Honing Bowl Gouge - How / Why / With What

[John Tisdale]

I do large hollowforms - roughing the log is no problem - no problem putting a bit of pressure on the gouge for it to cut. That being said, honing would probably make this step more productive.
My issue is after I dry (usually down to 6% MC) - mesquites and walnut are hard and warp like crazy. Because most are face-grain, tear-out can be an issue if the edge is not pristine and the cut is not light. Add to that, my lathe speed on a 20"-dia is typically 300-rpm (400 tops).
I'm thinking I should be honing - would like to know how some experts do it. My thinking is a very fine diamond slipstone, in the gouge channel, always pulled away from the edge. A CBN fine grit slip stone, to my thinking, would be ideal - is there such a thing?
John

 

[Jeff Gilfor]

I am far from being an expert, but do hone. I will typically hone twice before touching the edge up on the sharpener.

I have the DMT card-sized diamond hones, both 300 and 600 grit.
I also have the D-way CBN honing stone. It comes 360 on one side and 600 on the other.

I actually use the DMT card more often, probably because the D-way hone is much heavier. Except for skews, the card is more convenient and easier to find the bevel.

Again, I'm no expert.

 

[john lucas]

I almost never hone my bowl gouges. I sharpen them on a 180 grit CBN and that has almost always been sharp enough. I do hone my skews and use the Trend 300/600 paddle hone. This is the same hone I use for my bowl gouges when I find the need. Most of the time when my regular grind bowl gouge is giving me tearout I switch to a Stewart Batty grind that has a 40 degree sharpening angle. My usual bowl gouge has about 50 degree. If for some reason the 40 won't let me rub the bevel then I switch to a Hunter carbide cutter. That usually solves the problem.
I will often hone the inside flute of my bowl gouges using a cone shaped diamond hone that I also got from Trend. I find that quite often a quick swipe with this will work and I don't have to hone the outside of the flute. My gouges are ground with a very small bevel as the main bevel and it makes it somewhat difficult to keep the diamond hones flat on that bevel. I can still hone but it's really easy to round the edge a little, which is why I hone the inside most of the time.

 

[Jeff Gilfor]

Just curious John; you say that you gouges have a very small primary bevel. Many folks (myself included) grind a secondary bevel on gouges to allow more access to tight spots in work while still engaging the primary bevel and not crushing wood fibers with the heel of the tool steel.

What is the reason for having a very small primary bevel, rather than say a 60% primary and 40% secondary bevel (with regards to the entire sharpened surface of the gouge)?

 

[Bill Boehme]

Primary? Secondary? Tertiary? Warping ...

I turn lots of mesquite -- some green and some dry. One thing that I really like about mesquite is its stability. If I turn something green, I can go to completion with barely any warping when the piece is dry. Sometimes for things like lidded boxes, it is necessary to rough turn green and then let it dry before finishing. It is very hard when dry and makes a lot of noxious dust, but it has beautiful figure and is extremely stable. I have almost no experience with walnut, but I wouldn't be surprised to learn that it warps more than mesquite since almost everything except Corian[SUP]®[/SUP] does.

I am very surprised that you are having tear out on mesquite. Your statement, "no problem putting a bit of pressure on the gouge for it to cut" gives me a bit of concern. Perhaps if you explained what you mean because it sounds to me like you are saying the tool doesn't cut until you apply pressure.I don't hone and my gouges cut with a feather light touch to the wood. If the wood is green, I can get long streamers of wood with just a feather light touch. It might be a tool sharpness issue or it might be how the tool is being presented to the wood. If you are getting lots of tearout then it sounds like you might be scraping rather than cutting.

About the discussion on bevels, I wish that folks would clarify some of these terms rather than assuming that everybody automatically knows what they are talking about -- primary and secondary doesn't tell me what you are referring to.

I'll start with my perception of a bevel. To me a bevel is the surface on either side of the cutting edge although in woodturning we generally refer only to ground edges and not the inside flute on gouges. Everything else is just metal that is removed for convenience of using the tool. I have a couple gouges with the type of grind that Johannes Michelsen uses for turning hats. The bevel is approximately 1/16 to 3/32 inches wide. The tool started off with a more traditional swept back grind similar to the Ellsworth grind where the bevel was about 1/4 to 5/16 inches wide. But once the tool has been modified to the Michelsen style grind, the previous bevel is no longer a bevel. Johannes goes one step further -- the "heel" of the old bevel gets removed because it interferes with working in close quarters. The bottom that gets ground away and then rounded over isn't a bevel either. The end result is that very little of the old "bevel" remains. Since it no longer has any relevance to the cutting edge I wouldn't refer to it as a bevel.

Even though I think that one is enough, I have no issue with someone using the terms primary and secondary if I knew which was which. I'm not clear if the primary one is doing the cutting or if the secondary bevel is the cutting edge.

 

[hockenbery]

Because most are face-grain, tear-out can be an issue if the edge is not pristine and the cut is not light. Add to that, my lathe speed on a 20"-dia is typically 300-rpm (400 tops). John

Your hollow forms are impressive!

Face grain should not cause tear out if the cut is made rim to widest part and foot to widest part.
A face grain HF is like two bowls joined at the rims. The one on the top has a hole in it.

I do face grain hollow forms and face grain bowls. My hollow forms are single turned and much smaller a few 17" diameter most 10-14.
I have done a few 20 inch bowls I don't get tear out turning the outside in a twice turned bowl. Turned quite a bit if walnut.
Never turned mesquite. Have turned some dried Osage orange bowls it is a hard hard wood. (Bodark in some parts)

Light cuts, bevel riding. Sharp tool. A push cut and a shear scrape is usually all that is needed to get a smooth surface.
Turning at the rim and foot are easy because the form should be almost round. Turning at the wide part gets difficult because of the interrupted cut. The two end grains are cut first. A heavy cut here will tear the back side of the endgrain. As the tool cuts through the end grain a tiny part of the cutting component is up while most of the cutting force is toward the headstock or tailstock. In the small cutting force in up direction the last of the end grain to be cut has no fibers behind it to support the cut so it gets bent over or pulled out. Light cuts, sharp tool, bevel riding keep the handle locked against your side so the tool cannot feed over the tool rest when it is cutting air.
The difference in end grain diameter to side grain diameter is more in larger forms. Patience, light cuts, bevel riding.sharp tool.

In highly figured wood tear out can happen as the grain twists and some grain gets lifted because it goes opposite the way the rest of the grain lies.
I use a side ground gouge and usually a pull cut with a high angle will cut problem grain cleanly and a shear scrap cleans the surface nicely.
In the pull cut the wing has a bevel angle of 25-30 degrees and the cutting edge is presented at 45 to 80 degrees to the wood it is similar to using a skew with the nose down.

I use my gouges fresh off a 60 grit wheel no honing.



Al

 

[john lucas]

Yea I guess sometimes I write what my brain is thinking without thinking that other people won't have any idea what I'm saying. I actually have 3 bevels to my bowl gouges. What I call the main bevel is the one that comes straight off the grinding wheel with the Wolverine jig in the normal position. then I move the Wolverine jig forward and grind a secondary bevel below the first bevel. This one shortens the first bevel to about 1/8" or so. Then I remove the gouge from the jig and grind a 3rd bevel below the first 2. This one is simply to get rid of the sharp corners at the bottom of the secondary bevel and to remove metal from the bottom of the gouge to give me better access into some cuts.
The very short 1st bevel for me is sort of a cross between a regular concave grind and convex grind. The perfect grind for inside a bowl would be convex so that the metal supports the cut right behind the cutting edge. On the outside of a vessel the short bevel works really well in supporting the cut. The short bevel works more like a convex grind on the inside of the bowl. The shorter bevel also has less friction so I think I can "feel" the cut better and therefore less chance of pushing or forcing the cut. I theory it would take less effort to hone a short bevel because you remove less metal but most people probably only hone the very tip of an edge anyway.
Here is a photo of what my grinds used to look like. They are still pretty similar except the main bevel is far shorter. The grind I use most often is the second from the top and the one on the bottom.

 

[Jeff Gilfor]

After cutting for a while, even with the newest vanadium alloys, the edge of your gouge gets... Well... For want of a better term... Junky. I'm basing this statement on looking at the edge through a microscope. This isn't obvious unless you compare a fresh sharp gouge with one that has been used a while. There is probably a continuous degradation of the "feel" of the cut until you say to say to yourself, "time to resharpen." Obviously, the edge isn't razor sharp, and then all of the sudden becomes dull enough to require a trip back to the grinder. Our brains assign a set point, beyond which we feel the gouge is dull enough to resharpen, and before which we don't seem to mind. This. Despite that fact that the edge becomes ever duller with each inch of wood cut from first to the one that makes us resharpen. This set point is different for each turner, and is constantly being readjusted, based on experience and time pressure.

Anyway, this is going to be one of those things that will NEVER be an inviolate "law" of woodturning. Some folks like to hone, some do not. I can prove that it freshens the edge of my gouges when I do it, and saves me a trip to the grinder. I can tell that my tools cut much better afterwards, but the edge doesn't last as long as after a full sharpening pass on the grinder. Still, I do it, because it saves me some time, and allows me more time at the lathe.

Not right or wrong, and I will probably change my mind about this whole discussion next week, or next year. I have a strong suspicion that that is how one's woodturning "skills" evolve.

 

[Odie]

I do large hollowforms - roughing the log is no problem - no problem putting a bit of pressure on the gouge for it to cut. That being said, honing would probably make this step more productive.
My issue is after I dry (usually down to 6% MC) - mesquites and walnut are hard and warp like crazy. Because most are face-grain, tear-out can be an issue if the edge is not pristine and the cut is not light. Add to that, my lathe speed on a 20"-dia is typically 300-rpm (400 tops).
I'm thinking I should be honing - would like to know how some experts do it. My thinking is a very fine diamond slipstone, in the gouge channel, always pulled away from the edge. A CBN fine grit slip stone, to my thinking, would be ideal - is there such a thing? John

For what it's worth, John........

I've been using the diamond hones, several brands from CSUSA. They work, and work well......after all, the diamond is the hardest thing known, so the obvious conclusion would be that it would work well for this purpose. I've used Trend, EZlap and DMT brands. The DMT cone hone is the best usable shape to do the flutes of bowl gouges, but seems to be the worst for durability. The powdered diamonds don't seem to be bonded to the surface as well as the other brands, and I've worn out a couple of these in the past. The EZlap seems to have the bonding process down pat, but they only offer flat surfaces.....not much help with the flute, but great on the heel of the grind. The Trend has one half round diamond file that appears to be doing well, but it's not my "go to" for inside the flute. The flat side of the Trend seems almost worthless, but the rounded side works fairly well. The DMT cone shape works so well for my flutes, that it's hard for me to consider another shape.......darn that bonding process that wears out too soon, though. I try to keep the cone flat to the inside of the flute while stroking and twisting the tool on the axis......really works well for me, and this is the only one available in this particular shape.

The folding handle of the DMT is also worthless for my needs, as well. I've been removing the "butterfly style" handle, and simply mounting it onto a dowel......this is what works for me. This DMT cone shape only lasts for several years, before I need to replace it.....and, I'm almost ready to buy another, darn it! We use a flat diamond coated slow speed disc for sharpening carbide where I work. These discs last far in excess of the kind of use I put the DMT cone through......so, I know for sure that DMT just doesn't have it's act together yet for their bonding process.

 

[robo hippy]

Well, maybe I never did it right, but I don't hone. I have never noticed that it did any more to the edge then my CBN grinding wheels. I have been using them for maybe 10 years now.

robo hippy