Folder Questions: Sticky locks and hardening

David Schott

David Schott

Joined
Sep 27, 2004
Messages
3,041
I am starting my second folder. Upon taking apart my first one, it looks like the detent has scored a good circle in the tang. Because this is damascus, I have lost that total glassy smoothness and I feel like i can feel the damascus layers. Not a huge deal but im picky.

I have several ideas on what caused this and how to fix it.

Is this caused by:
-Too much bend in the lock?
-Detent too far out/not set deep enough
-Too small a detent ball (1/16")
-softened tang

This brings me to hardening. Do you guys fully harden the entire folder blade? I had this problem because i quenched holding the blade in vicegrips, so hardened it like a fixed blade...which I suspect left the tang soft. Do you guys just dunk the whole blade when quenching?

This next brings me to locks. I have very firm lockup....absolutely zero play in any direction, full lock engagement. The lock, however seems to "stick" at times. Especially if i flick it open like a gravity knife. Is this caused by overbending the lock? Sharp faces on the lock bar? I am nervous about taking material off the bar or blade and create a sloppy lock, but something needs to happen....my guess is that its an overbent lock bar, causing the left edge of the bar to dig into the lock face? Possibly helped along by the softened tang I have spoken of?

Any experts, thanks for chiming in on this!
 
Your whole blade should be hardened that's important. If your has detent made a good track in your blade the blade is too soft. At this point the detent ball is harder than the tang and will continue to cause wear. If the tang is soft enough for the detent to cause wear what do you think the pivot is doing? It will also wear the pivot hole.

Your lock might be biting because of too much bend. I bend just enough so the liner almost touches the right one when the knife is assembled without the blade.

Your detent should only stick up the same height as your washers are thick. .015 thick washer, .015 of detent ball sticking up.
 
Like Striper28 says the entire blade needs to be hardened. The lock will really stick if the tip of the lock is able to embed itself into the tang, same goes with the ball digging a trough into the tang. The pivot hole oblong will be next. Just reharden the blade and problem solved. Etched damascus always look better with a harded blade also.
 
I am an idiot....Dont know why I didnt think of that to begin with. It makes sense if the lock bar can cut in, that it will stick. i dont know why I didnt think to just re-harden the blade, though i run the risk of creating some slop if the lock no longer fits. Hopefully I can re-harden, and clean up the lock face and back gently enough that I do not wreck the lock-up. I can always re-make a right liner if I need to and re-cut a lock, or totally scrap the whole thing and use the blade on my next folder.

Anyone know a good way to HT Thunderforged Damascus with little to no scale? Haha...im thinking scale thickness is certainly thick enough to ruin the lockup....though it will not last long how it is anyways....
 
PBC from Brownells will allow you to harden without scale trouble. I use it for everything because the blades come out clean with little or no sanding. I use a salt shaker to put the PBC on the blade. Just bring the blade up to about 500-600 degrees and salt it good with the PBC, put it back in the oven and quench when ready. The stuff washes off with hot water.
 
Prior to etching the blade, you want to have the area where the ball travels polished. Then "mask off" that area and the pivot hole, so the etchant doesn't cause a rough surface. Most usually use finger nail polish, paint it on the area to protect, etch the blade in ferric, then use acetone to clean it off.

This will leave a smoother area for the ball bearing to travel on.

Kelly
 
A fried uses white out as anti-scale. Heat treat the blade again. If you take too much off of the lock during cleanup you can always stretch the lock.
 
im still waiting for someone to try my idea of modifying the design of liner locks. since i dont have a machine to do it.

my idea is instead of making the lock bar and area of the blade tang to meet up as a wedge. to cut out/ counter sink an area so the bar fits into the tang and lock up. the tang would have to be a bit longer than most designs i have seen but my theroy is quite sound i just dont have the tools to make it

here is a rough drawing of the idea

blade here
________
l l tang
l l pivot whole here in genral area
l ___ l
l l l l lock bar fits into tang counter sink slot
l__l__l___l
l l
l l lock bar
l l
l l
l l
l l
l l
l l
 
I think I get it....very similar to a pusbutton auto. The tang would have a slot cut into it the same shape as the lock bar, which would be able to fall into that slot at the right blade extension. I think that may be harder than a normal liner lock unless I have it wrong....
 
I learned a neat little trick from Mike Erie the other day. If your lock bar is too short you can stretch it a couple of thousandths using a punch on the end.
 
I may just need to do that! Luckily the lock bar only engaged less than 1/4 the way across, so i think i can clean it up without getting slop. Crossing my fingers....we will find out tomorrow night!
 
CigarMan said:
You can also use foil for the heat treat for a scale free blade. A little trickier to use.

Bill
Click to expand...
And when you are using the foil, throw a match, or a piece of paper into the foil envelope.
In the second it takes for it to burn, it eats up residual oxygen from the envelope.
 
tiktock you are on the right path of thought.

it would be a little harder than your conventional liner lock but well worth the effort. the lock bar should lock into the blade tang when in the opened position. all that would be needed to be done is the tang would need to be machined to allow the lock bar to set in the tang when it is opened. if done correctly it would eliminate blade play and insure a tighter lockup.


on another note: you could cut the end of the tang like saw teeth and match the lockbart with saw teeth to interlock with the tang teeth. to imagin this take you hands and currl your fingers and spread you fingers apart and match them up with your other hand and interlock them together. since there is spring tenntion on the lock would secure tighter to the blade tang.
 
I dont know.....due to the curve the bent liner creates, i think you would still need a bevel on that lock face. Otherwise, you will always have slop of some degree since the lock bar would need to be machined SO close to the tang shape without it. The lock face bevel causes the lock face to contact it anywhere along its bevel, at the exact, exact point where the lock bar and lock face are equal....so wouldnt you still need a bevel, making it just a much more complicated liner lock?

Lookit me, made one folder and i am talking like i know something....pfft!
 
you could put a bevel on it if you want. but it realy shouldnt be needed if done correctly.


if you want another thought you could anchor a pin to the lock bar to act as the detent and have a hole in the blade tang for the pin to fall into exact place and lock up.

just thought of that idea while typing this lol. wouldnt take much work for it. just a little calculation and a drill press and know how to make the pin stay in the lock bar.
 
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