Spring Frustration

[Traok]

Spring Material 440c

Grr.. okay in an effort to regain some sanity I am hoping some sage might be able to bonk me on the head with why I cant do this right.

So my biggest problem in making slipjoints is getting the spring to the right RC. I understand it needs to be in the 45 Rc area.

Yesterday did some HT in the new Sugar Creek Kiln. Brought the temp up to 1850d F and started the 25 minute timer. Pulled everything out and Air Quenched.

Placed the blades and the spring in the oven at 225 for 2 hours

after the first hour I took out my spring and placed it back into the kiln for the last hour.

Kiln temp bounced between 1090 - 1110d F ( goes up comes down should be 1100 inside the oven). Evenheat's website shows 440C Rc of 43-45 1100d F for 1 hr 1 time

After everything cooled down I pre assembled the knife .. Very nice opens and closes no complaints. Kept working it because it didnt feel right after the 3rd time. At this point I knew something was up took off the one side of the liner to see what was going on.. Sure enough the blade was cutting a nice circile into the spring.

I dont understand what I am doing wrong. I was using a torch and just eyeing the color in the past with mixed results so I figured the oven would be a fool proof plan. ( HAH whose got the last laugh?)

Compeltely discuraged , and in need of some help

James

[Don Robinson]

James, I wish I could simply give you the answer, but I have some questions.

1. Steel type?

2. Did you finish and polish the area on the spring and blade tang that make contact before and after HT?

3. Some of the modern alloys can be tempered at a higher temperature than let's say, carbon steel, and still make a good spring.

I'm usually satisfied with anything between 45 to 50Rc for my springs.

4. How much tension is the spring applying.

5. Geometry: Can the spring flex, or is it too thick or wide? This is very important.

I make sure my springs aren't too thick to flex.

That sounds like it may be your main problem.

[Traok]

Hey thanks for the reply Don, Its funny I was in the middle of rewatching your liner lock DvD when I saw your post

1. Steel type? 440C

2. Did you finish and polish the area on the spring and blade tang that make contact before and after HT? filled and sanded this area so it was smooth

3. Some of the modern alloys can be tempered at a higher temperature than let's say, carbon steel, and still make a good spring.

I'm usually satisfied with anything between 45 to 50Rc for my springs.

4. How much tension is the spring applying. I marked the spring with the blade removed the blade and moved the spring 1/16th clamped and drilled

5. Geometry: Can the spring flex, or is it too thick or wide? This is very important.
It should be pretty close to your Texas toothpick design

( They said make something over and over untill you can get it right, long way to go aparently I think im on like the 10th or 11th since our toothpick build)


Thanks for your help Don, I am definnitly having better luck with this liner locker Nice video


James

[Ray Rogers]

You say that the blade is cutting into the spring. Can I assume that you have enough experience at building slipjoints that you know the knife's geometry was correct when you made the parts and the edge of the blade could not reach the spring when the parts were made?

If that's true then that should mean the spring has bent as you opened and closed it those first few times. If it bent, the spring is too soft, 43 - 45 RC is too soft for a spring and it's possible the spring is even softer than that since published heat treat figures are accurate for laboratory conditions but can vary a good bit according to your individual conditions. So, temper at a lower temperature. Some experimenting will be required to get it just right, start around 600 F and then re-temper higher if it seems necessary.

You said you air quenched which is normal for 440C but you didn't say for how long. Let the steel cool until it is under 150 F, no problem to hold in your bare hand. You also did a stress relief at 225 F. That doesn't hurt anything but I've never found it to be necessary on 440C.

440C loves cryo treatment, if you can add cryo to your process your 440C springs will be much tougher.....

[Don Robinson]

Two things that may be helpful:

1. The distance between the locking area to the spring pivot- This takes quite a bit of experience to do right. The distance must be matched to the spring thickness in all the areas between the spring pivot and the lock area in order to let the spring flex without bending or breaking.

Start with a rule of thumb: Make the spring pivot pin 60% of the spring length away from the blade pivot.
After HT, if the spring is too strong, remove some material from the spring between the pivot pin and the blade pivot to allow more flex.

2. I forgot my second point. I need a nap.

[Don Robinson]

Oh yeah, 1/16" rise should have worked. Your spring is too soft.

Put it in a vise, place a 3/8" pipe over the end, and carefully bend the spring a very slight amount to increase the tension.

Refinish the spring/tang contact area.

Re-heat treat it to give about 45-50Rc.

Assemble and regrind the back of the knife with the blade open so the spring lines up with the handle again.

Take a picture for us, and put your new EDC in your pocket.

Now I surely don't want anybody to think I've resorted to this myself. I must have learned about it from somebody else.

[GHNorfleet]

I know that you would never have done anything like that Don, surely you learned about it from another shade treee knifemaker.

[Don Robinson]

Hi there, Gil.

Yep, and it was probably a shade tree knifemaker on one of these forums.

I could never come up with anything that clever. Probably.

Now don't you guys start spreading rumors around.

Actually, bending a spring doesn't hurt anything if it's re-heat treated afterwards. That relieves the stress caused by the bending.

So,, nothing lost, everything gained once you regrind the back of the knife.

[CWKnifeman]

I am afraid that I just have to ping into this one. I agree that the spring is to soft, I prefer a 48 +/- 1 for slip-joints of 440-C. The reason I pinged into this is how hard is the blade tempered? If the blade is 59-61 then just opening the blade would scar the spring if the tension is tight. Where as droping the blade RC to around 57 +/- 0.5 you should not scar the spring, it might mar the spring but it wouldn't actually take metal off of the spring as in scaring it.
Also I have to agree with Ray about using the cryo treatment on 440-C It will change the cutting ability and the overall strength of the steel to equal ATS-34 or so close that you will not be able to tell the difference.
I hope that this is of some help.
Curtis

[Traok]

So there was no hope in saving the original spring as 3/4 of the spring had been eaten away . I did make a new spring and fit it the same way as before. Nice and tight. Heat treated it normally pulled it out and let it sit under a fan untill I could pick it up with my bare hands about 10 minutes. Put it into the oven at 225 for about 30 minutes.Took it out and placed it in my HT oven at 700D for an hour not right so I put it back in for 800 and then 900 and finnaly 1000. Seemed right here

Asembled the knife . Things were still nice and tight. Opened and closed no grinding or any other noises to give cause for concern. As I continued finishing the knife I noticed the blade was developing a wiggle in it. A little side to side and a little up and down about a 1/16 of a gap will show between my spring and the top of the knife... So I take it the spring bent ? again? Surely this wiggle is not normal right? I cant beleive I am letting a silly little spring get the best of me . BAHHHhhh

Thanks for reading

James

[argel55]

I have been told on the area where the spring and the blade tang meet , make sure the spring is not polished above 400 grit. The surface then holds oil film to help lubricate it,otherwise you will have galling and rubbings.

[Don Robinson]

James, can you give us some pictures of the dis-assembled knife? The spring, blade and liner?

Does the blade tang have a sharp corner?

At this point I don't know how to help you. Evidently your HT method is off.

[CWKnifeman]

James how did you temper the blade, to what temp and for how long? Like I said earlier If the blade is to hard it will gall amd mark the spring. With slip-joints there needs to be a ballance between the two (spring & blade). If the spring is to hard it will snap over time. If the blade is to hard it will scar the spring eating it away over time. If the spring is too soft it will either bend over time, or be scared and eaten away. If the blade is to soft it will be mared/scared and lose material in the heal lock area.

The only other solution to your problem is the rise and fall area of the blade is off.
Curtis

[Traok]

Okay for the blade and spring I brought the oven up to 1850 and let it soak for 25 minutes

Took them out of theoven and placed in front of a fan for about 10 - 15 minutes.. Untill I could pick them up with my hands.. they were still warm but not hot

Placed the blade and the spring in the oven at 225 for 2 hours

after the first hour I took out my spring and placed it back into the kiln for the last hour.

The spring in the kiln was at 900 degrees for an hour.

Placed all peices together again andstill felt like it was grinding away.. Gave up on the kiln and torched the spring right past blue /purple

reaasembled knife felt a little better

heres the results >

Again thanks for any input

[Mike Zima]

Looking at your photo's I can see something. Square corners on the back of the blade. These are going to dig at the spring when opening & closing. At least that's been my experience. Try rounding off the square corners. Also, after sanding everywhere the blade and spring come into contact. Use a felt bob on your Dremel and polish those areas, green compound will do.

Hope it helps.

Mike Zima
www.zimaknives.com