Thanks, Brandon. I'm glad to hear the knife tools works for you. It works pretty well for me, too.
The Rex 95 is a good tool bit; 5% cobalt but a fair amount of tungsten so it will handle the heat with harder materials like tool steels. A square tool will cut tool steels fairly well but a tool ground specifically for tool steels will work better. If you tell me what you're cutting maybe we can come up with something that will work better.
The square tool will also work on aluminum and is pretty good for mild steels. However, again, a tool ground for aluminum will work better than the square tool will. I know I gave the tool angles for an aluminum tool somewhere in this thread and it works well for me. The key difference between the square and aluminum tools is the back rake - this gets the cutting forces right up near the tip of the side cutting edge and it also really accelerates the chip flow, which keeps temperatures down. The square tool works pretty good in aluminum, too, so you might try both and see what you think.
As for grinding boring bars and flycutter bits, let me take them one at a time.
Boring tools can be ground to work very well. I can't even remember how many I've ground but what I've learned is that no matter how well the tool is ground or how hard the blank is, that old modulus of elasticity comes into play. A steel bar of any kind is still limited to a depth of 4 times its diameter. We can go deeper with care but consistency suffers. Contrast that to a carbide shanked bar of the same diameter that will go 8-10 times its diameter before running into deflection issues - big difference in depth, consistency and accuracy. For these reasons, I only use solid carbide inserted boring bars for most holes or Micro 100 solid carbide boring bars in small bores. I use inserted carbide bars because of their consistency; I can rely on them to take the cuts that I dial in all the way down the bore, whereas a HSS bar will not consistently do that.
Some guys like to grind HSS tool bits that fit sideways in the end of a steel bar. I've tried those but again, you are limited to the depth of the material the bar is made from. This doesn't work for me when I need to go deep so I don't bother with these anymore.
As for fly cutter bits, yeah, they work fine. However, they do wear faster because almost every cut is an interrupted cut so edge wear is a factor. I clearly remember fly cutting a longish piece of O-1 steel and having the finish change as I neared the end. My inserted carbide fly cutters don't do that if the insert is in good shape, which mine usually are. With that said, if you want to try a HSS tool then go with M2 steel; it handles interrupted cuts better than the cobalt or high tungsten tool bits will. A left hand tool like
@ttabbal said will work quite well in a fly cutter. The thing you want to avoid is a huge nose radius. I know that some guys like that sort of thing but it causes too much radial deflection so I don't use them.
Anyway, I'm glad you've joined us here. If you would like to share your tools or otherwise query, have at it and we'll all pitch in to help. The guys are now quite experienced and I've seen them step in to help others in other threads, which is awesome to see.
Edit: I have used Rex 95 and Cleveland Mo-Max and many others but am not familiar with the others you listed. Cleveland Mo-Max is M2, Mo-Max cobalt is 5% cobalt, and Super-Mo-Max is 8% cobalt; these are some of the finest tool bits made. Anything from Crucible/Rex is also very good. European tool bits tend to be really good, also. I know and have used ETM from Israel and feel they are as good as a Mo-Max bit.
I just looked at all my keeper bits, the ones I use the most, and they are made from either Cleveland, Crucible/Rex or ETM. One of my oldest knife tools is made from a Vasco Supreme T-15 bit - tough as hell.
). I have only taken about .030” off the 7/8” CRS so far using the knife tool. I have been taking very light cuts ranging from a few tenths to .002”. I tried turning the tool bit towards the chuck, parallel to the chuck and towards the tailstock and have not been able to get a decent finish although I will admit that I can take skim cuts on the diameter and take off as little as a few tenths and the diameter in 3.5” only differs by .0003” which I have never ever been able to do with any tool. I cant believe it can skim tenths like this! Anyway, I tried all different speeds and feeds and it has made no difference. I should have made the square tool instead of trying the knife tool as Its my understanding that this tool wasnt designed specifically for turning as much as it was designed for facing or turning into shoulders. I dont want to seem like I am going back on saying how wonderful the knife tool works because it works wonderful, just not for what I am trying to use it for. It faces beautifully but I need to get a good finish on this CRS.