Thread: For those who use CBN sharpening wheels.

180 grit is the best compromise for all - lathe chisels, bench chisels, and plane blades. When you do get another, aim for around 350 grit.

Regards from Perth

Derek

100% agree with Derek.

I've an 80, 180 and 350.

The 80 removes material at an alarming rate. The 350 can hone a beautiful edge but takes ages. The 180, with a light hand, quickly provides a lovely sharp edge.

I have 2 x180s but my oldest CBN wheel (~8 years) has been used to sharpen CROBALT Metal work lathe bits which means it is now more like about a 360 grit wheel.

FWIW CROBALT is a cast alloy that contains approximately 50% Cobalt. The remaining 50% consists of Tungsten, Chromium, their carbides and minor additives. It has the cutting characteristics cutting properties of tungsten carbide at high speeds and HSS at low speeds.

You should have mo problem with CBN on plain HSS.

I have mine for sharpening woodturning tools.

Prior to CBN wheels being readily available at an affordable price I had a Woodriver diamond* resin matrix #120 grit wheel that behaves more like a #400, but it grinds slowly, so I decided to get a faster grinding CBN wheel when they became affordable.

For the first CBN wheel I purchased was a #180 CBN, which was the most commonly available CBN wheel at the time. I understood that it would become less aggressive with use, which it has. I then bought a second CBN wheel with the intention of leaving the #180 to do any re-profiling of gouges, etc.. and using the second wheel for resharpening, which is my main requirement.

The second CBN wheel I have is a #360 and is my workhorse for putting fresh edges back on my turning tools. Now that it has run in it is just about right for me. I did think briefly about a #600 at one stage, but as I still have the diamond wheel I can always get a finer edge if I feel the need for that, which I don't very often.

In retrospect, if I could only have one CBN wheel for the foreseeable future what would it be? Probably a #360 and continue to use a white Alox wheel for any tool re-profiling until I could afford a #180 later on. The advantage of having the #180 for re-profiling is that it will always have the same diameter so moving across to the re-sharpening wheel will be seamless. Eliminating the Alox wheel will also avoid all of that bad grit dust coming off the wheels when dressing and using it.


* BTW, I still use the diamond wheel on most days I am in the workshop and my experience with it is that there is little to no indication that the iron in my tools is eating up the diamonds in the wheel (as often written and probably so in some industrial grinding processes )... however, if it is so, that wheel is still going to outlast me. It may be getting a little slower at getting the job done, but so am I...

I made up a little constant force jig from a piece of Al tubing with a constrained spring at the bottom of the tube, into which I inserted a length of 6 x 6 mm HSS.

Then compressing the HSS to the same extent between the CBN wheels and spring, I ran the wheels for the same time period and afterward determined the amount ground away by weight.

The 8 year old CBN wheel removed about 65% of the HSS that the newish wheel removed.
So the older one still works but is a bit slower.

I have nothing useful to add to what others have said about outcomes. However FWIW - I do a little woodturning (badly) at a local society which has a shed and some CBN wheels permanently set up.

There is a signposted rule that they are not to be used for reprofiling, and sharpening only (white and pink wheels for that).

I asked someone knowledgeable whether that means really do noticeably wear out or whether it's just precautionary and was told they certainly have gone through them when people have used them for reprofiling.

That is a dedicated woodturning hall that has workshops multiple days a week, so the use would be at the more extreme level. But did confirm anecdotally, but from good quality sources - they do have a lifespan.

I do note that woodturners have a whole different sense of what sharpening is and means. For me who is used to fussing with chisels and plane blades on high-grit stones chasing perfection... it is quite different to see how an experienced turner will really hit a wheel for a touch-up sharpen. It is a different mindset - you really have to treat a tool as consumable. Although when you consider really just how much turning you will get done before you wear away a turning tool, it's no problem.

I am very happy with a Tormek T8 with the stone (SG) and a CBN wheel on a grinder. The Tormek stone wheel is terrible for re-profiling or grinding out a chip or damage due to speed but shines for re-sharpening where you are only trying to remove a whisker (and provided you are using it to *find* your existing profile and hit that, not try and continuously chase a jig setting). The CBN wheel for repairing/reprofiling.

Originally Posted by BobL

The 8 year old CBN wheel removed about 65% of the HSS that the newish wheel removed.
So the older one still works but is a bit slower.

Very useful information, thanks Bob.

So is there a big difference in brands? I notice some have wider sides, presumably for side grinding.

Originally Posted by Cgcc

.....
I do note that woodturners have a whole different sense of what sharpening is and means. For me who is used to fussing with chisels and plane blades on high-grit stones chasing perfection... it is quite different to see how an experienced turner will really hit a wheel for a touch-up sharpen. It is a different mindset - you really have to treat a tool as consumable. Although when you consider really just how much turning you will get done before you wear away a turning tool, it's no problem.

Unfortunately many wood turners have learned quite bad sharpening habits, particularly bowl turners & more tool steel is wasted than is ever necessary because of those habits.

Club tools and grinding wheels etc will always cop a hiding, as individual members use them like somebody else is paying for them - because they are.

Originally Posted by Mobyturns

Unfortunately many wood turners have learned quite bad sharpening habits, particularly bowl turners & more tool steel is wasted than is ever necessary because of those habits.

Club tools and grinding wheels etc will always cop a hiding, as individual members use them like somebody else is paying for them - because they are.

At the mens shed they had range of grinders from, a 6" no-name brand that most members flogged the pants off to a 10" pedestal beast with 50mm wide grey wheels that nobody used.

The 6" had white a grey wheels on it that one of the members (who should have known better but liked dressing grinder wheels) dressed once week during the regular Friday arvo maintenance sessions. He did this whether it needed it or not and as a result the first set of wheels barely lasted 3 months. Fortunately he moved on. Some members preferred to use the 8" grinders for tidying up crappy welds which usually mangled the wheels. I suggested they use the 10" grinder for that but no one did probably because they were too scared of it. Eventually the 10" grinder was removed from the shed floor and I adopted it. The keen turner member had his own chisels and was one of the few member who I ever saw grinding regularly and with a soft touch.

We ran regular sessions on PPE use but it was common to see members using grinders with no face/eye protection.