Maybe I need to get a CBN wheels part 2 article done.... As far as what you can grind on CBN wheels, well, pretty much anything, but...... CBN is made specifically for 'hardened' steel/metals. So bench chisels are fine, shovel blades (well most of them) axe heads and similar metals. The soft metals like lawn mower blades are not good for the wheels, same with aluminum, brass, and copper. With the hardened metals, the powder comes off of the wheel as you sharpen. With the softer metals, the shavings/dust tend to stick to the abrasives, the wheel loads up, and you get a ticking sound and/or bump as you sharpen. Yes, I did load a wheel up intentionally with all of the above metals on an old set of wheels. To clean the wheels, just take a scraper and spend some time sharpening on the wheel. It may take several sharpenings to remove all of the build up, and some lapping fluid helps as well. It took a month to remove all of the visible build up. I always sharpen my Big Ugly tools on the CBN wheels, which is tantung silver soldered to cold rolled (softer steel). The tantung pretty much cleans up any build up as I sharpen, but I still grind most of the heel/cold rolled steel off, kind of like relieving the bevel on inside bowl gouges. I did finally retire a set of CBN wheels, but I have no idea how old they were, at least 7 or 8 years, maybe 10. I haven't done production turning in several years, but still they got a lot of use, but finally they just didn't cut well. Interesting to me is that the old wheels (80 and 180) left a more polished surface than my new 600 grit wheel. Coffee hasn't kicked in, but I think it is Glenn Lucas who 'finds good homes' for his CBN wheels after a year.
I used to suggest an 80 and 180 grit wheel for standard. Now, I would say 180, and then maybe a 600 or so grit wheel, but I haven't experimented with the 320 to 400 grit wheels, so don't really know. The 180 raises an excellent burr for my scrapers for heavy roughing and shear scraping, and does just as good of a job as the 80 grit wheel. I really don't see any significant differences. I will note here that I prefer a burnished burr on my scrapers for shear scraping. The 80 grit wheel will take off metal pretty quickly, which is pretty good for minimal reshaping of tool profiles, but if I want to get serious about it, I take the tool to the 36 grit belt sander. The 600 grit makes for an excellent finish cut edge, but that edge is lousy for heavy roughing because it goes dull so quickly. Pretty much the same for scrapers or gouges. If you want to so some shaping of your tools, a 36 to 60 grit wheel is better than an 80 grit CBN. Dave Schweitzer of D Way uses a 60 grit 10 inch wheel on a high speed grinder for his shaping of tools...
Once you use a CBN wheel for sharpening, it is kind of like variable speed lathes. It is so far better, that you have no problem justifying the expense, and will never go back to standard wheels for tool sharpening.
On diamond wheels, years ago, I had a conversation with the Cuttermaster/Tradesman wheels and grinder up in Canada about wheels. Diamond wheels on slow speed or high speed grinders degrade really quickly because the diamond won't handle the heat from sharpening. On really slow speed grinders, like 300 to 400 rpm, they work fine. I don't think they load up though. I do have a set of DMT 3 by 8 inch plates for honing tools, and had pretty much retired them after 20 plus years because they just didn't cut any more. Perhaps due to loading up, but Ajax and water didn't clean them up. I got some Trend Lapping fluid to see how it would help clean up my CBN wheels (did a pretty good job actually...), and put some on the plates. They started cutting very well again. Not sure what other options there are for cleaning them up, but water as a lubricant/cleaner does not do the job.
robo hippy
