Sharpening inserts, revisited

[Larry$]

Today found a piece of steel that had been used as as a punch. It had started life as a bearing shaft. I decided to see if the mushroomed end was work hardened. Chucked up in the lathe and tried a pass with HSS. No go, too hard. Then used a inserted tool and it cut but not very well. Inspected tool and found that the edge was well worn. Over to the tool & cutter grinder. I free handed a bevel on the tip. Less than 2 minutes. Back on the lathe. .020 DOC, 650 RPM, high range feed, medium feed # on about a 1.25" steel shaft. cutting dry. Chips came off as nice 6s & Cs and the surface was beautifully smooth. I'm an expert! No, actually just lucky. I've occasionally done something similar before but trying to maintain a nose radius. This time I just went for the simplest, a flat bevel, original clearance angle. Where the insert engaged the work the flat grind up to the top of the chip breaker "dome." The cutting action was a shear on a sharp edge. Well worth doing for lathe tools. For guys with lighter machines, the sharper cutting edge and reduced forces might make carbide a good solution. There are carbide inserts that come sharp edged for softer metals. Sharp edges will wear faster but you can get several regrinds. Diamond wheels can be had pretty cheap and can be run on many different kinds of grinders. Dust collection should be used.

 

[Jubil]

I have some cheap inserts and brazed carbide tools that get dull or chip. Sometimes I will use a diamond knife sharpener to touch them up, same as you would hss. (I think this idea actually came from HM forum). As Larry states above, the sharp edges work very well in the softer materials.
I also have some diamond wheels for a grinder that work work when I want to get aggressive

Chuck