Lock Rock

JRB Blades

JRB Blades

Well-Known Member
So I made my 2nd and 3rd liner lock knives recently. Got pretty much everything done and fitted up. During the final fit and test, I noticed that both had some lock rock. Meaning I could move the blade slightly in the open/close direction. It isn't much, but enough to not let it be. These aren't for sale, they were gonna be gifts for family members, so I'm wondering if anyone has any ideas on a "fix" short of making a new blade or lock side liner. There isn't much play at all. I have to use some just a little bit of force to get the "play" in the blade. They was only 30-40% lockup when I test fit it during my lock face grinding, so I don't know if something happened during heat treat or what. It is 1084 steel.

I have read that I could peen the lock bar to elongate/flatten it a bit. Which in theory may work.

The solution I am leaning towards is replacing my 1/8" stop pin with a 9/64" stop pin and see if that will change the lock up position enough in the open position to eliminate the lock rock.

What do you guys think?
 
Too much contact on the lock face. Color the end/face of the lockbar with a sharpie and open and close it several times. Take it apart and see where it contacts by where the sharpie is rubbed off.

This is the first thing to check before making major changes.

Only a small portion of the leading edge of the lock face should make contact.
 
I will try that tonight. I did notice that I could manually push the lock bar almost to the other liner when the knife is slammed open, so I've got to do something to either elongate the lock bar by peening the leading edge or by putting in a larger stop pin so the blade doesn't open quite as far. If I cut down a #29 drill bit (0136), it may be just large enough to help.

But I'll sharpie the face of the lock bar and see what it tells me.
 
Yeah if it goes all the way to the other side that easy, it may very well be too short already.

Peening or a larger stop pin, either should do the trick. A little can go a long way.
 
Yea, I was afraid of that. It was a nice 30-40% lock up when I initially ground the lock face. I don't know if the heat treat did something to the metal (1084) or what happened. My heart sank when I assembled it and saw that.

So now I'm debating whether to peen the lock face (permantely distorting it) or to ream the stop pin hole to a #29 and use the #29 drill bit to make a slightly larger stop pin. I know that will change my blade geometry in the open position, but very very slightly. I am worried that my detent ball will no longer "rest" in the hold I drilled in the blade for that nice snap closed position. I guess I could gently file the closed position stop pin spot on the blade until it engages with the detent ball again.
 
If the lock is moving almost to the other liner you have troubles, you could enlarge the stop pin like suggested but you open a whole can of worms doing so. like you said it changes the position of the open blade and the detent ball position.
it's hard to say without actually holding it and seeing how bad it actually is, you may just have to chalk it up to a learning experience and keep it yourself...my only suggestion before replacing the stop pin would be to possibly peen the lock bar with a small flat peen that wouldn't mark it badly, go over it with jeweling and try carbidizing it.

What degree did you cut your lock face at?
 
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Yea, I was afraid of that. I've started making some new blades. I really don't want to mess with the geometry or permanently change the lock bar and stuff. Oh well. Learning opportunity I suppose.

I ground the lock face at 8.5 degrees. From what I can see, it is locking up at the lower corner of the lock face only.
 
barlowchiro said:
Yea, I was afraid of that. I've started making some new blades. I really don't want to mess with the geometry or permanently change the lock bar and stuff. Oh well. Learning opportunity I suppose.

I ground the lock face at 8.5 degrees. From what I can see, it is locking up at the lower corner of the lock face only.
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8.5 degrees is good.

By "lower corner" do you mean lower with cutting edge down or cutting edge up when the knife is fully open?
 
When holding the knife in the open position, tip up and cutting edge towards me, the lock bar is contacting the lock face on the left side closest to me. I ground the lock face so that the lock bar isn't contacting the lock face towards the spine of the knife, only towards the edge side of the lock face.

Hope that makes sense.
 
If your lock is only contacting the outer edge and you have rock it sounds like you dont have enough lockbar tension. If you are able to push it over it means its not traveling all the way using spring tension alone. This can cause your lockup to seem earlier when you set it. It eventually just stops moving as you remove more of the tang. Hope that makes sense. One good test is to wedge the lockbar as far over as it will go in the locked up direction. If this removes the lock rock thats your issue. 8.5 degrees is likely good. Best of luck.
 
As it sits now, it has around 30-40% lockup. If I push it over, it will go to around 70% lockup, but the lock rock goes away. So I can either bend the lockbar more so it has a higher % lock up. I can peen the lock bar to deform it a bit and get that earlier lock up. I can put a larger stop pin in to keep the blade from opening quite as far. All of these options make changes that I can't undo. I think I'm gonna make a new blade and see if I can fix it that way. If not I can always do the above changes.

IMG_7099.jpg
 
barlowchiro said:
It's around .040-.045
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Sounds decent...

What I would do is this... Remove scales and reassemble without them (use washers/etc if you need clearance). Then open and lock the blade in a vise, edge up. Use a bright flashlight and attempt to slowly force the knife closed while looking at how the lock reacts at different angles. Should be able to tell you what's actually going on.
 
I'll give that a try and let you know. In the meantime I have started another blade. I'm going down a rabbit hole with this one.
 
JRB Blades said:
Yea, I was afraid of that. I've started making some new blades. I really don't want to mess with the geometry or permanently change the lock bar and stuff. Oh well. Learning opportunity I suppose.

I ground the lock face at 8.5 degrees. From what I can see, it is locking up at the lower corner of the lock face only.
Click to expand...
I personally use 7.5
 
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