Repairing a Coil Spring ?

RobinHood

RobinHood

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Premium Member
Since I have lots of time in the shop with all the stuff going on in the world, I decided to work on a new to me pallet jack. The spring is to return the handle and pump plunger and get ready for the next stroke.

Has anyone got experience repairing coil springs (if it can / should even be done)? The spring is about 90mm x 48mm x 6mm with ground ends.

C3497346-A8F5-4875-A5FA-347F15D41DC5.jpeg

I have the following processes available:

Brazing
TIG
Stick

I have not checked to see if I can just buy a new spring - might be the way to go though.
 
DPittman

DPittman

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I suspect the heat from welding/brazing will ruin the temper of the spring material. yo might be able to re-heat and temper it tho......
 
John Conroy

John Conroy

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A spring can be welded with compatible filler rod but it should be annealed before welding and re-heat treated after. If you just weld it it will fail quickly. The farmer fix John mentioned is likely the best if you can't source a new one.
 
turner

turner

Active Member
I have one in my hand right now, a little different by measurement though. 110mm high unsprung, 53mm OD, 5mm wire. There is likely a little more to that though, the spring will have a working pressure at a given height. Measured in PSI at a given compressed height. This is achieved by the size and type of spring wire used, I can measure my spring if you have any idea what you would need. The one I have is yours if you want it!
Todd T. Red Deer
 
RobinHood

RobinHood

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John Conroy said:
A spring can be welded with compatible filler rod but it should be annealed before welding and re-heat treated after. If you just weld it it will fail quickly. The farmer fix John mentioned is likely the best if you can't source a new one.
Click to expand...

That thought had crossed my mind. I had played with much smaller springs before (easy to heat and get glowing) and they got soft. I reheated them and quenched, and did what I would call temper with a heat gun. It worked for the little springs. I don’t have any proper heat treat equipment. It looks like maybe welding this much bigger spring is not the preferred method in my case.
 
H

historicalarms

Ultra Member
Johnwa said:
The farmer’s solution would be to put a washer between the two pieces.


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Click to expand...
Yup, bin-there-done that...I also use that method on a smaller scale for re-setting gun springs that have lost their set/ tension over time from guys leaving their guns cocked in a safe or barn for years and then try to fire them. I do use the same trick to set target trigger weight on hammered guns when removing one coil is too much so I split the difference with a thin washer. I have found that spring tension for very tricky usages can be set to a very fine tolerance with such a simple method.
 
RobinHood

RobinHood

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Well, it is back in one piece...

47DA56F8-D1CB-47E8-9CFB-539E15A8A0A0.jpeg F5F756E7-14B8-4530-84A9-C0D64793FF4A.jpeg

It does carry my weight and I can bounce on it. (Not a very scientific assessment of my work, I know).

Few challenges TIG welding it:
* I really don’t know what I am doing (should take a course). A while ago I used Jody’s Welding Tips And Tricks basic set-up for my welder and saved it to program 1 for future adventures. Seemed to work.
* My eyesight for close-up work is not what it used to be. 2X magnifiers had lots of parallax and I kept dipping the tungsten into the puddle; resharpened the thing 1/2 dozen times.
* very limited torch access - especially inside the coil
* melted the coil right through trying to blend in the weld on the first attempt. It was well joined, just did not look nice - that’s why I tried to blend it.
* second attempt was more difficult as I had a good glob of metal missing from the first, failed attempt when the coil melted off. This time I left the chrome socket in the spring until I was done all welding. That actually worked well as both a heat sink and a backer. Nothing stuck to the chrome.

A little filing and blending completed the job.
 
RobinHood

RobinHood

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Thanks Tom.

I am hoping that it will hold up under the low amount of use it will get in its new home.

Because of the broken spring (and the continued use in that state by the previous owner), the lowering valve activation chain adjust was also mashed. So I made a new one this afternoon.

DD41CAFF-E111-46E0-BFD2-BCAFE43E2FC3.jpeg

Used some square key stock I had around. Bit of turning, threading (M5x0.8), milling and sanding / hand finishing got that job done.
 
P

PeterT

Ultra Member
Premium Member
Tools to fix tools. Way to go!

I was curious about heat treating temperatures for springs. For a while there I was pretty sure I was going to be winding my own valve springs for the model radial but finally found what I needed commercially. That was going to be another headache because most of the common spring wire needs a temp outside of what a typical oven can do & its generally a long soak time.
https://www.acxesspring.com/how-to-heat-treat-spring-steel.html

I'm not realy sure what a hot repair like TIG does assuming its a good joint. I guess you would lose temper (like annealing) for as long as the TIG heat ran down the coil. So I assume that means less modulus (mushier) but not necessarily weaker as in it will fail there? I've heard of these miracle putties or that can insulate & slow down heat transfer but have no experience with this stuff. Anyways it was worth a shot at repair assuming nothing goes crunch if it does fail one day.
 
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