Pivot Questions

[Mark Behnke]

I've made 2 liner locks from kits a few years ago and recently made my first slippy from scratch so not a lot of experience with folders.
With my first lockback in the final stages the side to side blade play is noticeable.
I used an 1/8" pivot with a 3/16" bushing, blade reamed and lapped to a tight smooth tolerance. The pivot to bushing clearance is loose and I suspect this is my problem.

Questions are, but not limited to,
What are the advantages disadvantages of a bushing, should it not be used on this type of knife?
What are the " " of 1/8" vs. larger pivots.

I feel these are kinda dumb Questions but there are so many tolerance issues with the folders I've done that which ones are effecting each part of the knife is hard to determine at times.

Thanks Mark

 

[Calvin Robinson]

Mark,
I've never built a lock back so I'm just speculating here. You know your pivot pin dosent fit the ID of the bushing properly so proceed only if your willing to live with it. The pivot pin in this type of construction locates the bushing in the proper place and is peened to draw the sides of the knife together and keep it together. The blade will pivot on the bushing and the bushing is left a little thicker than the blade ,usually .00075 or .0005in order to keep from locking up the knife when peening. I believe a slipjoint would be more forgiving of loose tolerances than a lock back would be. Maybe some of the lock back experts will chime in to help us here.