Sharpening

Such people may exist, but most of us go straight from grinding, or perhaps power-honing, to cutting, and back to griding, and back to cutting...it's possible, but would be very tedious.

Fiddling with the perfect edge is an idea that does not survive too long when you need to cut wood in a reasonable fashion - you'll cut more distance in 5 minutes turning that you will in a month of hand-paring with bench chisels, which should explain why most of us do not typically use slow fiddly methods to get the ultimate edge on lathe tools. Fast methods to get a near-ultimate edge are far more effective in getting work done...

I'm probably in the minority, but I have a couple of tools that I stone the edge for. This is after using a file, sandpaper, coarse/fine hones, then a ceramic "stone" for the final edge.

Of course, I use these tools so infrequently and for such a short period of time that I don't mind the time or effort in keeping in practice with the old-slow methods.

Personally, I seldom grind and tend to do touch-up honing with a diamond hone from DMT. Two of them, actually. I have a medium grit bench stone and a medium and fine grit folding stone. I take a couple of minutes with that and even my ASP 2060 tools are shaving sharp.

Arkansas stones are nice for knives, but cut entirely too slow for me to want to try to hone my turning tools on them.

-- Chuck *#:^) chaz3913(AT)yahoo(DOT)com Anti-spam sig: please remove "NO SPAM" from e-mail address to reply. <

September 11, 2001 - Never Forget

I have found that the US made diamond fine Eze lap LF model very affordable for honing. Re- honing: The ground edge under a microscope is like lots of sharp icicles or fine points. Innitially this seems sharp but very quickly the points break off and the edge loses its keeness. When you hone the edge (under a microscope) looks like a gentle rolling wave and is much stronger and will last longer. In my opinion, comments welcome.

This is why it is important to have a hollow ground bevel on your tools, to enable the hone to touch only the heel and the extreeme cutting edge of the tool when applied. Re grinding must take place from time to time. If you sharpen on a belt or side of the grinder then honing is not as effective because the flat surface when honed produces a convex bevel which I nick-named a rock & roll bevel. Then the cutting edge of the tool is hard to define when applied to the wood. This is particularly noticable when using a skew but the same applies to a gouge when looking for a high level of finnish off the tool. "SANDING SUCKS THE LUNGS"

Hope this is of help Also the tool lasts longer honed

-- Cheers Ken Port Tool Designer

Sure, Ken. I'll comment.

Take your douzuki and crosscut with it. Smooth, isn't it? And even with those fragile, long teeth, it'll do it over and over

Now pull it sideways across your board. Looks like hell. Not to mention if you press a bit you'll bend and rotate some teeth.

That's why cutting angle is more important than honing.

I've seen this analogy before, and while it may seem to offer simple wisdom, it really isn't a proper representation of the geometry involved with turning tools.

If you examine a those japanese teeth, you will see that the geometry is such that the base of the tooth is much wider from front to back, than from side to side. The dozuki tooth is really not all different in geometry from a turning tool, except that it is comparable to only a narrow cross section of a turning tool edge. But along that cross section, there will be similar bevel angles and similar buttressing behind the cutting edge. The only place where crosscut (but not rip) teeth differ is that they are angle which is the "set" of the tooth.

From side to side, the tooth does not have the same geometry, indeed at the front of the tooth, the angle to the side is actually negative (i.e., like \--- rather than like /--)with respect to the body of the tool as a result of the set on crosscut blades and is verticle {i.e. |--) on rip tooth blades. There is not buttressing behind the tooth. So yes the tooth is weaker in this direction, but solely due to the nature of the geometry, a geometry that is not in any way comparable to a bowl gouge.

When it comes to cutting, the reality is that a more coarsely ground edge does not have teeth in line like a comb. Rather the are offset along each of those grooves you can see/feel from the coarseness of the grit. The finer the abrasive material, the less the offset, and the less the teeth are exposed with less buttressing. Honing lessens the amount of displacement by making smaller, more shallow grooves and leveling off the greatest areas of displacement.

Accordingly, Ken is right in his description. There are lots of objective tests that have demonstrated that a honed edge, for a given geometry and cutting angle, will be a longer lasting edge. I personally don't care if you hone or not, if you are satisfied with the results of your sharpening, that's all that counts for you. But objectively, a properly honed edge will make a cleaner cut and will last longer.

Lyn

George wrote:

Thanks Lyn J Its a shame some people take these things as a personal affront. It can be discouraging to people like myself who are just trying to give genuine professional advise with the view of dispelling some of the myth surrounding our trade. This is where your in depth explanation is most helpful by comparison to my quick simple summary (mainly because I don't have the talent you do Lyn

-- Cheers Ken Port Tool Designer

Good opinions and discussion, Ken & Lyn. I reckon one turner's myth is another turner's gospel. I didn't see any personal affront taken nor desire to discourage a professional opinion. Whether professionals or amateurs or we unwashed in betweens, all our posts are a bit of self embellishment, aren't they? ;) Arch

Fortiter,

White smoke, and the return.

Oh, yeah, you're incorrect.

"When you hone the edge (under a microscope) looks like a gentle rolling wave and is much stronger and will last longer. In my opinion, comments welcome. "

Ok, comments _favoring_ would have been welcome? You should have said so.

One quick try to twist your thinking a bit. Let us say we come off a 120 grit stone - scratches on average 102 microns. Broadside on, we can do no better than 120. If we take the same length of gouge in contact with the wood and rotate it 60 degrees from the horizontal, we've got the equivalent of 240 grit, with the numbers increasing very rapidly as we approach the vertical. Now, if we assume a gouge, we can actually have the leading edge - the attacking point - vertical, with the bottom of the gouge trailing away. At that point all the individual fibers see is the thickness of the edge, not the projections, and in a macro look, we're running maybe a 1000 grit.

As to strength, the process of honing, unless you are honing to increase the included angle (microbevel), actually makes the edge thinner by removing the high points. This makes a nice sharp edge, but one which may be broken by impact with harder sections or inclusions in the wood, and more likely to anneal because of reduced heat sink capability.

In my opinion, and I'm willing to say it is my opinion, the critical factor in removing wood "as it wants to be cut"on the lathe is the cutting angle, not the grit of the final hone, and for the reasons given. Not to mention the loss of time when honing. Deburring perhaps, one quick new edge with a diamond stone even, but certainly nothing near what I do to my carving tools or even my planes.

Well George, I wrote a fair number of lines detailing exactly why your analogy was incorrect, and tried to do so in a sincere and polite manner. In the end, the turners out there can read both and make their own judgment.

Lyn

George wrote:

I invite George and other turners to draw a few lines along their own gouge in the direction of their grinding marks and then look at the gouge as it is presented to the wood in the positions they use it to turn. The fallacy the of the above will be evident from this experiment along. But it really does not end here. George's example is basically based on a two dimensional model, while in reality the offset of the cutting points left from grinding occurrs three dimensionally.

Actually removing "high points" alone would make the edge more blunt. Refining the surface by honing, when done at the same angle (i.e. maintaining the same geometry) will in fact make the edge no thinner nor thicker at any given location. That is, the "planes" (i.e., the plane of the internal wall of the flute and the plane of the external wall composing the bevel) will meet at the same angles and offer the same geometry at a given point. Where things differ is that the points of a ground edge are not in a linear line due to the grooving of the abrasive grit. How far they are off linear will be determined by the coarseness of the grit, i.e., the depth of the grooves. Finer grits will leave shallower groves that result in a more linear edge, but the geometry will stay the same if the original angles are kept the same (and thus the same amount of buttressing of the edge at any given point).

V V V V V vs v v v v v v The actual difference is greater, but V V V V V v v v v v I can't reduce the line spacing for the

second narrower set. A sharp edge (where the planes meet directly and consistently along a line) is always desirable because it will, for a given geometry, generate less resistance to the cut and the points will be better buttressed by being closer together along that line both in terms of width and length.

Lots of things are significant factors including cutting angle (i.e., the angle of presentation of the edge to the wood), geometry of the cutting edge, and refinement (I actually prefer this term to "sharpness" as I think it more accurately describes the process and effect) of the edge.

In the end though, I would again say that there have been several empirical studies of edge life, and all have shown that the more refined (i.e, sharper, honed) edge lasted longer and cut cleaner longer. Thats not opinion, but rather impartial findings. One of the best of these studies was done in Britain and the other two have been done in the US. I have confirmed this, Steven Russell confirmed this, Fred Holder has commented on it and Jerry Glaser himself hones his personal gouges and has remarked on the desirablility of a very sharp edge and uses an EZlap or diamond paper on wood stick hone for his personal gouges. As I said before, it is up to every individual turner to determine for themselves if the advantages of a more refined edge are important to them, but it is really quite clear that when measured comparisons are made, the more refined edge will last longer and cut cleaner.

Lyn

BTW, has anyone used the new honing grinder with the plaid wheels and built in microscope, jig and bidet? Tools are said to be so sharp that the included angles meet at infinity. Arch

Fortiter,

Hi Arch, Just got the new model a few weeks ago. I immediately set to work on a multi-tool, multi angle investigation to determine the proper orientation of the plaid. As has been hinted at by others, the correct orientation of the tool to the plaid lines is the crucial factor in performance. If I get a chance, I'm going to try to come by finer and finer plaids (which is where the microscope will really come in handy). I figure that if I can get down to .5 micron plaids, the real benefits will come to the fore.

It will take me a while to get that testing out of the way, but then I hope to move on to varying the colors of the plaids. Tartans, etc. I have a suspicion the proper Scottish plaids will do best for the O-Donnell grind, but perhaps not so well for the Celtic grinds. Probably won't make any difference on the Jordan or Ellsworth grinds, but I'll try to write up the findings nonetheless. I was hoping I might be able to entice you into serving as consultant on the appropriate tartans.

The jig really is essential, and the rate of carraige action is almost sure to be the deciding factor, but I don't think I will know for sure until the influence of the earlier two variables are clearly defined. Actually the Scottish influence comes through here as well, making me suspect that the manufacturer is revealing a bloodline not particularly consistent with their surname.

Anyway, I sure you can appreciate that after this near herculean researh endeavor, the need for the bidet becomes quite apparent.

Lyn

Arch wrote:

Hi Lyn, Touche! ROTFL while I await your expose. Arch

Fortiter,

Too funny Lyn!! I think you've been hanging out with Arch too long... ;)

Peter Teubel Milford, MA

Wonderful response Lyn. Glad you're back in the groove.

Fred Holder

Lyn,

Actually, the feed sack burlap weave works best for the Appalachian-American grind I prefer

John Jordan