CBN grit size vs abrasive wheel grit size

[David Wrate]

I was watching this video by Doug Thompson. He talks about using Norton K hardness 46 gr wheel for roughing and 80 gr for finishing.
I have some experience with industrial surface grinders and a 46gr wheel will leave a near-mirror finish on tool steel.

When I read about CBN wheels here the grits most recommended are 80 for roughing and 180 for finishing.
I'm about to lay out for a 8" slow speed grinder which comes with 60 gr and 120 gr white AlOx wheels so I'm trying to figure out if these will work till I refill the kitty for the CBN wheels which are nearly $200 each locally or online in Canada.

 

[William Rogers]

Yes, they will work. It is what was used before CBN. There are multiple advantages to CBN, Wheel size doesn’t change and take off less metal than the ALOx wheels are two important changes.

 

[David Wrate]

Yes, they will work. It is what was used before CBN. There are multiple advantages to CBN, Wheel size doesn’t change and take off less metal than the ALOx wheels are two important changes.

Thank you.
I will almost certainly switch to CBN, just trying to ease the all-at-once wallet damage!

 

[Lyle Jamieson]

The 120 grit stone wheel is a bit to fine for sharpening and heats up easily. I would go to Woodturning Wonders and get the grinder with the CBN wheels right from the start. 180 cbn is the right grit for sharpening.

 

[David Wrate]

The 120 grit stone wheel is a bit to fine for sharpening and heats up easily. I would go to Woodturning Wonders and get the grinder with the CBN wheels right from the start. 180 cbn is the right grit for sharpening.

I'd love to but with the exchange conversion at 25% and shipping I'd spend about $725 CDN for an 8" grinder and two CBN wheels.

 

[hockenbery]

which comes with 60 gr and 120 gr white AlOx wheels so I'm trying to figure out if these will work till I refill the kitty for the CBN wheels

. Those wheels will work fine provided you true and dress the wheels.
Similar to what I was using before I went to CBN.
There are lots of different opinions on what grits work best.

I sharpened my bowl gouges on the 60 grit wheel. Spindle tools on the 120 grit wheel
These I use off the wheel.
Skews I sharpen on Arkansas stones and hone

Other folks will favor different grits.

 

[Richard Coers]

Stock wheels will work fine, just get a diamond dresser to keep them clean and flat. I sharpened for 30 years before I bought a CBN wheel. First I bought the white wheels, then upgraded those to Norton seeded gel for a lot of use. Personally, the seeded gel could have worked just fine for the rest of my life. But I do love higher end tools.

 

[David Wrate]

Stock wheels will work fine, just get a diamond dresser to keep them clean and flat. I sharpened for 30 years before I bought a CBN wheel. First I bought the white wheels, then upgraded those to Norton seeded gel for a lot of use. Personally, the seeded gel could have worked just fine for the rest of my life. But I do love higher end tools.

Norton SG wheels are what I have on my 6" grinder and what I've used on my surface grinder.

 

[Tom Gall]

I agree with @Richard Coers. I used a 1"x42" belt sander for the first 8 years before I got a grinder. I used white, pink, blue wheels over the years and they worked just fine. Twenty three years later I bought my first CBN (2013) and my second two years later. Both were steel wheels which taxed start-up on my high-speed 3/4hp grinder - one was fine but with two starting was a little slow ... still worked! Three years later I bought 1hp slow-speed grinder ..... not because I had to - but because I wanted to!

 

[john lucas]

Good advice. I used the white wheels for a long long time. I do enjoy my CBN wheels.

 

[David Wrate]

As this is my first foray into grinding turning tools I'm hoping that the switch to a slow speed grinder will literally slow down the material removal rate.
I'm used to grinding cobalt 3/8" square HSS tool bits for a metal lathe and those take ages to shape compared to turning tools which seem to disappear as soon as they are close to the grinder!

 

[Dave Landers]

I'm hoping that the switch to a slow speed grinder will literally slow down the material removal rate

That is the point of the slow speed grinder. Gives us time to get the edge we want while there's still steel left in the handle.

 

[Hugh]

For most of my turning I have been using white grinding wheels. I made it work for me.
Then, one day, the club had Cindy Drozda come and do a demo. We did the demo in my shop. The evening before the demo, Cindy asked if she could go out and work in the shop. I told her "of course".
After she left, I went to use the grinder. Holy Cow.....the grinder worked wonders. Cindy had spent some time working on the grinder and made it work the way it was intended. I have tried to keep it running that way ever since.

 

[David Wrate]

For most of my turning I have been using white grinding wheels. I made it work for me.
Then, one day, the club had Cindy Drozda come and do a demo. We did the demo in my shop. The evening before the demo, Cindy asked if she could go out and work in the shop. I told her "of course".
After she left, I went to use the grinder. Holy Cow.....the grinder worked wonders. Cindy had spent some time working on the grinder and made it work the way it was intended. I have tried to keep it running that way ever since.

What did she do to it?

 

[Gerald Lawrence]

Has always been my understanding that slow speed was to keep from losing temper in carbon steels or slow down heat buildup.

 

[Timothy White]

Has always been my understanding that slow speed was to keep from losing temper in carbon steels or slow down heat buildup.

A CBN wheel on a high speed grinder is a recipe foe rapid steel loss.

 

[Bill Blasic]

Learning is fundamental in woodturning and you can learn to grind your tools with a lighter touch even using a 3400 rpm grinder as long as you keep the stone flat. For me I have a dedicated grinder for me that no one else uses ever. My Vector Grind Fixture is never moved so when a tool needs sharpening it is just a very light pass on the 180 grit CBN which I doubt that it removes more than .005 off the length of the tool. And since the only tools ground on said grinder are Thompson tools (which stay sharper longer) I do not foresee any of my tools wearing out. There are 3 other grinders available to students and hands on participants. Sharpening in Woodturning is an art unto itself and the better learned the better your woodturning outcome will be!

 

[David Wrate]

Learning is fundamental in woodturning and you can learn to grind your tools with a lighter touch even using a 3400 rpm grinder as long as you keep the stone flat. For me I have a dedicated grinder for me that no one else uses ever. My Vector Grind Fixture is never moved so when a tool needs sharpening it is just a very light pass on the 180 grit CBN which I doubt that it removes more than .005 off the length of the tool. And since the only tools ground on said grinder are Thompson tools (which stay sharper longer) I do not foresee any of my tools wearing out. There are 3 other grinders available to students and hands on participants. Sharpening in Woodturning is an art unto itself and the better learned the better your woodturning outcome will be!

Thanks Bill, I can certainly appreciate that I have only just started my learning journey!

 

[robo hippy]

For grinders, I consider the 1/2 hp Rikon to be underpowered. Yes, they do work, but the 1 hp model works a lot better. Not sure if you could drive to Seattle and get a better deal or not. As for standard grinding wheels, they do work fine, but haven't used them in ages because CBN wheels are far superior in any way you can think of. You may want to consider getting one CBN wheel. A 180 grit wheel will take care of 90% of the sharpening you will ever do. Scour your local want adds for grinders. They seem to pop up after you buy a new one. A local club could help find a cheaper model as well.

robo hippy

 

[David Wrate]

For grinders, I consider the 1/2 hp Rikon to be underpowered. Yes, they do work, but the 1 hp model works a lot better. Not sure if you could drive to Seattle and get a better deal or not. As for standard grinding wheels, they do work fine, but haven't used them in ages because CBN wheels are far superior in any way you can think of. You may want to consider getting one CBN wheel. A 180 grit wheel will take care of 90% of the sharpening you will ever do. Scour your local want adds for grinders. They seem to pop up after you buy a new one. A local club could help find a cheaper model as well.

robo hippy

Thanks Reed, my local Lee Valley has the 1hp Rikon for $360 CDN which is about what I'd pay with exchange and taxes. Now it is more than double the cost of a 1/2HP 8" low speed so that's the pause.
Just watched the video Ken Rizza did on the startup time for the 1 hp vs 1/2 hp. Pretty huge difference spinning up two heavy CBN wheels.

 

[Tom Gall]

Thanks Reed, my local Lee Valley has the 1hp Rikon for $360 CDN which is about what I'd pay with exchange and taxes. Now it is more than double the cost of a 1/2HP 8" low speed so that's the pause.
Just watched the video Ken Rizza did on the startup time for the 1 hp vs 1/2 hp. Pretty huge difference spinning up two heavy CBN wheels.

I believe the 1/2hp grinder would probably work fine with the new and lighter aluminum CBN wheels. Just my thought as I don't know for sure. Pretty sure Ken Rizza now sells some aluminum wheels as well as some other sources.

 

[Dave Landers]

I've got 2 of the Rikon 1/2hp grinders with Ken Rizza's "regular" CBN wheels on them, various grits. They're fine.
One takes about 5 sec to spin up, the other about 13 sec for some reason (it's not the wheels, same result if I swap them around - the grinders are just different).
I'm not a production turner, I can spare a few seconds every so often.

 

[David Wrate]

Thanks @Tom Gall and @Dave Landers your perspectives are appreciated.
For context, I spent $800 on my lathe and all the tooling that came with it; Oneway chuck, Steb centre and a number of Sorby tools.
Springing for the 1 hp Rikon with a pair of CBN wheels is basically the same money. I know that the grinder will serve me for this lathe and my next (see what I did there? ) so trying to make the smart investment.

 

[Marc Banka]

I now have my CBNs on a 1hp Rikon, but previously used them on the Woodcraft white label 1/2 horse grinder. It was a combo grinder and Wolverine jig. It worked just fine, and the slower start-up wasn’t an issue. It was just long enough for me to don my respirator and get the tool at the wheel.

No real need to break your budget for the higher hp.

 

[William Rogers]

I have a Rikon 1/2 hp and the old Woodcraft 3/4 hp no name grinder. The Rikon 1/2 has an aluminum CBN on one side and steel CBN on other. The Rilon does take time to spin up, but once it is at speed there is no way you would bog down sharpening tools. Sure the 1 hp will spin up faster, but I have no need or desire to replace my 1/2 hp grinder. Not much bang for buck IMO.

 

[David Wrate]

Thanks @William Rogers, appreciate that!

 

[Gerald Lawrence]

A CBN wheel on a high speed grinder is a recipe foe rapid steel loss.

Not what I was referring to. Thought we were talking ceramic

 

[Dean Center]

Thanks @Tom Gall and @Dave Landers your perspectives are appreciated.
For context, I spent $800 on my lathe and all the tooling that came with it; Oneway chuck, Steb centre and a number of Sorby tools.
Springing for the 1 hp Rikon with a pair of CBN wheels is basically the same money. I know that the grinder will serve me for this lathe and my next (see what I did there? ) so trying to make the smart investment.

As Dave said, if you're a production turner, the time to get up to speed would be a major issue, but if you're a hobbyist, it's not really a big deal. There are a great many times in woodworking where you have to decide how much you can afford for a tool and whether the additional benefit from a more expensive tool is worth the added cost. Only you can decide for yourself.

There are lots of 'buy once, cry once' advocates on this forum, and I have come to respect their perspective over the years. I also appreciate that not everyone here can afford an $8000 fully loaded lathe, and many of us make do with lesser gear. Do the best you can in gearing up and go make something. It's all good.

 

[David Wrate]

I may have found a 3/4 solution to my dilemma. Literally.
I was at my local tool store to pick up a 1/2 hp 8" low speed grinder for $149. Turns out they didn't have it in stock. They do have a 3/4 hp 8" low speed for $239. I think I may be able to get that for $200 or so. At 68 lbs it's 9 lbs heavier than the Rikon 1 HP so a real beast. I'll pop over tomorrow and get them to run it up for me.

 

[Neil S]

A CBN wheel on a high speed grinder is a recipe foe rapid steel loss.

All of my grinders are high speed and all of my wheels are CBN or diamond.

The rate of steel loss is just about right for my needs... any slower and refreshing a cutting edge would take too long and take time away from turning. The amount of steel that comes of each grind seems infinitesimal.

I collect most of the steel swarf that comes off the grinding wheels with magnets and periodically I clean that away (mainly to reduce the burn out you can get in the collected swarf) and one time I weighed it. It looked like a lot when suspended in the magnetic field but weighed only something like 11 grams from three months of grinding. If a bowl gouge weighs about 450gms of which 300gms is usable flute, then that's 3.6% of it. If you can buy a 5/8" BG for $100 in your money that is $3.60 for 3mths or $14.40 per/yr. Even if that isn't a precise calculation, that isn't a noticeable cost in a year of turning.

PS - CBN wheels cut slower once they are run in.

 

[Bill Blasic]

When the Rikon 1/2HP first came out it was a period when there were no reasonably priced grinders to be had. The grinders that had always been available at Woodcraft had a problem and they quit selling them (they were about a $100). Well the 1/2HP Rikon went on sale for $99 and I bought one. Yes it did not spin up as fast as my personal grinder or the older Woodcraft ones but it ran for about 12 minutes after turning it off, none of the others ran when shut off for 1/4 of that time. With 2 CBN wheels it was the same and sharpened tools without a problem. Now I have heard that many production workers leave their grinder running all the time so with them start up time is a mute point. And David I think that grinder will be fine but you will need different wheels as those grey ones are not conducive to good sharpening to the best of my knowledge. Too bad your in Canada and shipping is so expensive as I have lots of new aluminum oxide wheels just laying around.

 

[Brian Gustin]

Another maybe tip that may or may not be helpful - I have CBN on my Rikon, though I think maybe I got a 1 HP (never paid attention to that) and I always give it a spin by hand in direction it rotates, before I switch it on, and it seems to come up to speed much faster, IMHO, by a few seconds

 

[David Wrate]

Alrighty, I decided to go with the 1/2HP King Industrial, delivered to my door from Amazon. Enough debating for me! Thanks for everyone's assistance to this newbie!

 

[Dean Center]

BTW WoodTurnersWonders has aluminum CBN wheels which are lighter than the steel ones. They have worked very well for me.

 

[David Wrate]

Thanks @Dean Center Woodchuckers carries those wheels in Canada.

 

[Doug Rasmussen]

David,
Just a thought, but maybe too late...... You say you have a surface grinder, why not use that? The price is right if you already own it.

IMO a surface grinder would be about 1000% better than a cheapo bench grinder.

 

[David Wrate]

David,
Just a thought, but maybe too late...... You say you have a surface grinder, why not use that? The price is right if you already own it.

IMO a surface grinder would be about 1000% better than a cheapo bench grinder.

Sadly (but not really as I needed the space) I sold the surface grinder. Would have been a lousy way to sharpen lathe tools as it required elaborate jigging to create angles, tapers etc.

 

[Doug Rasmussen]

David, there several reasons why I would prefer the surface grinder. First the tool could be rigidly held in a fixture (I can think of several common grinding fixtures that could hold gouges, if you didn't have any appropriate fixtures you could always use one of the bench grinder fixtures). Second, you can accurately dress a composite wheel on a surface grinder which you can't do by hand (somebody likely will chime in and say you can accurately dress by hand, but you can't). Another reason is the spindle bearings of a SG are far superior to those on a bench grinder.

The main reason I'd prefer the surface grinder is the ability to grind with only .001" or less metal removal.

It seems odd to me there's an obsession with woodturners to have the ultimate lathe. On grinders, though, there's a tendency to buy whatever has the lowest price. To a certain extent I think we all buy on price when we're dealing things we don't fully understand.

 

[David Wrate]

David, there several reasons why I would prefer the surface grinder. First the tool could be rigidly held in a fixture (I can think of several common grinding fixtures that could hold gouges, if you didn't have any appropriate fixtures you could always use one of the bench grinder fixtures). Second, you can accurately dress a composite wheel on a surface grinder which you can't do by hand (somebody likely will chime in and say you can accurately dress by hand, but you can't). Another reason is the spindle bearings of a SG are far superior to those on a bench grinder.

The main reason I'd prefer the surface grinder is the ability to grind with only .001" or less metal removal.

It seems odd to me there's an obsession with woodturners to have the ultimate lathe. On grinders, though, there's a tendency to buy whatever has the lowest price. To a certain extent I think we all buy on price when we're dealing things we don't fully understand.

I’d be interested in seeing what grinding fixtures you’re thinking about to hold gouges.
I’m trying to imagine how a person would fixture a gouge to put an Ellsworth grind on it using a say a 6x18 grinder with a magnetic chuck.

 

[robo hippy]

Went to an estate sale yesterday, and just missed an 8 inch, pretty much new Baldor slow speed grinder with a price tag of $100.... New, at least $1,000.....I did pick up a nice set of mini Glaser chisels and scraper for $40. You just never know what you can find. Most of the time, when you buy the new one, a used one comes up for much cheaper..... Oh well.... When the need is there, you can adapt to using just about anything.

robo hippy