I have a parting tool that not only has a "T" shape to allow additional clearance, but also has a "U" shape along the top surface, which helps to curl the chip inward so that it is less likely to catch. However, the "U" shape means that it is a bit hard to determine where the actual cutting edge is, or should be set - at the bottom of the U? Or at the top? I find I have to set it with the top of the U a bit above center, so that the bottom of the U is on center.<regarding setting the parting tool on center-line>
I have seen it in writing from reputable sources (once on the Sandvik website even) although I do set mine as bang-on as I can. Too much away from the centreline against the rotation direction is obviously bad for dig-in and too much in the direction of rotation can lead to the work 'climbing over' the tool. I believe the recommendations I've seen that advocate for 'slightly high' (for a front toolpost) such that the deflection in the toolpost and the tool itself result in the cutting being done exactly on centre. Probably easy to refine in batches of hundreds on a CNC machine but not easy to do at home.
I'm not surprised, since I was confusing myself trying to explain it! But you've got the idea. Here are a couple of pictures that should help. First, here is a close-up of the business end of the parting tool:Struggling a bit with the U shape. If the front face is flat, where is the U? Along the top edge?
Yes, it seems like it would. I'm guessing the reason it doesn't dig in has to do with three things: 1) The advantage of the curled chip as described above; 2) the fact that the U is fairly shallow; and 3) the "horns" are sharp and small, so rather than digging in, they easily slice through the steel. Please note that I don't know any of these for sure - just my guesses!Seems that it would have two sharp points at the apex of each arm of the U. That would suggest digging in to the work.
I am making a rear mounted tool post. I will have to bore holes in the carriage for 1/4-20 cap screws. I am wondering if cobalt drills or even HSS drills will work. Also , will HSS endmills work for a counterbore. Only 4 holes are needed. I will start with #6 drill and try to tap the hole.