Flatten with a stone

In general, I use the "sandpaper on a flat surface" method to lap my handplane soles and chisel backs.  However, even the coarsest grit of sandpaper can take an awful long time to flatten the back of a blade, if it's out-of-flat enough.

Based on some advice I'd gained from the woodworking e-list that I follow, I picked up the coarsest grit Japanese waterstone.  The thing about waterstones, apparently, is that they "cut" faster than oilstones, diamond stones, and sandpaper -- because they're continually showing fresh, sharp surfaces.

The corresponding disadvantage is that you end up with a lot of slurry -- the cast-off sharpening particles mixed with the lubricant (the water).  But that's OK, if it gets the job done.


So, as I said, I picked up a 300 grit waterstone.  Seems to work.  Above is a snapshot of the back of my larger morticing chisel, polished to near-mirror smoothness -- at least, the important end.

Similarly,he's a shot of a smaller chisel -- also super-shiny.  And again, note the contrast of the shiny section to the "old" section near my thumb.


The point (pun unintended) of sharpening a chisel (or handplane blade) to such smoothness is that it provides a sharper edge:  If the two intersecting surfaces -- which meet to form the cutting edge -- are this shiny, this indicates that the microscopic cutting edge will be smooth, rather than jagged and rounded over.

A super-sharp blade then means that you can actually slice the wood fibres, rather than plowing through them and breaking them.  This, in turn, leads to cleaner results.


--GG