Particle Metal Steels

[Jamie Straw]

At this month's meeting, Tom Wirsing from Longmont, CO, will discuss "Emerging Technologies in Woodturning." Part of that talk and demo will be about Particle Metal Steels. Always something around the corner to tempt us with, eh? Anyone out there up to speed on this development?

 

[Bill Boehme]

Crown gouges have been using particle metal steel for as long as I have been turning (the black handle tools). Thompson tools are all particle metal steels. Probably also true for D-Way and Carter tools. Henry Taylor Kryo gouges are PM. I'm sure that there are others. The carbide cutters are micro particles of tungsten carbide in a matrix of something, not sure what. The latest thing own the pike is nano particle technology which really isn't new since it's had its roots dating back a couple decades. This can make for longer lasting edges ... at a price of course.

 

[Mike Brazeau]

Another of the early particle steel tools are the Hamlet ASP 2030 and 2060 alloys. Have had a 5/8 2060 bowl gouge for about 15 years and will put it up against anything.

 

[Andy Chen]

Another of the early particle steel tools are the Hamlet ASP 2030 and 2060 alloys. Have had a 5/8 2060 bowl gouge for about 15 years and will put it up against anything.

This "particle metal steel" must be something new. I have a Hamlet "3/8 inch" ASP 2060 bowl gouge that is a "powder metallurgy steel" tool. In fact, it is my favorite turning tool. It has the same flute that was on the Henry Taylor Superflute bowl gouges. Unfortunately the Hamlet ASP gouges are no longer available.

 

[Andy Chen]

Crown gouges have been using particle metal steel for as long as I have been turning (the black handle tools). Thompson tools are all particle metal steels. Probably also true for D-Way and Carter tools. Henry Taylor Kryo gouges are PM. I'm sure that there are others. The carbide cutters are micro particles of tungsten carbide in a matrix of something, not sure what. The latest thing own the pike is nano particle technology which really isn't new since it's had its roots dating back a couple decades. This can make for longer lasting edges ... at a price of course.

I don't know that much about metallurgy but I have only heard the term "powder metallurgy steel" not "particle metal steel". I think Thompson tools are high vanadium steel (10%) and I don't think they are equivalent to the PMS.

 

[Odie]

Another of the early particle steel tools are the Hamlet ASP 2030 and 2060 alloys. Have had a 5/8 2060 bowl gouge for about 15 years and will put it up against anything.

This "particle metal steel" must be something new. I have a Hamlet "3/8 inch" ASP 2060 bowl gouge that is a "powder metallurgy steel" tool. In fact, it is my favorite turning tool. It has the same flute that was on the Henry Taylor Superflute bowl gouges. Unfortunately the Hamlet ASP gouges are no longer available.

I also have one of the Hamlet 2060 bowl gouges. The reason turners go with harder steels, boils down to one singular reason......it's an attempt to have the sharpened edge last longer. Well, yes it does last longer, but consider the following: There is a point where the harder steels will work against the quality of the work produced.

How so, you might ask?.....😕

Back in the day, turners mostly used carbon steel turning tools, and they dulled fairly quickly. I still have a few carbon steel tools. When M2 steel became the standard, carbon steel tools faded into oblivion. Sharp M2 steel edges lasted longer, and were a great improvement. Since that time, we've seen quite a few new steels being marketed to turners......all with that singular purpose of longer lasting sharp edges. There comes a point where longer lasting edges actually work against the overall process......

Now, here's where my unconventional thinking is not in tune with the "group think" of the current times.......When I started using some of the harder steels, I agreed with the reasons they were being produced in the first place. Yes, the edge certainly does last longer. Because they last longer, a turner will be in a questionable state whether he thinks the edge needs to be trued up......or not.....for a longer period of time.

M2, in my opinion, has the best edge holding ability within that window of ultimate usability.....which, in turn, yields the best results. It's best that a turner get used to the idea of sharpening a few more times during the course of the day, than to struggle with edges that are in the "grey area" of needing to be sharpened. If a turner can spend less time in that "grey area", the tool he's using will be sharper for a greater percentage of the time he's using it.....the results he achieves will be better.....and, the only price to pay for that, is to sharpen more often.

I understand that newer turners just hate to sharpen their tools.....been there, done that. This dislike of sharpening is exactly why the recent flood of carbide turning tools have been so successfully marketed to new turners. Understand that it's much better, and the results will ultimately be better, if a turner just resolves himself to sharpen more often. Learn to sharpen, rather than worry about exotic tool steels.......😉

It's also my opinion that M2 steel is the best overall improvement in edge holding ability, if the thought that edge holding ability does, in fact, have inherent limitations......😀

ko

 

[Bill Boehme]

I don't know that much about metallurgy but I have only heard the term "powder metallurgy steel" not "particle metal steel". I think Thompson tools are high vanadium steel (10%) and I don't think they are equivalent to the PMS.

Both terms mean exactly the same thing.

 

[hockenbery]

Most folks agree that any wheel will sharpen a particle metal tool but particle metal tools take a better edge from a CBN wheel.

When I finsih turn a small bowl 12" or less in diameter.
I sharpen the tool:
when I start the outside
when I finish turn the outside
The right side of the gouge is sharp when I work the inside because It usually has not been used.
When I finish turn the inside.

With the particle metal I'm usually sharpening a sharp tool.

Bigger bowls or harder and more abrasive woods require more frequent sharpening.
When tool isn't cutting smoothly I sharpen. This is feel thing - whenthe tool begins to grab a bit I sharpen. The little bit of resistance from the grab is either from build up on the bevel or cutting edge beginning to dull. A trip to grinder polishes the bevel and sharpens the edge.

 

[Bill Boehme]

I don't know that much about metallurgy but I have only heard the term "powder metallurgy steel" not "particle metal steel". I think Thompson tools are high vanadium steel (10%) and I don't think they are equivalent to the PMS.

Now you've heard of particle metal steel. The steel used by Thompson is Crucible's CPM 10V and CPM 15V particle metal steels.

Nano technology enables smaller more stable martensitic steel particles during hot and cold cycling as well as smaller and more uniformly distributed carbides. Nano in science and engineering refers to things that are on the order of 0.000000001 meter in size In other words about eight times the atomic diameter of an iron atom. You could call that a particle and not get any argument from me. 😀

 

[Andy Chen]

Now you've heard of particle metal steel. The steel used by Thompson is Crucible's CPM 10V and CPM 15V particle metal steels.

Nano technology enables smaller more stable martensitic steel particles during hot and cold cycling as well as smaller and more uniformly distributed carbides. Nano in science and engineering refers to things that are on the order of 0.000000001 meter in size In other words about eight times the atomic diameter of an iron atom. You could call that a particle and not get any argument from me. 😀

By definition, quark and Higgs boson are all particles too, Bill.

 

[RichColvin]

Or, are quarks & Higgs bosons really fields ?

 

[Bill Boehme]

By definition, quark and Higgs boson are all particles too, Bill.

Or, are quarks & Higgs bosons really fields ?

From what I understand, which isn't much, Higgs described a field that explains why particles have mass. The things that have been observed at the Large Hadron Collider seem to be mass points in the Higgs field, maybe. I'm sure that there must be a tie in with woodturning somewhere here. I wonder if particle physicist forums sometimes drift off into woodturning. 😀

 

[robo hippy]

Well, the D Way and Carter tools, are M42HSS, and I think some of the Oneway gouges were as well, and Packard had a house brand that was similar. Not positive, but I think there is a considerable difference between the carbide type 'particles' and the V10 / V15 metals. Then there is the Serious lathe tool metal, and I have no idea what it is.

As far as the 'holds the edge 5 times longer', all that means is that you can do more roughing before you set off the smoke alarms.... I always use a fresh edge. On the few occasions where I go back to M2, it is really easy to notice how quick they lose the 'fresh' edge. About like the difference when roughing with a 180 grit CBN burr on my scrapers, and a 600 or 1000 grit burr...

robo hippy

 

[Gerald Lawrence]

I

M2, in my opinion, has the best edge holding ability within that window of ultimate usability.....which, in turn, yields the best results. It's best that a turner get used to the idea of sharpening a few more times during the course of the day, than to struggle with edges that are in the "grey area" of needing to be sharpened. If a turner can spend less time in that "grey area", the tool he's using will be sharper for a greater percentage of the time he's using it.....the results he achieves will be better.....and, the only price to pay for that, is to sharpen more often.

I understand that newer turners just hate to sharpen their tools.....been there, done that. This dislike of sharpening is exactly why the recent flood of carbide turning tools have been so successfully marketed to new turners. Understand that it's much better, and the results will ultimately be better, if a turner just resolves himself to sharpen more often. Learn to sharpen, rather than worry about exotic tool steels.......😉

It's also my opinion that M2 steel is the best overall improvement in edge holding ability, if the thought that edge holding ability does, in fact, have inherent limitations......😀

ko

Point taken Kelly,but think of this even with a new turner if you do not like to sharpen and the edge lasts longer you will get better work. The reason for this is that with less need for shepening more work will get done better. Now I agree with your point in that for many sharpening is a problem. For all new turners the hardest thing to learn is when to sharpen and that even more than the type of steel you use may be the factor to better turning.

 

[Dean Center]

Jamie,
Don't let Tom get away from the meeting without showing you how to use negative rake scrapers. Very good at both teaching and using them on his large platters.

 

[Jamie Straw]

Jamie,
Don't let Tom get away from the meeting without showing you how to use negative rake scrapers. Very good at both teaching and using them on his large platters.

OK, I'll see what I can do. We have an NRS booster in our club who has helped me quite a bit, but the more info the better!!

 

[john lucas]

I've been watching particle metal technology for quite a while. We had to photograph a plant in Jamestown TN that's makes all sorts of parts for tools and machines using variations of the Particle metal. The big advantage is they can make steel that has very different properties that cast or hammered steel. For example they make a gear that absorbs oil. It works better than bronz and is tougher so it wears better. For turning tools they can add a much higher concentration of Vanadium. Vanadium increase wear which is why many of the new tools claim 4 or 10 times more wear resistance.
There was an excellent presenter at one AAW symposium who had done a lot of experiments and studies of particle metal steel. they found that cryogenically treating them at various phases of the hardening process converted more of the steel particle to martensite which makes the steel harder.
Early on people claimed that the particle metal steels wouldn't get as sharp. The reason was simply, it takes a little longer at the wheel to get them really sharp. that has changed with CBN wheels because they cut so fast. I ran a test on Particle metal, HSS, and high carbon steel to see if one would get sharper than another. I sharpened them all far beyond what we would do as turners. All 3 tools took extremely fine edges and I could not tell one got sharper than another. what I did find was that it took a more aggresive stropping compound for the Particle metal steels. I found gold bar that they sell for carving tools worked a lot better than the Green bars we often use for planes, chisels and turning tools. The Green bar still works it just takes longer to reach that really really fine edge.
One cool thing I saw at the factory. They made gears for Black and Decker drills. It used to take something like 12 machining operations to get those gears which were pretty complicated. They can now cast them using particle metal steels so close to final tolerance that they only needed to do 1 machining operation to make the opening for the bearing that goes in them. Obviously saves a lot of money and time in the manufacturing of that drill.

 

[Doug Rasmussen]

All this talk of M2 ( high speed steel or HSS) and other more exotic steels makes me wonder. Has anyone done simple hardness testing on various turning tools (any commercial heat treater could provide this service for not much)? A tool could be made of HSS, but that doesn't mean it has been heat treated to it's maximum hardness.

When you buy a quality metal cutting tool bit of HSS it'll be in the 63 Rockwell hardness range. Sears used to sell router bits claiming them to be HSS. They were relatively soft which doesn't mean they weren't HSS, only that for some reason they weren't heat treated to max hardness and didn't hold an edge very well. They were no where near the hardness of the metal cutting tool bits.

My woodturning experience is mostly from my former business with two automatic wood lathes. Tooling was mostly HSS with maximum hardness. That tooling lasted far longer in hard maple than what I hear about hand turner's need for frequent sharpening.

Another thing that could make you suspicious about manufacturer's claims of their steels is their expense. A 36" length of M2, 1/2" diameter, annealed, today was a 100 bucks from an online supplier. Of course, a production operation might only pay 25% of that. Still. it's expensive, way more than high carbon type tool steels. Once you get into M42 and PM steels expense goes even higher.

 

[john lucas]

Maximum hardness is not what your after. If a tool is too hard it's brittle like a file. Most turning tools from what I've read or discussed with tool makers range from 58 to 63 Rockwell. Again certain steel types will become too brittle to hold a good edge when they get too hard so ideally the manufacturer has to weight tool hardeness against the toughness of the metal they use. Thompson tools used to be 61 but if I remember correctly Doug told me he was moving to 63. I would have to verify that. Carbide router bits for example are very hard but won't get to a keen edge because the metal is too brittle. The newer carbides like the Hunter tools have smaller carbide particles that will take a much cleaner edge. The Hunter cutters are very sharp right out of the box. I won't say they are razor sharp but they are far beyond what old carbide tools would get and I'd say they are as sharp as a freshly sharpened HSS turning tool. I can get a cut across end grain that is almost polished with them.
When I teach tool making I tell people to who want to use files, to place them in an oven and heat them to 350 degrees for 1/2 hour. This takes them from being very hard down to somewhere around 58 to 63 hardness so they are hard but not brittle. I don't know the exact hardness because I don't have any way know what type of steel they are. The files will be soft enough to grind to shape but hard enough take a good edge.

 

[Steve Worcester]

When you buy a quality metal cutting tool bit of HSS it'll be in the 63 Rockwell hardness range

(Not that this is for you Doug)
That number is after heat treating. Bought in a annealed state, it is easier to machine. Then depending on the process or heat treating, tempering, cryo tempering, it is brought to a specific Rockwell number. It is usually based on the shock resistance of the tool and its intended use.

 

[Bill Boehme]

Hardness isn't the most important characteristic. Toughness and wear resistance are more important in turning tools.

 

[Odie]

Hardness isn't the most important characteristic. Toughness and wear resistance are more important in turning tools.

This may be so, but there is a point where the rate of wear on the cutting edge leads to less productive results.....IE: the amount of sanding that will be required. Anything less than the best possible surface left from the cutting tool, is the direct result of lingering in that "grey area" of questioning one's self whether the tool needs to be sharpened......or not! 😀

A cutting edge being as sharp as is possible is the direct result of sharpening more often......not less often. The key to knowing without a doubt an edge needs to be refreshed, is seeing a quicker deteriorating result.

ko

 

[Doug Rasmussen]

Hardness isn't the most important characteristic. Toughness and wear resistance are more important in turning tools.

I agree Bill. But, what I'm not understanding is relating my past experience of the time between sharpenings using known quality HSS cutters in automatic lathes versus the more frequent sharpening hand turners mention.

Another issue that's contrary to what I came to learn about tool grinding is the way turning tools are sharpened. This is more related to metal cutting, it might relate to wood also though. When you look microscopically at the ground edge of a tool ground on a bench grinder with a typical turner's grinding guide it will appear like a mountain range with peaks corresponding to the wheel grits. Those relatively fragile peaks tend to break down rapidly. If you grind a gouge holding it horizontal to the grinder and roll it on the wheel you get grit marks parallel to the cutting edge without such distinct mountain peaks. Plus, by going to much finer than 180 grit you minimize the mountain peaks.

 

[Odie]

I agree Bill. But, what I'm not understanding is relating my past experience of the time between sharpenings using known quality HSS cutters in automatic lathes versus the more frequent sharpening hand turners mention.

Another issue that's contrary to what I came to learn about tool grinding is the way turning tools are sharpened. This is more related to metal cutting, it might relate to wood also though. When you look microscopically at the ground edge of a tool ground on a bench grinder with a typical turner's grinding guide it will appear like a mountain range with peaks corresponding to the wheel grits. Those relatively fragile peaks tend to break down rapidly. If you grind a gouge holding it horizontal to the grinder and roll it on the wheel you get grit marks parallel to the cutting edge without such distinct mountain peaks. Plus, by going to much finer than 180 grit you minimize the mountain peaks.

Hi Doug......All of what you're saying is true. Most turners go directly from the grinder to their work piece. That jagged "fragile mountain range" will always be a part of the edge. For other turners, the solution is simple......hone. I suppose, even with honing, and when viewed under a microscope, you'll see the distinct mountain peaks......but, they are going to be much smaller than those left directly from the grinder. It all depends on how fine a hone, a turner who hones, chooses to go with..........in any case, honing is part of the process that makes a sharper, and better cutting edge. I've been told by some turners that a super sharp cutting edge just doesn't last, and I can't argue with that.....but, a sharper cutting edge does, in fact, leave a better surface, prior to sanding.

 

[robo hippy]

Fine edges and high shear angle leave the best surfaces, but the fine edge is not good for heavy roughing. Most of the time 180 grit CBN wheels leave an edge suitable for most woods. Difficult woods that are softer or have wild grain will cut cleaner with a 600 or 1000 grit edge, and again, the high shear angle cuts better.

robo hippy

 

[hockenbery]

Many turners use a coarse wheel on bowl gouges 40-80 grit
This creates a sort of serrated cutting edge that works well on native hardwoods and especially well for turning green wood.

Honing is something most spindle turners do and something most bowl turners don't do.

The reason is the spindle work cannot be sanded much. I strive to sand finials with 320 and 400. NE bowls and hollow forms turned from green wood, I expect to start sanding with 220 on most of the surface with a few spots I work with 180 first.

Dry twice turned bowls I usually start with 180 sometimes 220 unless they are small bowls (10") which usually cut cleaner and can be sanded with 220. The light sanding on bowls brings the curve into sharp focus.

A bowl 14" diameter will have a 6-8" long curve from foot to rim. This long curve is a challenge. With a lot of experience the gouge cut leaves a pleasing curve. Shear scraping refines the curve an smooths the surface. Light sanding sharpens the curve.

In bowl turning some of the last finish cuts are done with scrapers or using the the bowl gouge for a shear scrape.
If I turn a bead on a bowl I do it with spindle gouge sharpened on a 180 CBN wheel.

In doing finish cuts on green wood and sometimes on dry bowls, I am usually sharpening to clean the bevel rather than because the edge is dull. The slight drag of the bevel sets up a vibration and interfers with getting a clean cut.

 

[Bill Boehme]

I agree Bill. But, what I'm not understanding is relating my past experience of the time between sharpenings using known quality HSS cutters in automatic lathes versus the more frequent sharpening hand turners mention....

Cutting metal and cutting wood are significantly different. You can use a skew with a 30° included angle to slice through wood fibers. A metal cutter shears the metal. With metal lathes there are also the issue of chip breaking, clearing the swarf from the cutter, and cooling the cutter. Although this is an apples to oranges comparison, slicing necessitates a sharper edge than shearing.

... Another issue that's contrary to what I came to learn about tool grinding is the way turning tools are sharpened. This is more related to metal cutting, it might relate to wood also though. When you look microscopically at the ground edge of a tool ground on a bench grinder with a typical turner's grinding guide it will appear like a mountain range with peaks corresponding to the wheel grits. Those relatively fragile peaks tend to break down rapidly. If you grind a gouge holding it horizontal to the grinder and roll it on the wheel you get grit marks parallel to the cutting edge without such distinct mountain peaks. Plus, by going to much finer than 180 grit you minimize the mountain peaks.

I agree wholeheartedly about the edge quality obtained from a bench grinder. This the main reason that I use a Tormek to sharpen my tools. It gives a very sharp clean edge that is longer lasting. The great majority of woodturners say that the ragged edge from a bench grinder is good enough. By definition, good enough is good enough, but a more refined edge is "good-er enough-er". 😀 I do understand that the high price of the Tormek makes it hard to justify the cost. I bought my Tormek about 17 years ago when woodturning wasn't even on my radar. I wanted to sharpen hand tools and planer and jointer knives. I also have a big Delta 23-725 bench grinder, Norton 3X SG matrix wheels, Wolverine fixture and various jigs for holding tools and dressing the stones. I probably paid More for all that than I did for the Tormek. If I had CBN wheels on the grinder then that certainly would have cost more than the Tormek. One cost factor that nobody notices is the long term cost difference in the life of turning tools.

To Odie: A disadvantage of having a very hard edge is that makes the edge more brittle and more likely to become dull from fracturing of the edge than becoming dull from wearing down due to abrasion. M2 is a very good all around steel for turning tools especially if you use a bench grinder to sharpen tools. My observation is that the difference in edge longevity between M2 and A11 (CPM 10V) becomes much more apparent when sharpening tools to a keener edge on the Tormek.

 

[Bill Boehme]

I've been told by some turners that a super sharp cutting edge just doesn't last, and I can't argue with that.....but, a sharper cutting edge does, in fact, leave a better surface, prior to sanding.

It would be hard to explain how a super sharp edge wouldn't last as long as an edge that isn't as sharp. If, on the other hand, somebody said that a super sharp edge isn't worth their time ... then that's a different matter and who could argue with that. My time isn't worth much, but I try to put it to I think is good use and don't mind the little extra time to refine tool edges.

 

[Bill Boehme]

I am usually sharpening to clean the bevel rather than because the edge is dull. The slight drag of the bevel sets up a vibration and interfers with getting a clean cut.

That is a very good point.

 

[robo hippy]

I do remember debates about the Tormek making a longer lasting edge than standard wheels, and I think this was before CBN wheels. I only use my Tormek for my kitchen knives now, and not for my turning tools or bench chisels as the CBN works much easier. Having the fine grit CBN wheels, to me, it should at least match what the Tormek can do with the 'graded' wheels. I had problems with that when I tried using it. It seemed that there was always a spot or 3 on the wheel that didn't take the fine grading, and when I would clean it off for the coarser edge, then there would be spots with the fine stuff on it. I now have a black wheel on it, which is far better than the older grey wheels. Don't know if you are supposed to, or even if you are able to grade it for a finer grit finish.

The debate about coarse vs. fine will go on forever. If for no other reason than each piece of wood is different. For sure, with the CBN wheels, the coarse edge lasts much longer for heavy roughing than the fine edges, 600 and above. Main reason for the finer finish cut from the polished edge, less resistance as the cutting edge goes through the wood. Main reason for high shear angles is the same, you lower the bevel angle when you go at a piece skewed. This is a common practice with hand planes.

We have a master spindle turner in our club. She sharpens her skew on a 6 inch 60 grit wheel, and doesn't hone. Her stuff looks as good as any I have seen.

I have yet to figure out why my once turned bowls always require starting at a coarser grit abrasive than my pieces that I turn from dry stock.

robo hippy

 

[n7bsn]

..... Then there is the Serious lathe tool metal, and I have no idea what it is....

robo hippy

I asked them and they refused to say, said what they used is proprietary

 

[n7bsn]

Then there is the entire matter of the exotic alloys used and breathing the dust.
When tools where just carbon and iron breathing the dust had no extraordinary health issues, other then the just breathing dust.
Now some of the metals in M2, M42, A10, 2060, etc have some additional health risks just from the bodies reaction to those metals.
Good dust control, at the grinder, is a must. I admit that I don't have as good as I should, but at least I know I should.

 

[Odie]

I have yet to figure out why my once turned bowls always require starting at a coarser grit abrasive than my pieces that I turn from dry stock.

Hiya robo......

I don't know the definitive answer as it relates to your statement, but I can make a guess. I'd say the initial moisture content is probably higher in the once turned bowl, than anything that's kiln dried. Wood that is stabilized to the ambient atmosphere is generally a little higher in MC, than KD wood. I've found that, generally, but not always, the cut can be made more cleanly when the MC is lower than higher. (given, the species and everything else is the same, or equal)

If I remember correctly, you are doing bowls that are once turned to a thin wall state, and letting them warp naturally at that point. If the MC is higher initially, as your turning progresses to a thinner wall, the surface may have a higher MC, but the heat created by the cut dries the wood at the surface after the cut has already been made, but during that time the MC is slightly higher.......

......or not! 🙂

ko

 

[robo hippy]

Odie, I have speculated that when the wet wood warps and dries, it makes minor imperfections much bigger. I have noticed it even in madrone, which cuts pretty nice no matter how you cut it. Possible the dry wood fiber is better supported because the wood shrinks first. Just another puzzle....

robo hippy

 

[Gerald Lawrence]

Hiya robo......

I don't know the definitive answer as it relates to your statement, but I can make a guess. I'd say the initial moisture content is probably higher in the once turned bowl, than anything that's kiln dried. Wood that is stabilized to the ambient atmosphere is generally a little higher in MC, than KD wood. I've found that, generally, but not always, the cut can be made more cleanly when the MC is lower than higher. (given, the species and everything else is the same, or equal)

If I remember correctly, you are doing bowls that are once turned to a thin wall state, and letting them warp naturally at that point. If the MC is higher initially, as your turning progresses to a thinner wall, the surface may have a higher MC, but the heat created by the cut dries the wood at the surface after the cut has already been made, but during that time the MC is slightly higher.......

......or not! 🙂

ko

Kelly I can add another supposition to that. When wood is turned green and dried the process results in fibers of wood being raised before it dries therefore making the surface rougher than that on the twice turned.

 

[john lucas]

There was an article in Woodturning magazine many years back where I guy sharpened gouges to a much finer grit edge and proved microscopically that a finer edge held an edge longer. There reason if I remember correctly was this. The "mountains" as we will call the microscopically fractured peaks all break down when used. The mountains have to break down to a certain size before we consider them dull. It took longer for the finer sharpened mountains to break down to this same point of "dullness". That's more or less what the article said.
I have been playing with different sharpening angles on my spindle roughing gouge. It takes a lot of abuse and use so it makes a good experimental tool. I gradually move up to 35 degrees, way sharper than most people use on this gouge. I did that because when turning my mirror handles I can almost completely turn the handle with the roughing gouge before going to the skew or spindle gouge. I have found that it holds a sharp edge longer. However on some woods it chips easily. I have gone back to 45 degrees which seems to work well with the woods that I use. It's still much sharper than most people use. I've seem them very blunt, which is fine if all you are doing is roughing to shape.

 

[Odie]

I have found that it holds a sharp edge longer. However on some woods it chips easily.

Hi John......Do you mean that a chunk of steel breaks away from the edge of the SRG, when you sharpen to 35°.....?

What steel is your SRG made from?

ko

 

[john lucas]

Yes a very tiny chunk. Same thing happens on my wood chisels. I have a set that is sharpened at 25 degrees and a set sharpened at 35 degrees. The 35 degrees will take using a mallet without chipping. If I use a mallet with the 25 degree edge I get some chipping on the edge. These are all quality steels. The chisels are High carbon steel. The Spindle roughing gouge is High speed steel and is a quality gouge. When you grind a roughing gouge to a more blunt angle the edge doesn't chip as easily or at all.

 

[hockenbery]

@john lucas i have seen that chipping with motising chisels with a 25 degree bevel.
I think the edge bends over and breaks leaving a chip.

In any event a more acute bevel angle on a tool makes it more difficult to control.
The difference between on the bevel and not is much smaller.
Not can be a nasty catch or a new spiral pattern.

 

[Zach LaPerriere]

In doing finish cuts on green wood and sometimes on dry bowls, I am usually sharpening to clean the bevel rather than because the edge is dull. The slight drag of the bevel sets up a vibration and interfers with getting a clean cut.

Excellent point, Al. The same is true in flat woodwork.

Recently I was planing a spruce plank in a thickness planer. The wood came out looking terrible..so I took the knives out and looked around for a new set. I didn't have a set, so I went back to the knives...sharp, but a bit dirty from pitch and old wood crud. A few passes on the 4000 grit ceramic stone, and the knives where polished on the back and cut as good as new.