Broken folder spring

JTknives

JTknives

Joined
Jun 11, 2006
Messages
8,650
well about a month ago i tryed my hand at making a folder and it came out realy nice. but i broke the spring, after about a month af being depresed i am now going to make a new spring today. The knife is a slipjoint and the spring has file work all the way along the back which is why i was so bumbed that it broke. well after heat treat i tempered it with a torch to a blue color and installed it. after lubing the pivot pin and liner it had perfect movement and would open and close with a snap. i was so happy and decided to take it to work and show my friend, apon oppening the blade there was this loud ping sound and the spring shot acros the room. it broke right in frount of the middle support pin and apon looking at the broken ends it looked like the center was still hard and did not get the temper. I gess my question is this, is using a torch not a good way to temper the spring because i have read some tutorials where that is what thay say to do. I gess im just looking for some tips of doing the spring so i dont break it agen. ill post some pictures of the knife tonight
 
I would personaly use am oven,kiln,oil or salt bath.With a torch its possible to heat the sufarce more than the internals.Plus doing it in an oven,etc,allows a much longer soak which will relieve stresses much better than a torch.Also make sure you leave no stress points in the file work by carefully sanding the inside corners of the sharp edges smooth.450-5oo for spring steels,1150 works well for most stainless.
 
ok here are the pictures, im sorry i thought i reduced them all to 640x480 but i did them at 800x600.

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I abslutley love making these, but there so time consuming that when theres a problem and somthing has to be redone its quite a bummer. let me know what you think about the knife. the finish is not done yet. the wood is cocobolo and it goes completley through the liner which is 1/8" O1.
 
VERY nice filework!!! I really like it.

What steel are you using? For instance, if you are using O1, the 450-500 tempering mentioned above would leave you about RHC 59-61 - a fine blade but hardly a spring temper. 600 would get you to 54 and 700 to just under 52.

If you are working with a torch, including for the hardening, you have to "paint" the heat slowly and evenly to allow even heating throughout. (This last part from Tim McCreight since I only temper by oven.)

There is obviously a weak point in the spring where the vine thins out, probably at about the same place you relieve the spring for proper tension. Look for a weak point in the spring and if it's there, try smoothing the relief over a longer area.

There has to be a way to make that work because it is just beautiful!!!!

Rob!
 
yep im using O1, ya i stoped once i hit a med blue. i gess i was still around 60hc. its amazing how much time you can put into somthing like this and not even relize it. i think my problem is that when i tempered with the torch i onley tempered half of it and it was the side that tuches the blade. i left the back end hard and it seames to have cracked where the 2 zones met. but now im gessing its better to temper the complete thing. yes it is a very nice knife and it will look even better once i bring everything up to 2000 grit.
 
That filework is an awesome conception , love the flames.
I know how frustrating back spacers and back springs can be.
I made a Slipjoint kit knife and I think I did a years worth of cursing in the month I spent piddling on it. The most difficult part was getting the backspring just right (after I peened the pins , fully assembled I realized I put the blade on the opposite end on the knife.....)
I did another kit recently that didnt come with a back spacer so I made my own out of aluminum stock , man what a PITA, and it still didnt come out right , finally gave up on that part of the knife.

Anyway , kudos on making your own complete folder , that's pretty cool :)
 
Just curious JT about how you did the inlays. Can you describe how you cut them and how you secured them in the liner. Thanks. Dave
 
It's very important to make sure all the inside surfaces of the back spring are scratch free and that all corners are polished. Scratches and sharp corners may cause a stress riser that creates a crack under stress.:eek:
 
I personally use an oven to do all of my spring tempering. I shoot for 48-50 rc for my springs. Usually thats about 750f for carbon. Early on I did some lock backs that the springs broke because they were to hard. Tempered them at 600f which was not high enough. Best bet is to do a bunch of test peices at differant temps and then rc them to see what temp works for the steel you are using.
 
Use the old spring as a guide to make a new spring. Filework and heat treat. When you temper the spring do the whole thing! I temper 3 times. Heat to light blue, quench in oil, clean up, and repeat. I have never had a spring break yet.
 
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