Do HSS turning tools loose their sharpness over time without use?

[Jesse Tutterrow]

The subject line describes my question. What is your opinion?

The long story:

Last October my club had a professional turner in to teach a wet wood bowl turning class. Being a new turner I signed up and purchased a set of three bowl gouges. The instructor sharpened all three gouges. Last month we had an open session where people could bring in projects that they needed help with. I brought the rough turned bowls in along with my tools. I had not used the bowl gouges since the class. The person managing the session declared that all three bowl gouges were dull. How can a HSS tool go from just sharpened to dull by setting on the shelf for ten months?

 

[John Torchick]

Don't know the answer but, IMHO, sharp is dependent on the individual. What is sharp to me might not be sharp to another. Did the demonstrator use the tool to determine this? There is sharp and then there is scary sharp. Working on getting my tools scary sharp. I visited a turning club where a fellow spent the time showing different grinds, sharpening tools- power and hand sharpeners, and how to sharpen your tools.

 

[Clifton C]

I believe the tears shed by the unused bowl gouges probably lead to the dulling of their formerly sharp edge. The first thing to do is a quick sharpen, apologize profusely and promise to never again let them languish, sitting on a shelf, for ten months...
c

 

[Jesse Tutterrow]

Sorry Clifton,
I doubt that the bowl gouges will see much use as I don't seem to be interested in bowl turning.

 

[Bill Boehme]

You were turning green wood in the class which cuts easily even if the tools aren't perfectly sharp. Since the wood has dried out the tools won't cut as well if they aren't truly sharp. Also, Clifton may have a valid point.

 

[hockenbery]

Tools can get dull without use for turning

Oxidation on the cutting edge, handling, abrasion from protective wraps, contact with storage rack, dust on the cutting edge.

We're the tools used at all in the class?

Hope you give bowl turning a reasonable try, however there are lots of good turners who do not turn bowls
And even more good people who do not turn at all

Have fun,

Al

 

[odie]

Don't know the answer but, IMHO, sharp is dependent on the individual. What is sharp to me might not be sharp to another. Did the demonstrator use the tool to determine this? There is sharp and then there is scary sharp. Working on getting my tools scary sharp. I visited a turning club where a fellow spent the time showing different grinds, sharpening tools- power and hand sharpeners, and how to sharpen your tools.

Hiya John.......You know......the definition of "scary sharp" might be subject to interpretation by different turners, too!......

-----odie-----

 

[John Torchick]

odie, I recall in my younger years of my grandfather sharpening his genuine Barlow knife and shaving the hair on his arm to check the blade. That is scary sharp! Haven't tried shaving with my roughing gouge....yet. A skew would be harder to master... as everyone knows.
A kind fellow sharpened some of my tools last winter. When he gave them back, the ends were wrapped in blue painter's tape. I now keep two rolls on hand. I sharpen after use and wrap blue tape around the ends if I'm not using them right away. When I got my Rikon grinder, he told me to color the end with a black Sharpie so I could tell if the grind was on target. Works great! Eliminates guessing where the wheel is touching. It's amazing how good a sharp tool turns wood or synthetics.

 

[john lucas]

Everybodies definition of sharp is different. I've had many people bring me tools that they thought were sharp and they weren't. At least in my opinion which is of course right. I used to think my various tools were sharp until I ran into someone who could really sharpen. Shaving hair. A lot of tools will shave hair and still not be really really sharp. I learned that just recently when trying to sharpen various steels to as sharp as I could get them. Yes tools can get dull sitting around. Not very dull but certainly not as keen an edge as when freshly sharpened. I like John Jordan's statement. If you think a tool is dull you have waited too long to sharpen it.

 

[Perry Hilbert]

scary sharp was my Dad's straight razor. So sharp I sliced my fingers, had blood spurting all over the floor and I did not feel it for a few minutes despite the blood. There is a reason why folks use the term razor sharp.) Some cutting tools aren't suppose to be razor sharp. the edge gets too much abuse during use that a fine edge wears away immediately. Capacity to be sharpened also is highly dependent on the material it is made from. Crappy dime store stainless steel knives are next to impossible to sharpen. Crappy carbon steel dime store knives were usually easy to sharpen, but didn't stay sharp for more than a minute or two. Some materials require specialty tools to sharpen and all the Arkansas stones in the world will do not good. I have trouble sharpening a bowl gouge but far less trouble with a skew. Probably because I do not use a wheel to sharpen the skew, I use a sharpening stone. There is a strange noise that comes from wood being turned against a sharp tool. More of a hiss noise, like the hiss from one of those little hand held pencil sharpeners when sharpening a pencil. No grinding, no bumping, no chatter. No tearing.noise like a saw, Just that hiss. and when long shavings sail off the work piece like a possessed piece of string fleeing the lathe.

 

[odie]

There is a strange noise that comes from wood being turned against a sharp tool. More of a hiss noise, like the hiss from one of those little hand held pencil sharpeners when sharpening a pencil. No grinding, no bumping, no chatter. No tearing.noise like a saw, Just that hiss. and when long shavings sail off the work piece like a possessed piece of string fleeing the lathe.

I like that description.....among the best I've ever heard!

-----odie-----

 

[john lucas]

Well the term razor sharp can have more definitions. All tools ideally should have an edge that is as sharp as you can get it. The included angle of the edge will often determine now well it cuts and how long it holds an edge. double edge razors for example are usually sharpened at less than 20 degrees. Same with my chip carving knives. This will not hold an edge long and has to be rehoned frequently. My skews are 25 to 45 degrees depending on how I use them. The 45 degree edge holds up longer but may not cut as clean even though they were all sharpened to the same high degree of Scary Sharp. Even that term depends on where you stop. for a test on what metals take a keener edge I sharpened using the scary sharp method to 2000 grit and then stropped the metal. Tested on a BESS sharpness tester they were sharper than a utility razor but not as sharp as a single edge razor. This was mostly due to the razor being sharpened at less than 20 degrees and my tools were 27. I found the 2000 grit sandpaper was finer than an 8000 grit water stone which is why I went that far.
I tested a spindle gouge that had an included angle of 45 degrees and sharpened on a 180 grit CBN and then honed with a 600 grit diamond hone. It came out sharper than high end cutlery but not anywhere near as sharp as a razor or my skews that I ground to 27 degrees for the metal test. The spindle gouge will cut you in a heart beat though.

Woodturning magazine had an article on edge holding capability and proved that a sharper edge (meaning how fine of a grit you sharpen to) will hold up better than the same edge with a less sharpening. In this case we are talking about using the same tip angle on the tool but sharpening to a higher grit. I have proven that myself in a test using my spindle roughing gouge. I was doing a production run of mirror handles and would go back and forth between 180 grit and 320 grit each time I sharpened. The 320grit not only cut easier the edge lasted longer.

Now there definitely is a correlation between how acute the edge is sharpened to. A gouge with a 55 degree edge will hold up longer than a gouge with a 35 degree. For that reason many people grind spindle roughing gouges to a more blunt angle than a spindle gouge because you are roughing a lot of wood away with the SRG and want the edge to last and you aren't worried about the finish quality because you will be going to the skew or spindle gouge for finish cuts. Damn that's a long sentence. Gotta work on that. Bowl gouges are often a trade off. we sharpen them at 40 to 55 degrees because we need to be able to rub the bevel when cutting the inside and you can't do that with a gouge sharpened at 35 degrees unless it's a really shallow bowl. You also want to be able to waste away a lot of wood without stopping to sharpen constantly. Of course you should sharpen before any final cuts.
The Hunter carbide cutters have a very steep outside bevel but the cutting edge is around 30 degrees. When I tested one straight out of the box it tested near the high end cutlery range as far as sharpness goes. On the Hunter Hercules the cutter is mounted so the bevel angle is about 55 degrees so you get the advantage of using it like a bowl gouge ground at that angle but it has the clean cutting of a skew ground at 30 degrees.
I'll be writing an article shortly for More Woodturning magazine on my findings on sharpening certain steels. I sharpened HSS, High Carbon Steel, and Particle metal to the same angle and degree of sharpness and each one sharpened the same for all practical purposes. When I got to 5000X magnification on a Scanning Electron Microscope I could finally see the edge deteriorating. This usually shows up at about 400X. There were very minor differences and when I tested them on the BESS tester the same was true. So for all practical purposes it doesn't matter what steel you use, they will all sharpen the same. Some will hold an edge longer because of the toughness of the metal but all will sharpen the same. The really cheap steels don't fit this same model because quality of the steel definitely affects how sharp they will get and how long they hold an edge.

 

[john lucas]

Oh and about the noise a tool makes when sharp. I had heard that Japanese planes make a whistling sound when you use them and the blade is truely sharp. I didn't understand that until one day I spend the extra time on my blades and you can hear a hiss or whistle as they cut. It's pretty cool.