Pivot screw retention

The General

The General

Joined
Jun 6, 2000
Messages
3,625
I am not criticising the Sebenza! But...

When I was breaking in my blade and looking for a good PTFE product, I loosened the pivot screw to make opening the blade easyer. The blade out of the box was quite painful on the thumb. I noticed that after loosening SLIGHTLY the screw would loosen quite a lot. by itself. This happened every time the knife was opened. I have had to put a drop of Locktite on the screw thread to keep it in place. I am sure I can still remove it for stripping and cleaning. Has anyone else had to do this? I noticed on other folders with pivot screws, the screw stays where it is turned even if you turn it as much as 180 degrees. Why then does a 15degree twist, cause the screw to flap about so badly? Still in every other regard (apart from the clip) this is a great knife!

W.A.

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"To strive to seek to find and not to yield"
Tennyson
Ranger motto
 
We have been advised in the past by the good folk at CR to never loosen the pivot pin.
Unlike other knives that is not how you free up the blade.
The screw and blade insert remain stationary (they do not turn) and the blade rotates around the blade insert.
 
General,

On both my large and small, the pivot screw is always tightened down, like all the other screws. The precision manufacturing tolerances should be at a level where when tightened normally the action should be smooth, but not overly "fast." CRK uses a bronze or oilite bushing between the blade and the pivot pin.

If you're having problems with the action, disassemble and clean the pivot area. That should help things out tremendously.

~Mitch

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My Hobby Page
 
The pivot screw should be tight. It should not need locktite. It should not have locktite applied.

If it is difficult to remove the screw after locktite has been applied, do not force it. Heat the pivot end with a hair dryer or by placing it in boiling water for a few minutes, to soften the locktite then remove the screw with the proper tool. Then clean off all of the locktite, clean and lube the pivot area and both sides of each bronze washer, preferably with flourinated grease, and reassemble the knife, making sure all parts are in their proper relationship.

It is very easy to get one of the bronze washers slightly out of position so that the pivot bushing is not perfectly centered. This may not be readily apparent when reassembling the knife and would cause the spacing to be off a bit when everything was tightened. That would throw everything off, including the lockup. It would also result in side-to side play of the blade.

If the screws are tightened too much in this condition, it would deform the center hole of the washer and prevent proper seating of the pivot bushing. The washer would have to be replaced.

The pivot bushing acts as a bearing and a spacer. It is a precision fit to keep the handles properly spaced and a pivot for the blade.

The drag you feel on the blade motion is caused by the locking bar pressing against the blade as it swings through it's arc. The detent ball rides on the side of the blade under considerable pressure from the lockbar. Friction against the opposing oil lite bronze washer accounts for the rest of the opening resistance. Proper lubrication of these areas goes a long way toward smooth operation.

After enough repeated cycles, the surface of the blade, where it contacts the detent, and the detent ball, itself, "mate in" and smooth out. Once this process is complete, the wear seems to slow to a virtual standstill. It appears that the surfaces have smoothed out so much that they just glide across each other without removing any material.

Once everything has worn in, you should be able to retract the lockbar completely out the path of the blade, to the point where there is no contact and the blade should swing freely, or very close to it.

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Dennis Wright
Wright Knife & Sporting Goods
La Mesa, CA
1-800-400-1980
wrightknife@ixpres.com
("Have a knife day!")
 
*General gives Dennis a waist level bow*

Thanks for the great advice and the time you took in giving such a detailed and thoughtful post. I was over eager to loosen the knife you, I had not given it a chance to wear in. Using some PTFE grease has helped a lot. I will get a hairdryer and remove the Locktite from the screw as you advise.

Thanks again!

W.A.

------------------
"To strive to seek to find and not to yield"
Tennyson
Ranger motto
 
Good advice Dennis, thanks!

I had not gotten to this post yet and made similar, but less detailed, comments on the question about lubricants.

Anne

 
If the loctite was blue, you don't need the hairdryer, if it was red on the other hand then heat away.
smile.gif
 
Touch the screw with a solder iron. It will come right out.

What is a man doing with a hair dryer anyway?

[This message has been edited by FNG (edited 02-16-2001).]
 
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