Detent Ball Flattening

WesWer_Blades

Active Member
I have heard a lot about flattening the detent ball to help the tension (pop) on a flipper.

My question – what is the best process for flattening a ceramic detent ball?
 

EdCaffreyMS

"The Montana Bladesmith"
When flattening a detent, it is a very difficult thing to get "right"..... you have a RAZOR THIN margin of error between it working and not... if you get the angle of the flat out of 90 to the blade, it causes more issues then it solves. Flattening a detent will also create a significant increase in drag/friction as the ball rides the blade throughout the action's motion.

An easier avenue, to achieve the same thing is adjusting the detent hole size.
What size detent ball and drill are you using? Try going up or down one drill size and see what you prefer. For a 1/16" detent (also works if you are using metric detent balls and drills) With a smaller detent hole , such as a #54, you will get a "softer" lockup in the closed position... and less drag to open the blade. There will also be less impact when the detent falls off the blade near the fully open position.

A larger detent hole, such as a #53... or some folks even go with a 1/16" or #52.... this will create a "harder" lockup in the closed position, and will require more effort to get the opening motion started. This is often the route people take to create that "pop" you mentioned.

Finally, there is a HUGE difference in a detent hole, that is drilled with a regular 118 or 135 degree drill bit, and one drilled with a a carbide, 135 degree, single flute bit, such as those from MA Ford. These bits create a sharper "shoulder" than standard bits, and will give far more of the "pop" versus other drill bits.

All that being said, none of it will help/change anything unless there is a high level of precision in the overall folder build. The higher the precision of the overall folder, the more impact those changes I spoke about will have. ;)
 

WesWer_Blades

Active Member
Thanks Ed for the explanation. Right now I’m just trying new things.
You are totally on the detent ball flattening angle. After the lock bar was bent I placed my lock liner on a granite block keeping the diamond file parallel to the block. Then I took my height gauge and off set the apex of the ball to incorporate the .020 space between my liner and blade with a clamp. Then I just taped the file to the bottom of the height gauge and just gave it a few passes.
I use a 2mm detent ball. I drill a #48 in the Ti liner and #52 in the blade. Once the ball is press fit is is roughly .023 extruding from the liner.
My ball placement is .017 from the lock face so I don’t have any problems with the lock face contacting the blade in any position.
Thanks for the advices on the drill bits. I will give them a try.
1740D904-8E2B-49B2-86E0-9C346E64A473.png
 

EdCaffreyMS

"The Montana Bladesmith"
Right now I’m just trying new things.
That is the name of the folder game!

I tried the same thing you are doing... the 2mm ball, but went back to SAE (1/16") because I couldn't get satisfactory results (because of the sizes versus the hole size).

Another tip.... don't discount "working in" a folder's action. Put dabs of good quality grease on the working parts, including the face of the detent ball, assemble, and then work the action. It's not uncommon for me to spend 5-10 mins with each folder, "working in" the action. I feel that it's a very important part of getting that "silky" smoothness. I've also discovers that tumbling a folder's parts is about the easiest method that can be used to create smooth actions.
 

WesWer_Blades

Active Member
Nice! I am going to need to try the tumbling method! For the 1/16" ball what are you using for drill bit size in the lock bar and the blade and how much of the ball extrudes from the lock bar?
 

EdCaffreyMS

"The Montana Bladesmith"
For 1/16" ball, I drill through the liner and into the blade with a #54 Hi-Roc bit, then ream the liner with a #53, and press the ball into place with an arbor press. For lighter action knives (gents and such), I leaved .015" of the ball exposed, and for heavier actions such as framelocks and/or "tactical" type folders, I leave .018-.020" exposed. That is with those folders using bearing pivots. I tend to lighten locks considerably if building a folder with washers.
 
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