How do you sharpen your edges?

[Kees Heiden]

I wonder about the accuracy of these measurements. It ain't easy to measure things so small!

(in this post um is micrometer. I don't have a mu on my keyboard).

First, the micrometer being used. Most of the Mitutoyo micrometers, even the most expensive digital ones with a 0.001 mm resolution have an accuracy specification of +/- 1 um or worse. So the fabled 2 um shaving could be somewhere between 1 and 3 um or worse.

Then you have the handling errors. Temperature must be controlled very carefully. Just holding the micrometer in your hands for a few minutes creates errors of several um's. Holding it upside down or horizontal, has influence too

And then about the measured shaving itself. Humidity has a direct effect on the thickness of the shaving. Imagine a hall full of people, the difference between the early hours and later in the afternoon? I don't know how large the effect is, but it could be substantial. Think also about dust. Planing is a dust creating exercise, so things need to be cleaned carefully before any measurement.

When the competition is fierce, winners and losers divided by a mere um, then the measurement technique becomes very important. And I think it is even harder to compare the results from one competition to the next.

I would presume this is a hotly debated subject on Japanese planing contest forums! (if such things exist).

[Patrick Chase]

I wonder about the accuracy of these measurements. It ain't easy to measure things so small!

(in this post um is micrometer. I don't have a mu on my keyboard).

First, the micrometer being used. Most of the Mitutoyo micrometers, even the most expensive digital ones with a 0.001 mm resolution have an accuracy specification of +/- 1 um or worse. So the fabled 2 um shaving could be somewhere between 1 and 3 um or worse.

Then you have the handling errors. Temperature must be controlled very carefully. Just holding the micrometer in your hands for a few minutes creates errors of several um's. Holding it upside down or horizontal, has influence too

And then about the measured shaving itself. Humidity has a direct effect on the thickness of the shaving. Imagine a hall full of people, the difference between the early hours and later in the afternoon? I don't know how large the effect is, but it could be substantial. Think also about dust. Planing is a dust creating exercise, so things need to be cleaned carefully before any measurement.

When the competition is fierce, winners and losers divided by a mere um, then the measurement technique becomes very important. And I think it is even harder to compare the results from one competition to the next.

I would presume this is a hotly debated subject on Japanese planing contest forums! (if such things exist).

Don't forget surface deformations and compressibility. The shaving isn't perfectly flat when it comes off the plane, which will tend to inflate the measurement. If too much force or too small of a head (~too much pressure) is used to try to flatten out the shaving (for example a ball) then the wood may compress, which will reduce the measurement. IIRC for Kez they use a single micrometer/head combination with pressure supplied by gravity and a fixed mass to normalize those effects. There's no telling what somebody might be using in their own shop for bragging rights though.

The thermal issues can largely be dealt with by zeroing immediately before measuring, and also by measuring a reference (or nothing at all...) before/after the shaving measurement. If the reference measurement drifts then the shaving measurement is invalidated. There are also some design features that can be used to make thermal drift largely self-cancelling within the micrometer itself (trust me, you do not want me to go there [*]) but I have no idea how the ones they use for Kez are in that regard. Again there's no telling what somebody is doing in their own shop.

I wonder if yellow cedar is reflective enough at some multi-micron IR wavelength[s] to make an interferometric measurement (i.e. measure the distance from front to back surfaces by looking at relative phase of their reflections)...

[*] OK, I'll go there. Here's one that everybody learns in their E-school advanced design course: The head of the micrometer is basically a "C" shape. You can cancel thermal expansion by making the C as a lamination of two materials with different thermal coefficients, such that the one with the lower coefficient is on the inside. The result is that the C "curves in" as it expands, and the points remain the same distance apart over some range of temperatures. There are more involved techniques as well as thermal calibration/compensation schemes (i.e. ones that allow drift to happen but correct the measurement), but you get the idea.

[Patrick Chase]

Delayed re-reply, but there's one point that I think is key here.

It's certainly a bizarre but highly entertaining form of woodworking. Interesting enough the surface finish is typically incredible. This is the surface finish on my test beam, during competition the beam reflected similarly. I recall having commented to some of the spectators to have a look at the reflection in the beam to provide some relevance to a real life purpose for this sort of competition. You're in northern california so actually getting wood like this is pretty easy to purchase, from what i've heard, with respect to your area. Either this or port orford cedar.

I don't doubt that planing a la Kez leaves a terrific surface. I don't think you could do otherwise while pulling a cohesive shaving that thin. There's simply not much margin for surface profile variation before the shaving parts and you DQ. Put another way, I think that "Kez planing" is definitely sufficient to get good surface quality, but I question whether it's necessary. Is the residual surface really that much better when you pull, say, an 8 um shaving versus a 20 um one?

FWIW I don't see much if any difference between 0.5 mil and 1 mil (13 and 25 microns respectively) in my own work.

[Frederick Skelly]

You guys are being ENGINEERS again!

[Patrick Chase]

You guys are being ENGINEERS again!

I can't help it. It's an incurable disorder. Besides, it pays for my tool acquisition syndrome.

[Brian Holcombe]

I agree with Patrick, zero the mic. The mic specifically used for Kez is one in which the operator has little influence so whatever the ultimate factors are they're consistent between competitors in a single competition.

At 2-3 microns the shaving would have to compress considerably to effect the measurement.

[Kees Heiden]

I guess they know what they are doing. It's a difficult thing though, at such a small scale weird things happen.

[Patrick Chase]

I guess they know what they are doing. It's a difficult thing though, at such a small scale weird things happen.

See this video (picked at random) for an example. A couple things of note:

1. The operator actuates a lever to open the gate so that shavings can be inserted, but actual measurements are taken with his hand off of the micrometer assembly, such that normal force is provided by gravity alone. This means that pressure interactions (flattening, compression) should be consistent between competitors.
2. The operator is super-careful about cleaning the micrometer after every measurement. He's doing so to address a source of error that I forgot to list: Stray wood fibers and/or dust. When you're down in the microns that starts to be a factor, as a stray fiber laying on the micrometer head could create locally high pressure and compression (i.e. it could create inconsistency even if it were there both both for zeroing and for the actual measurement by changing the geometry of the micrometer's contact area).
3. It appears that he is indeed zeroing between measurements. He doesn't appear to be doing before/after reference measurements to verify stability. I expect that would be unnecessary once the micrometer is equilibrated to its environment.

Fun stuff. Totally unrelated to woodworking as we know it, but fun nonetheless :-).

[Bill McDermott]

This is fun. It's the quintessential sharpening thread.
Anyone see the "Sharpen This" sticker, and follow the back story. Crude but apropos.

I have a set of floor tiles with Lee Valley and Otto Frei films. Most blades come off the course, dry, 8" grinder and then go into a Veritas honing jig. I used water from a spritz bottle to keep the film clean. I have a series of tiles ranging from 100 micron to 0.3 micron. I move through various grits to get what I need for the purpose. That stuff is simply astounding how well it works and how long it lasts. Far superior to sandpaper, IMHO.

I use DMT DuoSharps followed and a black Arkansas for curved blades.

I use green aluminum oxide on leather for all sorts of things all the time. That strop probably sees more action than everything else combined.

[Patrick Chase]

I have a set of floor tiles with Lee Valley and Otto Frei films.

LV and Otto Frei both resell standard 3M catalog items. There are some cases where one carries something the other doesn't. For example Otto Frei carries coarse-grit 3M 675L diamond microfinishing films, while LV sells finer grit 668X diamond lapping films.

[Mike Baker 2]

I use a couple of different methods, depending on the situation.
If I have to reshape a bevel, straighten an edge on a chisel, etc., I use low grit sandpaper on plate glass. 60/120 grit.
For initial sharpening of tools, a medium Norton India, followed by a Soft Arkansas, then a good piece of Slate, and then to a chrome ox pasted strop.
While working, I keep a 400/1k combo diamond plate and that same crox pasted strop nearby for touchup, although, if I stop and strop as soon as I notice any drop in sharpness, I seldom need anything but the strop to keep going all day.
I also occasionally go from the Slate to 1 um(one micron) lapping film, and then to the strop with good results.