Folder Tolerances

[Brian Avila]

I was curious about the tolerances people are shooting for when they make their folders?

-Brian-

 

[Harden Knives]

Let's be honest. Keeping everything half a tenths or a thousandth is shooting a little too high when you're like me and working out of a garage. If I can get my holes squared, I like to see three to five thousandths but a tiny bit over isn't going to give you any play. From my experience, what matter is keeping everything straight. If you can keep it straight you can be a little loose with your tolerances.

 

[Brian Avila]

Let's be honest. Keeping everything half a tenths or a thousandth is shooting a little too high when you're like me and working out of a garage. If I can get my holes squared, I like to see three to five thousandths but a tiny bit over isn't going to give you any play. From my experience, what matter is keeping everything straight. If you can keep it straight you can be a little loose with your tolerances.

Understood.... But what is good compared to what works? Is 0.001" ok?

 

[Harden Knives]

.001 is okay if your holes are square and lined up. I find myself sitting in the 5-7 thousandths range because the bearings in my drill press seem to hold about that much. I only do frikkys so I get less play due to tightening everything down. I don't get play on my folders until .0015 or so.

 

[SBuzek]

The tighter the tolerance the better your folder will function. On framelocks and liner locks I hold sub .001. Spend quite a bit of time lapping and measuring but the results are worth while. Lapping the inside of liners to make sure they are flat also helps.

 

[kc custom]

I'm not sure about an actual number but if there is no blade
play and the knife functions smoothly, I'm happy. With 4
surfaces both sides of the blade, and the liners being as close
as I can hold them to dead flat.----
Ken.

 

[wwells20]

I think all makers "shoot" for .000, then we go out to the shop and (for me) each knife takes on a life of it's own. Sometimes I get better than .005 but in reality, that a good mark to hit. As long as the knife functions correctly, I'm good with .005.

 

[Daniel Fairly Knives]

Pivots - I ream to .001"-.0005" under then lap to fit

through holes - I use less than the recommended sizes to keep them tighter

So I shoot for under and work from there.

Warp - I simply will not allow any that I can measure... recycling drawer!

Spacers to blade+washers - I match them to .001 ...I usually lap until they match dead on but at that point I might need to switch from calipers to a micrometer.

In the end I have no idea what my overall tolerances are or even what to measure... they have to work well or don't leave my shop.



I'm still trying to design the AK-47 of folders... throw it in a sandy river for three days and the action is still flawless!

 

[Frank Niro]

Brian, I wish I could give you some concrete facts. I work to what I believe is what it should be. I know that the work both Ken and Daniel do is what it should be. Is mine up to that standard? I sure hope so. I know I still try improving my work on each knife I make. I still am open to better ways of doing my work to achieve better results but am always ready to offer my present approach.
Frank
"It's not how good the materials are or what you use to get there: it's how good it is when its finished"

 

[javand]

Depending on the type of folder, lock, type etc. "Tolerance" is relative. If you're cnc/waterjetting prebuilt parts and you're trying to make mid-tech tactical folders with mostly just "assembly" and very little hand fitting required, you need to hold exceptional tolerances to get a nice high end folder.


If you're hand fitting all the individual components of a slipjoint, tolerance is extremely relative, since you've got the ability, and the necessity of dialing in each component interplay.


If you're using bushings or pivot bearings, etc, it's totally different ball game than if you're using peened pivot pins. It's also a different thing if you're fitting handle material to a stainless/carbon fittings where you're able to grind the materials together, vs a damascus knife where everything has to be finished separately and fit together with already etched parts.



I'll also add that from what I've seen of most people's shops, they think they're holding much tighter tolerances than they are. As they're rarely tramming, indicating run-out, etc. etc., and running hobby sized machine tools that hardly hold a thou under the most strict practices. Still, they're cranking out great work, that nobody can argue with, which only further illustrates the "relative"-ness of tolerance needed.