Micro-Bevel on Japanese Chisels

[drhuntsman]

Just received the latest copy of FWW. It has a section on Japanese chisels, and how to sharpen, etc. It mentioned that you should not put a micro bevel on Japanese chisels due to the type of steel and that the edge will not hold.

I am relatively new to Japanese tools, and wanted to hear what others have heard, done and recommend.

Thanks, Darrell

[Koot]

I am relatively new to Japanese tools, and wanted to hear what others have heard, done and recommend.
Thanks, Darrell

Chris did a series on his blog you'll find interesting.

http://thecarpentryway.blogspot.ca/2012 ... -test.html

Marv

[drhuntsman]

Chris did a series on his blog you'll find interesting.

http://thecarpentryway.blogspot.ca/2012 ... -test.html

Marv

Thanks - I spend all of my time on the study group site, I did not realize all of the great info on the blog.

[Chris Hall]

Hi Darrell,

I didn't read the FWW article, however if they stated the reasons for not putting a microbevel on a Japanese chisel are "due to the type of steel and that the edge will not hold", then they are wrong on both counts. The reasons for putting microbevels on a tool are simply as shortcuts to obtaining a workable sharp and durable edge. Most of what you will read in the popular magazines surrounds such things - neat tricks and 'shortcuts', how to do 'x' in no time at all, 'marquetry for dummies', how to do 'x' in the "quick and easy way", etc. Attractive, but I'm afraid really good skill does not arise from habituation to shortcuts.

A lot of people, I have noticed, are quite averse to sharpening. I have worked in several woodworking and carpentry shops, and my current shop is in a building with three other woodwork businesses, and I have rarely (well, never, actually) seen people who can sharpen or who have sharp tools other than new sawblades and router bits they have purchased. I have never seen people with sharp tools, and who know how to sharpen, even like to sharpen, outside of my time working for Eastwind in California. It's kinda sad.

So, with so much aversion to sharpening out there, it is no surprise I suppose that when sharpening methods are proposed they are generally along the lines of making it as painless and quick as possible. It's too bad, as I really think that getting savvy with sharpening is a great way to get savvy with your tools, and improving your woodworking. Tools, after all, exist in a relationship with one medium (wood) in which the interactions are characterized by the wood being sliced away rapidly and the tool losing steel slowly (hopefully!), while with sharpening it is the opposite case in that the medium (stone) is losing material somewhat slowly and the tool losing material somewhat more rapidly. In both cases, presenting the blade edge precisely to the medium is a key factor, and unless you plan to have your chisels operated exclusively by jigging, it is a helpful skill to sharpen freehand, as freehand is how the chisel is to be wielded most of the time.

Critical as well to the stone-steel-wood interplay, for most joinery work at least, is keeping each part of the equation flat as you proceed. A flat stone makes a flat edge, and a flat edge can make a flat surface on the wood, say when paring a tenon shoulder, etc. Paying attention to how sharpening affects both tool and stone flatness is no different than paying attention the relationship between tool and wood in trying to achieve a crisply cut surface.

One common approach to shortening the sharpening process is to use a grinder and hollow out the face of the bevel. That way, when running the bevel over a stone, the stone is only working two small areas of material on the tool, and thus getting to a sharp edge can happen quickly. In that sense, hollow grinding is not much different that the Japanese practice of hollowing the backside, or ura, of their edge tools to make them easier to sharpen. The problem with hollowing the bevel though is apparent when sharpening thin chisels - you take away a lot of support for the tool's edge, and this makes the edge more liable to deflect and probably chip.

I don't hollow grind any of my tools - don't even own a grinder. If I drop a tool on the concrete and badly damage the edge, I then must spend a good long time on coarse stones repairing the damage, and this sort of experience tends to reinforce habits that greatly reduce the opportunities to drop tools onto concrete, if you catch my drift.

The practice of placing a microbevel or secondary bevel on the tool is also to limit the area of the tool in contact with the sharpening medium so that the sharpening happens more quickly. Also, a chisel which has poor edge-holding retention can be improved by grinding the tip of the tool a steeper bevel angle. The problem with the microbevel approach, as I see it, is that it tends to make the edge geometry imprecise over time and makes one ever more dependent upon a jig to produce sharpening results. If an edge on a tool chips too easily, then steepen the entire bevel. Do it until the edge holds up. The tricky thing is when working a diverse range of woods. If you jump back and forth between pine and wenge, say, the tool geometry requirements are quite different. Pine will pare best with an acute edge, while wenge will require a steeper edge. So, unless one wants to have several sets of chisels, one dedicated to softer woods and one dedicated to harder woods, (not a bad idea at all, though not inexpensive), then one has a choice between setting up a chisel for an 'average' condition, so that the tool will be a little less than ideally acute for the pine and a little too acute for the wenge, or one must make continual changes to the bevel with secondary bevels, microbevels, etc.

I have found in practice that a good quality chisel will perform well in most conditions and have rarely found the need to mess around much with fiddling the bevel angles of chisels. A Keep It Simple Stupid approach has worked for me - a flat bevel, kept flat. It's something you learn to do by doing. Just as with a bicycle, if it helps to have training wheels for the first little while to get you muscle patterning used to the process, by all means get yourself a sharpening jig/gizmo. In time though, just like with a bicycle, you will want to discard the training wheels and roll on unhindered.

One of the challenges with learning to sharpen Japanese chisels is the composition of the tool having a hard cutting steel and a soft backing iron - when sharpening freehand it is rather easy to remove the soft iron more quickly than the hard steel, and thus easy to make the chisel bevel more acute with each round of sharpening. So, it is helpful to keep an eye on that sort of thing and have a bevel gauge set up to check your bevel angle. For striking chisels, a bevel angle of around 30~33˚ will work well, for paring chisels an angle of 25~27˚ works well. Once you get attuned to that tendency while sharpening, just as with a tendency one might have to sharpen the chisel with more pressure on one side than another (thus making the cutting edge non-90˚ to the side), observation and compensation will eventually steer you into consistent desirable results.

[drhuntsman]

Wow, very thorough and helpful insight. So what I did:

I do not own a grinder either; I never had the desire to get that aggressive with my tools.

Flatten the Back:

• Round 1: I use the DMT diamond plate at 1,000 grit
  Round 2: I use the Shapton Glass at 1,000 grit (not sure of of the actual difference between the two, but it makes me feel better)
  Round 3: I use the Shapton Glass at 4,000 grit
  Round 4: I use the Shapton Glass at 8,000 grit
  Round 5: I use the Shapton Glass at 16,000 grit

I flatten the stone with Shapton's diamond lapping plate (probably more frequently than needed) after I get a nice build-up of gray matter on the stone.

This gets me a nice mirror polish on the back about 1.5 - 2 inches from the cutting edge.

Flatten the bevel:
I keep that same angle that came from the manufacture.
I use Veritas MK II jig (I am just not confident yet, in my ability to hold a steady angle free hand)
Then I repeat Round 1 - 5 above.

Slicing / pairing / chopping on building the Japanese saw horse build is never better. Wow! I still like my Lie Nielsen chisels, but I found that I kept reaching for my Japanese Blue Steel chisels more frequently.

Darrell

[Chris Hall]

Sounds good. Once you have the back of the chisel properly prepped, it only needs to visit your fine finishing stone from here on out.