Sharpness vs. Edge Holding Clarification (practical experience?)

[Davis Stevenson]

Hi All,

I know this has been discussed over and over, but I have been finding a lot of conflicting information on this subject. The general rule that I've been hearing is that if you sharpen to a higher grit for a keener edge, it won't stay as sharp longer. It makes sense to me (in theory).

What I want to know though, is how do the edges deteriorate?

Will a 1000 grit edge go from razor sharp to dull enough to throw hot dust in less cutting time than a 180 grit edge takes to wear down to the same level of dullness?

-OR-

Does a 1000 grit edge lose it's super fine edge quickly, but stay "usable" for a longer amount of cutting time. (Could you sharpen a bowl gouge to 1000 grit for the last passes, then shelve it, and have it be comparable to a less keen edge for roughing out another bowl, for example?)

If the second situation is true, why don't I hear of more jig-sharpeners using high grit wheels? The standard seems to be an 80/180 combo for two, or a 120 grit if you have one. Since the sharpening time with jigs is in the setup, why not a 220 or 350 grit wheel and a couple extra passes? Just a guess, but even a 600 grit wouldn't add a significant amount of time to the total sharpening experience if you are using a jig.

This does relate to gouges-- my flat bevel riding tools don't see the grinder, and get honed to 1000 grit. I know some of you hone bowl gouges... Maybe I need to learn patience (and definitely practice honing more complex tool shapes!) and do that, if there's a benefit.

Not trying to turn this into a "what should I buy" thread, but some practical experience to help me make an educated decision on what grit CBN wheel to go for. I only have room for one grinder in the shop, and all kinds of metal sees one side of that grinder, so, at this point, I can only have ONE CBN wheel. The other would stay 60 grit white A/O, which would serve reshaping and scraper needs.

 

[robo hippy]

Well, if you remember the old Miller Beer commercial, "Tastes great! Less filling!"

The quality of the metal you are using has a lot to do with it, and the wood makes a difference too. The newer micro or nano grained carbides will hold their sharpness a lot longer than the standard M2 HSS. Other than that, there are some that say a more serrated/80/180 grit edge cuts better, and some who say a less serrated/honed or 600 grit wheel edge holds better...Tom Wirsing did an article in the AAW magazine where he said the 600 grit CBN wheel left a longer lasting edge than the coarser 180 or 80 grit wheels. Theory is that the finer teeth take longer to wear down than the coarser teeth. Some years back there were many claiming that the Tromek gave a finer longer lasting edge.

For me, most of what I do is bowl turning. I do all of my roughing with the Big Ugly tool, which has tantung as the cutting edge (think almost as hard as carbide, but easily sharpened on standard wheels). I can get 5 to 10 bowls roughed without having to sharpen. Most of the time I use a 180 grit edge on my gouges for finish cuts. I have found that a 600 grit edge is excellent for some finish cuts when nothing else works, in order to save sanding time. Since I don't rough with gouges any more, I don't have a lot of experience with that edge for roughing, but it does seem to go dull much faster than the 180 grit edge. Others disagree. Not sure what to think. I now have a 320 grit wheel and will be playing with that a lot come March or so when I get some logs and get ready for my summer show that I do.

I am not sure if there is any way to really measure edge durability. Too many variables. John Lucas has done some fancy microscope pictures of edges. Don't know if he has done before and after pictures.

robo hippy

 

[Davis Stevenson]

Well, if you remember the old Miller Beer commercial, "Tastes great! Less filling!"

The quality of the metal you are using has a lot to do with it, and the wood makes a difference too. The newer micro or nano grained carbides will hold their sharpness a lot longer than the standard M2 HSS.

robo hippy

I've definitely noticed that. My latest tool purchase was some Cryo M2 bowl gouges (a steal, IMO, at $50 a pop @ 3/8", and I think $58 @ 1/2" -- english measurements-- if you order from the UK) that are a huge step up from the generic HSS Hurricane tools. Supposedly the cryo treating gives a finer grain that can produce a sharper, longer lasting edge, and in my experience that is true. About 75% of what I turn for bowls has pretty heavy spalt, and I'm getting much less tear out (more like chunk out, sometimes!) using the same wheels and jig settings.

If the recommendations seem to be 180 in most cases, I wonder if a step up to 220 or 350 would benefit the Cryo tools moreso than standard M2 or generic HSS.

I wish I could try them all out for my style first, but I don't know anyone with CBN now, and scheduling issues mean I can't make it to our local club (also an hour's drive away)

 

[john lucas]

Well I've been playing and reading about sharpening for a long time now. So here is what i have found. There was an excellent article in Woodturning magazine out of England a good while ago where they did tests on sharpening to higher grits. They had micro photographs to prove what they came up with. Sharpening to higher grits made the edge last longer. I don't remember all the details but I think your comment about the edge wearing down to an acceptable sharpness was accurate. Simply put, the sharp peaks took longer to wear down to what they called a dull peak. I have done my own tests when I set up my strip sander. I sharpened tools at 600 grit and at 180. I was doing small production run and what I would do is make a few pieces, sharpen on the 600 grit, then make a few pieces and sharpen on the 180. It didn't take long to tell that the 600 held an edge longer.
Alan Lacer did an excellent article about 3 years ago where he showed that improving the edgy by honing really improved the cut quality. He had micro photographs to prove it. He did not do an edge holding test along with it, maybe for the same reason I didn't. There are just too many variables.
When the particle metal tools hit the market was about the same time people started Cryo treating tools. You had 2 things going on here. One was the particle metal tools could be loaded with more Vanadium and that made the tools hold an edge longer. Thompson came out with V11 and V15 tools at first. The V15 was supposed to hold an edge 10 times longer than standard HSS and the V11 4 times. (I may have my numbers wrong it's been a while since i read that but it's close). Kryo treating tools also changed the metal so that it holds an edge longer. The Thompson tools have both, high vanadium and Kryo. So can you tell the difference. Well at first I had trouble. I think partly because I sharpen really frequently and don't let them get dull. I was turning some aluminum blanks for a Glass artist and that was when it really showed up. With the HSS tools I had to sharpen 4 times to cut the shape, and I mean it was so dull it simply wouldn't cut. With the Thompson V11 tools I was able to turn 2 complete turnings before it needed sharpening and it was still cutting.
Ever since I was into woodworking there have been arguments about how sharp this metal got compared to that metal. It was generally written that High Carbon steel would get sharper than HSS and Particle metal simply would not get as sharp and carbide would not get sharp at all. Well things have changed a lot and Had some particle metal tools that I knew would get as sharp as any other tools I had so I I thought I would do a test. Here is the article so you can read my results rather than making it long here. The gist was, they all 3 got just as sharp. It was simply beyond my capbility to run any kind of scientific test on edge holding. Too many variables. I've done enough turning to know that High Carbon steel won't hold an edge long at all. There are different qualities of HSS and some hold an edge a lot better than others and a lot of that has to do with the quality of the steel and the skill of the heat treating. Unfortunately M42 had just come out and I didn't get to run any tests on that steel. This article was in Morewoodturning Magazine. https://www.morewoodturningmagazine.com/articles.php?articlesid=112&access=7e7d78763e40
So really what it boils down to. If your not that skilled at sharpening, don't go with the higher grits. If your off just a little in your angles it takes a long time to regrind and get the actual edge sharp. It goes pretty fast with 120 to 180. If you are really good at sharpening and can reproduce the same bevel each time then 600 to 1000 works great. Many years ago I took a class with Frank Sudol. He sharpened on a 400 grit belt he said was worn and actually produced an edge more like 600. I had one hell of a time getting my tools sharp that weekend. Now it's not problem using the really fine belts. I have refined my sharpening skills a lot. The average turner will have trouble telling that a tool holds an edge longer simply because they tend to wait too long to sharpen as is and probably don't turn enough to really tell the difference. That's not to put them down, I've been there.
Now if you want edge holding go with Carbide. However they don't get as sharp as HSS or Particle metal based on my tests with a sharpening tester. I don't have micro photographes to prove it however. I have done enough turning with them to know that for the most part I prefer the HSS and particle metal. The exception being the Hunter Cupped Carbide cutters. They don't have a very sharp cutting angle but because they have a highly polished top surface they cut very clean, which leads me back to the original question of will sharpening to a higher grit make a cleaner cut. I think the answer is yes.
It would be interesting to hear from Glenn Lucas since he is now sharpening with the Tormek and is obviously a production turner. Might have some interesting things to say.

 

[Davis Stevenson]

Wow!

Thanks, John. That's a lot of good information. It seems like the higher the grit for sharpening, the sharper (of course) and the ultimate length of time the tool will stay acceptably sharp for less demanding applications. The biggest hurdle, then, would be precision in tool presentation to the sharpening surface (also, of course).

Given that I my V arm and Varigrind settings for my spindle gouge and primary bowl gouge shape (everything else is on the platform with the 80 grit wheel and maybe honed, or hand ground and honed) are the same, and a CBN wheel would remove the wheel diameter variable, the last variable would be tool protrusion from the jig, which I manage with stop blocks for each individual tool, I *theoretically* could go as fine as I wanted, but could run into some trouble if I start fiddling around and lose the tight precision each time I reset.

I have heard that a 180 CBN wheel once broken in feels a bit like a 120 grit A/O wheel in terms of stock removal, so that makes sense as a good starting point-- sharper with a similar removal rate. I might split the difference and try one of the Woodturner's Wonders 350 grit and see how I like it. Seems like they're popular enough that if I hate it, I could resell it (or shelve it) and get something finer/coarser. With precision, it should net an overall benefit.

I also might have to start sharpening my SRG on the finer wheel, and see if it lasts longer. Right off the 80 grit wheel has always been "good enough to rough". Lately, I've gotten about 4' total length of 2" square stock roughed to a cylinder before needing to hit the grinder again. I'm sitting on a pile of nearly identical Maple rolling pin blanks. Could be a good opportunity to do some stay sharp tests!

 

[john lucas]

Changing grits will help all steels. There was an article recently saying that the particle metal steel is too hard for standard wheels and needs cbn to achieve a good edge.. I'm going to have to do a specific test on that because I still.sharpen on a white aluminum oxide and a CBN and both seem to do a.good job. What I will do is sharpen one or two tools and measure sharpness. It won't be real accurate because I have to sharpen on a 120 white wheel and 180 CBN but might tell me.something
Let me make one thing clear. Although it is fun and probably useful to buy the best tools and learn to sharpen them to the max, you would be equally or better served by simply learning to use the tools.more affectively. Cutting with the grain, having the wood cross the tool edge at the best angle, and letting the tool cut throughout the wood at the speed it needs to be cut will make more difference than how the tool.is sharpened.

 

[Davis Stevenson]

Changing grits will help all steels. There was an article recently saying that the particle metal steel is too hard for standard wheels and needs cbn to achieve a good edge.. I'm going to have to do a specific test on that because I still.sharpen on a white aluminum oxide and a CBN and both seem to do a.good job. What I will do is sharpen one or two tools and measure sharpness. It won't be real accurate because I have to sharpen on a 120 white wheel and 180 CBN but might tell me.something
Let me make one thing clear. Although it is fun and probably useful to buy the best tools and learn to sharpen them to the max, you would be equally or better served by simply learning to use the tools.more affectively. Cutting with the grain, having the wood cross the tool edge at the best angle, and letting the tool cut throughout the wood at the speed it needs to be cut will make more difference than how the tool.is sharpened.

Absolutely! My wife and I both used more generic HSS tools (Harbor Freight, Hurricane, etc) until the point where we were sure that limitations were of tools, not shortcomings in our technique (of course there is still a ton to learn!). Also, when learning to sharpen, it's much less painful to grind off too much of a $30 bowl gouge than one costing twice as much or more.

I come from a background in playing wind and stringed instruments, and I view many tools the same way as I view the quality of musical instruments:

*A professional on the cheapest instrument will always sound better than a beginner on a top of the line instrument.
*An expensive instrument will not make you sound/play better
*A high level of skill will be required to extract the benefits of the higher quality instrument
*A skilled individual will know when they can make use of the benefits of a nicer instrument
*A true professional can work around the shortcomings of a cheap instrument

Similar analogies can be made about photography, bikes (road biking is my chosen form of exercise), and just about anything, really.

 

[john lucas]

Well I'm a road biker also and have played guitar most of my life so we obviously approach things from the same point of view.

 

[Bill Boehme]

Hi All,

I know this has been discussed over and over, but I have been finding a lot of conflicting information on this subject. The general rule that I've been hearing is that if you sharpen to a higher grit for a keener edge, it won't stay as sharp longer. It makes sense to me (in theory).

What I want to know though, is how do the edges deteriorate?

Will a 1000 grit edge go from razor sharp to dull enough to throw hot dust in less cutting time than a 180 grit edge takes to wear down to the same level of dullness?

-OR-

Does a 1000 grit edge lose it's super fine edge quickly, but stay "usable" for a longer amount of cutting time. (Could you sharpen a bowl gouge to 1000 grit for the last passes, then shelve it, and have it be comparable to a less keen edge for roughing out another bowl, for example?)

If the second situation is true, why don't I hear of more jig-sharpeners using high grit wheels? The standard seems to be an 80/180 combo for two, or a 120 grit if you have one. Since the sharpening time with jigs is in the setup, why not a 220 or 350 grit wheel and a couple extra passes? Just a guess, but even a 600 grit wouldn't add a significant amount of time to the total sharpening experience if you are using a jig.

This does relate to gouges-- my flat bevel riding tools don't see the grinder, and get honed to 1000 grit. I know some of you hone bowl gouges... Maybe I need to learn patience (and definitely practice honing more complex tool shapes!) and do that, if there's a benefit.

Not trying to turn this into a "what should I buy" thread, but some practical experience to help me make an educated decision on what grit CBN wheel to go for. I only have room for one grinder in the shop, and all kinds of metal sees one side of that grinder, so, at this point, I can only have ONE CBN wheel. The other would stay 60 grit white A/O, which would serve reshaping and scraper needs.

Neither of those scenarios is quite what happens. A cleaner sharper edge stays that way for a longer time because there is less friction when slicing through wood. An edge "sharpened" on an 80 grit stone, by comparison, is more like tiny saw teeth than a knife edge. Ask any woodcarver which edge they would prefer. My experience is that a well sharpened edge maintains a usable edge far longer than one sharpened on an 80 grit aluminum oxide matrix stone. This is based on using a Tormek as my preferred sharpening tool for the past fifteen years. I also have a dry grinder with Norton 3X wheels.

The advent of 400 and 600 grit CBN wheels has enabled dry grinders to produce edges that are not too bad compared to a Tormek edge.

Twelve years ago Alan Lacer wrote an article in American Woodturner (Winter 2006) on sharpening scrapers that included photomicrographs using a scanning electron microscope to compare the bur wear on hand pulled vs. the bur straight off the grinder. More recently, Terry Martin wrote an article about the advantage of a refined edge produced with the Tormek (June 2014).

 

[Emiliano Achaval]

Well I've been playing and reading about sharpening for a long time now. So here is what i have found. There was an excellent article in Woodturning magazine out of England a good while ago where they did tests on sharpening to higher grits. They had micro photographs to prove what they came up with. Sharpening to higher grits made the edge last longer. I don't remember all the details but I think your comment about the edge wearing down to an acceptable sharpness was accurate. Simply put, the sharp peaks took longer to wear down to what they called a dull peak. I have done my own tests when I set up my strip sander. I sharpened tools at 600 grit and at 180. I was doing small production run and what I would do is make a few pieces, sharpen on the 600 grit, then make a few pieces and sharpen on the 180. It didn't take long to tell that the 600 held an edge longer.
Alan Lacer did an excellent article about 3 years ago where he showed that improving the edgy by honing really improved the cut quality. He had micro photographs to prove it. He did not do an edge holding test along with it, maybe for the same reason I didn't. There are just too many variables.
When the particle metal tools hit the market was about the same time people started Cryo treating tools. You had 2 things going on here. One was the particle metal tools could be loaded with more Vanadium and that made the tools hold an edge longer. Thompson came out with V11 and V15 tools at first. The V15 was supposed to hold an edge 10 times longer than standard HSS and the V11 4 times. (I may have my numbers wrong it's been a while since i read that but it's close). Kryo treating tools also changed the metal so that it holds an edge longer. The Thompson tools have both, high vanadium and Kryo. So can you tell the difference. Well at first I had trouble. I think partly because I sharpen really frequently and don't let them get dull. I was turning some aluminum blanks for a Glass artist and that was when it really showed up. With the HSS tools I had to sharpen 4 times to cut the shape, and I mean it was so dull it simply wouldn't cut. With the Thompson V11 tools I was able to turn 2 complete turnings before it needed sharpening and it was still cutting.
Ever since I was into woodworking there have been arguments about how sharp this metal got compared to that metal. It was generally written that High Carbon steel would get sharper than HSS and Particle metal simply would not get as sharp and carbide would not get sharp at all. Well things have changed a lot and Had some particle metal tools that I knew would get as sharp as any other tools I had so I I thought I would do a test. Here is the article so you can read my results rather than making it long here. The gist was, they all 3 got just as sharp. It was simply beyond my capbility to run any kind of scientific test on edge holding. Too many variables. I've done enough turning to know that High Carbon steel won't hold an edge long at all. There are different qualities of HSS and some hold an edge a lot better than others and a lot of that has to do with the quality of the steel and the skill of the heat treating. Unfortunately M42 had just come out and I didn't get to run any tests on that steel. This article was in Morewoodturning Magazine. https://www.morewoodturningmagazine.com/articles.php?articlesid=112&access=7e7d78763e40
So really what it boils down to. If your not that skilled at sharpening, don't go with the higher grits. If your off just a little in your angles it takes a long time to regrind and get the actual edge sharp. It goes pretty fast with 120 to 180. If you are really good at sharpening and can reproduce the same bevel each time then 600 to 1000 works great. Many years ago I took a class with Frank Sudol. He sharpened on a 400 grit belt he said was worn and actually produced an edge more like 600. I had one hell of a time getting my tools sharp that weekend. Now it's not problem using the really fine belts. I have refined my sharpening skills a lot. The average turner will have trouble telling that a tool holds an edge longer simply because they tend to wait too long to sharpen as is and probably don't turn enough to really tell the difference. That's not to put them down, I've been there.
Now if you want edge holding go with Carbide. However they don't get as sharp as HSS or Particle metal based on my tests with a sharpening tester. I don't have micro photographes to prove it however. I have done enough turning with them to know that for the most part I prefer the HSS and particle metal. The exception being the Hunter Cupped Carbide cutters. They don't have a very sharp cutting angle but because they have a highly polished top surface they cut very clean, which leads me back to the original question of will sharpening to a higher grit make a cleaner cut. I think the answer is yes.
It would be interesting to hear from Glenn Lucas since he is now sharpening with the Tormek and is obviously a production turner. Might have some interesting things to say.

Wish I had as much time as you to spend on the internet! Lots of info here. Thanks John.

 

[Bill Blasic]

I will tell you this 85% to 90% of my turning tools are Thompson tools and before CBN came about I sharpened them with white aluminum oxide. They got sharp and stayed sharp longer than any steel I had previously used. With the advent of CBN I found that for me the tools stayed sharper as with the sharpening with the stone but the biggest factor with the CBN is that they get that sharp without taking a lot of steel off the tool. A 5/8 V Thompson for me with the CBN wheels will last me a lifetime. I have a dedicated grinder with 1 1/2" CBN wheels that I alone use so nothing is ever moved and all I need is one light pass to freshen the edge (literally takes almost no steel off the tool). Now 90% of my tools that are not Thompsons are Hunter carbide tools that do not need to be sharpened and they too last for a very long time.

 

[john lucas]

Emiliano. I think you spend more time on facebook than I. Most of what I quoted from above was from magazine articles or my own research. I can't help it, I belong to the show me club. When people make quotes about steel or tools or whatever I have to go and find out. I have to ask questions and find out the answer for myself. Fortunately there are a lot of really knowledgeable turners out there who can help me go in the right direction or simply tell me it's bullshit when I'm barking up the wrong tree.

 

[Davis Stevenson]

Thanks for the great info, all. Way more variables than I ever thought. Good to know about the attitude about a lifetime pair of a Thompson gouge on a nice CBN. As someone who started off freehand sharpening (very poorly, as was my early turning!) trying every grind imaginable, I'm sitting on 2 bowl gouges, a spindle gouge, and an SRG that are ground down to nubs this year.

An edge "sharpened" on an 80 grit stone, by comparison, is more like tiny saw teeth than a knife edge. Ask any woodcarver which edge they would prefer. My experience is that a well sharpened edge maintains a usable edge far longer than one sharpened on an 80 grit aluminum oxide matrix stone.

I experienced this quite readily the last few days. I somehow left the tool platform loosenon my grinder, which fed a scraper and the tool rest edge right into the grinder, causing a nasty "catch" and a crack in my fine wheel. Can't get them locally, so I tried the 60 grit. Truly awful edge without honing. That moved up my timescale for new wheels-- Norton 3X or CBN, still out on which grit for the main wheel, too.

 

[Bill Boehme]

That moved up my timescale for new wheels-- Norton 3X or CBN, still out on which grit for the main wheel, too.

Get the CBN ... it's a couple orders of magnitude above any matrix wheel. If possible, put CBN wheels on both sides or at least remove all matrix wheels from the grinder. The difference in eliminating vibration caused by matrix wheels will make a huge difference in edge quality. You can't truly sharpen a tool surgically sharp when the grinder is vibrating. Save a matrix wheel for the rare occasion where you might need to shape a tool or get a 180 grit CBN wheel fort that purpose. Formal edge touch up I think that a 400 or 600 grit CBN would be ideal ... I am leaning towards the 600 grit wheel, but I'm not in a hurry because my Tormek does a better job in about the same length of time.

 

[Mike Brazeau]

My go to bowl gouge is an almost 20 year old 5/8" Hamlett ASP 2060 which is no longer available except at estate sales. My turning career will end before I replace i, especially now that I have a CBN wheel. I would interested in trying one of the new Hamlett /Taylor M42 gouges. The Hamlett parabolic profile is about as close as you can get to the Crown Ellsworth. ASP 2060 was a powder metal allow from Sweden and had a significant amount of Cobalt and sharpened to a very fine edge possibly due to fine crystal structure. M42 also contains Cobalt but I believe somewhat less. Some in the past some commented that Cobalt was not needed in WT tools as in metal cutting it holds an edge when red hot and we never encounter that wih wood. It does contribute to the hardness or wearability though. I am comfortable with anything that is sharp and turn for fun not for $.

 

[Davis Stevenson]

If possible, put CBN wheels on both sides or at least remove all matrix wheels from the grinder. The difference in eliminating vibration caused by matrix wheels will make a huge difference in edge quality. You can't truly sharpen a tool surgically sharp when the grinder is vibrating.

Are there potential issues/wear to look for with a 4lb imbalance between sides of a small low speed grinder with a CBN on one side and nothing on the other? (mine is a Rikon 1/2 hp)

That also makes sense about eliminating vibration. Even after balancing and dressing, cheap A/O wheels seem to generate a lot of vibration.

If I ever wear out my pair of Cryo bowl gouges I'll definitely look at Thompson. Crown's new Razor's Edge look intriguing, too-- Cryo M42. Maybe by the time my Cryo gouges are nubs there will be new tech, too. Who knows!

 

[Bill Boehme]

Are there potential issues/wear to look for with a 4lb imbalance between sides of a small low speed grinder with a CBN on one side and nothing on the other? (mine is a Rikon 1/2 hp)

No, it's just a motor and most motors only have the shaft sticking out one side. The bearings don't know the difference.

Since you mentioned that your grinder is a Rikon, there has been a lot of discussion about the half horse Rikon being a little wimpy coming up to speed with two CBN wheels so in order to save wear and tear on the start winding and start capacitor it might be a good idea to just let the grinder run while you are turning. I suspect that the grinder is actually more like a quarter horse than a half horse.

The Thompson tools are very good and I have a bunch, but I recently got a D-Way (Dave Schweitzer) bowl gouge that uses triple tempered M42 cobalt steel. I like the very polished flute of this gouge. Of course, all of this just amounts to nits that only a crazed woodturner like me would obsess over.

 

[RichColvin]

Get the CBN ... it's a couple orders of magnitude above any matrix wheel. If possible, put CBN wheels on both sides or at least remove all matrix wheels from the grinder. The difference in eliminating vibration caused by matrix wheels will make a huge difference in edge quality. You can't truly sharpen a tool surgically sharp when the grinder is vibrating. Save a matrix wheel for the rare occasion where you might need to shape a tool or get a 180 grit CBN wheel fort that purpose. Formal edge touch up I think that a 400 or 600 grit CBN would be ideal ... I am leaning towards the 600 grit wheel, but I'm not in a hurry because my Tormek does a better job in about the same length of time.

Bill,

I’d be interested in seeing your experience with and photos of comparing CBN vs Tormek.

Kind regards,
Rich

 

[RichColvin]

Are there potential issues/wear to look for with a 4lb imbalance between sides of a small low speed grinder with a CBN on one side and nothing on the other? (mine is a Rikon 1/2 hp)

That also makes sense about eliminating vibration. Even after balancing and dressing, cheap A/O wheels seem to generate a lot of vibration.

If I ever wear out my pair of Cryo bowl gouges I'll definitely look at Thompson. Crown's new Razor's Edge look intriguing, too-- Cryo M42. Maybe by the time my Cryo gouges are nubs there will be new tech, too. Who knows!

I’m interested in better understanding the value of Cryo tools.

Kind regards,
Rich

 

[john lucas]

A lot of the new tools on the market are are using Cryo treating on their tools even if they don't advertise it. Cryo treatment helps produce Martensite in the steel and more evenly distrubutes it. This makes the steel tougher and the edge will get sharper. It's just one factor in over all hardening. Heat treating itself only goes so far. Cryogenic treating is just further enhances the hardening process that heat treating starts. The new particle metal steels have both. They have higher percentages of particles such as Vanadium that you simply can't get in melted steel, and they are properly heat treated and Cryogenic treated so you get the best of all worlds.

 

[robo hippy]

In pondering sharpness, again, I am thinking a couple of things.

One, the fineness of the grit is a big determining factor in how fine the edge is.

Another is 'How sharp is too sharp?' I have a friend who was a spoon carver. He had a honing stick with 4 different compounds on it for the final burr free edge. He was commenting about the burr being too big on one tool, and I couldn't feel the burr, and I wasn't feeling it with my guitar fingers.... I think most will agree that the particular edge he was wanting is not suitable for heavy duty roughing on bowls. So, there appears to be a range of grits where if you go higher you don't benefit, and if you go lower, you won't get quite as clean of a cut... So, what is that grit? I am figuring some where between 320 and 600, but that is a guess....

And, for John Lucas, and others, has any one ever tried honing the carbide tipped tools to bring back the factory edge? Not in diamond hones, but the honing compounds.....

robo hippy

 

[john lucas]

I tried the yellow and green honing on flat.carbides and it didn't work. I did use diamond powders on a flat carbide and it does work but I'm just not into the flat carbide tools performance even when sharp.
I tried all kinds if things to sharpen the Hunter carbide and never found what works.

 

[Davis Stevenson]

A lot of the new tools on the market are are using Cryo treating on their tools even if they don't advertise it. Cryo treatment helps produce Martensite in the steel and more evenly distrubutes it. This makes the steel tougher and the edge will get sharper.

Here's a quote from The Tube and Pipe Journal, 2013, Eric Lundan:


Cryogenic processing—dispelling the myths, mysteries
A Denser, More Stable Material. Cryogenic processing does more than convert retained austenite to martensite. Another effect is the precipitation of microfine Eta-carbides, a process that fills the microvoids in the steel.

“Imagine filling a bowl with cornflakes,” Paulin said. “You could crush the cornflakes with your fist, compressing them to the bottom of the bowl. Now take a second bowl and fill it with cornflakes. The precipitation of microfine Eta-carbides is similar to adding a pound of sugar. The sugar fills in the gaps between the cornflakes, providing quite a bit of compressive strength. It limits your ability to compress the cornflakes with your fist,” Paulin said.

“When it closes the grain structure, it fills in all the microvoids in the steel, which are the weak spots—this is where the blades would chip and break,” Bond agreed. “Eliminating the microvoids makes the tooling tougher.”

“We can actually measure the increase in carbides using a particle counter, which counts particles up to 1 micron in size,” Paulin said. “Heat-treated A2 steel typically has 30,000 particles per mm2. After cryogenic treatment, A2 typically has 83,000 particles per mm2. Closing the interstitial gaps makes the material denser, stronger, and more able to resist loading, or impact force,” he said.

Cryogenic processing also stabilizes the material.

“When you cool it, you get thermomechanical compression; then you raise the temperature back to normal, then repeat this a couple of times. It’s like taking a brand-new rubber band and stretching it. The first pull doesn’t stretch it much, but the next several pulls stretch it more and more. Eventually it reaches a practical limit, the point at which it’s stable,” Paulin said.



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Of course, A2 steel is different, but this section gives a good visual of the other benefits of Cryo treating.

 

[Davis Stevenson]

Since you mentioned that your grinder is a Rikon, there has been a lot of discussion about the half horse Rikon being a little wimpy coming up to speed with two CBN wheels so in order to save wear and tear on the start winding and start capacitor it might be a good idea to just let the grinder run while you are turning. I suspect that the grinder is actually more like a quarter horse than a half horse.

Ugh. I wish I would've bought a bigger grinder, then. My wife and I live in a beautiful historic house, and our workshop has a single 20A 120v circuit to it. I sometimes feel like the scene in Apollo 13 where they're counting amps and equipment on the shuttle. I think I'd have to start turning out lights to leave the grinder running!

 

[Bill Boehme]

Actually when it is running, but not doing anything it only draws a couple amps.

 

[Davis Stevenson]

Actually when it is running, but not doing anything it only draws a couple amps.

I just rechecked specs on the motor-- 3A. No way in hell that's 1/2 HP. Our "3/4 HP" drill press is 7.5A, and our "3/4 HP" bandsaw is somewhere around the same . Sharpening is a negligible load above keeping the wheels at speed, so I think I could get it to work, especially since there will be no cutting load on the lathe.

Where do manufacturers come up with HP ratings anyway? Our lathe, bandsaw, and drill press seem to scale appropriately, but the grinder does not, nor do any of our highly exaggerated construction industry type tools (where the hell do they come up with *those* numbers?)

 

[john lucas]

Craftsman used to be the worst about HP ratings. My understanding is they often use Peak horsepower which it can only maintain for a few seconds.

 

[Bill Boehme]

Imported machines are terrible about inflating HP numbers. Worst of all were air compressors where the typical motor actual horsepower ranged from 1/4 to 3/4 for most consumer grade compressors, but the advertised numbers would range from 5 to 10 HP using some nonsense contrived justification. A number of years ago there was a class action lawsuit in which each compressor owner would receive a token gift. Meanwhile the attorneys were awarded millions as compensation for their inflated legal expenses. Somehow, Sears, the worst offender managed to extract themselves from the suit and continued on as before.

 

[Dennis J Gooding]

Ugh. I wish I would've bought a bigger grinder, then. My wife and I live in a beautiful historic house, and our workshop has a single 20A 120v circuit to it. I sometimes feel like the scene in Apollo 13 where they're counting amps and equipment on the shuttle. I think I'd have to start turning out lights to leave the grinder running!

Well, I may be alone, but I have been using the 1/2 HP Rikon 1800 rpm grinder with two of the steel CBN wheels for two or three years and have had no problem. Yes, it takes a few seconds to get up to speed, but less time than it takes to mount a gouge in the Varigrind jig. As Bill said, the current draw while idling or sanely sharpening a turning tool is very low. You will never use more than a fraction of the 1/2 HP unless you were grinding something like axes or mower blades.

 

[Davis Stevenson]

Somehow, Sears, the worst offender managed to extract themselves from the suit and continued on as before.

That explains the "2.75 HP" Craftsman tablesaw I briefly owned stalled out ripping 4/4 birch (with a ripping blade). Got rid of it in a hurry.

Well, I may be alone, but I have been using the 1/2 HP Rikon 1800 rpm grinder with two of the steel CBN wheels for two or three years and have had no problem. Yes, it takes a few seconds to get up to speed, but less time than it takes to mount a gouge in the Varigrind jig. As Bill said, the current draw while idling or sanely sharpening a turning tool is very low. You will never use more than a fraction of the 1/2 HP unless you were grinding something like axes or mower blades.

That gives me good hope for not killing my grinder.

I might have to a killawatt or something and experiment for fun Before I switched the 200w of incandescent bulbs and all the tube lights to LED, the lights would dim and my VFD would shut down on a big heavy push cut. Haven't tripped the VFD since then.

 

[John Jordan]

If I had to pick a desert island wheel, used to be it would have been a 60 grit aluminum oxide. These days I guess a 120 or 180 CBN wheel-I find that's the rough equivalent of the 60 grit A/O. Any of these edges can be refined with one or two strokes from a fine ceramic slipstone if you want. I find it rarely pays off for the kind of green wood turning I do-the admittedly "ragged" edge works very well for this. Other types of turning, like spindle turning, can benefit from more refined edges. There is no doubt that a refined edge can last longer, particularly in a nice working wood-the ragged edges don't fracture or break. On the other hand, wood that's a little or a lot abrasive will make that a moot point.

If one is a good sharpener with either jigs or freehand, it takes about the same amount of time to sharpen a tool no matter the grit wheel (though freehand grinding is a bit more difficult on the very fine wheels for me-its hard to "feel" the bevel.)

A lot of folks have given a lot good information from their experiences in this thread, and covered a lot of ground. Don't get so focused on "how long" an edge will last that frequent sharpening is neglected. Someone using a cheap grinder and wheel with a basic brand gouge, that sharpens several times before the tool is noticeably dull, is better off than someone with exotic steels and high end grinder setups that don't sharpen before the tool really needs it.

For a simple small bowl, I would sharpen before I start the outside, before I make the finish cuts on the outside, again to shape the rim and make the inside cuts, and once more for the finish cuts on the inside. That's a minimum of four times for a basic bowl, more if needed. Strictly speaking, that's probably not always needed, but its just part of the process or routine for me. It shouldn't take more than 20-30 seconds to sharpen-it takes me about 10. I never have to think about this, and the less I think about tools and lathes and speeds and grinders and all those things, the more I can focus on actually making a nice piece.

Tools never become sharper as you use them, and they can never be too sharp.

John

 

[John Jordan]

A lot of power tools like Craftsman used to say something like 5 HP (developed). Probably should be 5HP (developed, once) .

John

 

[Davis Stevenson]

For a simple small bowl, I would sharpen before I start the outside, before I make the finish cuts on the outside, again to shape the rim and make the inside cuts, and once more for the finish cuts on the inside. That's a minimum of four times for a basic bowl, more if needed.

John

You sharpen between finish cuts on the outside and hogging off the inside? Don't rim to foot cuts on the outside use the gouge left of the tip, leaving the right side more or less freshly sharp when you start on the inside? And shouldn't the left side be fresh when you work on the outside?

For small bowls in decent wood, I sharpen twice: right before finish cuts outside and in. Of course there are usually trips back to the grinder before finishing cuts, but because of the above I don't sharpen before starting the inside, and I hang my gouge up for the next bowl after finishing the inside.

 

[John Jordan]

The outside finish cuts are done with the piece in the chuck, so use the right side of the gouge, same as the inside. As long as one incorporates some regular method of sharpening, that includes a fresh edge for finish cuts, that's what I mean. People's step by step vary a little. I always want the easiest cut, so always sharpen before I start.

John

 

[Bill Boehme]

You sharpen between finish cuts on the outside and hogging off the inside? Don't rim to foot cuts on the outside use the gouge left of the tip, leaving the right side more or less freshly sharp when you start on the inside? And shouldn't the left side be fresh when you work on the outside?

You should be cutting foot to rim on the outside ... not rim to foot. And which part of the gouge is being used depends on whether you are doing a push or a pull cut and sometimes I sweep across the whole bevel if transitioning from a pull to a push if working on the headstock side.

Typically when working on the interior you go from rim to center and use the nose and left (not right) side of the gouge. However, you can have the gouge follow an arc trajectory to the center in which case the gouge would roll from the left side of the nose to the right.

Tools get dull often sooner than we recognize because it happens gradually so you do notice it.

 

[hockenbery]

Like John, I sharpen at set points in the turning sequence including before finish cuts and before shear scraping

As @Davis Stevenson is quoted there are occasions where one side is used and the other side is fresh.

There are turning steps where hogging and finish cuts keep alternating so it is impractical for me to sharpen before each finish cut. One of these is hollowing a NE bowl.

Fortunately there is a cool way to deal with it if you get some advanced instruction on using the side ground gouge.

I hollow NE Bows using a method I learned from David Ellsworth. It is an advanced cut that very few will ever learn on their own without getting horrendous catches. I had good instruction from Liam O’Neil and then David.
The hogging out is done with a push cut on the right side of the tip and the finish cut is done flute up on the left side of the tip. One side for hogging - one side for finishing.

 

[robo hippy]

The '6' hp motor on my compressor is about 1/4 to 1/3 the size/mass of the 4.5 hp Baldor motor on my big bandsaw.... Never could figure that out. My old blue/grey no name grinder from Woodcraft was 3/4 hp, and had a bigger watt draw than my 3/4 Baldor, and maybe half the power. I do prefer over powered to under powered, which is why I went with the 1 hp Rikon. I don't like waiting for it to come up to speed, in part because I don't use jigs, just the free hand for me. Much faster...

robo hippy

 

[Davis Stevenson]

You should be cutting foot to rim on the outside ... not rim to foot.
.

Yes, that's what I meant. D'Oh.

Foot to Rim on the outside, Rim to Foot inside.

On shapes where it's possible, I try to shoot for a single light push cut to clean up the outside, usually 2 push cuts on the inside with a bit of shear scraping near the transition. That leaves the edge plenty sharp for hogging off in the next stage.