Question of the day......

[odie]

Does hot steel dull quicker than cool steel?

As someone who regularly goes directly from the grinder to the lathe, it sure seems like it does.....but probably not too many turners would deny that cool steel is a little more comfortable to turn with.

Regardless, I always dunk my turning tools in some H20, prior to returning to the lathe....

-o-

 

[Richard Coers]

How hot is hot? My tools don't come off the grinder hot.

 

[Leo Van Der Loo]

Of course Odie, and yes I dunk the tool while and after sharpening, then again TOO cold is detrimental as well

 

[hockenbery]

My tools don’t get hot from sharpening while turning. One or two light passes doesn’t generate much heat.
I’m using 80 grit CBN for the bowl gouge and 180 for the spindle gouge

A finer grit wheel might produce more heat.

Reshaping a new tool from square ground the Ellsworth can build up heat.
There is lots of metal to remove and I probably use extra pressure

When I started out tools got hot a lot. I was heavy handed and not dressing the wheel often enough.
Also before jigs I would mess up the Ellsworth grind every 5th sharpening on a bad day and every 10th sharpening on a good day.
Then have to work the bad spot out - more time on the wheel. 4-5-6 passes to fix.


light passes no noticable heat
This is a bowl gouge. It needed 1 pass. I will do more passes until I see sparks break over the whole edge.
This is 60 grit wheel


This is the spindle gouge.
This is a 120 grit wheel

 

[William Rogers]

@odie My tools are not hot coming from the grinder either. I believe you are still using friable wheels for grinding and your tools may be hotter coming from the grinder. I would recommend you consider CBN wheels for sharpening tools. You do not take off near as much material to sharpen compared to friable wheels and your tools will last longer. There times where the “herd” has a better method/solution than the non-herd.

 

[odie]

How hot is hot? My tools don't come off the grinder hot.

Hot, but I could go directly from the grinder to the lathe with no problem. It's not to hot to handle, as I suspect you are thinking it is. As I said, it is more comfortable in my hands to be a little cooler, though.

@odie There times where the “herd” has a better method/solution than the non-herd.

William, I think we're going to disagree whether the "herd" has a better method for grinder ops, my friend!

==============================

The point I was trying to make, or discuss here, was whether heat has any influence on the longevity of a sharpened edge. I suppose I should point out that I'm using M2 steel for my tools, and this may make a difference to those who are using the more expensive exotic steels that are currently available. I believe heat does make a difference with M2 steels, but with the exotic steels, the loss of sharpness due to heat caused by grinder sharpening may be less noticeable.....or maybe even none at all. (That is the discussion I was hoping to have by initiating this thread.)

I don't wish to discuss whether the exotic steels will hold an edge longer than M2.....that is a given, and I'll concede that they do.....with the stipulation that I've made it known why I feel the lesser ability to hold an edge is an actual advantage in keeping the sharpest edge possible to wood an overall higher percentage of the time.....even though it requires sharpening more often. I've explained my beliefs about this elsewhere in the forums.

-o-

 

[William Rogers]

William, I think we're going to disagree whether the "herd" has a better method for grinder ops, my friend!

Oh no! not again.

Well, it doesn’t matter if I am using M2, M42, or V11 my tools are not hot. I can’t tell any difference in temperature regardless of the steel when sharpening and it has been way to long for me to remember if there was a difference when I was using friable wheels if there was a difference in regards to heat.

 

[Gabriel Hoff]

I have M42 Carter and Son tools, and if they come off the lathe warm from turning say a big bowl or something, the edge does heat up a bit more then usual. But most of my work never involves my tool getting hot, so I can go directly to the grinder with no problem. I use a very light touch, and because the bevel angle is the same, so I'm taking off very little steel. Now for the friable vs CBN wheel debacle, I took a class from Matt Monaco last year, and he is the only one who likes friable wheels. I asked him why and he said, because the edge coming off of a friable wheel is more aggressive, it leads to a smoother and longer lasting cut. He doesn't have to resharpen as often and can hog off more wood in a pass. I thought it was an interesting observation!

 

[Rusty Nesmith]

My tools don’t get hot from sharpening, just a little warm. They actually get hotter from cutting wood So I don’t see the need to put in water after sharpening.

 

[Steve Tiedman]

There is likely a sliding scale of heat build-up and edge retention, but I'm not the guy to explore that. That said, I think a metallurgist is going to offer to us lay-folk that if you can touch that fresh-from-the-wheel bevel without causing injury, at that temperature any amount of heat that could contribute to a shortened edge service life is probably negligible, and that similar temperatures, or even higher, are likely attained at the lathe from friction with the wood. Only scientific study could prove or disprove odie's hypothesis- clocks and thermometers and the gadgets that measure edge sharpness, something like this-
https://www.sharpeningsupplies.com/What-is-the-BESS-Scale-of-Edge-Sharpness-W395.aspx

Gabriel's mention of Matt Monaco's observation of friable wheels (I like friable wheels, so the count is at 2)- I think there may be some missing information from Matt's claim. To start, what grit wheel is the tool coming from when it goes back to the wood? (Not important to answer here.) That question alone could be the starting point for a whole separate thread of discussion (and probably not for the first time) but not here, not to mention the continuing debate of friable vs. CBN wheels (again, not here).

 

[odie]

Oh no! not again.

Ha,ha.....Yeah, I'm getting used to it. You are among many with whom I differ in opinion on these forums. Well, it doesn't make much difference to me, because I always think of the results I'm achieving, and this is the bottom line......wouldn't you think?

There is likely a sliding scale of heat build-up and edge retention, but I'm not the guy to explore that. That said, I think a metallurgist is going to offer to us lay-folk that if you can touch that fresh-from-the-wheel bevel without causing injury, at that temperature any amount of heat that could contribute to a shortened edge service life is probably negligible, and that similar temperatures, or even higher, are likely attained at the lathe from friction with the wood. Only scientific study could prove or disprove odie's hypothesis- clocks and thermometers and the gadgets that measure edge sharpness, something like this-
https://www.sharpeningsupplies.com/What-is-the-BESS-Scale-of-Edge-Sharpness-W395.aspx

Gabriel's mention of Matt Monaco's observation of friable wheels (I like friable wheels, so the count is at 2)- I think there may be some missing information from Matt's claim. To start, what grit wheel is the tool coming from when it goes back to the wood? (Not important to answer here.) That question alone could be the starting point for a whole separate thread of discussion (and probably not for the first time) but not here, not to mention the continuing debate of friable vs. CBN wheels (again, not here).

Thank you, Steve..... This is the kind of response I was fishing for in my original post here.

You are right, that all aspects of this question seem to be open for discussion or debate, and no "generally accepted" conclusion is immune. To answer your question about my friable wheel.....it's a Norton 80gt experimental SG friable wheel that was available prior to the finalized version of this wheel became available. I'm not sure what the difference is, because I've never bought one of the newer versions of this wheel. I'm pretty certain there is a difference, judging from the feedback I've received from those with the newer version, though.

I also tend to think my SG wheel probably does produce more heat than the cbn wheels that are so popular......but, I also feel this is of little concern, because I do dunk my tools in h20, prior to returning to the lathe....it's an easy fix!

-o-

 

[William Rogers]

because I always think of the results I'm achieving, and this is the bottom line......wouldn't you think?

Oh N0! We agree!

 

[robo hippy]

Well, not some thing I have ever noticed. For tools, I use tantung, M42, and V10. I don't remember anything about hot tools from the days when I used M2. My tools almost never come off the grinder hot. Warm, yes, and some times I do reshape a bit, so they will be warmer than normal. Some times I will sharpen a bunch of tools all at one time, so no heat issues there that I know of. Other than some woods, like walnut, seem to dull tools more quickly, I don't know.

robo hippy

 

[Kent Reisdorph]

My tools don’t get hot from sharpening while turning. One or two light passes doesn’t generate much heat.
I’m using 80 grit CBN for the bowl gouge and 180 for the spindle gouge

A finer grit wheel might produce more heat.

I have a 320 grit CBN on my sharpening side. Usually I'm doing three passes on each side of the gouge. Very little heat is generated as long as I'm on slow speed (1750).

 

[Leo Van Der Loo]

See I come from a place and time when carbon steel was still used for tools with HSS just getting used more and more, carborundum wheels where the grinder wheels, and heck yes rotating sandstone wheels where still used.

So heat was is the enemy of the tool, and I learned to make sure to keep the edges cool, does not harm anything to dip the tool in the cooling fluid, same reason coolant is used when machining any material, saves tools.

 

[Timothy White]

As I understand it (AIUI) HSS all flavors were designed for the metal cutting industry HSS could be red hot and not loose its temper or cutting edge. The chip or curl could be white hot and the tool will still cut effectively. HSS doesn’t loose its temper when turned blue from grinding. Quenching with water can cause fractures on the cutting edge from the rapid shrinking of the metal.
I dip my tools in water before I grind to loosen the gunk that builds up in the flute this makes it easier to wipe the gunk off.
@odie I understand that you hone your tools if so the tool will be cool enough to cut with by the time you finish honing.
The edge of the HSS would have be critical (at forging temperature) for the wood to dull it. At this temperature it would burn he wood and set the chips on fire.

 

[odie]

The edge of the HSS would have be critical (at forging temperature) for the wood to dull it.

If that were true, the edge would never get dull from the effects of heat during use.....and we know that isn't true. There may be a "sliding scale" of how the dulling effect of the heat acts on the very tip of the cutting edge, and this is a topic that could be discussed further.

@odie I understand that you hone your tools if so the tool will be cool enough to cut with by the time you finish honing.

I'm speaking here of the heat from grinding, and when I hone, there is never any heat from this process.

HSS doesn’t loose its temper when turned blue from grinding.

This is very true, although I almost never get bluing on my M2 HSS tools while grinding. In the rare times when I do, I immediately back off, and start over with the grind I'm attempting. I should note here, that the harder you push the tool against the grinding wheel, the more heat is generated.....that point should be obvious to the reader. With that in mind, I suspect that I take more time, and less pressure when I'm grinding a turning tool than the average turner here.

We do know that heat is created when cutting wood, and this is most evident when taking heavy aggressive cuts. As explained above, the dulling effects, as well as the heat build-up during these aggressive cuts are more pronounced than they would be with light delicate cuts....and this is an important consideration. Often times, with these aggressive cuts, I continue to use the tool longer than I would when the best/finest cut is the objective.....because this is the time when the quality of the cut is not as important as removing large amounts of wood quickly. This discussion revolves around the dulling, or cutting ability of lathe tools more so with the finest, most sharp cutting edge's ability to maintain that keen edge when the ultimate goal is the cleanest, most tearout free cut.

-o-

 

[Timothy White]

If that were true, the edge would never get dull from the effects of heat and use.....and we know that isn't true. There may be a "sliding scale" of how the dulling effect of the heat acts on the very tip of the cutting edge, and this is a topic that could be discussed further.

I'm speaking here of the heat from grinding, and when I hone, there is never any heat from this process.

This is very true, although I almost never get bluing on my M2 HSS tools while grinding. In the rare times when I do, I immediately back off, and start over with the grind I'm attempting. I should note here, that the harder you push the tool against the grinding wheel, the more heat is produced.....that point should be obvious to the reader. I suspect that I take more time, and less pressure when I'm grinding a turning tool than the average turner here.

We do know that heat is created when cutting wood, and this is most evident when taking heavy aggressive cuts. I believe the dulling effects of these aggressive cuts are more pronounced than they would be with light delicate cuts. Often times, with these aggressive cuts, I continue to use the tool longer than I would when the best cut is the object.....because this is the time when the quality of the cut is not as important as removing large amounts of wood quickly. This discussion revolves around the dulling, or cutting ability of lathe tools more so with the finest, most sharp cutting edge's ability to maintain that keen edge when the ultimate goal is the cleanest, most tearout free cut is the goal.

-o-

Odie what I’m trying to point out (very poorly) is that the heat produced by turning wood or metal isn’t the main issue in dulling tools. Wear is the issue the better the tool steel resists wear and the finer the edge the longer the edge will last. Wear resistance in HSS is mostly defined by the amount of vanadium in it M1=1percent vanadium M2=2 percent M4= 4 percent CPM10V=10 percent
M42 uses cobalt as its anti wear additive to much vanadium will cause the steel to be too brittle. The only time you can produce the kind of heat that might damage a turning tool would be at the grinder.

 

[odie]

Odie what I’m trying to point out (very poorly) is that the heat produced by turning wood or metal isn’t the main issue in dulling tools. Wear is the issue the better the tool steel resists wear and the finer the edge the longer the edge will last. Wear resistance in HSS is mostly defined by the amount of vanadium in it M1=1percent vanadium M2=2 percent M4= 4 percent CPM10V=10 percent
M42 uses cobalt as its anti wear additive to much vanadium will cause the steel to be too brittle. The only time you can produce the kind of heat that might damage a turning tool would be at the grinder.

OK, got it.....thank you for the correction, Timothy.....

-o-

 

[Leo Van Der Loo]

As I understand it (AIUI) HSS all flavors were designed for the metal cutting industry HSS could be red hot and not loose its temper or cutting edge. The chip or curl could be white hot and the tool will still cut effectively. HSS doesn’t loose its temper when turned blue from grinding. Quenching with water can cause fractures on the cutting edge from the rapid shrinking of the metal.
I dip my tools in water before I grind to loosen the gunk that builds up in the flute this makes it easier to wipe the gunk off.
@odie I understand that you hone your tools if so the tool will be cool enough to cut with by the time you finish honing.
The edge of the HSS would have be critical (at forging temperature) for the wood to dull it. At this temperature it would burn he wood and set the chips on fire.

Yes I have sheared steel on the lathe coming off blue (never red hot), and that is another difference between cutting wood and the removal of steel, it is actual not cutting like wood.

I certainly never would get the tool so hot that it would be blue and then might fracture when grinding the tool, and yes maybe there is no reason to quench the tool, just a habit that stood the test of time.

 

[Steve Tiedman]

I fear this discussion is rounding the last turn and heading for the finish line, and if it still has momentum, into circles it will go. As I mentioned in an earlier message, this is all hypothesizing until someone breaks out the proper scientific instruments and actually documents facts.

Although there is one variable that I don't think has been discussed- pressure loads on the edge itself. At the grinder (or whatever metal removal instrument is used), we are dressing one facet (bevel) to meet another at a zero-radius line. We aren't "cutting" the grinding wheel, it's cutting the metal tool. Then we step back to the wood and do something completely different- we rub the bevel on the wood (in the exact same orientation we rub the bevel on the grinding wheel), but then we tilt/lift the tool a fraction of a degree to catch the resulting zero-radius line (edge) into the wood fibers and pair them away.

At this point more scientific instrumentation is needed, because even though the wood is easily yielding to the harder metal edge, the wood is also at war with the invading edge (the bevel we ground at the wheel isn't causing harm to the wood, but the friction between the two is creating heat, and that heat has to disperse along all of the metal, even the edge), pounding the daylights out of that zero-radius line with... several thousand(?) psi of force (and some amount of heat), maybe removing a few metal particles at the microscopic level, but just as much, if not more, rolling over and blunting that zero-radius line (think the hook on a scraper) to become a radius- we no longer have a 2-dimensional line as a meeting point of two facets (bevels), and we've lost the sharp edge. The more acute the angle of the bevels (skew chisel vs. traditional bowl gouge), the easier it blunts. Back to the grinder we go to grind away that rolled-over edge.

Theoretically, if you want to preserve tool steel, we should be using a burnisher more often, applying several thousand psi of pressure (which takes very little effort by hand) to simply re-align that rolled edge back into a zero-radius line. This probably isn't as practical with a gouge as it is with a scraper (or a turkey carving knife), so we grind the tool instead for a few seconds, then get back to work.

 

[odie]

I fear this discussion is rounding the last turn and heading for the finish line, and if it still has momentum, into circles it will go. As I mentioned in an earlier message, this is all hypothesizing until someone breaks out the proper scientific instruments and actually documents facts.

Although there is one variable that I don't think has been discussed- pressure loads on the edge itself. At the grinder (or whatever metal removal instrument is used), we are dressing one facet (bevel) to meet another at a zero-radius line. We aren't "cutting" the grinding wheel, it's cutting the metal tool. Then we step back to the wood and do something completely different- we rub the bevel on the wood (in the exact same orientation we rub the bevel on the grinding wheel), but then we tilt/lift the tool a fraction of a degree to catch the resulting zero-radius line (edge) into the wood fibers and pair them away.

At this point more scientific instrumentation is needed, because even though the wood is easily yielding to the harder metal edge, the wood is also at war with the invading edge (the bevel we ground at the wheel isn't causing harm to the wood, but the friction between the two is creating heat, and that heat has to disperse along all of the metal, even the edge), pounding the daylights out of that zero-radius line with... several thousand(?) psi of force (and some amount of heat), maybe removing a few metal particles at the microscopic level, but just as much, if not more, rolling over and blunting that zero-radius line (think the hook on a scraper) to become a radius- we no longer have a 2-dimensional line as a meeting point of two facets (bevels), and we've lost the sharp edge. The more acute the angle of the bevels (skew chisel vs. traditional bowl gouge), the easier it blunts. Back to the grinder we go to grind away that rolled-over edge.

Theoretically, if you want to preserve tool steel, we should be using a burnisher more often, applying several thousand psi of pressure (which takes very little effort by hand) to simply re-align that rolled edge back into a zero-radius line. This probably isn't as practical with a gouge as it is with a scraper (or a turkey carving knife), so we grind the tool instead for a few seconds, then get back to work.

Thanks, Steve... This is a great post, with plenty of food for thought....and, as I type here, I'm still contemplating the content.

One comment though: If the tip of the edge is being (microscopically) "rolled" over, that could be burnished back into place. My thought is maybe instead, the very tip is being removed, which we are calling "dulled". We do know that all steels, no matter how hard the composition makes them, are subject to wearing, or removal of the metal itself. This may be very minutely observable, and at a microscopic level.....but in that depth of awareness, the wood cutting ability of the very tip is what we're contemplating here.

You're right, in that the contents of this thread could be delved into a little more thoroughly with a scientific and documented study.

-o-

 

[robo hippy]

For some reason or another, this makes me think of water and how it wears every thing down. I always found the pot holes, created by water and rocks in side the pot hole getting swirled around and making the nice pot holes.....

robo hippy

 

[Leo Van Der Loo]

Somehow I think you have not changed your habit of dunking your tools Odie , I know I have not.

 

[odie]

Somehow I think you have not changed your habit of dunking your tools Odie , I know I have not.

That's true @Leo Van Der Loo ....my habit is to grab the tool in my hand after grinding, and if I feel it's too hot for comfortable turning.....I dunk. Only takes a second, and it's no big deal.

Somehow, I wonder why all the resistance by present-day turners to doing things the way our Grandpas used to do it. After all, it's all about the final results, and just because the "herd" is rolling in another direction, it doesn't mean it's better than the tried-and-true methods that used to work well...

(I suspect some of the resistance revolves around those who have spent a lot of $$$$ on specialized grinding wheels, and exotic steels.....and, there is a psychological need to justify these expenses... )

-o-

 

[Greg Hislop]

I like edges of my tools to be blackened after their first sharpening. Teaches them a lesson for the future.