Mitsubishi Boring Bars

[Neil LickfoldParticipant @neillickfold44316]

That's roughed to the centre line with a 80 grit diamond compound wheel along with the backing off taper and the relief diameter and general shape. Then the centre line split is finished with a 180 grit diamond compound and the same with the finishing of the tool shape. So it is done in several stages, a roughing and wheel change then a finishing. The finishing is only done on the centre line split near the outer edge, just visible, about 0.02mm is left for this op, and then only on the leading and trailing of the form. The nose radius is done by hand very carefully with a fine diamond EZ lap. These are a desic diamond lap and the finest/smoothest grit that is readily available. Just don't use much pressure when using the desic laps ,or else the stuff just strips off them. Like I said earlier, I only make tools that are not redilly available from a tool supplier. The front edge of this tool is just big enough to cut a 0.5mm pitch thread. It will not cut a 0.75mm pitch thread. This particular tool is made from a micro grain carbide where the main part of the original cutter broke off. i just use their scrap high end endmills etc to make these special tools from. This blank is from Kobelco in Japan, but believe that Mitsubishi carbide has purchased the company at some point. That was the name on the tool blank. I have a 6mm ground stock D bit split to the centre line that I use for setting the tool height to the correct centre line, before using this tool. Micro tools are a lot less forgiving so extra care is required when setting up with them.

I make my circlip groove tools is a similar manner, so are roughed out and then finished.

Neil

[Roger HeadParticipant @rogerhead16992]

Thanks Neil. I've never had a problem with EZ Laps separating, but they do load up fairly easily (especially the super-fine), so I generally have a little pot of kerosene and a toothbrush on the bench. I use them for touch-ups on HSS and brazed carbide tools that I reshape with a diamond disk in a Dremel-style tool.

Roger

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