Ok, for the life of me, I can’t seem to get the first inch or so of the backs of my chisels dead flat. Stones are DMT xcourse, course, fine, xfine lubed with 50/50 mix of water and Simple Green. I’ve tried running the chisel crosswise, lengthwise and across the stone’s short side with the same results. I’m using two finger pressure: one directly on and approximately tangent to the bevel and one directly behind the bevel. I “think” I’m putting equal pressure on both locations, however, I’m consistently getting a “hump” about 3/8″ back from the cutting edge. Having tried 3-4 different chisels with the same result on all, it has to be operator error.
The xcourse stone removes ALOT of material quickly and I haven’t bothered going on to finer stones until the back is initiially flat. “Flatness” is the light test using an engineer’s square as reference. As of yet, I haven’t tried facing east while balancing on one foot or any other undocumented solutions. It could be as simple as my 60+ year old fingers just can’t generate enough pressure anymore.
Be that as it may, any and all tricks, methods and advice will be MUCH appreciated. TIA
Gavin in Columbus
Replies
Check your stones for flattness
Gavin:
On a tool as small as a chisel, once you have a convex back it is really hard not to rock the tool on the finer grits as you continue to polish the surface. I would check the course stones to make sure they are truly flat before continuing to use them. I prefer to do the initial flattening of new tools with a granite lapping stone and sandpaper. I've also used my tablesaw top when I'm in a hurry.
I tend to get better results working chisels lengthwise to flatten the backs. It is too easy to rock narrow chisels side to side when lapping the back. One of the tricks I've come up with is to adhere a narrow strip of sandpaper to the granite, about two thirds as wide as the chisel is long. In working the chisel I run the cutting edge off of the paper when lapping the back which prevents me from creating a convex surface since the cutting end gets abraded less than the middle of the chisel. Think about it, if lapping lengthwise, you can't avoid running the handle end of the back off of the grit regardless with medium you are using. This approach sort of evens things out. I also color the back with a magic marker so I can check my progress and make corrects to my technique early in the process.
gdblake
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