17 June 2010

Sharpening - John Juranitch

This is the first of a number of posts about sharpening.

First on the list is John Juranitch a sharpening consultant since 1951 and published a book about sharpening in 1985 The Razor Edge Book of Sharpening. His main expertise is knife sharpening although he is also specialised in a dull axe sharp and shave within 15'. His book covers knives as well as axes, plane blades and scissors.

No oil
Given his time frame Juranitch sticks to traditional oil-stones.  He does not use oil on them for two reasons:
- He stopped using oil to avoid the mess on his stones and discovered as an unexpected bonus that the stones did not degrade faster.
- Oil does not improve the sharpening as once loaded with debris it dulls the top of the edge when sharpening.  Juranitch compares it to pushing an edge through sand and refers to electron microscope imaging to make his point.

Coarse and Fine
Juranitch uses two stones only. A 100# for shaping and somewhere around 600# for finishing.  For shaping he also uses a self made low speed grinder, a must for hollow grinding .  And fine honing is completed with a sharpening steel.

Sharpening steel
Juranitch worked hard to use and understand the sharpening steel.  He uses thin rods and favours a light touch on a constant angle with alternating strokes. He expects that a knife blade that would have lasted half an hour of usage could stay sharp for four hours if steeled regularly.
I suppose the sharpening steel is close to a burnisher and that the light alternating strokes shapes the edge to a straight hardened bur.  Something like cold hammering or rolling the edge on a microscopic level.
A sharpening steel is probably not appropriate for short blades like chisels as it could easily dent the corners.  The asymmetrical edge will also need extra attention. A simple maybe more appropriate alternative could be stropping.

Testing
Testing is important and apart from shaving arms and faces a specific tester is used.  A 10x magnifier is also often used to look for problems (and a 1000x electron microscope :).

Guiding
Like he favours thin, small (<6") knives over more manly cutting equipment, he also claims that a sharpening guide is better than free hand expertise. I suppose that after shaving with an axe there is not much left to prove and he can focus on technical practicalities.

The story
John Juranitch gives a good story full of anecdotes but sticks to a basic sharpening method and applies it to different tools.  He repeats that to get results you need attention, slow movements and a light touch for finishing.  His attention for testing was innovative for me but I lacked details about the possibilities.

Toolset
Back to my basic toolset  with its twin oilstone.  Based on what I learned from Juranitch I can now remove the sharpening oil and look for a cheap sharpening guide.
I could experiment a little with the burnisher to see if it can take the role of a sharpening steel.
A 10x magnifier can be a good start to get some feedback on sharpening quality.