Follow up on CBN wheels for flat woodworkers

[Steve Voigt]

Yes that's what I do now with a 3X wheel. It's a messy wheel though, creating a lot of dust. I hoped the CBN wheel would be an answer to that, but I understand your concern too.

Yeah, the 3X wheels are still pretty hard. I think most people use the softer white wheels for profiling--not necessarily less dust, but faster and easier to profile. The 3X are great for more general grinding, though.

[ian maybury]

I guess that if the work is guided/supported in 3D as it tracks in a straight line across a wheel then a little irregularity may be no problem, but if it's relying on the wheel for support then it may well be.

Don't know enough to have a clue what the situation might be here, but CBN wheels are used all over industry for very high precision grinding tasks. e.g. http://www.reishauer.com/en/CBN-prof...wheel-103.html A specific enquiry made when buying my wheels (which are of a different brand) resulted in an assurance that they were accurate to within a small part of a thou. So far as i can tell before use they check out fine.

It doesn't seem all that likely that this is a fundamental flaw/anything to do with the nature of the beast - more that if there are instances of issues that it's a quality problem. To do with the manufacture of the specific wheel, or a batch or some examples of them. The sort of thing the original manufacturer might be expected to stand over?

[Tom M King]

My feelings as well Ian, that it was probably some manufacturing error, but not a universal one, since my CBN wheel is fine. I'm still loving mine, and won't ever go back to anything else. I expect mine has already paid for itself in hours not spent doing other, slow grinding.

[Derek Cohen]

Ian, my thought is that there are a few rogue wheels - just like any tool - and I had one (actually two, both radius wheels from different sellers). In both cases, the back up service has been superb, and one should have no fears purchasing one of these wheels in case of a dud.

Steve, I agree that one needs to be careful when recommending any tool and that there is a high level of reliability included, which is generally something that occurs with re-testing over time. If I report something enthusiastically, as I did, I take responsibility if turns out faulty. I had looked into the history of the wheels beforehand, and in this respect the information about the product was not premature. I do not know the answer here - one of my conclusions must be that my report was too soon, however.

As mentioned before, the CBN technology is the future. I have no doubt. The question is whether the accuracy level is there for guided tool rests, such as the BGM-100, not whether they work. I am confident enough that the technology is indeed here, and will report back later on the new wheels.

Regards from Perth

Derek

[Derek Cohen]

One more piece for the follow up file ...


Dave at D-Way returned my payment for the wheel, which I then sent back to him. I plan to keep and use the 180 grit radiused wheel for lathe chisels. It may not be suitable for bench chisels but it will be fine for the lathe. I plan to hook it up to a grinder alongside the lathe.


In the meantime, the 180 grit 1 1/2" wide straight CBN wheel arrived from my Oz supplier. It is nicer than I imagined, with a wide, flat section on the side that may be useful for flattening the backs of blades. The 80 grit wheel is on its way back to the US supplier, who will exchange it for a straight wheel. He has been just superb in his service.


I have set up the new CBN wheel and and I think that we are back in business. So far the grinds are straight. Time to let it settle in. Feedback at a later date.





Regards from Perth


Derek

[Tom M King]

I really like the looks of that wheel. I've been waiting for the right thing to go on the other end of my grinder that I have the one CBN wheel on-just wish that one wasn't on the upside down part of the globe. Looks like when you turn that grinder off today, that it will still be spinning tomorrow.

[Jack Vines]

I was asking a machinist friend about CBN wheels and showed him this thread. He read it and said,

"Doesn't anyone there see the irony in using power grinders with CBN wheels and expensive tool holding jigs for sharpening hand tools in a forum called "Neanderthal Heaven?"

jack vines

[Brian Holcombe]

We're very well kept neanderthals.

[Reinis Kanders]

That looks like the one wheel to rule all wheels How heavy is it?

[Derek Cohen]

Reinis, you wouln't believe how heavy! The 80 grit wheel I shipped back was a feather by comparison (and my shipping cost to the USA was $62 AUD). I have not weighed the new wheel, but the package was Heavy! So at least twice the weight of the other.

I have no doubt at the new wheel is available in the States. There are not a lot of manufacturers for CBN wheels. Use this photo and ask around.

Regards from Perth

Derek

[Reinis Kanders]

Thanks Derek. I have a wheel envy now
I might get a wider wheel for my grinders other side, but I will wait for a bit and see how it plays out with my current wheel. So far it has been great and I appreciate that you started the CBN wheel movement on this forum. I don't do any turning yet and had no idea that such a nice solution exists.

[Chris Parks]

Derek, where did you get that wheel from, CWS?

[Derek Cohen]

Hi Chris

Yes ... http://www.cwsonline.com.au/shop/cat...rinding-wheels

Jim Carroll is the guy to work with.

Regards from Perth

Derek

[ian maybury]

Think that ideology has no place in woodworking - whether or not it's hand tool based...

The new wheel looks the business Derek - spot on for flat bevel grinding off the side too.

To be fair to D Way it sounds like he's very much standing over the product, and that whatever problem is likely to be restricted to a batch.

There's however another issue in the CBN wheel situation that has the potential to be troublesome when grinding tools requiring accurately flat bevels.

The machining of the spindle on your average Eastern made grinder isn't necessarily a high precision deal. It's not just about straightness and concentricity, it's also about how square the step the wheel is tightened against is, and how squarely the threads on the end of the shaft and in the nut have been cut. The relatively small diameters used on most grinders and the soft steel mean they have very little resistance to bending.

The point here is that spindle precision not so important in the case of friable stone that's dressed in the traditional manner - because the dressing will likely ensure that it ends up being cut to run fairly true. A CBN wheel doesn't have this 'adjustability'.

The shafts on my own grinder clock with a dial gauge as running pretty true, but one end when the securing nut is tightened up develops a bit of a wobble. Most of which (subject to final checking) seems to have been eliminated by fitting the previously mentioned spherical washers like those offered by WTW.

Presuming reasonable manufacturing significant eccentricity is not so likely, but some side to side wobble is a definite possibility. Unlikely to be avoided in fact. There's also the matter of how precisely the wheels are bored, and how that adds to or compensates in the mix.

How some mix of slight eccentricity and sideways wobble might work out in terms of the straightness of the bevel grind and uneven wear is potentially a bit unpredictable - it'll make a difference whether the iron pivots forward on to and is supported by the wheel a la Tormek jig, or whether the jig locates the iron firmly in all axes as in the case of say the Lee Valley jig. It needs some calculation to figure out how much out flatness inaccuracies in the various directions may induce for both types of jig.

The good news i guess is that we're grinding primary bevels here, so there is presumably some tolerance for a less than perfectly flat bevel - especially if the subsequent honing is micro bevel over hollow grind based. Less so if the target is a flat bevel Japanese chisel style - but it will still be OK if the bevel pretty quickly cleans up all over on say a 1,000 grit waterstone. Or even using a honing guide on the top disc on a WorkSharp if you have one - the real benefit of the CBN wheel for me is for low heat heavy rates of metal removal when e.g. changing the primary bevel angle on a thick iron.

It'd be interesting if you were to clock your latest wheel set up with a dial gauge on a stand (running a gauge on an abrasive surface isn't ideal, but still...) and see what eccentricity and side to side wobble you are getting with everything done up tight, as it'd provide some context for what you experience in terms of grinding results. Depending on the nature of any issue there might be scope to do a little dialling in too.....

ian

[Tom M King]

I ordered one new grinder when I first got the D-way radiused edge fine wheel. I sent that one back and tried another brand. The Metabo runs dead true. My D-way wheel was flat when I bought it, and after grinding a years worth of stuff on it, it's still nice and flat on the flats. I wouldn't have any reservations about getting another one of these wheels. Get a grinder from cpo, and wheel from D-way, and if it doesn't work out, they send a pickup label, and charges are taken off your card. cpo picked up the Dewalt grinder, and shipped me the Metabo. The Metabo does require a bushing for proper offset, but runs dead true. This setup has already paid for itself in time saved for me, if I had to buy another one tomorrow, but it still cuts as good as it did the first time.

I can't imagine anyone trying a CBN wheel, and going back to a friable wheel, if time means anything to you. Two minutes on a Tormek, is 5 seconds on mine (maybe 3). Not to mention, the diameter of the wheel never changes, and there is no need for dressing.

I've posted this picture before, but if runout was a problem, I don't think this stuff would have balanced on the grinder while I went to the truck to get the camera. I think maybe I still haven't thought to tighten those nuts holding the grinder down to its plywood base.