensile tube about an inch in diameter, this was skimmed inside and out to give a thickness just over a millimeter. The spring made from this was too soft so I hardened and tempered to just blue. This now seems to work well so I would suggest you might try some medium carbon steel rather than tool steel.>>

Best of luck with your endeavors.

Peter.

I apoligise to all for the font size I do not know how it came out so large or how to change it.

Edited By Peter Tucker on 28/04/2013 20:16:26

Hi Neil,

As I have already said Silver steel is not a suitable material for springs, and with respect to Grey neither is gauge plate the best material. It will work and can be used but it is not a good substitute for a specialist spring steel such as EN45, EN42, EN47. The most "forgiving" of these is EN45 and I would recommend this for your application. It is used widely for springs with multiple compressions, motor vehicle springs, press tool springs and shotgun V & flat springs for example.

Greys method of production is a good method and if I was making it I would bend the material hot, this will enable you to get a better shape, also leave it a little longer so you can make a closed roll then cut out the opening for the legs etc prior to hardening and tempering.

To harden and temper heat to a cherry red and quench in oil, degrease and polish up with emery, make sure the last polishing is with a new piece of fine emery and do not touch the surface. Temper to a full dark blue in shaded daylight [nor bright sunshine]. Alternatively you can put a small amount of tempering oil in a tin with the spring in the tin --not need to polish, then heat the tin until the oil catches fire [outdoors of course] keep playing the torch on the tin just enough to keep the oil burning until the flame goes out--all oil burnt. Leave to cool and you should have a correctly tempered spring.

If tempering by colour it is best to heat indirectly by placing the component on a plate or in a tube then heat the plate or tube until the colour shows.

If I root around I can probably find a bit of material but its not a thickness 1/16th that I use much. PM me with your address and the size you want and I'll send you some to play with.

John.