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First mod, pivot issue

Posted: Sat Aug 08, 2020 8:06 pm
by FestinaLente
I’ve done some minor work on knives over the years. However, I decided to finally try properly “modding” a knife. I found a D2 CRKT Pilar with carbon fiber scale in great shape and for cheap.

The metal scale with lock was cleaned up with some sanding to fix rough spots and scratches. I gave the metal scale an acid bath to darken it up a bit and hide the sanding/filing. I also polished the blade and metal scale at the pivot and replaced the Teflon washers with phosphor bronze. I also replaced the backspacer with a custom made red notched one.

The blade is centered and I oiled the area for the washers during assembly. It moves smoothly without issue but no matter what I do I can’t seem to correct a slight wiggle issue unless the pivot is tighter than I want. There is no horizontal blade play and the lock engages but the blade sometimes wiggles a little forward and back unless the pivot is tightened to the point where it’s uncomfortable to open with my thumb. The knife functions well and is safe, however as a perfectionist the wiggle irks me. I expect my blades to lock up like a rock with no movement whatsoever unless the lock is disengaged. Any ideas how to correct this issue or have I taken this cheap knife as far as I can?

Re: First mod, pivot issue

Posted: Wed Aug 12, 2020 8:58 am
by soc_monki
Vertical (forward and back) blade play is usually and issue where the tang of the blade and the end of the lock bar do not contact each other tightly. This can be a machining error (like on a cheap kershaw I had where the tang was ground too much) or the end of the lock bar has been dented in (which can happen when someone spine whacks the knife, or batons with a folding knife locked open). Or just poor tolerances in general and being a CRKT, they don't usually have the best fit and finish or tolerances, although my only example (a Caligo) is pretty nice and worth the $30 I paid. they're $40 now and I wouldnt recommend them for that but I digress...

How far has the lockbar traveled on the blade tang? if it has reached, or almost reached, the opposite scale its pretty much worn out. if it's not, you could try bending the lockbar over a bit to see if you can get it to go over further and lock up better. or you can peen the lockbar (use a punch and hammer to squash the metal a little and get earlier and tighter lockup.

Another possibility is that the pivot is out of tolerance (undersized) and is allowing the blade to move around. Sometimes vertical play on Benchmades is attributed to this, and it can be a factor, but if the other contact points are solid (stop pin and lock bar or axis bar) it is usually not a big factor. I have plenty of knives where, when unlocked, you can pinch the blade and move it forward and back and feel it move. Once locked up there is no movement however, so a slightly undersized pivot may contribute but probably wont be the biggest factor. If you suspect it is, I think you can get aftermarket hardware for it, or even contact CRKT and maybe they can send you some! I hear they have really good service.

Hope that helps!

Re: First mod, pivot issue

Posted: Wed Aug 12, 2020 9:13 am
by spyderg
If the new washers are even just a touch thicker than the old ones, the lock bar may not travel quite as far over. This may result in play. If you can push the lockbar over and it eliminates the play then there is your issue. You can then sand down the washers a little and put them back in, and/or bend the lockbar so it engages more. The back spacer may also be the culprit, if it’s a touch too thick or if it impedes the lockbar at all.

Re: First mod, pivot issue

Posted: Thu Aug 13, 2020 1:02 pm
by FestinaLente
I tried bending the lock bar as you both suggested and that seems to have corrected the issue. The bar travels further over than I would like but not too far and now the lockup is completely solid. I think the main issue is a mix of poor machining and tolerances with CRKT as mentioned by soc_monki and the spacing of the washers as described by spyderg.

I know I can’t expect the same fit and finish as a Spyderco when the knife’s value is so much less. My thoughts for this were that I should start with something cheaper so I didn’t risk ruining a knife I really wanted to keep. Thank you both for helping me finish this project.

Re: First mod, pivot issue

Posted: Thu Aug 13, 2020 5:53 pm
by soc_monki
no problem! always good to start cheap!