Stainless Steel Balls

Our stainless balls are Grade 10 440C.

They are heat treated and cryogenically treated to HRC 59-60.

Bearing Grades

Most knifemakers and collectors do not discuss bearing grades. We think this is a mistake. The grade of a bearing defines the manufacturing tolerances. A lower number means higher quality. We recently upgraded our stainless and ceramic balls from Grade 25 to Grade 10. All the balls in our caged bearings have also been upgraded to Grade 10. We are the first and only supplier to offer this level of quality.Why does the bearing grade matter? Collectors want folding knives that are smooth AND have no blade play. If you work to tight tolerances and have fine finishes, your knives will be smooth. When ball diameter varies, the largest diameter ball and smallest diameter balls will have different loads. Minimizing diameter variation evens the load amongst the balls and makes a knife feel smoother.

We thoroughly researched bearing suppliers before selling bearings to knifemakers. We were shocked to learn some of the suppliers were selling Grade 200 bearings to knifemakers. Even now, some suppliers do not list the quality of the bearing they sell. It is important for knifemakers to educate themselves and know the quality of the materials they buy. Don’t be penny wise, quality foolish.

What is the difference between the bearing grades? The table below shows tolerances:

Grade	Sphericity	Ball Diameter Tolerance	Surface Finish
3	.000003″	+/- .00003″	0.5
5	.000005″	+/- .00005″	0.8
10	.000010″	+/- .00005″	1.0
25	.000025″	+/- .00010″	2.0
50	.000050″	+/- .00020″	3.0
100	.000100″	+/- .00050″	5.0
200	.000200″	+/- .00100″	8.0