Heat damage to blades when grinding...

[Derek Cohen]

mmm ..... David, there appears to be a big difference in our wheels. I wonder if this is the grit level (80 vs 180) or the make? My 180 creates a surface similar to the Tormek (which is 220).

Can you remove your guard altogether to determine if the grit spraying out is bouncing off this?

Regards from Perth

Derek

[David Weaver]

I could remove it at some point. When I do, I'll report back.

I think your wheel and my wheel are made by the same place, and if not the same place, the same spec. I think the grit on my wheel is probably 2 or 3 times the micron size (based on a grit conversion chart, that would be exactly the case if the grits are graded properly - vs. 180 and 220).

When I look at the pictures of the radius wheel from ken rizza, the 180 and 220 grit wheels look very similar to the dway, much finer than 80 grit.

[ian maybury]

It seems that grading of CBN wheels is a bit of a hit and miss job - one UK supplier of turning tools that I spoke to today really didn't want to talk in terms of grit sizes at all - just extra fine, fine, medium, coarse etc. Arguing that it doesn't correlate to performance (finish and metal removal rate) in the same way as with say AlOx. Which may well be the case, but means that it puts a lot down a lot to getting some experience.

I'm thinking seriously of trying a counterbored/recessed/cup wheel on a bench grinder solely for grinding new bevel angles (heavy metal removal - occasional requirement) and re-grinding bevels/grinding off honing bevels (moderate metal removal) on the flat/side/end face of a CBN wheel - it looks like there are some available in the UK with a roughly 15mm wide cutting band on that face. The CBN sounds very promising re. low dust, no wear, long life, minimal heating etc.

Do you think at this early stage that it's possible that a CBN wheel can handle the above (by AlOx standards) pretty wide range of removal rates off a single wheel on say a low (single speed) bench grinder? Or might it require say the 80g for occasional rapid metal removal on heavy pieces, and the 180g for regular lighter work/re-cutting the bevel before honing on waterstones? (two would be starting to get expensive)

PS Think i've answered some of my own questions. Digging through the turners sites 80 grit CBN is typically presented as being for 'shaping' tools, while the 180 is for 'sharpening'. Another complication emerging seems to be that only Optigrind do coated sides for side/flat surface grinding, but only in the 180 grit. The sharpening supplies guys seem to figure there's not much demand for side grinding in the 80 grit. There's far fewer 8in wheels about too.

[Noah Wagener]

Ian,

You had mentioned grinding on the side of Norton 3x wheel. I bought one of those precisely for that. For jumpstarting lapping badly pitted tools. For some reason the side of my wheel mirror polishes. It may be the hard grade and finer (relative, it is 80) grit and larger contact area than intended. Even the intended grinding face of it is not much faster than a sandstone wheel.
That sandstone wheel i have is actually probably faster on my tools than the Norton when i use a lot of pressure but i can not keep the wheel spinning when i do that. Cooler running as well despite no water. I may experiment with a bigger crank but I ordered one of those Sigmas as they are only 25 dollars US with shipping and if that works as tauted i think i will clear up some space jettisoning the grinders.

[ian maybury]

Thanks Noah. I thought of the 3x, but moved on to considering the CBN option based on Derek's very helpful comments. CBN wheels are made in lots of formats, including specifically for side/face grinding: e.g. http://www.cuttermasters.com/portfol...inding-wheels/ Norton have long lists of various types of CBN wheels too - it might even be a cheaper way to buy if we could tie down the required specification. Optigrind/Holzer Hartsstoffteknik in Austria (possibly ex of UK) also do some wheels with a band of CBN on the side as well as on top - they pop up in the catalogues of quite a few wood turning supplies places in the US and around the world.

One issue to be solved with using the side of a wheel in a material like 3x is that it presumably needs to be dressed to keep on cutting, but i'm not sure how this might be done. Wonder if your wheel was possibly glazing? (just a guess - i don't know how fast they cut when freshly dressed) Bench grinders and wheels may not be intended to handle much side force either, although it likewise may not be an issue.

More crank should increase your torque a bit, but might slow your eprson powered grinder down. Could help though. I remember building a pedal powered potter's wheel once - one immediate discovery was that the human body/our legs are very sensitive to getting the gearing right. Too fast/high and we can't turn it, but too low and we just as quickly run out of rpm. Maybe a ten speed grinder?

[Noah Wagener]

Wonder if your wheel was possibly glazing?

it is brand new. polished right out of the box. it is the first wheel i have ever bought and i do not know the standard operating procedure for them. maybe you are supposed to dress them when new.

maybe a ten speed grinder?

That is what i originally wanted to do. i tried this:

Pig-29-A-simple-foot-power-grinder.jpg

but i use my bike and did want to take of the fork. you can see how uncomfortable it would be leaning forward with the pedals behind you like that and with the fork on it was worse. plus you had to pedal backwards. i was not handy enough to mount a second wheel next to the rear wheel as a fly wheel.like these people:

[Mike Holbrook]

I just talked to Ken Rizza at WoodTurner's Wonders. Turns out Ken is in Lawrenceville, GA not far from where I live. Ken's CBN wheels are a little different than the D-Way Tools wheels. Ken offers 1 1/4" wheels that fit on the newer shorter grinder arbors better. Ken's wheels do not require a bushing. Ken also offers 80, 180, 220 and 350 grit wheels. Ken's latest wheels, which apparently arrived just before my call, not only have a radius on the wheel corners but also have grit on a 1" area on the side of the wheel. The grit on the side of the wheel is for flat bevels. Another interesting product Ken sells is a 3 piece set of self-aligning washers that help keep grinder wheels running smooth without wobble. Ken's price for the wheels with the additional side grit are lower than D-Way Tool's for the regular radius edge wheels.

[Mike Holbrook]

WoodTurner's Wonders (same .com address) has a picture of their new wheel on line now. This CBN wheel has rounded corners continuing into a 1" flat CBN covered area on the wheels side. Check it out in the catalog. The picture will zoom in for a close view and out for an over all. Then click the picture and get more info.

This one does not come with washers, but they have a special "Self Aligning Spherical Washer 3 piece set" (For One CBN Wheel). I did not figure this out so I guess I am ordering the 3 piece set now. I will post more information when I get the washer set and have a chance to compare the 180 D-Way to the 350 grit WoodTurner's Wonders. Ken informed me that he frequently uses turning tools right off the 350 grit tool so I went down vs up in grit for my second wheel. From what I have read I think the 180 will be great for forming new/different bevels and I am hoping the 350 will be great at refreshing and smoothing the bevels off the 180. From there I hope a few swipes on my Spyderco medium and extra fine stones will keep my tools very sharp very fast with little or no water. I may spritz my CBN wheels with water to consolidate the smaller refuse.

Yes, I am serious about being able to sharpen fast. Now all I have to figure out is what to use as a tool rest/guide. Derek apparently made something to hold a Tormek bar. I assume this allows him to use Tormek tool holding devices at his CBN grinder or Tormek. Dave at D-Way mentioned another jig that I have not been able to run down yet. Then there is the Lee Valley rest...From what I understand, the CBN wheels stay the same diameter so I am hoping there will not be the constant issue of adjusting to a changing wheel size. It might be possible to set a jig with a scale up and be able to switch between angle settings for different tools, BU plane blades at different angles....and not have to adjust it all the time. Yes, even more speed!

[ian maybury]

Thank you very much for sharing that Mike - those WTW wheels are exactly the sort of thing I've been searching for in that they can handle flat bevel grinding off the sides.

This is the Lee Valley grinding tool rest i've seen: http://www.leevalley.com/en/Wood/pag...=1,43072,45938 Sorby do something fairly similar it looks like, but no idea how well it works: http://www.robert-sorby.co.uk/universalsharpsys.htm I've been toying with the possibility of setting something like the Veritas up at 90deg to the usual direction to grind off CBN wheel sides to do flat bevels - but it'd have to very accurately maintain its setting/reliably stay locked.

One issue from my perspective (probably not in the US where it seems many have 5/8 shafts) is to find an 8in grinder (the WTW sheels seem to be 8in OD x 5/8 in bore X 1 1/4in wide) with a 5/8in shaft and able to handle 1 1/4in width. It's hard to know whether or not the cheaper Eastern ones on offer are likely to be good enough - smooth enough running.

It could end up requiring getting the wheels bored out to fit a stock larger diameter reducing sleeve to match whatever grinder I guess - but would need a decent machinist to ensure it all was properly centred and fitted.

I've been thinking towards 80 grit in the CBN for fast metal removal/forming new bevels in plane blades, and maybe 180 for refreshing before honing - but don't know if this is a good call. (you are thinking finer) It'd be even better if a single wheel would handle both forming and refreshing bevels…..

The other call is whether or not to go for a low or high speed - the choice in the former is very limited here. Not sure which would be best with the CBN - the answer depends I guess on just how well the promise of very low heating is delivered by it, and on what else gets done/other stones will be run on the grinder.

The last (for now) question on CBN wheels is perhaps life - given the cost they definitely need to last more or less indefinitely as advertised.

It's more or less simultaneously emerged that the Sorby Pro-Edge looks like a decent option too - it's not cheap (similar to the cost of a grinder with 2x CBN wheels), but seems very well engineered and solidly built. There's a supplier in the UK doing belts for it in a wider range of grits and abrasive types than the stock items (e.g. coarser than the stock 60g) which should help widen up its capability. I'm inclined to doubt that the stock 700ft/min will remove metal fast enough for forming new bevels on plane blades when a lot of metal has to come off, but a VFD seems like it should (?) sort that out by maybe doubling the stock speed.

It's also claimed to be a 'cool running' solution, but the question I guess is (a) how cool, and (b) how fast cutting when equipped with say a coarse ceramic belt.

It really needs getting hands on with both solutions - there's otherwise (for me anyway) a fair amount of guesswork and hence risk involved in making the call between the two.

Decisions decisions.

Think i may have the opportunity to test run some CBN wheels during the coming week with a local wood turner who has some set up. It seems that Sorby's rep is demonstrating the Pro Edge in our local shop the coming weekend too, so maybe for once the stars are lining up...….

[Steve Friedman]

Mike,

I'm not Derek, but he has his grinder set up with the Bench Grinding Mounting Set from Tormek. Here's the link to his site where he describes it. http://www.inthewoodshop.com/Woodwor...ngNirvana.html

I have spoken to the Tormek folks about it and it accommodates a few of their jigs. I don't know enough about the Tormek to understand why some jigs don't work with it. I have the LV one, but the Tormek one definitely looks like it might be better for carving tools with the Tormek jigs.

Steve

Steve

[Edward Moore]

It doesn't matter if you burn the tool's edge.

You'll do it once, maybe twice. Then never again.

When you do burn a edge, you just need to sharpen it again a bit sooner. No big deal. If you are really pedantic about these things you could just grind it back a bit, which is only 10 minutes of your life gone.

If you sharpen with a honing guide then your grinding can be rough as guts. Just don't grind past the honed edge and use that as a visual reference for your progress. If you want to be more accurate you can clamp a honing guide onto your blade and reference that against the tool rest.

I have been using a hand-cranked grinder with a very course wheel and Veritas tool rest. It takes slightly more practice than a powered grinder because you can only use one hand but it is still easy to get a nice, even grind. You have precise control over the speed, obviously, so it is really difficult to burn the tool and you can grind right to the edge.

I also have Stu's 120 grit Sigma stone. It does cut very quickly indeed but it is unpleasant to use. The clogging problem is overcome by regularly lapping with course silicon carbide grit and by using the stone while almost submerged in water. For course flattening work it is excellent. (Although I suspect David's idea of using a steel plate and loose diamonds would work better).

I have only been playing with sharpening for a few years. I am still learning and improving. However, the grinding seems like the least difficult and least important part of the process. I don't understand why a special machine is necessary. Buying a Tormek for a home woodshop seems like buying a Lie Nielsen scrub plane (although the comparison is unfair because Lie Nielsens are, at least, pretty).

Incidentally, hats off to Derek's grinding. That is like the Platonic form of a chisel bevel.

[Derek Cohen]

I have only been playing with sharpening for a few years. I am still learning and improving. However, the grinding seems like the least difficult and least important part of the process. I don't understand why a special machine is necessary. Buying a Tormek for a home woodshop seems like buying a Lie Nielsen scrub plane (although the comparison is unfair because Lie Nielsens are, at least, pretty).

Hi Edward

"Platonic form", eh

I must say that I have a morbid fascination with sharpening. It is my least favourite part of woodworking. I know it has to be done, and do not look forward to it. At the same time, working with sharp tools is a pleasure - there is something magical about a blade sliding effortlessly through wood to create a desired shape. The wood I work with is so abrasive that I have to sharpen frequently. Trying to use less-than-razor edges is a errand in frustration.

Now I disagree that grinding is the "least difficult and least important part of the process". Indeed, I consider it the most important. It is the key to all that follows.

Yes I know that some do not grind at all, and some use a different grinder, but that is simply because there are many methods of sharpening. When it comes to hollow-grinding-based sharpening, the hollow can make all the difference in the edge obtained.

Simply put, a hollow that is to the edge of the blade leaves the minimal amount of steel to hone. Getting to the edge without burning the steel and altering its temper is the challenge. Doing this on a wet grinder, such as the Tormek, is pretty easy, but it is slow.

Grinding a ragged hollow - where the metal has not been removed evenly - means extra work on a coarse stone to straighten the steel along the hollow. This also removes the hollow and increases the amount of steel to hone ... which leaves you back at step one with more steel to hollow. Slow.

There are a number of ways to achieve a good hollow, and one does not require a CBN wheel to do it. I've posted pictures of some pretty decent hollow grinds that were done freehand. I've been doing this for a while now. I would not recommend a beginner start where I am - not because I think that one should earn the skills first (that is advisable), but because what is right for me is not necessarily right for others. I do not love sharpening. I just want a fast way of getting back to the wood.

Regards from Perth

Derek

[Mike Holbrook]

Exactly what Derek said only different. I agree with everything Derek said, in spades, except I actually like to sharpen. I know it may be a sickness, but I find it a little meditative. I may be a little OCD too, because I yearn for the same perfect bevels Derek's tools exhibit.

Flat Vs Hollow bevels
For me the whole argument about whether to hollow or flat grind has become a mute point. Show me a perfectly "flat" bevel! I look at it like matching edges for glue ups. We know we are going to leave the "matching" surfaces either a little concave or convex. We know slightly concave edges make a better glue up. We know convex edges tend to rotate when pressure is applied while concave edges hold together. For some of the same reasons, I think a slightly concave bevel is better too. I use to think a convex bevel was fine and might have some sort of advantage. What I have learned from doing things the hard way for quite a while is a convex bevel rocks around on a flat stone or wheel and prevents solid registration of the bevel against the sharpening devise. The hollow grind holds tight against a wheel or flat surface, making registering the tool much easier. I also prefer to sharpen by hand as much as possible which personifies any rocking issues. Try registering a concave and convex ground bevel against both a wheel and stone by hand and I think the difference becomes clear. Since I will not ever be able to regain all the steel I have ground off bevels trying to make a straight convex bevel I finally decided to try it the easy way. So for me, bevels are not just an important factor in sharpening they are THE factor.

Grinders
I have not been able to stir up much if any discussion of various grinders Ian. Everyone on SMC seems to use a different type and there seems to be very little loyalty to brands or models. I talked to both of the CBN guys about grinders and although they both mentioned slow speed grinders I understood that they both prefer to use higher speed grinders. Ken at WTW says he started making his wheels 1 1/4" wide vs 1 1/2" because grinder manufacturers seemed to be making arbors shorter on newer models.

Why CBN Wheels & which ones
Although I can not confirm via personal experience yet I hear that one can hand hold a blade against a CBN wheel without stopping while sharpening and not create enough heat in the blade to make it unpleasant to hold. The WTW wheel I just got came with a little card in it- Lifetime Guarantee. Dave at D-Way says he has sold thousands and has yet to have one returned because of wear. Assuming they live up to expectations, the CBN wheels start sounding like a long term bargain to me in terms of longevity, safety, ease of use, repeatability.... I wanted two wheels and decided on the 350 grit as my second wheel via discussion of my needs with Ken at WTW. I want speed and the 80 and 180 wheels may leave deep grooves in the steel that my Spyderco finishing stones may not remove easily, slowing me down. I understand Ken uses a 350 as his second wheel and finds the edge it produces works as a final edge for his turning tools. The little I have read suggests that grit changes on CBN wheels may not provide the same difference in grinding aggressiveness as in other wheels. I elected to go down to 350 instead of up to 80 for my second wheel because I think the 350 will quickly produce a surface that my Spydercos can polish easily/quickly. I suspect the new WTW 1 1/4" wheel is heavier than the D-Way 1 1/2" wheel. The WTW wheel has a solid metal 1" edge, which is covered in abrasive. The solid 1" metal edge adds substantial weight on an 8" wheel.

Tool Rests for grinders
The information I read on LV's tool description of their general purpose tool rest suggests that their rest has a 1" opening for the wheel, which may not accept my 1 1/4 & 1 1/2" wheels without modification. I am still trying to locate the rest Dave at D-Way tools uses in his CBN wheel demos before making a purchase.

[David Weaver]

I have something to do today that should give an idea about heat buildup.

A while ago, mel fulks sent me a couple of chisels in trade. They are both 1/2" timber framing mortise chisels that he found in his travels and he mentioned that he already has enough of such a thing that he'd pass them along, and thus he's got no use for them and hasn't used them.

I looked at the one and got a chuckle, the yard saler who sold them to him had ground the bevel upside down on one of the chisels - they are the type that has a curved taper along their length, and I'll bet the person using that chisel wondered why the bottom of the chisel "wasn't flat"

So, I figured I'd set it aside because there's two and one has the bevel on the proper side.

I will sometime today take the chisel that has the bevel on the wrong side and hold it against the wheel and literally grind the entire bevel off and grind another one the other way (effectively two entire bevels of work), and I'll see how much heat is generated and how long it takes to do that. I'll check the loupe then and see if there are any temper colors anywhere near the final edge.

This is a job I haven't done yet only because I don't have water at my grinder and this literally would've required it and some discretion in grinding. With a regular wheel when grinding something like this, i grind in facets so as to work a small surface at a time and build less heat (though I won't do that with the CBN wheel), and only grind the full bevel as I'm finishing the grind.

The other thing about that kind of work is while a pink wheel like I like to use leaves a nice surface and doesn't build up a lot of heat, heavy grinding wastes a pink wheel if you get heavy handed with it.

[ian maybury]

Have to agree Derek - ability to sharpen effectively is arguably the primary gateway to working to a high standard. Also that grinding matters a lot. Depends on what you're shooting for, but it's got to be a big deal/the foundation if you ony want to run very fine micro bevels like you showed with the Spydercos, and that has the side benefit of minimising the need to regrind. Likewise when sharpening chisels single bevel the ground surface must be flat and very accurately aligned/angled, and that angle accurately transferrred on to the waterstones (hence my interest in using the Veritas Mk 2 guide to align both grinding and honing without disturbing the tool in between - not sure yet how to do this on CBN wheels) to avoid the need for lots of waterstone work.

Sharpening has a certain sort of fatal fascination for me - boring, but also highly dependent on doing it just right. There is something deeply satisfying about seeing a polished micro bevel emerge, and finding that it delivers a wickedly sharp edge.

Be careful of your CBN wheel David - although your information Mike suggests that the things are pretty much bullet proof. Agree that if they balance properties as claimed (balance of heat/metal removal/speed insensitivity/wear/cleanliness/life/safety) that they are a vey attractive proposition indeed. The safety issue is no minor factor.

Reading what gets published (says a lot when a mag refuses to apply a rating) the problem on DIY/hobby grinders it seems to be that it's very easy to get stuck with one that's not very well balanced, or has runout/poor fits. They are pretty much the primary example of a power tool made down to a price i think. Those Baldor ones Tools for Working Woood sell look great, but the price tells all. One of the UK turning supplies outfits sells a budget one that they say they check before shipping. As ever it's not a big deal if you can buy up the road, but is a disaster if there's significant shipping cost involved. Turns out there are some grinders on sale in the UK with a 5/8 shaft, although so far all are std speed and run narrow 1in or so wheels.

It'd simplify things a lot of it proved that stock RPM was OK on an 8in grinder - but both David and Derek are on Low speed with 8in CBN wheels.

It'll be dead interesting to hear how you get on in terms of heating and rate of metal removal David. It's at the centre of the decision as to just how coarse a CBN wheel is needed to shift large amounts of metal - in that once the metal removal and heating rates are acceptable then the finer the better..