Making a spring steel spring?

[john_morris_uk]

A spring that acts on a pawl in one of our davit winches has broken. The davits were made by Whittalls and spares are no longer available. Whittalls taken over by Cooney’s of Northampton who make Simpson Davits but took over the name only and have no spares. Their solution is to offer to sell us a new pair of davits!!!)

The spring is made of spring steel exactly 1/2” wide but 0.4mm thick. Mixing units interestingly.

I could buy some spring steel but I only need a few inches and the thought of reliably heat treating it worries me. Getting an even tempering after hardening would be my problem as I understand you need a special oven.

Any suggestions? Is this something a small engineering shop would routinely do?

Here’s a bit of the spring.

 

[Fr J Hackett]

Rotrax is your man.

 

[john_morris_uk]

But isn't he sailing in New Zealand atm? Sold up his workshop etc.

Rotrax is your man

 

[Fr J Hackett]

But isn't he sailing in New Zealand?

Not sure but I think not but he would give you the best advice on the forum.

 

[Poignard]

I have loads of old clock springs and could probably find a piece near to that size but it wouldn't be stainless steel.

Clock springs are supplied hardened and tempered.

You would just need to snap off a piece equal to the length you need with pliers and tidy the ends with a sharpening stone or a grinding disc in a Dremel or suchlike.

 

[john_morris_uk]

I have loads of old clock springs and could probably find a piece near to that size but it wouldn't be stainless steel.

Clock springs are supplied hardened and tempered.

You would just need to snap off a piece equal to the length you need with pliers and tidy the ends with a sharpening stone or a grinding disc in a Dremel or suchlike.

Thank you. I guess the bit that’s broken was stainless? I’ve got a Dremel and grinding bits on board as well as a Makita battery grinder so assuming I can form the bit of clock spring into roughly the right shape and grind out the hole it’s fixed in place with, a bit of clock spring might work. I could coat it with grease to stop I rusting away inside the davit..

It just a matter of getting it to somewhere in the Caribbean where we’ll be. Let me get back to you and thank you again for the offer.

 

[Lee Shaw]

Could this company help? Their web site suggests they can be adaptable. Only a suggestion, I've no knowledge or interest in the company.

Spring Steel Strip to Hobbyists and Model Engineers

 

[rotrax]

I'm here!

Very probably wont be going to NZ again as First Mate and I have found the current cost of flights and travel insurance, now we are past 75 years, is becoming too much. We will throw some money in and help the kids come here. Even sold the Kiwi boat.

I have made, repaired and modified many springs in my time. Perhaps metric and imperial are not mixed, .4mm is about 15 or16 thou.

To work a davit pawl, hardly an arduous job, a bit of springy brass would get you out of a hole and would be easy to work. It would be nice to see an undamaged spring so I know exactly what is required..

When recoil start springs have broken, as well as motorcycle kickstart springs, heating the end to dull cherry. bending or drilling the now annealed metal as needed, re-heating and then quenching in a bit of old engine oil and parafin seems to work for me. An old Rotivator recoil starter I did that very thing on forty years ago still performs ok. You sort of know its about right if the end of the spring has rainbow stripes after quenching I expect that is not exact enough for Vyv Cox, but I have got away with it..

It is a bit of a black art, but perfectly possible. Thinking outside the box, what about a bit of expanding measuring tape?

Bet you have one of those on board.

 

[john_morris_uk]

Could this company help? Their web site suggests they can be adaptable. Only a suggestion, I've no knowledge or interest in the company.

Spring Steel Strip to Hobbyists and Model Engineers

That’s a great find. In my searches I’ve only found mills that want to sell me metres of the stuff. I’m going to try and dismantle the davit enough to get the other bit of the broken spring out. A perfect but (might be expensive) solution would be to send them the bits and ask them to make a new one. I see rotrax has replied and he’s come up with some ideas too.

 

[john_morris_uk]

I'm here!

Very probably wont be going to NZ again as First Mate and I have found the current cost of flights and travel insurance, now we are past 75 years, is becoming too much. We will throw some money in and help the kids come here. Even sold the Kiwi boat.

I have made, repaired and modified many springs in my time. Perhaps metric and imperial are not mixed, .4mm is about 15 or16 thou.

To work a davit pawl, hardly an arduous job, a bit of springy brass would get you out of a hole and would be easy to work. It would be nice to see an undamaged spring so I know exactly what is required..

When recoil start springs have broken, as well as motorcycle kickstart springs, heating the end to dull cherry. bending or drilling the now annealed metal as needed, re-heating and then quenching in a bit of old engine oil and parafin seems to work for me. An old Rotivator recoil starter I did that very thing on forty years ago still performs ok. You sort of know its about right if the end of the spring has rainbow stripes after quenching I expect that is not exact enough for Vyv Cox, but I have got away with it..

It is a bit of a black art, but perfectly possible. Thinking outside the box, what about a bit of expanding measuring tape?

Bet you have one of those on board.

Nice to hear from you and all understood re New Zealand.

Your metal working description all makes sense and it’s given me some confidence. I’ve got a blow torch on board but I don’t think I can get above cherry red, but if that’s hot enough I’ll give it a go. I’ll try the engineering shops here in Le Marin Martinique to raid their scrap bins. Next stop as we head South is back to St Lucia so if nothing suits here, I can have a wonder round the engineering shops that are next to Rodney Bay.

 

[Norman_E]

My first try would be to take the good spring from the other davit to an engineering shop and ask if they can make a copy, or even better two copies in case the "good" one is also near the end of its life.

 

[john_morris_uk]

My first try would be to take the good spring from the other davit to an engineering shop and ask if they can make a copy, or even better two copies in case the "good" one is also near the end of its life.

You and Mrs M are of one mind. She’s said several times, “Let’s get several made so we’ve got spares.. “

 

[Daverw]

You can get short lengths of spring steel from musical instrument repair suppliers

 

[Rum Run]

A lot of simple springs are only formed and not heat treated at all, either before or after forming. I'd buy the material and have at it with pliers!

 

[rotrax]

A lot of simple springs are only formed and not heat treated at all, either before or after forming. I'd buy the material and have at it with pliers!

Looks like it has a depression or hole in it. It wont be dented or pierced easily without anealing.

 

[Rum Run]

Looks like it has a depression or hole in it. It wont be dented or pierced easily without anealing.

I see what you mean, though it might just be a splodge of dirt, it's difficult to see clearly.
If there is an indentation it might be for the purposes of stiffening the middle section by adding depth, in which case another way of achieving the same would be to glue a short bit of the spring strip into the middle with rubber solution glue.
Trying a bit of metal tape measure would be a good start for sure

 

[john_morris_uk]

There’s no hole in that bit in the photo. The other half is bolted on anc has a hold in it and I haven’t got it off yet. I can turn the screw but there’s a nut I can’t get to without removing the davit arm. It’s on the to do list.

In clock repairs there’s a technique where you make a hole in a clock spring by punching a dimple in the spring steel and then grinding off the dimple leaving a hole.

 

[skedaddle]

You may like to try a Gunsmith. I mean a real Gunsmith not a High Street retailer. They are the always making replacement leaf springs for older firearms. Most "exposed hammer" firearms use leaf springs and they are a regular point of failure. Any spring they make would be steel not SS. Just provide the two pieces as a sample.

 

[Thistle]

You may like to try a Gunsmith. I mean a real Gunsmith not a High Street retailer. They are the always making replacement leaf springs for older firearms. Most "exposed hammer" firearms use leaf springs and they are a regular point of failure. Any spring they make would be steel not SS. Just provide the two pieces as a sample.

Similarly, clock repairers may have old springs in their waste bins which they would be happy to part with.

 

[Daydream believer]

Steel strapping tape from a pallet?
You could certainly start the experiment with the heat treatment on that & you should be able to find a couple of metres in a skip around a dock yard