Door lock spring steel

[Andy Freeman 1Participant @andyfreeman1]

[Andy Freeman 1Participant @andyfreeman1]

I have been asked to repair this old door lock. The 10mm wide, 0.5mm thick spring has snapped where it fitted over a 5mm pin. I have tried to sketch this in the photo. What is the best method to create this? I can buy different sizes of spring steel flat from RS Components but I assume that this can not be bent.or would I form it from mild steel and then heat / temper it?

Edited By Andy Freeman 1 on 13/03/2016 20:23:45

[Clive HartlandParticipant @clivehartland94829]

It is a spring, so it is not mild steel and you will have to search for spring steel. Forming it hot and then harden and temper.

Clive

[JasonBModerator @jasonb]

Reeves do annealed spring steel strip in various weights and widths just form and harden

[Bob StevensonParticipant @bobstevenson13909]

All good locksmiths keep a large selection of lock springs and will certainly be able to match that spring…you may have to shorten one or both arms etc for perfect fit but that is easily done now by scoring with the miniature cutting disc on a Dremel type rotary tool. locksmithing businesses buy these springs in a large packet of assorted shapes and sizes so that they can always match a spring.

[Neil WyattModerator @neilwyatt]

Get some soft iron wire. Clean up the spring.

Wrap this very tightly around the two parts just above the ring, don't worry about the gap.

Stick the main length of the spring right into a raw potato

Coat the wire with an active flux and working as quickly as you can soft solder it in place.

Now clean up every trace of flux.

Job's a good un' to coin a phrase.

Neil

[Andy Freeman 1Participant @andyfreeman1]

Lots of ideas there thanks. I have ordered a length of annealed spring steel from Reeves, well two actually as I'm learning

I will try and learn the art of hardening and quenching in oil. I will also visit local locksmiths. I have visited one – he said, sorry mate, that lock is too old, you'll have to buy a complete new one. The lock is from an internal door at my church, so about 150 years old.

Good idea Neil, the photo is not to clear, the end of the long arm has also broken off about 15mm down.

[AjohnwParticipant @ajohnw51620]

I have the same problem – house and locks date from 1911 and the most used one on the lounge door broke. I used clock spring and had to anneal one end so that I could drill a hole in it. However it was a very strong spring that holds the brass handle rather than a knob up and the latch out.

One leaf of the clock spring isn't really strong enough but at the moment the door does latch if the handle is held up. It should be ok if I add another 2 or 3 leaves. The original one had 2. Probably explains why it has lasted so long.

John

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[JohnFParticipant @johnf59703]

Andy, best what is make a former to make the bend, it will need to be a little smaller than the finished peg size though looking at it's function it is not too important as long as it fits the peg in the lock. Harden by heating to a cherry red, quench in oil. Now comes the tricky bit, tempering ! One method is to blaze off in oil or tallow. The idea is after quenching hold the spring on the edge of a soft flame i. e. not full power on you torch, and turn regularly until the oil ignites then move out of the flame but hold it above the flame thus adding a small amount of heat to keep the oil,alight turning regularly . You may have to add a little more oil just befor the flame goes out and continue until this burns off. Then you should have a spring ! You can dip in tallow and burn off, tallow has a higher ignition point than oil thus a higher tempering temperature.

If you want any more advice feel free to message me. John

[CirclipParticipant @circlip]

Why do so many choose to ignore the standard tempering oven in every household, The COOKER. Once the part is hardened, clean it by washing in whatever to get rid of ANY surface crud, set the cooker to the required tempering temperature and hang the bit in there. Providing you've cleaned it properly there's nothing to contaminate the inside with. Same for blueing parts, cook and then drop into oil. Good time for doing this is Sunday after lunch when the oven's up to temperature anyway.

Regards Ian.

[JohnFParticipant @johnf59703]

Circlip, yes ok for some operations but not for springs it ain't hot enough , most are about 250 deg C and springs need be tempered at 300 to 340 deg C depending on the material, application, type of Spring etc.John

[CirclipParticipant @circlip]

And there was me thinking bits of metal exhibiting a dark blue colour was hot enough. Just shows how wrong I've been.

Have used same for tools too, sand gets all over.

Regards Ian.

[Howard LewisParticipant @howardlewis46836]

If all else fails, several lengths of piano wire, bent to shape, and possibly soldered to the original?

Surprised that it has failed after 150 years, must have had more than 10^7 operations in that time, so should have passed the fatigue tests.

Howard

[Ian S CParticipant @iansc]

Probably a bit of intercrystaline corrosion.

Ian S C

[JonParticipant @jon]

Annealed it will be easy to make.

Start with the 5mm pin fixing down the length and cut off after, its easier. Shaping best done by eye.

Most off the shelf spring steel is pretty soft when hardened, especially the new stuff the last 30 years or more. Can try quenching in a bearing oil but think that may not be hard enough, could cool the oil? Temper in equivalent whale oil burnt off, leave to cool job done and will be on the softer side.

Equally easily produced with ready hardened and tempered spring steel. Just need smaller diameter peg to bend round, rest as above by eye.

[Andy Freeman 1Participant @andyfreeman1]

Thanks to everyone for your help. I bought two lengths of annealed spring steel from AJ Reeves. Yes, it was very easy to form into the shape I needed.

Heated it until straw colour (as hot as I could get it) Immediately quenched it in cold water. Quickly dried it with heat then put it in engine oil (all I had at the time). Removed from oil then burnt off oil with gentle heat until dry. Put it back into the lock and hey presto, it worked a charm!

I must admit, this was after a couple of attempts. One spring just snapped like a piece of glass, another one just failed to return to its original shape. It seemed that when it was straw colour, it had to be quenched very quickly. I was heating it right above the can of water so I could just drop it in.

All in all, an interesting learning experience.

Could not have done with out help though

[Sam Longley 1Participant @samlongley1]

Get a straight bit of spring steel & cut to length. Insert it with one end so it is against the peg at the 2 o'clock position. just opposite the handle spindle insert another peg so that it pushes the spring forward making a bending motion so that it applies pressure to the free end of the spring. If necessary superglue a small piece of steel to the free end to increase the bending motion

Alternatively, chuck the spring away & insert a lump of rubber behind the ward & super glue the opposite end of the rubber to the lock case. Rubber supply would be from a flexible joint, such as a sailboard mast foot, or a shock absorbing stop on the axle of a car. Perhaps a tube of polysulphide mastic ( not the cheepo silicon stuff)  squeezed out into a large blob, Allow to set for a couple of days, then trim to shape with a stanley blade & insert it in the end of the case so it pushes the ward. Then stick it in place with a bit more mastic.

Edited By Sam Longley 1 on 23/03/2016 05:30:12

[Speedy Builder5Participant @speedybuilder5]

has band saw blade got enough carbon in it to make spring steel ?

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