Sharpening brazed carbide tip tools for the lathe.

Watch out for using 8mm holders, your manual says the height between the bottom of the tool post slot and lathe ctr height is 7.85mm which will put your tool tip over ctr height

If you have access to a microscope, you will see that the green wheels microchip the carbide edge being ground. There is a myth that carbide can't be damaged from heat when grinding. My experience is that carbide that has been hot when ground does not hold it's edge as well as the same tool ground that did not get hot. Dull green wheels and dull diamond wheels will both burn carbide. Lapping the tool back beyond the microchipped area with a lap is another option. I prefer to use diamond wheels as they generally do not microchip the cutting edge. There are very many different grades of carbide these days, it is hard to keep up. They do not all grind the same either. When brazing carbide, make sure that the tool is allowed to cool naturally, instead of quenching in oil/water etc.

Neil

I based my idea of the size it would take around a sieg baby lathe compound slide I have. 15mm slot for the tools. Maybe this is done to make the photo's look good, don't know. The screws are unusually long.

7.85 +0 -0.8mm is sort of fine for 5/16 tool bits. Maybe it's another bit of americanization like the chuck fixing screws. ( notice i used a zee, we brits hardly use them at all ).

6mm shank holders are available but they look like they use 9 or 11mm tips to me. Not that matters if the part that is actually cutting is supported at the bottom. If Brian does buy a set of these do remember to buy ones that come with a torx key and screws - not hex socket screws.

Light pressure and movement across the tool is the answer to green grit supposed chipping. Grade doesn't have that much to do with it which is why diamond wheels are often fairly coarse. Friable ones are also reckoned to be better than the surface coated types. A tool grinder with traverse and a controlled feed can make a much better job with both types.

John

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Thank you Jason...so I need 6mm indexable tools ? There are so many traps to all this so maybe I will just wait a bit longer and have a think before I rush out and buy more tools which turn out to be useless to me. Blackwoods do not sell a diamond wheels for my 6 inch bench grinder so I am not sure where I can buy something like that. I need to make more enquiries.

Edited By Brian John on 14/10/2015 07:37:00