(08-22-2019, 04:52 PM)Alan S Wrote: Do you need to regrind the carbide? What if you just angled the steel end where the carbide is screwed on? You could make a few handles with different angles of attack, to see which you prefer.
OK, I will admit that my experience is based on metalworking carbide inserts and some of the woodworking specific carbide inserts may not adhere to this, but generally, no you can't just re-angle the toolholder of a positive rake carbide bit. To put it succinctly, if you take each carbide insert type and look at them on the edge, negative rake inserts have straight edges and meets the top side of the insert at a right angle, the cutting edge is formed in how its ground on top via the chipbreaker and you change the cutting edge angle via the sloping on the tooling that holds the carbide inserts, positive rake carbide inserts have sloped edges and the cutting edge is formed from the angle of the top side and edge as well as the chipbreaker, if any, positive rake tooling holds the bits flat, you don't change the angle of how the toolholder holds the insert, usually because positive rake inserts are not intended to handle the stresses of cutting in positions other than with the insert on a flat toolholder. If I recall, I believe all negative rake inserts have a chipbreaker while positive rake inserts can be had with no chipbreaker.
To throw even more confusion into the mix, there are carbide inserts that have positive rake cutting edges on negative rake inserts. The chipbreaker is ground to produce a positive rake cutting edge, but the insert itself still has straight edges and can be used in any negative rake toolholder. For the most part, the nomenclature for any of those inserts ends in "xxxP" (i.e. TNMP, CNMP, etc). These inserts are less common.
Edit to add: To expand on the difference of negative vs. positive, in case someone's having trouble envisioning the difference, negative inserts have taken off in industry because you get twice as many cutting edges out of them. For ex. a triangular insert has three points that form cutting edges. Positive rake inserts, because of the slope built into the edges, can only utilize 3 cutting edges. Negative rake bits, because the edges are straight, give you 6 cutting edges, 3 on top side and 3 on the bottom side.
Paul
