I have to disagree somewhat with Stick on that although it certainly can be dangerous and needs extra respect. I've had and used one for at least 25 years although I have need for it only occasionally. A company called Corob Cutter still makes knives for that head and they sell for about $17 per set if I remember right. It was originally meant for use only with radial arm saws since you cut away for wood that often needs to support the piece if used on a TS, therefore you use the same method as with the bearing-less router bits. Leave wood on either side of the cut for support until you're done and then cut those parts off.
One other thing to note with the use of that head is that it requires a spacer on the inside of the head up against the fixed inside blade washer. Otherwise, without the spacer, you will hit part of the arbor framework. If you try to use it make sure you can spin the head by hand before you turn the power on. The spacer washer is approximately 1/4" thick without me going out and measuring mine for a precise measure. It hopefully came with the set. It sounds like you are chopping wood at high speed when you use it so be aware and be careful not to get your hands too close to it.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.