Pivot fitting slop

J

Jared Dinwoodie

Joined
Jan 1, 2014
Messages
67
I have been trying tighten up the action and fit of my folders and have been trying to undersize the pívot hole so I can lap it to final size after heat treat. I made the pívot hole .002 undersize and was initially tight and I even made an undersize pívot to use during the build before final lapping. The problem I’m having is that with all the assembly and disassembly checking geometry, lockup etc. it seems to naturally wear down the pívot hole and now I have some slop with a finish pívot before I even get to HT. Has anyone else had this issue? Should I leave the pívot hole even smaller than .002 undersize?
 
The lapping and fitting is done after HT. What you did is like buying a tailor made suit before you start a diet. It won't fit right later on.
 
Like Stacy said, it sounds like your order of operations isn’t correct.
Also u should be trying for a fit of .0005”

final pivot size after ht with a carbide reamer and then barrel lap
 
Stacy E. Apelt - Bladesmith said:
The lapping and fitting is done after HT. What you did is like buying a tailor made suit before you start a diet. It won't fit right later on.
Click to expand...
Perhaps I didn’t explain it well. In the process of making the knife I need to check the action clearances etc. therefore I need some type of reference or in my case a .002 undersized pivot and pivot hole With the intent of lapping and fitting correct size after heat treat. After assembling and disassembling during the building process checking stop pin positioning etc. it seems to have worn the hole for the pivot and created some slop before I have even had the chance to heat treat or lap. I only noticed when the undersized pivot was getting sloppy and then for giggles tried what would be the finished pivot which wouldn’t fit originally was now slightly loose.
 
You explained the same thing as u did in your first post....
What kind of knife? Slipjoint?
How many have u made?

how sloppy? Wouldn’t U expect a .002 u/a pivot to be sloppy?

I still think your order of operations is strange. I haven’t made slipjoints for a year but what you are experiencing I haven’t had to deal with.

I did my final fitting after hardening and reaming and lapping
 
HSC /// said:
You explained the same thing as u did in your first post....
What kind of knife? Slipjoint?
How many have u made?

how sloppy? Wouldn’t U expect a .002 u/a pivot to be sloppy?

I still think your order of operations is strange. I haven’t made slipjoints for a year but what you are experiencing I haven’t had to deal with.

I did my final fitting after hardening and reaming and lapping
Click to expand...
Frame and Liner locks. I’ve made 7 all together. It sounds like everyone else checks the mechanics ,geometry and does blade profiling after heat treat and then fits the blade to the liners/frame. The way I have been doing it I get it all done but the final lockup, minimal grinding and blade finish before heat treat. It just seems to make sense everything looks and works properly before going through the whole process of heat treating and then finding out the clearances don’t Work or the lines are crap etc. The only change I’m trying to make is doing a final lapping of the pívot hole after heat treat to keep the tolerances as tight as possible instead of doing it pre heat treat to avoid pívot slop. Maybe I’m over thinking this whole thing...I’ve been known to do that.
 
I don't do a lot of folders anymore, but I always finished the blade before any final fitting to the frame. That way once things were fitted there was no more adjusting needed.
 
all fit up needs to be done after heat treating of the pivots/bushings/blades
otherwise every one of them could change ever so slightly making you do everything again...
most steels change a little when heat treated so why try to do fitting on un heat treated parts??
 
I've never made a folder but I've spent a lot of time in a machine shop. A round pin should not significanly enlarge a round hole in the time it takes to check for fitup. I suspect you started with an oversize hole with a burr that made it seem like the correct size.
 
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