Need help picking bearings for folder

Justin Presson

Well-Known Member
#1
Hey guys I need some help from the folder makers.
I want to try some bearings instead of PB washers. I have been using 3/16 pivots but I'm not sure exactly what bearings to get.
Here are my questions.
1. What size outside diameter?
2. What size inside diameter?
3.how thick or ball size?
4.What size counterbore?
Then do you need race washers if I'm using titanium for my liner material?
I might be overthinking this but not sure how they are supposed to fit.

Tracy if you could link anything you all sell I'm all for it.

Thanks
JP
 

BossDog

KnifeDogs.com & USAknifemaker.com Owner
#2
I use these caged bearings. I do not use the races included, I use the stainless washers linked as a race against the Ti liner. They are quite a bit thinner. If you don’t use a race, you will wear a track in the liner and/or feel rough spots where the bearings got over tightened a bit.
There are stainless and ceramic bearings. I prefer the ceramic but go cheaper for the first few maybe.
The counterbore is carbide I had custom made for these bearings.
I also use the 64 TPI pivots so I have a bit finer control over the tension.
They are .063” thick and I usually counterbore .040” to leave the bearing around .023” proud of the liner.

https://usaknifemaker.com/bearing-f4-10m.html
https://usaknifemaker.com/stainless-steel-caged-bearings-with-ceramic-balls-187-pivot-size.html
https://usaknifemaker.com/washer-bali-ss-189-id-x-015-thick-x-3115-od-sold-by-the-pair.html
https://usaknifemaker.com/counterbo...r-caged-bearing-fkp-twb-cb-197x-357x-066.html
 

EdCaffreyMS

Forum Owner - Moderator
#3
Before I jump into your specific questions, I'll voice some insight on building folders..... First, there is a HUGE difference in the quality of components! Buying and using the cheaper, made in China stuff creates a LOT of issues. Most of the time the import parts are +/- .002 to .005" tolerance....that means they can be as much as .005" undersized, or oversized. I STRONGLY encourage you to find parts that are as precision as possible. Prioe to switching from import to the super tight tolerance parts, it was common for me to finish a folder, then have to mess around with it for a day or more to get everything where/how it needed to be.
Many times, you may have to choose your bearing sizes (ID and OD) based on the tooling that is available/you can get.
Keep in mide that the OD size of the bearings you use will dictate the size/shape/configuration of that area of a folder....... you have to have enough room in the piovt area of a folder to fit all the parts/pieces. ;) So designs will be effected if you decide to use more than one size of bearings, pivots, etc.

1. What size outside diameter?
Most common is 3/16"ID X 3/8"OD. Ball size is usually 1/16". The balls are most often 52100 steel. Like Tracy, I like ceramic bearings, but they are spendy, and sometimes difficult to get.

What size counterbore?
Get the counterbore that's the same size OD as the bearing OD you're using.

Then do you need race washers if I'm using titanium for my liner material?
No. Normally, with bearings, they will actually cut/work harden a "race" of about .001-.002 in titanium.

I might be overthinking this but not sure how they are supposed to fit.
There's a LOT of things to think about with folders.... probably the most important is to train yourself to think "more precision"...... what the means is that with straight knives, we often can get away with thinking in fractions of an inch...... but when it comes to folders, you MUST think in fractions of a thousandth of an inch...... the up side it that once you build a few folders, your straight knives will benefit from the increased precision.
 
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