Follow up on CBN wheels for flat woodworkers

Hi Don,

I have two CBN wheels now (one on the Tormek) and just ordered a third from Ken Rizza. I have used these wheels on both HSS and high carbon steel for turning and otherwise and have seen no loading with the standard tool steels. From what I've read elsewhere hardened steels in general should be no problem.

Reed Grey addresses this nicely:

"The advice on what you can and can not grind on CBN wheels differs a bit from manufacturer to manufacturer, but general advise is not to grind non hardened steel or other softer, non magnetic materials on them. Main reason is that they can load up and the wheel might be damaged. I have ground my bench chisels on them, and they work fine, with no loading at all. .... To me, this means, save the old grinding wheels if you want to grind away some soft steel or other things. You might get away with it a time or two, but for anything but the lightest touch ups, keep it restricted to hardened steels, not soft carbon..."
http://www.robohippy.net/featured-article/

BTW, I just noticed the other day that Ken is now carrying flat CBN hand hones in a great size: 2.75"x8". He orders these with a choice of two grits, one on either side. I ordered one yesterday with 300/600 to try it out. This might be just the thing for some of my carving tools. If it works out I might get some finer grits.
http://woodturnerswonders.com/collec...ucts/hand-hone

JKJ

I'd echo what Reed said, CBN turning inserts (for metal working) are recommended for materials over 45 HRC. High carbon steels like 1085 & 1095, are well over that in their hardened state.

HSS steel is not harder then good old high carbon steel. Practical values for both are in the 60 - 62 HRc range. HSS wears a lot slower because of all the alloys and it keeps its hardness at much higher working temperatures. I also don't think the common HSS steels like M2 and M4 are much tougher when toughness is defined as how well the steel survives impact damage usually tested with a kerf test.

Edit, no indeed according to Crucibel steels. M2 and M4 are less tough then A2 for example.

Attachment 328284

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Originally Posted by Kees Heiden

HSS steel is not harder then good old high carbon steel. Practical values for both are in the 60 - 62 HRc range. dSS wears a lot slower because of all the alloys and it keeps its hardness at much higher working temperatures.

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Some of the more modern PM high speed steels can be taken to much higher hardness than that. Crucible claims Rc >70 for CPM Rex 121. The HAP-40 in my PM-HSS chisels is hardened to Rc 66 or so.

For that matter, the M4 datum in the Chapy C-Notch comparison you posted likely corresponds to a hardness of Rc 63.5.

I believe you immediately, but in the context of "CBN wheels are for hard and tough HSS turners chisels" I think we can easilly take the M2 or M4 example, and compare it to A2. If I am not entirely out of mind then I think O1 is even a little tougher then A2 at the same hardness.

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Originally Posted by Kees Heiden

I believe you immediately, but in the context of "CBN wheels are for hard and tough HSS turners chisels" I think we can easilly take the M2 or M4 example, and compare it to A2. If I am not entirely out of mind then I think O1 is even a little tougher then A2 at the same hardness.

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Yes, but... Toughness both as classically defined (area under the stress-strain curve to failure) and as measured by the Chapy C-Notch test aren't the same thing as or even correlated with "abrasion resistance". In that sense I think we're discussing the wrong thing here, and I probably should have come out and said that rather than quibbling with your numbers :-).

HSS is *very* wear-resistant stuff despite its lack of classical toughness. Carbides are a much more extreme example of very low toughness and very high abrasion resistance.

I think that if the original statement had been worded "CBN wheels were designed for abrasion-resistant HSS alloys" (which is a true statement AFAIK) we wouldn't be arguing about it...

I think we are in total agreement here.

Thanks for sharing this important issue with us, Derek. Happy New Year to you and your gal.

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Originally Posted by Derek Cohen

Hi Matthew

Some have reported a slight concave, like mine, and others have not found this. I don't know what to conclude. I have had a report from the factory to say that the section between the radii is ground flat. The radii are ground after the faces are ground flat, and it could be that on some wheels this pushes the steel up a little - I am hypothesising here. Please do not take this as fact. The point is, however, that the radiused wheels are fine for turners and that the straight wheels are probably better suited to flat woodworkers. I trust this assumption enough to get two replacement wheels, both straight.

Regards from Perth

Derek

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I've been using the same radiused edge wheel like Derek had trouble with for something over two years now. Mine was never dished, and has remained flat. I've never used the curved edges for anything though, and if I ever get another one, it will be a flat one.

I doubt I will ever use anything else for grinding on chisels and plane irons, just like I won't ever have another car or truck with cranks to roll the windows up and down.

I was removing the edge that came on a Veritas PM-V11 plane blade, made for Stanley type planes, last night. I will use the blade on a Stanley 5 1/4 plane. I intend to use the smaller width blade more as a scrub type plane. I marked a 8" radius on it and ground it down slow, which on a CBN wheel is very fast. I was working "slow" because I was checking for any issues of the nature Derek mentions in this thread and trying to maintain a relatively precise radius and hollow ground edge. I am not seeing the issue Derek mentions probably due to my Stuart Batty tool rest, from Woodworkers Emporium. I run it on a relatively cheap Delta Variable Speed grinder. I have noticed significant visual wobble on start up with both my wheels. I have been checking for it as I believe I read some of the same things Ian has about the arbors, threads etc. on these machines. I have a set of the washers Ian mentions which thus far have not dialed out the wobble.

Although I have not seen the issues I have some concerns about damaging my wheels on a grinder that costs less than they do. I have had issues with this particular Delta Variable speed grinder due to the body shape and arbor length apparently being different than older models. The arbor on my grinder is so short all the threads on the locking bolts do not extend all the way through, which adds to the issue of dialing in correction. I can set a small wood screw on the center of the machine with it running and the screw stays in place but movement is occasionally visible on the tip of the screw and I can feel vibration in the body of the machine. It may be that having a slightly wider heavier wheel on one side and a thinner aluminum wheel on the other contributes.

I like my SB tool rest. I have the one with the round rear section. It holds a plane blade very steady against the wheel. Once I figured out how to use the SB devise for setting the tool rest angle to the wheel that has become very easy and precise too. I am able to hand grind hollow radiuses in plane blades with very little effort. I should say I have had a great deal of difficulty doing this on my Tormek or other grinder and belt sander set ups. I am apparently "grinder impaired" but have no problems hand working plane blades on this rest. I can even relieve the corners of a plane blade relatively precisely with little difficulty. I think the fact that the CBN wheels cut fast enough for me to see what is going on helps a great deal. I can work at a pace that gives me a relatively precise hollow grind all along the radius, adjusting out any error with minor effort. I thought I would like the sliding attachment on my Veritas tool rest for working plane blade. After trying it a few times though I just took it off and use the Veritas without it. I am thinking about replacing the Veritas with another SB. I suspect that, as Derek mentioned above, the ability to adjust and move my plane blades during grinding allows me to compensate for any error in the wheels, arbor, grinder...regardless, the system is allowing me to do things I have struggled with for years on other systems.

I bought two different grinders, and sent them back, before I found one smooth enough for me. Having no vibration makes a big difference. CPO is a great place to deal with. I just wish Metabo made a slow speed grinder, but I've gotten used to the regular, full speed one. I'm also using the Veritas stand, which is amazingly stiff. Sometimes I use the jig on it, but most of the time not for plane irons, but do for chisels.

I came close to returning the Delta grinder Tom, If I could have found another slow speed grinder that wasn't too expensive I would have done it. Tools for Working Wood offers slow speed Baldor Grinders they customize but they are not cheap and I think some of the mods are directed at stone wheels. I got lost in the dizzying array of grinders out there. I made a post on the subject a long time ago but still did not come up with the solution I was hoping for. I may just buy a Baldor at some point but I am concerned about whether or not the specific jigs I will want to use will fit properly or not. I would like a grinder set up that works well with CBN wheels and tool rest like the Stuart Bally and the OneWay Wolverine. Who is CPO? If they are ok with taking a return if things do not fit they may be the place to buy from.

Attachment 328469I don't think there is such a thing as a cheap, smooth, slow speed grinder. I've posted this picture enough that some are probably tired of it. This was the first day I stuck the wheel on this grinder. I kept setting stuff on it, and finally went to the truck and came back with the camera. It still runs that smooth a couple of years later, and I don't know if I ever tightened those nuts down or not. I have a really old Baldor grinder on a pedestal in the mechanic/metal shop that belonged to my Dad. It's still smooth as can be, but I didn't want to drag that one around, and it gets used for metal, and I didn't want to spend that much for another one either.

Do a Google search for CPO tools. It'll come right up. I don't think I've bought a power tool from anyone else for some years. I got a couple of "refurbished" 7518's from them cheap, and they were like new, as was a 2" 23 ga. pinner a couple of weeks ago. I always look for their reconditioned tools as first choice when I'm looking for something. I think the return label comes in their box. Quick shipping, best prices, and easy returns.

Derek,
I am wondering if you have tried hollow grinding the thicker Veritas plane blades used in their bevel up planes using a CBN wheel? I have read your post about grinding 25 degree bevels on all of these blades and then making a much smaller "micro" bevel to alter the plane blades angle of attack and to sharpen it. I am just wondering if the much greater speed of the CBN wheels might finally make it reasonable to just hollow grind these blades? I have a couple PM-V11 and A2 38 degree BU blades that I have put off working until I figure the CBN wheels out better.

I believe I can regrind the blades with the CBN wheel. I am just wondering what a hollow grind in an edge that wide would end up like functionally. Using the normal surface of the CBN wheel ends up making a hollow unless the one doing the grinding does something different, I do have a CBN wheel that has a flat side with abrasive on it, but I don't know how hard it might be to grind one of those wide edges flat using the small area on the side. I am not excited about regrinding 38 degree BU blades to 25 using a stone or diamond plate. Maybe Derek has ground flat bevels on the side of a Tormek wheel or a belt sander?

I am using my old Stanley planes for the rougher work, requiring more cambered blades. The thinner blades are easier to grind cambers in for one thing. In my case this means my Veritas BU planes" jointer, LA jack, BU smoother and BU block will need only minor cambers or rounded edges, some or most of which might be done during the honing rather than the grinding.

I have ground some of my PMV11 BU blades to around 35 degrees. I do not camber though, this is for my BU Jointer that I use for the edge jointing. Seems to be ok, but my standards are fairly relaxed. I would not bother to grind all the way back to 25 unless you want it for the endgrain. At 35 degrees tearout is not much of an issue with the jointer.

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Originally Posted by Mike Holbrook

Derek,
I am wondering if you have tried hollow grinding the thicker Veritas plane blades used in their bevel up planes using a CBN wheel? ...

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Hi Mike

I have not compared an 8" hollow with the 10" hollow (which is shallow) or a flat primary bevel (which is not too different to a 10" hollow). Part of the reason is that I have moved increasingly to double iron planes.

I do use a straight 40 degree bevel on a BU Jointer. I use a cambered blade on a Custom (BD) #7.

Regards from Yorkshire

Derek

Derek,

Thanks for the update. Sounds like there is a dearth of information on the topic, unless Reinis means he hollow ground a BU PM-V11 to around 35 degrees. I guess I will be breaking new ground. I think I will try an older A2 BU first, mine are use to being tortured over the years. Sounds like Derek is growing fond of the new Veritas BD planes.

Derek I missed a question you asked earlier in this post about deflection of the universal bar on a Tormek. I finally found the answer, which I believe to be unique to early model machines. My older Tormek, 2000, does not have a locking knob on the left side of the mechanism for holding the bar in place, which all the other models do have. Even when I have the right locking knob and the locking washer up tight against the right side, I have discovered that the left side moves within the housing. I missed this for years because it looks solid and is hard to see until you start playing with the end of the universal bar looking specifically for deflection. I might never have found it if Derek had not posted about the need for the bar to remain dead parallel to the wheel surface, even though I was suspicious that something was going badly wrong. I can deflect the end of the bar on mine by something like 3/8" with fairly light pressure. I am fairly sure this is why I have had such a horrible time getting consistent results.

Seems like Derek is bringing the new year in with a little travel, Scotland now England, stay safe and bring back some good info. on proper english woodworking.

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Originally Posted by Mike Holbrook

I came close to returning the Delta grinder Tom, If I could have found another slow speed grinder that wasn't too expensive I would have done it. Tools for Working Wood offers slow speed Baldor Grinders they customize but they are not cheap and I think some of the mods are directed at stone wheels. I got lost in the dizzying array of grinders out there. I made a post on the subject a long time ago but still did not come up with the solution I was hoping for. I may just buy a Baldor at some point but I am concerned about whether or not the specific jigs I will want to use will fit properly or not. I would like a grinder set up that works well with CBN wheels and tool rest like the Stuart Bally and the OneWay Wolverine. Who is CPO? If they are ok with taking a return if things do not fit they may be the place to buy from.

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I have the same Delta variable-speed 8" grinder and was dissatisfied with the amount of wobble/vibration even with CBN wheels. Traditional wheels were a disaster, requiring endless fiddling with the washers to get even halfway-decent performance.

I upgraded to the half-speed Rikon from Highland Woodworking, and it's a night and day difference. I can balance 2" 1/4-20 screws on end on the housing while it's running with either type of wheel, just like Tom can with his Metabos. Admittedly the fact that the Rikon is only running at 1750 rpm makes that somewhat less impressive, but it's still a very smooth-running grinder. As Highland says, the washers are very thick with ample registration on the arbor and inner flange, so they serve to stabilize conventional wheels (they don't help CBN, but the bushings for CBN wheels serve the same purpose).

One useful benefit that isn't listed on the product page is that it has a built-in wheel brake that auto-triggers below a certain speed. With conventional wheels it takes about 20 sec to come to a complete stop. Changing a single wheel from conventional 8x1 to 8x1.5 CBN adds about 20 sec to that (mostly spent spinning down to the brake's trigger speed), so the grinder takes about a minute to spin down with 2 CBN wheels.

I hollow ground it on 180 CBN wheel. to 35 degrees, worked fine.

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Originally Posted by Mike Holbrook

Derek,
unless Reinis means he hollow ground a BU PM-V11 to around 35 degrees.

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I learned from the D-way videos that one can easily stop these wheels via friction by holding up a rag to the wheels side. I use an old rag, works well.

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Originally Posted by Patrick Chase

One useful benefit that isn't listed on the product page is that it has a built-in wheel brake that auto-triggers below a certain speed. With conventional wheels it takes about 20 sec to come to a complete stop. Changing a single wheel from conventional 8x1 to 8x1.5 CBN adds about 20 sec to that (mostly spent spinning down to the brake's trigger speed), so the grinder takes about a minute to spin down with 2 CBN wheels.

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Originally Posted by Reinis Kanders

I learned from the D-way videos that one can easily stop these wheels via friction by holding up a rag to the wheels side. I use an old rag, works well.

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I use a block of MDF as a brake on the Delta. Same idea :-)

http://i1009.photobucket.com/albums/...psttaqohud.jpg

http://i1009.photobucket.com/albums/...psaqrckn0y.jpg

3 Speed machine; 240V;1 AMP; 50HZ;
Manufacturer ELECTRO DENTAL, Sydney Australia.

Watch this video from 10.30 min. to see how complex sharpening a plane iron needs to be; also note the top surface of the stone looks to be slightly bellied.

http://www.rts.ch/play/tv/la-suisse-...d=3464421#t=27

Stewie;

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Originally Posted by Reinis Kanders

I learned from the D-way videos that one can easily stop these wheels via friction by holding up a rag to the wheels side. I use an old rag, works well.

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Hi Reinis

I press a finger (!) against the inside of the wheel to act as a brake. I would say that a rag or, better, a piece of leather (finger of a defunct glove) would be better, however the steel is smooth and a resulting grimy finger can be washed. :)

Try that on your set up, Stewie!:eek:

Regards from Perth

Derek

Derek. If your stupid enough to put your finger where it shouldn't be to slow down a 2800rpm grinding wheel;

Stewie;

http://i13.photobucket.com/albums/a2...psyleve1mf.jpg

What is the fascination with this? Why not just walk away and let er spin down???

I usually do just that, but in more public setting it probably is not a good practice to just walk away and leave a spinning machinery.

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Originally Posted by Pat Barry

What is the fascination with this? Why not just walk away and let er spin down???

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Originally Posted by Pat Barry

What is the fascination with this? Why not just walk away and let er spin down???

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Hi Pat

A more serious answer - most of the time I do let it run down, but when grinding more than one blade, you need stop the wheel to set the angle. These CBN wheels run so smoothly (because they are so well balanced), that their own momentum lasts a long, long time. Many, many times that of a white wheel ... 10 minutes after the power was switched off they are still spinning!

Regards from Perth

Derek

The other reason that I don't put another wheel on the other end my the Metabo, other than I don't need but the one, is that if I did, and turned it off today, it would probably still be spinning tomorrow. With no vibration, and no fan to make noise, it doesn't make enough noise to notice, and at 3k+ rpm, it's got a good start.

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...turned it off today, it would probably still be spinning tomorrow

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Ha! My Metabo is the same - it's the best of all my grinders. But I can see the silent rundown could be a problem with more than one person in the shop. I wonder if adding a small plastic vane or even a piece of tape somewhere would add enough noise to alert it's still spinning. Mine is in my weld shop and I have a wire brush on one side which makes plenty of air noise.

JKJ

Derek. Is there such a thing as a CBN flat stone ?

Hi Lasse

Yes. D-Way sell one. I think it is 600 grit. There may be another as well.

Regards from Perth

Derek

Thanks, I just ordered the 360/600 Grit plate. Its going to be very interesting how they perform manually

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Originally Posted by Lasse Hilbrandt

Thanks, I just ordered the 360/600 Grit plate. Its going to be very interesting how they perform manually

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CBN is mechanically softer than diamond, and is bonded to the plate in exactly the same way. The only reason to prefer CBN to diamond is for cost/availability and maybe to avoid carbon exchange between the wheel and the workpiece, but only if you're grinding HSS at temperatures approaching 700C (the threshold/activation temperature for the aforementioned carbon exchange reaction. It's a nonissue below that).

Neither of those applies to D-Way's hand hones...