what causes vertical blade play

Wildcat

Wildcat

Joined
Apr 14, 2003
Messages
925
a few days ago i received a case 41549L. its a beauty and feels great. nice and tight. then today i was helping a freind skin a deer and noticed vertical blade play as i was pressing down to cut. what causes this play? when you grab the blade with your hand there is no play. only when you press down. the backspring seems to lock up tight to the blade with no gap.

i guess i will contact case.

thanks
 
My guess is you're about to leverage more force pushing for in the handle than you are up on the blade. Lockbacks often have vertical play like that, or worse, detectable by just pushing on the blade, because of how the lock interfaces with the notch in the blade Tang and the not-sky-high tolerances the makers like Case are able to achieve.
 
Even if the lock bar fits the Tang perfectly, there is some small amount of clearance between the pivot pin and the blade Tang as well as some between the lock bar and it's pin. The locking spring pushes the lock bar and blade one way, pressure on the cutting edge of the blade will push everything the other way. The length of the blade magnifies the movement from a couple of thousandths of an inch into something you can feel. If those few thousandths of clearance weren't there, the blade wouldn't move.
 
yablanowitz said:
Even if the lock bar fits the Tang perfectly, there is some small amount of clearance between the pivot pin and the blade Tang as well as some between the lock bar and it's pin. The locking spring pushes the lock bar and blade one way, pressure on the cutting edge of the blade will push everything the other way. The length of the blade magnifies the movement from a couple of thousandths of an inch into something you can feel. If those few thousandths of clearance weren't there, the blade wouldn't move.
Click to expand...

This.
In a classic lock back, both the lock bar and the notch in the blade into which it fits are exactly square.
upload_2018-12-22_22-44-17.png
If the fit between the bar and the notch in the blade is not dead nuts, there is a bit of play. A bit of play can also develop as the the locking mechanism wears in a bit.

Modern lock backs (cough Spyderco cough) seldom have any movement because the designers have fiddled with the geometry of the locking parts. They don't actually use the classic lockback geometry.
 
thanks. im going to contact case after new years and see what can be done.

merry christmas!
 
I have the same knife and it has the same type of play that you describe. I just thought it was the nature of the design and accepted it as an annoyance. I'd like to know what Case says about it.
 
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