a small problem

G'day Gents,

I have a small problem for you. I'm building a couple of liner-locks and I find that the blade lays off-centre in the closed position. My frames (.050" titanium) are flat and true with all holes being reamed to size and they are all pendicular to the frame. I've checked my grind (between 2 flat plates) and it's OK, I've bent the spring the width of the blade (.125") and everything locks up nice and tight yet I have a strong feeling that something is forcing the blade to close off-centre. I've also checked that my detent ball is protruding the thichness of my washers (.0125" nylatron).
The images are in the open and closed positions.

Any suggestions?


Open position


Closed position

Regards from Australia

Check your pivot screws to make sure they are not too long and butting up against each other in the pivot.

Done that Bob, everything seems OK, when I mike the knife in the closed position at the front middle and rear it measures .250" plus or minus .0005". My pivot pin is fractional narrower than that and I'm debating whether I try a slightly longer one.

I had same problem with my first folder (only folder.. )

I found that the backspacer was slightly thicker than the blade and washers.......the lockspring would force the blade to the side. After finetuning the backspacer it was ok.

As Jens said check to make sure the thickness of the spine is no thicker that the thickness of the blade and the washers. It looks kinda like that might be the case. A couple of other things , is the pivot hole in the blade drilled straight. The liners could have a slight twist, only one of them will cause it to do this. Make sure the detent ball is sticking out past the liner no more than the thickness of one washer. Try polishing the pivot pin a little more or try another one. If everything seems to be right on then you may have to set the blade to the liners. With the folder in the open position, hold the handle in the left hand and get a good hold of the blade with the other. Pull the blade towards the side of the liner that it is laying the closest to in the closed position. Sometimes you have to get a little rough with it to get the blade to lay center. This wont hurt a thing and sometimes its the only way to get the blade to lay center. It just means something somewhere was a fraction off and you just helped line it up a little. Since I'm a lefty you may want to hold it in the other hand, either way will work as long as you force the blade center. Give it a try it should work.

What Terry Hearn said is correct, but you also might want to try this. When tightening the
pivot pin, put lateral pressure on the blade towards the way the blade is off center. I use
Terry's way first, then I try the pivot pin. What ever works.

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My two cents worth. Have yet to make a folder. However, my knife making friend with 25 yrs experience adds a second detent ball in the liner opposite the lock detent ball. I don't mean to steal my friend's thunder. He is a fantastic bladesmith and knife maker. Hope this is of some help.

Thanks for all the assistance gents, I've fixed it. I took Terry's suggestion and it worked a treat although I've yet to figure out why.

Regards from Australia.

The one that I just did looked fine and was centered before I heat treated the blade. It must have bowed slightly during the process, because after HT it was off to one side slightly, so I too just took Terry's advice and made it right again. Thanks for the help.
Mike

Hi Neil. Are you using the third hole (1/16) as Jason sugested? It could be that when you counter sink some miss alignment is created.So very little miss alingnment will create a visible error. Of course you should have a pin through the three pieces before going ahead with the counter sinking. If your liner locking end is quite a ways away from the pivot when your knife is closed there may be extra force being placed on the side of the blade. Narrowing the lock will allow you to place it deeper into the blade. With the good geometry you have where the lock mates with the blade you would be amazed how narrow you can make the lock without fear of it failing. Also as Jason also said don't over load the lock.If it will move the width of the blade plusthe washers, then that is enough. Long blades of course produce evn more of a challenge.The best of results! Frank.

If you have checkd to see if all the parts are the proper thickness, then the blade might be to loose. I noticed that the blade is forced away for the liner in the closed position, it may be to loose or the blade can be tapered. don't be afraid to allow a couple of thou. clearence on the detent ball.

Well it may help.

You said you checked the blade with a straight edge did you mess. the front and back of the pivot area on the blade? Are both faces parrellel?

Now remember I'm fairly new at the liner locking, But what I have done in the past by putting a bind on the blade in the open position to get the blade to go the other way, I have squeezed my teflon washers out of shape making them thinner on one side than the other, & having to replace them, to still have the same problem. On some of mine I've been able to, in the closed position, put thumbs in the middle, actually looking like your trying to break the knife in half. If you'll torque it like that, everything seems to shift somewhat & will make the blade line up. I think that taking them apart & putting them back together they tend, I think to line up different some how even though everything is reamed & lined up as straight as possible. I've found a little torqueing one way or the other will be all it takes. Those of you who know me know I don't usually have that much to say, Dwayne

Also, someone said something about blades bowing in heat treating; What I do is while blades are still pretty warm out of the oven, is put them between two pieces of flat 3/8" micarta, Have the blade top almost sticking out of the sides of the micarta & the point of the blade almost riding out, you can check real quick weither the blade is straight or not, if not it still movable, then I temper, it's always worked for me. Dwayne