Thread: Slow Speed bench grinder with CBN wheels

You could make a variable speed grinder using bearing blocks, a cheap & small 3 phase motor and a VFD. It would be far more versatile than a dedicated single speed bench grinder. I Have seen a sort of line shaft with more than two wheels set up using bearing blocks for more flexibility.

I guess I'm thinking veritas with a wider table will run about $150, and the replacement table might be hard to source.
The vicmarc setup looks to be good value, and sturdy.
V00438.jpeg

Originally Posted by Chris Parks

You could make a variable speed grinder using bearing blocks, a cheap & small 3 phase motor and a VFD. It would be far more versatile than a dedicated single speed bench grinder. I Have seen a sort of line shaft with more than two wheels set up using bearing blocks for more flexibility.

This sounds great, but I know it's a 3 day rabbit hole to work out what to buy and where from, and then probably a weekend to get it up and running. With my particular set of circumstances right now, I'm off the shelf all the way!

Originally Posted by rogerwilco

The Vicmarc V00438 has got my attention. The grinding rest has the slidey slot with the triangle gauge. I'd probably only use 90 degrees and 23 degrees, but I like that it's repeatable and holds the tool steady for side to side grinding for wide plane irons.

I do know this system is aimed at turners though. So I'm not certain it will suit basic chisel and plane iron sharpening.
Can someone who knows more set me straight?!

We had a Vicmark system at our guild but replaced it with a Tormek set up; you are correct in stating it is sturdy. Every part of adjustment mechanism was very stiff, nothing moved freely and you had to tap everything into position. As you say the system is designed for turners; the gauges don’t cope well with anything over an inch wide and the fit between them and the slot was looser than I liked. In addition the bar that rides along the slot isn’t the same width along its length; only the outer ends actually fit the slot so as soon as one bar end leaves the end of the slot the gauge then flops around losing the 90 degree angle you need. For plane irons you would be grinding freehand unless you made your own gauge. The supplied angle setting tool is pretty useless for your needs as it only accommodates the preset angles of 22, 33, 44 and 66 degrees which are needed for the Vicmark sharpening jig.

My recommendation would be for a simple aftermarket rest; Timbecon and Carbatec both sell their own models and there’s plenty similar like this snazzy looking one from Amazon. The wheel slot in each one is less than 40mm but five minutes with a file will fix that. I have three of the original Delta branded rests that these are all derived from and they’re perfectly adequate for plane irons.

Thanks a million Chief. Gold. This info is exactly what I was looking for. You're a gent.
I did suspect that plane irons might be too wide for Vicmarc rest, the slot might not be very precise because it's plate steel and not a machined slot, and the angle setter wouldn't be helpful for me (where's 25!).

I'm just gonna keep it simple. Put the money into the grinder, get a cheap copy grinder rest, and start with an alox wheel. I'll mess around with some second hand chisels, and I suspect I'll find out that I don't actually need the CBN wheel, as a few people have pointed out. But if I do, it's easy to add one.

At furniture school, it's just a wolverine flat rest up to a full speed grinder with an alox wheel.

Ive had three 8" grinders looking for the right one to work with my CBN wheels.

All three have had runout that have made them useless for CBNs.

All three are excellent brands - but simply aren't acceptable.

Ive used the imported wide washers and concave things, but they simply won't correct the tiny flaws. A CBN at high speed demands a precision shaft, otherwise its TING TING TING and entirely unsatisfying.

So, On my last grinder, I simply turn it on for a bit until it spins up, turn off, grind a bit while it free-wheels.

I plan on making my own jigs/grinder/mount with a cheap Makita trim router knock-off and plywood! I can then get the speed right just by making new pulleys of the right size, or reduce the speed on the router motor

Originally Posted by IanW

There is one other factor that hasn't been discussed so far - grit size. It's a common tendency amongst amateurs to go for finer grit wheels because they leave a 'better' surface. However, they do so at the cost of slower (& hotter) grinding. It is often better to use a very coarse grit when there is any significant amount of metal to remove, it's not only faster, but can also be cooler. In fact, the surface off my 60 grit wheel is surprisingly good and the scratches are easily removed on my medium diamond stone. Unless you are a turner, I'd get a coarser CBN wheel than 180 - which is good if you want to take HSS tools directly from grinder to wood, but for general grinding I think you may find a coarser grit both quicker & safer....

Cheers,

This man utters truth. A secondary honed bevel will eliminate the deepest scoring from a 60 grit wheel in no time.

This afternoon, I locally picked up everything that I need (for now).
Abbott and Ashby 8 inch industrial grinder, 60 grit Alox wheel, generic grinding rest. We'll see how we go. I will report back!

Originally Posted by woodPixel

Ive had three 8" grinders looking for the right one to work with my CBN wheels.

All three have had runout that have made them useless for CBNs.

All three are excellent brands - but simply aren't acceptable.

Ive used the imported wide washers and concave things, but they simply won't correct the tiny flaws. A CBN at high speed demands a precision shaft, otherwise its TING TING TING and entirely unsatisfying.

So, On my last grinder, I simply turn it on for a bit until it spins up, turn off, grind a bit while it free-wheels.

I plan on making my own jigs/grinder/mount with a cheap Makita trim router knock-off and plywood! I can then get the speed right just by making new pulleys of the right size, or reduce the speed on the router motor

The biggest problem is not shaft runout but poor nut to shaft tolerances. If you want to test this put a nut on the shaft, if you can move the nut then the tolerances are poor and I think conical washers were invented for this problem. Personally I have used conical washers on several grinders and the runout problem has gone away.

Originally Posted by The Spin Doctor

This man utters truth. A secondary honed bevel will eliminate the deepest scoring from a 60 grit wheel in no time.

It depends on how much you want to hone away on stones. A 60- or 80 grit wheel will leave a ragged edge compared to one off a 180 grit CBN wheel. This is honed to about 10K.




Now this hollow will sustain several sharpening sessions with just a few strokes needed each time. The basis for this is a clean edge off the primary bevel. There is no way you can do this with a coarse wheel.

I also have a 80 grit CBN wheel, and the edge is decent, but not as good, and the 180 grit is still going strong after 7 years.

I wrote this article in 2015. I was not the first to use CBN wheels by a long way, but I believe I was the first, or among the first, to write about them with bench plane blades and chisels in mind. http://www.inthewoodshop.com/Woodwor...ningSetUp.html

With regard to tool rests, I have used them all. They all work. 25 years ago I made a “Tormek” type from a bar, as Ian showed. In fact, the original design in print came from another Ian … Ian Kirby … who wrote prodigiously for a magazine all those years ago.

The reason I use the Tormek BGM-100 is that I once had a Tormek Supergrind, and the tool rest was the best thing about it. It simply makes for the best hollow grind with the cleanest edge. That straight, clean bevel edge is the foundation of efficient sharpening.

Regards from Perth

Derek

Originally Posted by derekcohen

It depends on how much you want to hone away on stones. A 60- or 80 grit wheel will leave a ragged edge compared to one off a 180 grit CBN wheel......

Derek, of course it will, the finer the grit, the better the edge, that's axiomatic. Indeed, there is a little more arm work to refine the edge if you regrind plane blades & chisels on a coarser stone (doesn't take long on a diamond plate), but given what I've seen most amateurs do with powered grinders, I say be careful when selecting the grit size. Fine is fine if you are well-practised, but can be dangerous (for the tools!) with beginners.

My point is simply that while 180 grit wheels are ok for light work such as re-establishing bevels on plane blades & chisels and great for bowl turners going from grinder to lathe, a coarser grit can be a better alternative for general grinding and definitely better for heavy work (like chipper blades). This is particularly so with grey wheels and even Alox wheels. Most woodworkers will probably find a 180 grit CBN wheel suits them fine for their tool grinding requirements, but I would certainly not advise such fine grits in the older vitrified wheel types unless you know what you are doing.

CBN wheels have a great built-in feature: because they cut so much cooler, you can place a finger on the object just behind the edge to keep it flat on the stone & monitor the temperature very comfortably. With vitrified wheels, the heat builds up so quickly the message from the pinky often goes from early-warning to pain a little too quickly....

Cheers,
Ian

Ian, I hope I was being clear that my recommendation of 180 grit was ONLY for CBN wheels. If using a vitreous wheel for plane blades and bench chisels, I would never go beyond 46 grit, and likely lower. We are on the same page here.

The CBN wheel is a game changer, and it turns grinding upside down. A newbie here may become confused by the grits discussed.

Regards from Perth

Derek

Thanks everyone for the great advice so far.

Pretty steep learning curve. I've got the grinder set up.
IMG_1464.jpg

The tool rest is pretty junky. Not precise in any way, and I hated using the sliding gauge, much preferring the flat MDF base and free hand grind. I might replace it later, or might not.
I seem to be able to get a pretty square edge, although yes, pretty rough on the 60 grit Alox wheel. And sometimes a little rounded (lower on the sides).
I should be able to work this out with some practice.

Having ground a couple of chisels, I can see that CBN is likely a good idea!

For now, I think I'll grind primary bevel and leave enough meat on the end, and finish on diamond plate for the secondary. Grinding a fragile edge with 60 grit seems a bad idea. I can see the benefit of being able to go from 180 grit CBN with a nice clean edge, making honing a lot faster and easier.

Hi Roger I have that exact set up. With a little practice you will be able to grind right to the edge with no burning. I keep a tin of water next to the grinder and refresh the wheel with a diamond dresser. I put a cloth buff wheel on the other side to 'unicorn' the edge. Sharpening is so quick and easy now. Grind, hone, buff and you're done.

Edit: having seen Derek's set up first hand, there is no doubt that it is superior. But if your careful at the grinding stage with this set up, the rest of the process is very quick and straightforward. The buff also leaves you with a polished, fortified edge.

Thanks, Zac