I have often sharpened the end of 2 flute cutters on the off-hand grinder. Colin

Big downside of three flute stuff is measuring the things once they are re ground. I can't justify the special micrometer required.

This cut-and-measure method will only give accurate answers if you can eliminate all the flex in the machinery. One side of the cutter is working up-hill and the other side downhill, and the working part between works sideways, shoving the mill head etc all over the place. Perhaps one answer instead is to drill a slightly undersize hole, and then to ream it with the 3-blade cutter at the same position, so it cuts evenly all round. Measure this hole and I suspect you will get a more useful answer.

Not that I know anything about it, you understand.

Cheers, Tim

I use all three types, although I use 3-flute centre cutting by default. For cutting accurate slots in one pass 2-flute cutters are recommended. That's possibly less important now with carbide cutters that are much stiffer than HSS.

It also depends upon the material. For aluminium, with high chip loads, I use 2-flute or 3-flute cutters to minimise choking of the gullets. For harder materials with lower chip loads, like steel, I use 4-flute cutters to maintain the metal removal rate.

I suspect that the introduction of 3-flute centre cutting tools has been largely driven by CNC, where they are a compromise between chip removal and overall metal removal rates. Centre cutting tools also make it much easier when engaging the workpiece with CNC than non-centre cutting.

Andrew

Brian,

I have acquired a variety of cutters over the years, some sharp but the majority in need of refreshing. Most have clearly had the flutes sharpened in a professional environment (because the diameters are undersize). With no T & C grinder and a reluctance to spend the required time to build one, I opted for Harold Hall's solution using a bog standard bench grinder. It is probably a bit tedious to set up for grinding the secondary clearance, a job best done in 'batches' but the principle works surprisingly well. See how simple it is here:

http://www.homews.co.uk/page121.html

Alan