chisels

[Farrell]

> Now I wonder. Why all the extraordinary trouble to mirror 
> polish the back sides of chisels and plane blades dead flat? 

I think only my trouble. I have been polishing the back side of my chisels and plane blades on the leather wheel of my Tormek. I suspect even someone with good blade sharpening skills would have a tough time making a blade back dead flat on a wheel. When someone with limited skills (or lack thereof), you start putting a small bevel on the backside.

Whomever suggested that I keep my Shapton stones, I think might have a good suggestion for me - maybe I'll try working the backsides of my blades on the stones. The only thing I didn't like about the stones is that you need to have the skill to hold a blade at the correct angle to sharpen the bevel - I have never been successful at that.

> The control and precision required to fit traditional Japanese 
> joinery is far beyond that needed to notch a bridge, or much 
> of anything else we do to pianos. A notch scoop with only one 
> nominally critical edge is somewhat different from maintaining 
> straight lines and tight fits on three axes in a complicated 
> joint in finish carpentry. And why would a plane blade need a 
> hollow behind the edge under ANY conditions? As friction 
> relief and fine depth control with a freehand chisel used in 
> microfitting joints, yes. In a plane blade that is wedged in a 
> block that handles the cut depth, friction, and presentation 
> angle, what's the hollow for?

Are you referring to a hollow on the backside of the blade or on the bevel? I did ask about a hollow on the back side of a Japanese chisel, but my plane blades do not have any hollow at all. On the 1/2-inch-thick Mazzaglia chisels, grinding the entire beveled surface (on my 1" chisel, you have about a one-inch-square bevel surface) is extremely time consuming. If you put a slight hollow on the bevel, you only have to grind on a thin swath at the edge and the other end - makes sharpening go much faster.

Is that what you were addressing?

 
> Virtually all my sharpening is done with a coarse 6" DMT 
> Diasharp "stone" and a steel or ceramic rod if necessary, or a 
> worn out fine grit EZE-LAP (I think it is). Major chisel or 
> plane blade reshaping, in the rare instance of need, is done 
> carefully on the bench grinder with a coarse wheel. My 
> notching chisel has an intentionally slightly rounded back 
> edge (maybe 1mm), because I can steer it better through the 
> scoop than a flat backed blade.
> 
> There is nothing magic about Japanese chisels other than the 
> extremely hard steel that the laminated construction allows at 
> the edge (which is admittedly terrific). The presumed need for 
> a mirror finish on an absolutely flat back, I don't see as 
> valid for the uses we make of them. If someone made laminated 
> long bladed paring chisels with flat backs, I'd likely upgrade 
> my chisel collection. Does anyone?
> 
> Ron N
>
----- Original Message -----  
>> Something that has been troubling me ever since I bought my Japanese 
>> chisel: Starting just a few millimeters back from the sharpened edge, 
>> the entire backside has a hollow ground out. Why? Is that to make 
>> flattening the backside easier? After many sharpenings, the edge of my 
>> chisel is getting very close to the beginning of that hollow. Of course, 
>> as soon as the edge gets right up to the hollow, the chisel dies. Is 
>> this just a feature to sell more chisels?
>>  
>> Terry Farrell
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