Presentation vs sharpness

[Mike Novak]

This post by @odie got me thinking. If your cuts are not a clean as you like, how can you tell if it’s a presentation or a sharpness issue? (Or both!) Which one has a bigger impact on the cut?

I was working on some hemlock today, which has very soft wood between hard growth rings. Like pine but worse. I was getting horrible deep tear out in the soft part of the rings using my bowl gouge. Only way I could clean it up was by dozens of very light shear scraping passes, sharpening often.

This is very much like those who swear their tools are sharp, when it's obvious their results require much more sanding than would have been necessary if the hypothesis were true.....

-----odie-----

 

[john lucas]

Tough question. I think there are 3 things critical to getting a clean cut. Sharpness is one. The angle the woid crosses the edge which we can call presentation. How fast the tool.is pushed through the wood. They all work together. If any one of the 3 is not is ignored you get a less than clean cut. Of the 3 I think how fast the tool is pushed through the cut may be the most important but the other two are critical.

 

[Kevin Jenness]

If your tool is sharp it's not a sharpness issue. If you're not sure whether it's sharp, try paring the endgrain of a pine block held in a vise. If your tool movement is slow relative to rpms (high cuts per inch in flatwork terms) it's not a feed rate issue. That leaves presentation. And material choice. Some chunks of wood just are too mean to turn.

If you can get nice clean results in eastern hemlock you should pat yourself on the back. I once milled a batch of gnarly old dry hemlock rosettes on my cnc router with a sharp bit, high rpms, small stepover and low feedrate and still had 50% with minor but unacceptable blowout - no way would I have attempted to turn them on the lathe. Maybe Odie could do it.

 

[odie]

If your tool is sharp it's not a sharpness issue.

This is true, Kevin.......However, it's my opinion that sharpness is the biggest issue preventing a clean tearout free cut for most turners who don't achieve it on a regular basis. It's correct to acknowledge there are other things that will prevent the best possible cut. John Lucas cites "presentation", and this is a big factor, along with the kind of wood being turned....as you have pointed out. All of us can properly conclude that the level of sharpness of the tool being used is only one component of the total equation, and that's a truth that just can't be ignored.

I regularly work with woods that have the overall highest levels of Janka hardness, and I can say with confidence that even if everything else is at high levels of perfection.....if the sharpness isn't there......the opportunity to have the best possible cut is also not there.

-----odie-----

 

[Kevin Jenness]

Odie, I would only add that sharpness is equally important with very soft woods and those like hemlock and Doug fir that are alternately hard and soft from growth ring to ring. I often work directly off the grinder and my turning tools are rarely as finely polished as my carving tools and plane and chisel blades for flat work, nor will the ultimate edge last for long at 30 mph, but keeping the tools up to whatever level of sharpness one needs for a clean cut is where it's at.

There are a myriad of opinions on how to get to "sharp" but it's the results that count. Paring softwood endgrain with little resistance and no scratches or crumbling is a good test.

 

[odie]

There are a myriad of opinions on how to get to "sharp" but it's the results that count. Paring softwood endgrain with little resistance and no scratches or crumbling is a good test.

Yes, I agree....it's a good test. However, there is no realistic comparison to woods that have high levels of Janka hardness.....along with grain patterns that are notoriously opposed to obtaining a perfect cut.

keeping the tools up to whatever level of sharpness one needs for a clean cut is where it's at.

Yes.....this is another truth that can't be ignored.


-----odie-----

 

[hockenbery]

I think soft woods and punky woods are a bigger turning challenge than harder woods.
harder woods will almost always allow shear scraping to improve a surface.
shear scraping often degrades the surface of soft woods so cutting gives the best turned surface on most of the soft woods.

edge presentation, bevel angle of the edge, sharpness, bevel pressure and feed rate all combine to get the cleanest cut possible on soft woods. Off on any and a poorer surface results.

 

[odie]

Hello Al......

I think soft woods and punky woods are a bigger turning challenge than harder woods.

Softwoods are debatable, as to how much they compare on an overall basis. Punky wood is another issue entirely.....well, if a sharp circular saw can't get a decent cut on punky wood, it doesn't matter how sharp your lathe tool is.....a clean cut is not possible, no matter how well the other components of the equation are applied.

harder woods will almost always allow shear scraping to improve a surface.

This it true to a point.....it depends on just how much improvement is needed. The hypothesis is conditional.

edge presentation, bevel angle of the edge, sharpness, bevel pressure and feed rate all combine to get the cleanest cut possible on soft woods.

Agree completely.....it is an equation where any one component can degrade, or completely nullify the possible result.


-----odie-----

 

[Doug Rasmussen]

Every poster has mentioned "sharp" or "sharpness". What exactly do those terms mean in your usage?

Does sharp mean a small included angle of the cutting edge as in a razor blade? A razor blade is a thin piece of metal ground such that the included angle is likely very small. Obviously you can't duplicate that in a turning gouge or can you?

Or, does sharp refer to the quality of the cutting edge where it might be finished with a super fine abrasive grit like 2000?

 

[odie]

Every poster has mentioned "sharp" or "sharpness". What exactly do those terms mean in your usage?

Does sharp mean a small included angle of the cutting edge as in a razor blade? A razor blade is a thin piece of metal ground such that the included angle is likely very small. Obviously you can't duplicate that in a turning gouge or can you?

Or, does sharp refer to the quality of the cutting edge where it might be finished with a super fine abrasive grit like 2000?

Good questions, Doug.

I can only respond theoretically, and the only thing I can use to support my theories, is the results I'm able to attain under difficult circumstances.

In my opinion, the very tip of the spear is what initiates the cut, and the angle behind the tip is only a minor contributing factor.....(given bevel angles that are commonly used with lathe tools.) The bevel angle of my gouges is entirely dependent on the overall grind shape I choose to use for the moment....and the sharpness is not dependent on the angle of the bevel.....it is dependent on the tip of that spear. (so to speak!) A 2000gt wheel in a single direction is probably not as capable of a sharp edge as a 600gt diamond hone applied in multiple directions. I don't know that as a fact, but in my opinion, it is. It would be interesting to compare the possible sharpness of the two edges by the results attainable in capable hands.

-----odie-----

 

[robo hippy]

Sharpness is one of those debates that will never end. The sharpness of bowl gouges, skews, and bench chisels and hand planes are all very different, we could throw in kitchen knives here as well. For gouges, that ranges from 60 or 80 grit like Mike Mahoney prefers, to 1200 grit which some prefer. For the bench chisels and plane irons, they go up to 30,000 grit stones and stropping. For sure, you want slower cuts, or slower 'push' rates for softer problem woods. I did find that with some punky maple, having 600 or 1000 grit surfaces and stropping really helped the cuts. Some times, just using a spray bottle to dampen the surface and using very light cuts to remove the damp wood will do wonders. Bevel angles come into play as well. Again, with Eric Lofstrom, he uses a 60 grit CBN wheel for sharpening his skews, a diamond card, 1000 or so grit to touch up that edge and then he strops the burr off. He gets glass smooth surfaces that way. Scrapers, having a more blunt angle, generally are more coarse for working edges. A 'mulberry' knife, which is a specialty slicing and dicing style of Chinese cleaver, supposedly for fine slicing of mulberry leaves for the silk worms, has about 30 degree or less included bevel angles, which is far different from a chopping cleaver, and a straight razor is more acute than that. I guess there is no end to variations..... More experimenting ahead...

robo hippy

 

[Marc Banka]

Just for reference, I‘m a bowl maker.

All of the factors, sharpness, presentation are important, clearly.
I think the included angle is really a big deal. Consider that when your tool cuts the wood,,the cut fibers have to bend away from the surface being cut. If it’s a sharp bend there will be more tendency to break them, pull at the fibers, which also tend to drive the bevel against the wood being cut. This is why tear-out happens with 50 or 60 degree nose angle gouges, and is almost unheard of with a 40 degree.

The keener the edge the better the cut (all other things being equal). Consider the differences between an ax and chef’s knife, 35 degrees vs 12, both sharpened to the finest the material can handle. The ax has to cut the fibers, then bend them back to expose the next fibers to cut, while the chef’s knife slides between the fibers with very little lift.

So, in consideration of my thinking, (I use a Wolverine 40-40 style grind) and the great suggestions to remove the heel of the gouge, I’ve modified my shaping/sharpening of my grind.
I set my jig for 40/40, then advance the v arm so that my nose angle is actually about 32 degrees and do my shaping (this is on my coarse wheel). Then advance another inch or so to grind away the heel. Then on my fine wheel, make my 40 degree bevel. It’s quite narrow, maybe 1/16”. (The next 4 or 5 sharpenings only require the fine wheel)

So, in use the keen 40 degree edge slices, and fibers bend but then clear that micro bevel and thereafter meet zero resistance.

Ive been using this gouge methodology for a year or so and am happy with how it’s been working. Doing things like natural edge bowls without ever knocking the bark off (knock on wood!) and just the ease and cleanliness at which it cuts.
Ive found woods like hemlock can be cut as cleanly as desert ironwood.

 

[Mike Novak]

This is super helpful.

My go to gouge is an Ellsworth style with 60 degree nose angle. I also have a 40/40, but mostly use that for roughing. I’ll try it for finishing.

I sharpen them on a Tormek clone with 220 grit using Tormek fixtures. That’s a long way from Odie’s 600 grit hand honing. I may try hand honing after grinding, but not sure I can manage that due to tremors. I can try honing on the leather stropping wheel with honing paste.

Next time I get to the lathe I will try slowing the feed rate first. Next try the 40/40. Finally, I’ll try honing.

Thanks for all the feedback

 

[Gabriel Hoff]

Just took a class from Matt Monaco Monday and we covered a lot about clean cutting and sharpening. The bevel angle is essential as is the the wheel grit it is sharpened on. The best clean cuts happen when the speed is really fast, a relief bevel on the tool to minimize vibration, and a good presentation of the cutting edge to the wood. Also the speed of cutting is important. I was able to get 220 grit like sanded surfaces. Of course pine is really crappy wood in my opinion!!

 

[Dean Center]

Nobody has mentioned depth of cut in preventing tear out. Probably because it's so obvious to all but brand new turners. I would state it as "to get the cleanest cut, you want a very shallow depth of cut, taking off just a wisp of wood."

 

[Gabriel Hoff]

Dean is right. Angel hair shavings, as my teacher says...

 

[Richard Coers]

Turning always improves after you sharpen.

 

[Mike Novak]

For this wood, honing the gouge on the leather wheel made the biggest improvement, but I needed to use every suggestion here to *almost* eliminate the tear out.

This piece was scrap for testing only. The only difference between the top and bottom is speed of feed. Top would need 150gt to clean it up, 250gt would work for bottom section. I don’t have a “before” picture, but no amount of sanding would have cleaned it up.

I turned some bowls with this when it was fresh and it was much more forgiving. Now that it’s been seasoning for a year it’s much harder to get good results.

 

[robo hippy]

Wish I could remember exactly what Eric Lofstrom said, but it was some thing like you can get clean shavings at both high and low speeds, but it is easier to get good/smooth form shapes at higher speeds.

robo hippy

 

[Doug Rasmussen]

Has anybody come up with a reasonable explanation why HSS turning tools need to be sharpened so frequently? Some turners mention re-sharpening in the middle of a bowl turning project.

It makes no sense. We use HSS tools to turn metal and plastics and they stay sharp a fair amount of time.. My wood planer and jointer use HSS knives and they don't require frequent sharpening. We use HSS in the milling machines with good tool life.

Back in a former life I owned an automatic lathe that was made to turn small parts like knobs and handles. It used knifes made of high carbon steel designed to do a complete part contour with a single knife using a peeling action on the work piece. We made knives out of thin auto leaf springs, heating them to form to the part contour then heat treating again. The knives could be used all day without need to sharpen.

 

[Brian Gustin]

Has anybody come up with a reasonable explanation why HSS turning tools need to be sharpened so frequently? Some turners mention re-sharpening in the middle of a bowl turning project.

It makes no sense. We use HSS tools to turn metal and plastics and they stay sharp a fair amount of time.. My wood planer and jointer use HSS knives and they don't require frequent sharpening. We use HSS in the milling machines with good tool life.

Back in a former life I owned an automatic lathe that was made to turn small parts like knobs and handles. It used knifes made of high carbon steel designed to do a complete part contour with a single knife using a peeling action on the work piece. We made knives out of thin auto leaf springs, heating them to form to the part contour then heat treating again. The knives could be used all day without need to sharpen.

My theory is, to quote Indiana Jones, "It's not the age, It's the mileage" - That plus the relative effective length of the cutting edge - Planer blades you got like 12 inches (or more) of surface , even hand planes at 2" , chisels as narrow as 1/8 inch... but how many feet does the planer actually cut (figuring linear feet) compared to the gouge on a spinning block of wood? Even hand planes and chisels , comparatively speaking insofar as the distance cut , have to be sharpened (more often that turning tools, actually) A Planer you might run 20 board feet through 20 passes (so perhaps 400 feet) , while a gouge on a say 6 inch diameter blank (using PI to find circumference figures to around 18.8 inches per revolution , so a foot and a half , 600 times a minute (at 600 RPM) , your gouge is cutting what 900 feet in a minute, compared to your planer cutting 400 feet... (in considerably MORE than a minute, I imagine) Likewise with a router bit despite them spinning at 18000 RPM, they still are not cutting as much linear feet of wood as a bowl gouge might.

Same question might be applied to why an HSS plane blade or chisel requires re-sharpening so much more often than a set of planer blades , but the answer there is, sharpness is relative - If your hand planes got as dull as your still-working-good planer blades, you'd have an awful hard time using your hand plane. There's Sharpness, which for powered cutter blades, don't need to be quite as KEEN as hand held blades - and then there's KEENNESS , which for precision fine cuts and butter smooth surfaces, you are gonna want them to be as razor sharp as possible - far sharper edges than any powered tool even really needs.

 

[Randy Heinemann]

Has anybody come up with a reasonable explanation why HSS turning tools need to be sharpened so frequently? Some turners mention re-sharpening in the middle of a bowl turning project.

It makes no sense. We use HSS tools to turn metal and plastics and they stay sharp a fair amount of time.. My wood planer and jointer use HSS knives and they don't require frequent sharpening. We use HSS in the milling machines with good tool life.

Back in a former life I owned an automatic lathe that was made to turn small parts like knobs and handles. It used knifes made of high carbon steel designed to do a complete part contour with a single knife using a peeling action on the work piece. We made knives out of thin auto leaf springs, heating them to form to the part contour then heat treating again. The knives could be used all day without need to sharpen.

Just think how many times a bowl rotates over the edge of a gouge in the course of turning, both rough and finish turning. And, from my experience with HSS gouges, it's not that the edge isn't still generally very sharp when the surface isn't as smooth as when you started, it's just that, to get the best surface, the tool must be really sharp. I sometimes don't resharpen until I get to the point I want to refine the surface and shape. Then is where a really sharp tool shines. So, maybe just to save yourself extra sanding, it's just worth it to get the tool edge just a little bit sharper before finishing.

 

[Randy Anderson]

In addition to the mileage we cover with gouges that pass by quickly, the abrasiveness of the wood makes a big difference. Some soft woods that one would think easy to work through can take an edge off after a few passes. I've been told the silica content makes a difference but no idea if this is even true. I just know I'm sometimes surprised at how a soft wood can take off an edge so fast. And yes, I know I likely take deeper cuts on softer woods so I'm adding fuel to the dulling fire.

 

[odie]

Has anybody come up with a reasonable explanation why HSS turning tools need to be sharpened so frequently? Some turners mention re-sharpening in the middle of a bowl turning project.

This is a very good question, in that it brings up the maxim that no matter what kind of steel, the edge begins to dull immediately.

Not only do I re-sharpen in the middle of making a bowl, I may not have enough fingers and toes to count the times I sharpen during the time I'm working on a bowl! .....and, believe it, or not.....this is an advantage, not a disadvantage!

An edge that lasts much longer is something hard to imagine being a disadvantage......but, since the edge will last longer, the point at which that tool needs to be sharpened becomes less clear and defined. Because of that, there is a lot of wasted effort using tools that could perform better if they were just a tad bit sharper. Remember, you can only remove wood once. Think of it as that one-and-only opportunity to have the best possible cut, and it's now gone forever! Then, the only thing you can do to remedy the situation is remove more wood.....or aggressively sand it into submission!

After experimenting with some of the exotic steels in the past, I have returned to using nothing but off-the-shelf tools made from M2 steel.....for all the reasons I mentioned above. There was a thread about this awhile back, and there was a lot of push-back from those extolling the virtues of their exotic steels. Some have a lot of money tied up in their investment of these very expensive tools, and it's understandable that they would be committed to them. (That's just human nature!)

The only thing that really matters, is the results you are able to get......not the intellectual debate!

-----odie-----

 

[Bill Blasic]

Odie this "The only thing that really matters, is the results you are able to get......not the intellectual debate!" is the only thing you said that really matters. I myself will always use my Thompson tools which stay sharper longer and spend less time at the grinder as the most important cut is the last one not all the ones to get you there. I guess you can say that's My 2¢

 

[odie]

Odie this "The only thing that really matters, is the results you are able to get......not the intellectual debate!" is the only thing you said that really matters. I myself will always use my Thompson tools which stay sharper longer and spend less time at the grinder as the most important cut is the last one not all the ones to get you there. I guess you can say that's My 2¢

Hi Bill.....hard to say how your comment applies, since you have no AAW member gallery or link to see your turnings. It's always an important reference to see another poster's work, so that comments have some yardstick by which to evaluate the information they put forth.

-----odie-----

 

[robo hippy]

You can rough out a lot with the M42 HSS or the V10 before it really needs sharpening, but you have to have that fresh edge for finish cuts.

robo hippy

 

[Bill Blasic]

Hi Bill.....hard to say how your comment applies, since you have no AAW member gallery or link to see your turnings. It's always an important reference to see another poster's work, so that comments have some yardstick by which to evaluate the information they put forth.

-----odie-----

Oooh I see I must have struck a nerve, Odie I have never felt the need to flaunt my work. What has been important to me is the over 50 published articles I have done to help woodturners. The hands on with noted woodturners who have taught in my shop for the last 15 years to help club members in the Tri-State area become better woodturners which continues again this year. And the new students I have taught who have become pretty good woodturners. I do have thousands of pictures of my work but those pictures won't help anyone turn better nor do anything to inflate my ego.

 

[odie]

Oooh I see I must have struck a nerve, Odie I have never felt the need to flaunt my work. What has been important to me is the over 50 published articles I have done to help woodturners. The hands on with noted woodturners who have taught in my shop for the last 15 years to help club members in the Tri-State area become better woodturners which continues again this year. And the new students I have taught who have become pretty good woodturners. I do have thousands of pictures of my work but those pictures won't help anyone turn better nor do anything to inflate my ego.

Hmmmm..... Just who is it that has struck a nerve, Bill?

Asking to see one's (current) work is not such an outlandish thing to request from those who contribute to a woodturning forum.

-----odie-----

 

[Rusty Nesmith]

I didn’t see it mentioned but for me at least direction of cut has a lot to do with it. For example if I cut from the tenon to the rim on the outside and the rim to the bottom on the inside I get very little to no tear out. If I cut the opposite directions I get a lot of tear out.

 

[odie]

I didn’t see it mentioned but for me at least direction of cut has a lot to do with it. For example if I cut from the tenon to the rim on the outside and the rim to the bottom on the inside I get very little to no tear out. If I cut the opposite directions I get a lot of tear out.

This is true for most commonly used straight grained woods, Rusty....

It's true for the majority of wood that we turn. However, when you introduce erratic grain patterns, such as quilt, burls, curls and such.....the rules tend to bend to accommodate the wood you are turning at the moment. The following is a drawing I made years ago that was inspired by a sketch John Jordan showed in one of his early videos. For the most part, it's best to stick with this plan, but as mentioned, sometimes going in a direction opposite to the sketch can produce good results.....and, that is dependent on the particular grain pattern you are dealing with at the moment...

-----odie-----