Grinding HSS

[David Witton]

I know very little about working with steel - let's get that out of the way first. In the past, I've been very cautious when working steel on the grinder, fearful of damaging the tool by overheating. However, in viewing sharpening videos on the internet I get the impression that HSS is more tolerant of heat. I'm about to create a swept back grind on a Hurricane bowl gouge, and I'd like some advice. In the videos I've seen, folks are happily grinding away for a minute at a time, and in some cases not cooling the tool in water at all. My grinding wheel in a Norton ceramic alumina - how aggressive can I get, and what should I watch out for?

 

[odie]

Use that water frequently!

You lose the temper only if the excessive heat goes deep, and the steel start glowing.....not many people are that ignorant about grinding their fine tool steels, but I suppose it does happen with a few newbies until they get the hang of it! Just apply a little common sense about it, and use your water frequently. Don't worry about a little blue coloring on the very tip of the cutting edge where the steel is at it's thinnest. You can easily remove it after cooling it down and re-doing it.

-----odie-----

 

[robo hippy]

Some say keep the water handy, some say the water can cause micro cracks which will let the edge go dull faster. With the HSS, well, if it is real HSS and not just named that to help it sell, you can not get it hot enough for the metal to lose its temper. Still, I always keep the tool moving, never sitting long in one spot. If you have some major reshaping to do, use a 36 grit wheel, which used to be standard on the old grinders. I think the major brands, like Rikon, come with 80 and 120 wheels, the white aluminum oxide ones. The old grey wheels are generally more coarse.

robo hippy

 

[hockenbery]

High speed steel is tolerant of grinding heat.

Step one is to joint the top of the wing profile.
Put the tops of the flute on a platform and grind flats on the top of the wing.
Push the tool up and down on the wheel to get the desired wing profile.

Not put the flute up and using a jig ( or by hand) grind the bevel until you make an sharp edge

If you don’t joint the top first grinding just the bevel can create a very thing edge that just sort of bends over instead of bringing to a sharp edge.

 

[Bob Vaughan]

I think if its your job to get the temper out of HSS with a bench grinder, you can't do it. Yes, intense heat will soften the steel, but the temper comes back when it cools.
Good carbon steel like what's found on better wood chisels is an entirely different world of grinding.

 

[odie]

The following was taken from a knife forum, and may have some application to turning gouges here:

"Knife edges are easily overheated during powered grinding due to the small volume of the edge and the friction buildup from grinding. This softens the edge and worsens edge retention. The use of steels capable of high temperature tempering treatments help to some extent since they can withstand more heat. Hand sharpening or water cooled sharpening are the best methods for preventing overheating of edges."

This information does apply to my method of sharpening, since my gouge edges are all completely hand honed. I use the grinder for removing metal up to, and just short of the previously honed edge......and, I use water for cooling during that process. My grinder is for only removing metal, and not to establish a cutting edge.

As I stated previously, I consider the edge to be needing further grinding, if the steel turns "blue".....and only if the blue color is at the surface, and not below the surface. (Which would require holding the steel to the grinding wheel for an extended period.) The quote above would indicate the edge may have softened the steel at the edge, so it needs to be removed.

-----odie-----

 

[john lucas]

HSS would have to be heated very hot and held there for a period of time to change the temper. You cannot do that with a grinder. I tried to anneal a piece of HSS with a mapp gas torch and fire bricks and did not succeed. That's how good HSS can handle red heat.

 

[Bob Vaughan]

My grinding wheel in a Norton ceramic alumina - how aggressive can I get, and what should I watch out for?

For aggressive grinding, the wheel is the weak link here, not the steel. Being too aggressive dulls the little abrasive rocks on the surface of the wheel and can load the wheel. A dull and loaded wheel surface heats the steel quickly and doesn't cut well like it should. Three or four seconds of heavy push with a Huntington #0 star dresser will knock off the dull abrasives and expose new sharp stones.

 

[Bill Blasic]

I always have 1 aluminum oxide wheel on one of the grinders for reshaping.

 

[john lucas]

me too Bill. I have a 40 year old craftsman and I have no idea how old that course gray wheel has been on there. I did put a lee valley tool rest on it years ago. I reshaped a friends gouge on it the other day and with careful grinding I was amazed at the quality of the edge. Very usable right off this stone which must be something like 60 grit or courser. So it's much more about the skill of the sharpener than the grit of the stone.

 

[David Witton]

I still have a 60 grit gray wheel that originally came on the grinder, but bought the 80 grit Norton wheel based on reading about HSS being better served by the ceramic alumina wheel. Would I be better off shaping with the gray wheel? It certainly would go quicker!

 

[Bob Vaughan]

Both of those wheels will do a good job, but if the wheel's surface is dull, neither will be as satisfactory as they can be. The Desmond Huntington #0 dresser is the key to keeping the wheel's surface sharp. As I said, just a few seconds hard against the wheel while moving the dresser side to side will do the job of restoring sharpness. Without dressing the wheel, you'll be left with frustration and tempted to keep buying new wheels hoping they will do the job.

Note that on top of the tool tray is a diamond dresser. I use this to true up the wheel but it does dull the abrasives so after the diamond dresser comes the Huntington #0 star dresser. Shape the wheel with one tool and sharpen it with the other.





Side Note: The grinder shown is a standard Baldor 7" that I've tricked out a bit. I did the same with a similar Baldor grinder shown in the AAW Journal Spring 1999, Vol 13, issue #1, page 22.

 

[Bill Blasic]

That's a good dresser for a grey friable wheel but I use a diamond dresser for aluminum oxide.

 

[hockenbery]

I too like the Diamond wheel dresser for a/o and ceramic wheels.

I have used the diamond jim from Packard for at least 25 years. About 2/3 of the diamond matrix is still remaining.
Now that I have CBN Wheels it would last another 100 years easy

There is a small learning curve for effective use.
I like to rest the flat on a platform and hold it lightly on the right corner at about 30 degrees to get a smooth running flat then in 5 or 6 sweeps I move the angle toward 0 and move the dresser across the wheel until it comes off the wheel. The last move goes across the whole surface.
Just like turning an uneven surface make a smooth surface and work from smooth into rough.

Just holding a dresser straight into the wheel cleans the surface but follows the out of roundness. Just like poor turning technique follows the out of roundness

 

[Bob Vaughan]

I've seen those diamond dressers come and go over the decades. They all work for truing up vitrous wheels but until the wheel has been sharpened by the star dresser, the wheel is still dull. I recommend anyone who hasn't tried one, borrow one and try it. Its just a few seconds worth of work and makes the wheel cut like you want it to cut.
The word: "dresser" is sort of confusing because so many makers of gadgetry seem to use it in hopes the buyer will make incorrect assumptions about the performance. Diamonds true the wheel, the star dresser makes it sharp.

 

[Bill Blasic]

You are confusing sharpened with jagged because that is what the star wheel does. Doug Thompson uses the star wheel when putting on the edge form the virgin tool because it cuts faster. I would use it when starting from a tool with no grind. The diamond smoothes the wheel and gives a smoother feel for actually sharpening the tool and I can reshape. I sharpened with the oxide wheels for years until CBN came out and with diamond refined wheel the tools were very sharp. Now with CBN not only do they get sharp but the CBN does it without taking as much steel off the tool. And like I stated I keep one for reshaping not sharpening.

 

[Gerald Lawrence]

The following was taken from a knife forum, and may have some application to turning gouges here:

"Knife edges are easily overheated during powered grinding due to the small volume of the edge and the friction buildup from grinding. This softens the edge and worsens edge retention. The use of steels capable of high temperature tempering treatments help to some extent since they can withstand more heat. Hand sharpening or water cooled sharpening are the best methods for preventing overheating of edges."

This information does apply to my method of sharpening, since my gouge edges are all completely hand honed. I use the grinder for removing metal up to, and just short of the previously honed edge......and, I use water for cooling during that process. My grinder is for only removing metal, and not to establish a cutting edge.

As I stated previously, I consider the edge to be needing further grinding, if the steel turns "blue".....and only if the blue color is at the surface, and not below the surface. (Which would require holding the steel to the grinding wheel for an extended period.) The quote above would indicate the edge may have softened the steel at the edge, so it needs to be removed.

-----odie-----

Odie I have never heard of a knife made with HSS so that may be a mote point in reference to turning tools.

 

[odie]

Odie I have never heard of a knife made with HSS so that may be a mote point in reference to turning tools.

That could be, Gerald......I was assuming.

-----odie-----

 

[Leo Van Der Loo]

Yes HSS as in High Speed Salad shopping knife .

HSS has several ingredients in the steel that makes it capable of withstanding high temperatures, there are several different ones but most still have carbon in them, and so keeping the grinding temps down is a good idea, at the threshold of red hot like about 525 Celsius, at (540C) regular HSS will start to loose hardnes, so yes it it is better to not get the tool too hot.

I've always gone by grinding till the tool gets too hot for hand holding close to the cutting edge and I then let it air cool, quenching can cause micro cracks and just letting it air cool is better IMO.

When using regular grinding wheels they can get clogged up, just using a diamond dresser does remove the top of that crud, but a star wheel will crush the vitreous material and make any stone wheel open and clean again, it is still the best way to clean a grinder wheel.

As for the amount of metal removed, a dull tool has the edge rounded over, so to get it sharp again you remove all the metal till that round edge is gone and sharp. again.

It does not matter what or which way you do it, you do need to remove all that steel to get there, and that is usually very little.

 

[Bill Boehme]

You can get custom-made hunting knives that are made of M2 HSS. I also found that you can even get knives that are made from powdered metal steel such as CPM M4 and CPM V3 tool steel (not sure if this one is considered HSS). Just Google "HSS hunting knives".

 

[Leo Van Der Loo]

This is the place I got schooled in iron-steel and metals, that is better than 75 years by now, probably forgot more about it than most do know about it.

 

[Jamie Straw]

I know very little about working with steel - let's get that out of the way first. In the past, I've been very cautious when working steel on the grinder, fearful of damaging the tool by overheating. However, in viewing sharpening videos on the internet I get the impression that HSS is more tolerant of heat. I'm about to create a swept back grind on a Hurricane bowl gouge, and I'd like some advice. In the videos I've seen, folks are happily grinding away for a minute at a time, and in some cases not cooling the tool in water at all. My grinding wheel in a Norton ceramic alumina - how aggressive can I get, and what should I watch out for?

Not all HSS is created and tempered equally, even if it carries the same designation (M2, or M42). Inexpensive tools are likely to be unevenly tempered or only part of the tool bar done (say the first 1.5" for example). I've sharpened many brands of turning tools at various stages of use in demos and classes, and even some of the well-known or much hyped brands were disappointing.

A couple of unsupervised students in three years have managed to blue the ends of three different M2 tools, not bad really. I've watched Dave Schweitzer sharpen M42 at high speed with great gusto. Rarely, very rarely, is there even a hint of color change on an edge. His tools are tempered throughout the bar, as they hang suspended and deep, and the process is tightly controlled.

 

[John Jordan]

I would add that even though you may not lose the temper, any significant bluing indicates that something is wrong. Wheel too fine, pressing too hard etc, wheel needs dressing etc. What Bob Vaughn said about star wheel dressers is true. Water is fine, but take your time.

John

 

[Bill Blasic]

I am lucky enough to have 4 double wheel slow speed grinders so I have 1 dedicated just for me that no one else can use. So it is set to my grind setup (Vector Grind Fixture) with a 180 CBN wheel. 1 light pass is all that's needed and I can do this about 4 times before I have to refresh the secondary bevel. Even though I had good sharpening on the white stones with the CBN I'm taking off a whole lot less steel so the tools are lasting longer. It is so easy to take a light whisper cut on the CBNs.

 

[Leo Van Der Loo]

Of course we have heard all of this before of sharpening the tools with a different wheel or other ways, and it is then claimed to remove less steel.

So my take on this is no matter what you use, fast or slow any color wheel etc, you do need to remove all the steel to get that sharp edge again.

A picture here that is supposed to show a blunt nose on a tool, and the line to where the steel has to be removed for the edge to be sharp again.

The orange colored part is the steel that has to be removed to get that sharp edge again/

 

[odie]

Great illustration Leo......

This brings up my belief that when overheating occurs, the very tip might have been 1500°, while the rest of the steel was not nearly that hot.....therefore not losing it's temper anywhere else. At the very tip of the edge, the thicknessof the effected steel may be .0001" thick, and does not have the ability to distribute the heat like where it is thicker. Therefore, the ability to hold the edge has been lost. The steel is still ok, it just needs to be re-sharpened. After you get the bluing at the very edge, if you use it that way, it will dull faster......if you just cool the steel and re-sharpen without getting any bluing, all will be ok.

-----odie-----

 

[Bill Blasic]

Ridiculous, I'll bet that I'm taking .010 or less off the tool to resharpen. My cutting edge to the first secondary bevel is about a 1/64" and after 4 sharpening it may get to be 1/32". I then hit the secondary bevel again to get the bevel back to that 1/64". You know that tool that you feel is dull would still slice through your skin and leave you very open to stitches.

 

[Bill Boehme]

This brings up my belief that when overheating occurs, the very tip might have been 1500°, while the rest of the steel was not nearly that hot.....therefore not losing it's temper anywhere else. At the very tip of the edge, the thickness of the affected steel may be .0001" thick and does not have the ability to distribute the heat like where it is thicker.

You have made a very good observation. Compared to most other common metals, steel is a relatively poor conductor of heat. And, we need to make a distinction between "heat" and "temperature". Heat is the transfer of thermal energy measured in Joules. When you grind the bevel of a tool, thermal energy is transferred essentially uniformly to the bevel, but because the incremental volume of steel is less at the edge than it is at the heel of the bevel, the temperature at the cutting edge will be significantly greater. How much greater? The oxidation color of the steel is a pretty good gauge. For dark blue color, the temperature is about 600° F. Here is a picture I found on Wikipedia that shows the colors that are the result of various tempering temperatures.



If you consistently blued the cutting edge it probably has a small effect o the hardness of the cutting edge. For high carbon tool steel, we know it's bad news for edge durability. But, high speed steel is designed for fast machining of steel with resulting high temperatures even with coolant being sprayed on the cutter. So, my guess is that a little blueing is OK, but I still avoid getting the cutting edge hot enough to cause bluing. I just feel like using a light touch I can get a sharper edge.

 

[Bob Vaughan]

My grinding wheel in a Norton ceramic alumina - how aggressive can I get, and what should I watch out for?

I'm new to this group. Help me out here. How does any of this address David's original question?

 

[Gerald Lawrence]

I'm new to this group. Help me out here. How does any of this address David's original question?

Everything went astray. Basically :
1. do not force the tool into the wheel
2. do not grind for extended times, basically just one pass from one side to the other or both sides nd then touch the nose. The longer you grind continuously the more danger from damaging the tool.

By the way when using a CBN wheel you could never get any overheating if you only do one pass and done. That is all I ever need anyway. I know a different story with ceramic wheels and it will take at least two passes.....now that woulu be really HOT ,

 

[Bill Boehme]

As I stated previously, I consider the edge to be needing further grinding, if the steel turns "blue".....and only if the blue color is at the surface, and not below the surface.

The color that comes from heating the steel is oxidation so it is basically just a surface color.

 

[Bill Boehme]

I'm new to this group. Help me out here. How does any of this address David's original question?

If you see a rule violation (uncivil behavior, spamming, etc) then the proper response is to report the offending post using the Report link. You never ever take matters into your own hands. When somebody asks a question some replies will be more helpful than others. The OP can decide what information they find helpful. Just as in face-to-face gatherings, on social media platforms, and in threads on Internet forums the discussion topics evolve over time. That's just the nature of the beast. The answers to many questions are opinions so there may be many "right" answers or maybe a "right" answer doesn't exist. There's usually nothing wrong with offering supplemental information. And, sometimes the question asked needs to be refined through discussion.

 

[robo hippy]

Discussions tend to wander/wonder all over the place.... Human nature.

robo hippy

 

[Doug Freeman]

Diamonds true the wheel, the star dresser makes it sharp

What Bob Vaughn said about star wheel dressers is true.

I have attempted to verify that star dressers are better for “sharpening” a wheel vs diamond. The wheel mfrs only mention diamond for both truing and dressing. Any links to info about thhis?

 

[robo hippy]

Hmm, I would say no, but it has been eons since I used standard grinding wheels. I do know they get dull when they load up. Properly applied diamond dresser will clean the wheel and can true it up, if used properly, as in on a tool rest and gently eased into the wheel to nibble off the high spots till it is true again. Can be used on the sides as well. If the wheel is 'clean' as far as I am concerned, it is sharp. Well, at the very least sharper than it was before you cleaned it off.... There are other variations of a truing/cleaning set up, but can't remember who makes them. I think Oneway had one, and there was another variation some one else made. I always used the cheap T shaped ones.

robo hippy

 

[John Jordan]

I have attempted to verify that star dressers are better for “sharpening” a wheel vs diamond. The wheel mfrs only mention diamond for both truing and dressing. Any links to info about thhis?

Star wheel dressers have been around many decades longer than diamond dressers. Before I mostly switched to CBN, I used diamond dressers on my wheels mostly. But I use an expensive ceramic wheel every day in my tool-making business and it's dressed often with a star wheel dresser because the star wheel dresser chips away used grit and exposes new, sharp grits. A diamond effectively levels the grit, making the wheel somewhat finer than its actual grit. Doesn't typically matter for sharpening a bowl gouge and a diamond dresser is easy to use. I need all the coarseness I can get on my ceramic wheel.

Moving a diamond dresser very slowly makes the wheel finer. I've learned to sort of rough up a conventional wheel with the diamond by sort of poking at it if I'm using a grinder with a very fine wheel. Learning to use a star wheel dresser was and probably still is a basic machine shop skill that's learned early.

John

 

[Kevin Jenness]

I use an expensive ceramic wheel every day in my tool-making business and it's dressed often with a star wheel dresser because the star wheel dresser chips away used grit and exposes new, sharp grits.

John, what is the advantage of the ceramic wheel for that application?

 

[Doug Freeman]

Star wheel dressers have been around many decades longer than diamond dressers. Before I mostly switched to CBN, I used diamond dressers on my wheels mostly. But I use an expensive ceramic wheel every day in my tool-making business and it's dressed often with a star wheel dresser because the star wheel dresser chips away used grit and exposes new, sharp grits. A diamond effectively levels the grit, making the wheel somewhat finer than its actual grit. Doesn't typically matter for sharpening a bowl gouge and a diamond dresser is easy to use. I need all the coarseness I can get on my ceramic wheel.

Moving a diamond dresser very slowly makes the wheel finer. I've learned to sort of rough up a conventional wheel with the diamond by sort of poking at it if I'm using a grinder with a very fine wheel. Learning to use a star wheel dresser was and probably still is a basic machine shop skill that's learned early.

John

Thanks John. I do have tool room and mfg grinding experience, and have used star dressers also. From experience and researching the topic, star dressers are more for creating a rougher surface for faster material removal, and particularly for harder wheels. For turners I’m not sure there is a need for them. The 46 gr wheel I use for shaping cuts fast enough for me. Ive never used a star dresser on alox wheels, as the diamond seems to restore them to expected performance, and I had concern that I could chew up a lot of the wheel with one. For high material removal rates in a production oriented environment and surface finish is not a concern, they would make sense.

 

[John Jordan]

Thanks John. I do have tool room and mfg grinding experience, and have used star dressers also. From experience and researching the topic, star dressers are more for creating a rougher surface for faster material removal, and particularly for harder wheels. For turners I’m not sure there is a need for them. The 46 gr wheel I use for shaping cuts fast enough for me. Ive never used a star dresser on alox wheels, as the diamond seems to restore them to expected performance, and I had concern that I could chew up a lot of the wheel with one. For high material removal rates in a production oriented environment and surface finish is not a concern, they would make sense.

No Doug, I agree they aren't needed for most turners. I have a very specific need for grinding my little hollowing cutters and want the fastest grinding wheel at all times. I got stuff to do. LOL

John

 

[odie]

View attachment 42734

I have a tool with excessive bluing, and it's not one solid color. It's actually a combination of the last four examples on the right side of the scale, with it graduating toward the lighter blue, as it gets closer to the cutting edge. I'm assuming it continues to get hotter the closer to the cutting edge it gets, and it sure does seem to effect how long the edge will last. If the very edge of the bluing isn't removed and a new edge is established, it still has some life to it, but it dulls faster.

-----odie-----
This is a great photo, Bill.....and, I've saved it to refer to it in the future.