CBN wheels

[screwpainting]

I've just been looking into sharpening drill bits, as it's something I've never done before but as I am very keen to become increasingly ensconced in my workshop (to avoid the modern world) this looks like a great learning curve and another skill worth having.
Then I found this..

https://www.youtube.com/watch?v=IOXXiPK1L4s

These wheels would appear to be the ultimate sharpening aid. No loss of temper, both mental or metal, in the tool (me?) I am trying to sharpen, indestructible, and very safe.

Has anyone got, or used one of these, they do seem to be worth the additional cost.

 

[katellwood]

I've got a 180 grit 40mm x 200mm axi one on a metabo grinder, transformed the way I sharpen. Less risk of burning the steel and also deals with much harder steel, does not wear, does not clog never needs cleaning/dressing.

However the suggestion is that mild steels and anything softer (brass, ali etc) should not be used on them, another issue is that they are heavy and take a while to get to speed

one other benefit I have found is that they sharpen TC masonry bits with ease where I struggled with traditional grinding wheels

and apparently you can remove the large guard as there is no risk of CBN wheels shattering

they have 15mm down the sides as well

 

[custard]

A question for Katellwood, did you need to have the CBN wheels balanced or centred on your grinder?

 

[katellwood]

Custard

will get back to you tomorrow with a couple of pics

 

[woodbloke66]

Slightly off topic, but I've just ordered the coarse diamond wheel for my T7 Tormek (unfortunately on 'back order' from Ax) which is similar to a CBN wheel. The issue of grinding softer materials (iron etc) from diamond and less hard wearing CBN wheels can be addressed by using a 400g cleaning stone which makes no difference to the cutting ability of the wheel - Rob

 

[Woody2Shoes]

I've got pretty much the same wheel as Katellwood on an Axi slow-speed grinder. I've taken off the guards. I only use it for turning tools but it's fab. I didn't need to do any centring - I did need to get the correct pair of mounting bushes for the stone/grinder from Axi.
When I first used it, a couple of the abrasive grit pieces were slightly proud, giving visible 'streaks' - I poked them repeatedly with a sharp and hard object and they ceased to be a problem. My only concern - as with any grinding setup is the dust. Cheers, W2S

PS I've not needed to do it yet, but I'll use the white alox wheel, that came with the grinder, to dress the CBN wheel if required - rather than buy a separate piece from Axi specially

 

[D_W]

I have one from a seller in the US (a wide wheel with a radius on each side, aluminum center, 80 grit). I bought it because it was a sale deal at the time ($125). It's not a necessity, but it's nice and it's certainly cooler than regular wheels without spitting friable grit everywhere. You will, of course, have flying metal grit, but no abrasive going with it.

worth the cost is something for you to determine, but they do deliver what they say they will. I keep a standard wheel on the left side of my grinder for grinding mild or annealed steel to shape. I have cheated and used the CBN from time to time. Over a period of years (5?) the wheel has slowed down a little but seems to have settled in and I would suspect that for typical things (hollow grinding small hardened knives, refreshing bevels on tools, restoration of tools, etc), it should last decades.

I guess that does lead to one comment with the tools - I grind a lot of laminated irons. I suppose that should be against the rules because the backing is generally iron or mild steel. No problems that I'm aware of, and if the wheel couldn't survive that, I'd rather ruin it and go back to old wheels than have a bunch of different methods in the shop.

To custard's comment above, there's no balancing to do. The size of the hole on most of the CBN wheels is extremely precise. I was concerned about that, but mine runs really true, and I'm (almost) sure it was an imported wheel. If the arbor on a grinder is off just a little bit, there may be some fixing needed- either to bring the arbor to spec, or have a machine shop open the CBN wheel a little bit.

No guards for me. They are ultra unsafe if kids are around, though, as they will spin for a long time (with gobs of energy), they remove skin quickly if you get a fingernail against them or something like that.

 

[katellwood]

Hi all sorry for the delay in replying

This is my setup

Got it mounted on a Wadkin RS lathe stand on wheels. when I first got the wheel, literature from both the wheel and grinder suggested that the wheel would mount straight on the grinder, unfortunately the grinder bushes where too large, however I have a engineering lathe which is old and may not be superbly accurate.

To accurately resize the bushes I initially turned a piece of bar to the dia of the grinder shaft to produce an accurate fit of the bush. I then CA'd the bush to this shaft and turned the bush to an accurate fit on the wheel. I had to shorten the bush somewhat to facilitate fitting the nut but all ended fitting accurately

On first fitting the wheel there was some vibration on the setup however I found that loosening the wheel and re-positioning it on the shaft I eventually got it running extremely smoothly.

As can be seen I have got it setup for turning tools, a grinding platform and have also got it setup similar to a tormek which is excellent for plane irons/chisels etc and much quicker than a tormek style wet wheel. the whole setup works great, the only time I go to other grinders is a 6" equipped with wheels dressed to different diameters and one with a wire/buffing wheel.

hope these help if anyone is considering a CBN wheel. they are worth purchasing

 

[katellwood]

One slight thing which you possibility need to be aware of

On my wheel the grit on the sides appear to be much coarser than the face (possibly 80g as opposed to 180G)

 

[shed9]

IMy only concern - as with any grinding setup is the dust.

This is often overlooked and ignored in terms of CBN's. They create different issues to the usual abrasives via their inherent properties. As they run cooler, the metal is not being 'sparked off' but simply pushed into the air. Additionally as they have almost zero chance of disintegrating people will often remove the guards which themselves will retain the dust to some degree. It should also be noted that whilst the wheels last for significant periods they do still release boron nitride.

It's good practise (in my opinion) to place high quality high strength magnets in the path of of the ejected debris (usually behind plastic or metal sheet to prevent grabbing) and to retain the wheel guards where you can.

I drastically changed the way I use grinders (of all types) after taking the time to see what was coming off them - it is shocking what hangs in the air and by extent ends up in your lungs.

Not looking to wail the safety brigade siren, just sharing info that affects our health is all.

 

[screwpainting]

Thanks for those replies guys, I think I will be investing in one after your comments. I have this thing at the moment
https://www.machinemart.co.uk/p/cbg8w-w ... e-grinder/
which it probably wont suit or fit, so I might have to treat myself. I think I've probably ruined the temper of most things I've ever sharpened in the past through lack of knowledge so this will be a good move for me.
The dust issues with grinding wheels in general is something I hadn't considered before either... I think these wheels will sell themselves, very good for lots of reasons. =D>

 

[D_W]

IMy only concern - as with any grinding setup is the dust.

This is often overlooked and ignored in terms of CBN's. They create different issues to the usual abrasives via their inherent properties. As they run cooler, the metal is not being 'sparked off' but simply pushed into the air. Additionally as they have almost zero chance of disintegrating people will often remove the guards which themselves will retain the dust to some degree. It should also be noted that whilst the wheels last for significant periods they do still release boron nitride.

It's good practise (in my opinion) to place high quality high strength magnets in the path of of the ejected debris (usually behind plastic or metal sheet to prevent grabbing) and to retain the wheel guards where you can.

I drastically changed the way I use grinders (of all types) after taking the time to see what was coming off them - it is shocking what hangs in the air and by extent ends up in your lungs.

Not looking to wail the safety brigade siren, just sharing info that affects our health is all.

I'm curious as to the effects of boron nitride. What I read about it is that it can lead to pneumoconiosis (black lung here in the states for anyone who is familiar with coal miners). It takes a long time and a lot of material to get pneumoconiosis, and I don't see this being an issue with the CBN, there's just not enough on the wheel.

I also remember larry williams contending that we should not use any alloyed steels because we'd be breathing chromium and other toxic metals (I'm not aware that any of the elements are freely available for us to absorb).

I still do get sparks with CBN, and they are hot, and if you push the issue, you can make the tool hot, too - it just takes longer. When I first got my wheel, I had a 1/2 inch architectural mortising chisel that had the bevel ground on it upside down. I ground it in one shot (think a triangle of metal (isocoles) about 1/2 inch tall and somewhere around 1 1/2 inches at the base, and it got very hot. That took a little bit of the brand new aggression out of the wheel, but it works fine.

Absolutely agree that it's probably better not to breathe any dust, nor any products of combustion whenever possible, and there is a coating of black in the corner of my area behind my grinder. Everything of mine is pointed into that corner because I'm OK with the dust being there.

 

[shed9]

Agree that the quantities of boron nitride likely pose no major risk however it's one of those metals that once you get it in your system it's there for the long haul. With the exotic alloys now used in some tool steels I'm just a little cautious myself. I noticed one day the sheer volume and spread of metal particles after 30 minutes of grinding and it was an eye opener. When you catch the light at the right angle you can see it suspended in air.

Like I say up there, not looking to play parent just raising the concept of dust associated with sharpening. Given our understanding of the dangers of fine wood dust it would be a little counter productive to not give metal a thought as well - even if just to assess it.

 

[D_W]

Personally, I think some of the fine wood dust issue is overblown given that most of the folks gearing up with thousands of dollars worth of plumbing and cyclones are working in their shops a couple of hours a month. I notice the fine dust if I sand (which is rare) and am doing something that doesn't have a vacuum attached, but as you say, I also notice that on the rare occasion that I make a tool and do heavy grinding, it's in my hair, on my face (which means it's up my nose) and on my arms, etc.

If I did it on a regular basis, I'd be a lot more cautious. We'll probably never know much about whether or not the elements in exotic steels get free and do harm to us, because it's unlikely that they'll be in us in a quantity to do much (as hobbyists).

The big common dangers seem to be from volume of dust and not type (e.g., if you talk to older farmers where I grew up, who farmed before tractors with cabs were common, a lot of them end up with COPD or other similar lung issues as they get old because they breathed a lot of dust. quantities we couldn't begin to imagine.

Not trying to be argumentative, but just saying that I'd decide what I want to do in the shop first, and then mitigate when it sort of feels like it'll be an issue. Far different situation than chrome plating or getting creosote all over your skin. There are only a few really really toxic things left in standard shop work (japan drier comes to mind, but few use that).

I'm personally kind of curious about the crosslinked water-based finishes. I spray them sometimes, and when I do, I always wear an OV respirator. One time in the past, I didn't and learned my lesson (I had childhood asthma - the simple "safe and non-toxic" acrylic finish set me off and I had to use a rescue inhaler).

 

[shed9]

I agree D_W, risk is all relative to the situation and individual assessment.

I would say however that the risk associated to dust is not necessarily proportional to the quantity of dust itself. The risk is in the individual user and their comparative susceptibility to dust, i.e. not everyone reacts the same way and volume is not the deciding factor. Some people will react to very small amounts the first time they come in contact whereas some never will. If that makes sense?

The bottom line is we need to make stuff to be at risk so here's to risk!

 

[hodsdonr]

I've got a 180 grit 40mm x 200mm axi one on a metabo grinder, transformed the way I sharpen. Less risk of burning the steel and also deals with much harder steel, does not wear, does not clog never needs cleaning/dressing.

However the suggestion is that mild steels and anything softer (brass, ali etc) should not be used on them, another issue is that they are heavy and take a while to get to speed

one other benefit I have found is that they sharpen TC masonry bits with ease where I struggled with traditional grinding wheels

and apparently you can remove the large guard as there is no risk of CBN wheels shattering

they have 15mm down the sides as well

I see you got the 200x40 wheel. I was looking for the 200x32 wheel but they are out os stock. (to replace a 120 grit white wheel ) why did you go for the 40vs the 32?