Brett,
The IKBS patent covers the fact that you put a recess into part of the knife and throw in some small balls to create a frictionless thrust bearing so the blade will rotate freely. The size of the balls does not matter. Putting your recess in the blade may or may not matter from the patent's perspective. That would be for lawyers and a court to decide. You can use a counterbore or an end mill or chuck it in a lathe and bore it, but the end result is the same, you have a recess for the loose balls in the liners or handle of the knife. In order for you to legally use this system you have to be granted a license from the original patent holders. They'll give that to you if a. your test knife passes, b. you etch the IKBS logo onto your blade, and c. they bother to get back to you with the approval.
The IKBS system does work well. However, there are several drawbacks. One is the fact that you have about 26 loose balls to deal with during the entire construction of the folder. You drop a "bearing set" and you've pretty much lost 13 of the balls. On assembly you have to deal with holding one set of balls in place while holding it upside down and putting the other set in its liner in place. You can learn it, but it's a bit of a pain. Another drawback is that the thrust bearing surface diameter is only around 1/4". On many conventional folders using thrust washers you have a diameter of 1/2" which gives more support to the blade around the pivot. On my IKBS test knife I made the counterbore larger and turned a couple of brass spacers so that the balls ran in a larger diameter circle. Here is another concern that I and some others have experienced. My test knife was returned to me 2 years ago and was discussed by myself and the man who does the examination here in the US. All sounded well, but even after emails asking about it I have never heard whether I passed or not. I know of others with the same problem. Without that approval and the artwork for your stencils you can't use the system without the possibility of a lawsuit.
You do not want to use a ball end mill for your counterbore. You can round off or chamfer the corners of a flat bottom end mill if you like (that's what I did) but the "race" you are creating needs to be flat and parallel with the sides of the liners and blade tang. If you use a ball end mill your balls will be forced to the lowest point which is right up against the pivot. You would have the balls rubbing up against both the liner and the pivot and there would be some drag, defeating the purpose of the system.
There is an alternative to the IKBS that works as well, is easier to create, and requires no certification of the patent holder. USA Knifemakers Supply and Alpha Knife Supply both sell frictionless bearing sets for thrust bearings. Tracy's and Chuck's bearings are different, but work in the same way. You counterbore the liners/handles and/or the blade, and set the bearing sets in place. These bearing sets have the bearings held by a "cage" of steel (USA) or nylon (AKS) so that when you drop a whole bearing set on the floor you simply pick it up, blow off the dust, and go back to work. Sure beats chasing down all those loose balls! They are not particularly expensive to buy. There is only a little more time involved in an extra set of counterbores, and that is offset by simply dealing with a bearing set, a single thing per side, and not a bunch of loose balls. And you don't have to get stencils and etch someone else's logo on your knife. Many of my knives are at the art and presentation level. I don't even etch my own logo onto the blade, but place it inside so as not to detract from the art I've created. I sure wouldn't want something as large as the IKBS logo out on the blade as well. This is the only way I'll be making a folder with frictionless bearings from now on. I recommend you look into it.
David
