Sharpening Grit

[john lucas]

I finally had time to do a grit size sharpening test. I picked a piece of wood that easily shows any error in cutting or sanding lines. I used African Ebony. I sharpened my Thompson 1/2" V bowl gouge using the 40/40 method to 40 degree nose angle using mu 350 grit CBN wheel. I made a pass across the ebony. then I ground the same gouge to the same angle using a 36 grit gray wheel. Made a short pass on the end of the ebony. I could not tell the difference. The course grit is the right end and the fine grit is just past the groove. I did it 3 times ( it hurt to grind away that much steel but really it was only probably .010") The test came out the same all 3 times. If I have time tomorrow I might try another wood but I've found the ebony to be a really tell all to how well my tools are cutting. Anyway. I guess the important part of sharpening is to get repeatable angles, make sure you sharpen all the way to the tip ( which can be harder with the finer grits) and sharpen frequently. What grit you use is apparently unimportant. OK now that I said that the finer grits do have some advantages. One is you remove less steel each time you sharpen. An edge ground with a finer grit will last longer. I have seen this in my own experiments but it's well documented in The English magazine Woodturning and there was also an article in American Woodturner the showed this.

 

[JeffSmith]

John - I started sharpening with cbn wheels nearly 12 years ago - using 180 grit for all my gouges. The first thing I noticed (as you point out) was that the edge lasted longer and it took less time to sharpen, using less steel in the process. I'm still using the same wheels - by now the 180 is probably equivalent to a 360, but the effect is the same.
Thanks for validating what I suspected all along. I've also gotten more use from my gouges along the way.

 

[Ron Solfest]

John, not sure if I’m viewing your pic properly. I’m pretty sure I see multiple small groves on the right side of the big grove that I don’t see on the left side.

 

[Brian Gustin]

Agree with Ron, I can see small serrations on the right side of separation groove that are not as obviously present on the left. I'd bet if you ran some 320 grit sandpaper over the whole thing and then applied a single coat of some kind of finish, the difference would quickly become glaringly obvious..

 

[Earl McLain]

John, not sure if I’m viewing your pic properly. I’m pretty sure I see multiple small groves on the right side of the big grove that I don’t see on the left side.

I thought that as well, and had no memory of which end was which. Fine grooves about 2/3 of the way to the groove. (Still better cutting than my best day)
Earl

 

[Bill Blasic]

I see the lines you are talking about on both sides, more so on the right but my guess is the camera angle is more why one side is more prominent than the other. As I posted before I have found that the 180 grit CBN wheel gives me the best combination of sharpness and how long it stays sharp. I use the Vector Grind Fixture and my first grind I have a small cutting edge of a 64th of an inch or less and after 2 or 3 sharpenings when that edge gets to be a little bigger than a 32nd of an inch I then go down to the two lower positions on the jig to get the cutting edge back to that 64th. That's the beauty of the CBN wheel where with a light touch you get back to sharp with minute steel removal. I seriously doubt that I will ever come close to wearing out my current 5/8V Thompson gouge.

 

[Paul M. Kaplowitz]

I have used 80 grit CBN wheels for years. One light pass and I'm finished. The razor sharp edges last about 3 seconds.

 

[john lucas]

its using my phone that is t hff e problem. Even with vfc a good camera it's hard to see. Live in person there isnt any difference. The only difference I was able to see in the 3 different times I did this test was due to not being able to maintain identical travel speed across the wood. I lubed the tool rest and tried my best to maintain the same speed and depth of cut.

 

[Richard Findley]

That’s really interesting John, I read lots on here about people honing and polishing edges but I use my tools straight from a 180 CBN with no trouble at all.

 

[William Rogers]

I also use my gouges straight off my 180 and sometime 80 CBN. I never bought in to having a 600 grit as many have said needed for a final cut. Higher grit “may” have some advantage over punky wood, but I get along fine with the grits I have.

 

[robo hippy]

I have played around with it some as well. What I did notice was that the 600 grit wheel left a better surface on some punky maple. I can't say that I notice a difference with the 320 grit wheel. Might have to dig out the 1000 grit wheel to see how it works. Use it mostly on my skews. They still need to be honed/stropped to get all of the burr off. The honing compounds go from black being about 800 grit to the red/rouge, which is about 16000 grit. More experimenting ahead... This has me wondering if the honing compounds would work for the carbide cutters, to get them back to factory sharp.

robo hippy

 

[john lucas]

Well I did another test yesterday. It was suggested that my test wasn't accurate because I was cutting into the grain. So I turned a couple of beads and did new side grain cutting. Here is the test. Please excuse the shape of the beads. I don't normally turn beads this small with a bowl gouge. The bead on the left and the left side of the spindle portion were turned with the 350 grit CBN wheel gouge. The bead on the right and the right end of the spindle were turned with the 36 grit gray wheel gouge grind. The 2 flat areas at the far left and to the right of the beads were turned with a skew sharpened to 1200 grit and stropped. Again the photo doesn't do it justice. This could easily be sanded with 400 grit. I've turned enough of this wood on Christmas ornaments to have a pretty good feel for how it cuts. By eye I cannot tell the difference. The jury is still out on honing the edge. I frequently do this when turning the outer rim of my hand mirrors. Just like bowls if your cuts aren't perfect you can get very minor tearout on the 2 grain areas where you are cutting uphill with the grain. I have found that I can hit the edge with a 600 grit diamond hone and make another pass and it will remove it. So it is possible that sharpening honing the edge will improve the cut.

 

[Leo Van Der Loo]

To me the whole thing boils down to, do you or don't you still need to sand, I would think if it needs still sanding, then the whole thing is a wast of time and effort, just IMO

 

[Randy Heinemann]

I have not done a test but have seen the results from people who sharpen to various grits. I don't think I've ever seen anything that indicates the finish is much different. However, I do think (no evidence of this) that sharpening with a finer grit will give a longer lasting edge before sharpening again. A smoother cutting edge is less likely to fracture and should stay sharper longer. Again, I don't have evidence of that, but that is the reason that, when I bought diamond wheels for my Tormek I bought a 300 grit and 600 grit. Turns out that to maintain gouge and scraper edges, the 600 grit wheel gives a very sharp edge that stays a long time. Since it really comes down to that what you are comfortable with when turning works the best, I have decided to never test my theory; just use it and enjoy the results.

 

[Odie]

Everything you need to know about sharpening lathe tools has been known for 100 years!

The purpose of the grinder is to remove metal.

The purpose of the hone, is to create the edge.

Used to be the finest of craftsmen created their cutting edges with stones, but the only real major advancement in the art of honing since ancient times, has been the introduction of diamond hones. The level of sharpness possible hasn't changed, though.

One real advantage a hand-honed edge has over a machine created edge, is the direction of the hone changes when it's done by hand.....very much in the manner that random orbit sanding creates a finer sanded surface than a surface where the abrasive is cutting in a single direction.

Another major improvement has been the introduction of M2 HSS. Any of the hybrid steels since M2 is a waste of money and effort. If you need an edge that lasts and lasts.....then you need to improve on something else to get that fine tool finish. (I know that statement is bound to raise a few hackles!)

Sure is nice to spend a few minutes sharpening and creating a set-up, and then turn on the lathe to make one well thought out precision cut in about ten seconds time.....creating a tooled surface that requires very little sanding!

I know that what I know to be truths will not change the direction of the herd......and, that's why I'm the maverick here.

-----odie-----

 

[john lucas]

To me the whole thing boils down to, do you or don't you still need to sand, I would think if it needs still sanding, then the whole thing is a wast of time and effort, just IMO

Well om picky so yes I need to sand but starting at 400 grit. I would like to say that this applies to turning not other tools. My hand planes and carving tools for instance I sharpen to at least 2000 grit and then strop. there is a definite difference in finish quality on the wood with the higher polished surface of the tool. One thing I haven't done yet and I guess I will have to try it is to turn a larger spindle with each tool to see if I can feel the difference. The finish might be the same but i know that when I come back from the grinder the tools cut like butter. Not sure I noticed the difference on a small turning like this one.

 

[Kevin Jenness]

I know that what I know to be truths will not change the direction of the herd......and, that's why I'm the maverick here.

-----odie-----

No offense Odie, but whenever you get all mavericky I can't shake the image of Tina Fey impersonating Sarah Palin. VP debate

 

[Odie]

No offense Odie, but whenever you get all mavericky I can't shake the image of Tina Fey impersonating Sarah Palin. VP debate

Ha,ha.....you mean you don't think Sarah Palin can see Russia from her porch?

On a bit more serious note......I am well aware that there is a lot of skepticism about my claims, but the only relevant truth is: "the final result is the only thing that matters"!

My final results can be seen by clicking on the links in my "signature" below...

-----odie-----

 

[hockenbery]

The @john lucas Pictures tell a story - indicates an 80 grit ground gouge would work well on the wood being turned.

Experience often represents a tiny portion of the woodturning spectrum.

I have used 80 grit CBN wheels for years. One light pass and I'm finished. The razor sharp edges last about 3 seconds

I also use my gouges straight off my 180 and sometime 80 CBN

seen the results from people who sharpen to various grits. I don't think I've ever seen anything that indicates the finish is much different

I know that what I know to be truths will not change the direction of the herd......and, that's why I'm the maverick here.

In my small corner of the woodturning spectrum
I use the 80 grit CBN for my bowl gouges
180 grit for my spindle gouges, parting tool, scrapers, and pyramid tool
The tormek and it’s leather strop wheel for my skews

The tool I hone is the skew.

 

[Lou Jacobs]

Kevin, loved the SNL clip! Hard to believe that it is possible to long for those simpler times.

 

[Dennis Weiner]

@john lucas
“An edge ground with a finer grit will last longer. I have seen this in my own experiments but it's well documented in The English magazine Woodturning and there was also an article in American Woodturner that showed this.”

This may be true depending on the steel, the sharpening, and the use. It is not a rule or an absolute fact across the woodturning continuum.
Many of my tools are M2. However, I do know that my 10v sharpened with CBN has improved the strength of our tools available as well as the edge of those tools.

A few years ago, I attended AAW Kansas City symposium where Tom Wirsing and Stuart Batty had a session on tool steel discussing sharpening and wear. We had the opportunity to see on a digital microscope the edge of the tools before sharpening, after sharpening, and after 1 short pass cutting a few inches of material on the lathe. After turning it was observed that the fine edge was not strong enough to withstand the violent forces that the act of woodturning placed on it. The edge was gone but the tool still cut. This observation altered my thinking about sharpening, After 20 years of woodturning, I never again honed my woodturning tools. So much for what the heard does!

I think it’s important to note that a carver can use his tools(on average) for about 20 -25 feet before he has to resharpen. So hypothetically, if I used them in woodturning on a 10” bowl how far and soon would I have to resharpen at 700RPM?
Let’s do the math: Circumference = pi x diameter 3.14x 10” = 31.4 inches per one revolution or about 31.4/12 = about 2.62 feet in one revolution. Well, 25 feet would be 9.5 revs. That would transpire in .0136 minutes or the effective carving edge would be gone in .81 seconds. So hurry and hone and get your ultimate cut in there fellas!


Of course, Our tools are thicker and their angles are not as steep so they can still cut but not as much and as long as we like. Still, I would like to know if the new steel is strong enough to hold a better edge and increase the time between sharpening. The answer of course is yes, but I would like to see With CBN grits 80,180, 320, 600 and 1000. and just 10v. These additional grits came after the Tom Wirtsing demo. I wouldn't count them out of the equation. To this end, John I think that you are on to something. I would not be looking at the cut or finish produced from the gouge. I don’t think you want to spend the money on a 10” diameter piece of ebony either. I think looking at the edge of the gouge will tell a better story rather than what the tool produces.

I'll handle this:

View: https://youtu.be/i0GW0Vnr9Yc?t=8

 

[hockenbery]

would transpire in .0136 minutes or the effective carving edge would be gone in .81 seconds. So hurry and hone and get your ultimate cut in there fellas!

Great point.

That time frame tracks with the time a negative rake scraper stays sharp.
Using different parts of the edge extends the time between sharpening to 10-20 seconds.

Edge contact needs to be factored into the time equation.
Carving a flute in wood with a carving gouge the center of the gouge flute is in contact with every pass.
With Turning tools contact point often moves along the turning edge and the

Turning a convex curve with a turning tool it is common to start on the tip a roll to a sweet spot off the nose.
When I do pull cuts on a convex surface the contact point on the cutting edge moves so it distributes the cut along a 1/4-3/8” of the wing.

 

[Dave Landers]

I think it’s important to note that a carver can use his tools(on average) for about 20 -25 feet before he has to resharpen. So hypothetically, if I used them in woodturning on a 10” bowl how far and soon would I have to resharpen at 700RPM?
Let’s do the math: Circumference = pi x diameter 3.14x 10” = 31.4 inches per one revolution or about 31.4/12 = about 2.62 feet in one revolution. Well, 25 feet would be 9.5 revs. That would transpire in .0136 minutes or the effective carving edge would be gone in .81 seconds. So hurry and hone and get your ultimate cut in there fellas!

Another way to look at this... At 700 RPM on a 10" bowl, you cut a mile of wood in less that 3 minutes. So imagine driving down a mile of wooden road dragging your tool along beside you. We got some tough tools to take that sort of abuse.

 

[Randy Heinemann]

I'm sure that the material the tool is made of makes difference. I have used the Crown Pro-PM Ellsworth gouge since I started turning bowls with a bowl gouge. The edge lasts a long time. Would it last longer if I used a coarser grit than the 300 grig diamond wheel I use on the Tormek? I don't know. All I know is, using my current wheel and method, it lasts a long time, long enough that I wouldn't change the sharpening method or the material it's made of. I think what it really comes down to is that turners use whatever sharpening method and tool they have experience with and works for them. I've found out that there is no one way to get the result you desire. For example, I have a detail spindle gouge which I bought mainly for creating tenons. Problem is, I haven't mastered kit and, when I run into problems and want to move forward, I use other methods. I practice once in awhile but enjoy turning and creating so I more often just go to my tried and true method. It makes me feel better.

 

[Kevin Jenness]

@john lucas
“ I would not be looking at the cut or finish produced from the gouge. (...) I think looking at the edge of the gouge will tell a better story rather than what the tool produces.

I won't dispute that the edge tells a story, but I think it's the same one the finished surface tells. The surface is easier to see and feel for me, and is what I am interested in. I often can feel a difference in the cut and see a difference in the cut surface before I can see the edge dulling.