19 June 2010

Sharpening - James Krenov

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

In his book The fine art of cabinetmaking (1972, 1992) James Krenov discusses (p 109-115) sharpening tools.

Hand-type bench grinder
He goes for a 5-6' fine grit wheel combined with a sturdy wooden toolrest that allows one handed operation. The hand type is for low speed.  The small diameter is for a good hollow grind.  Krenov proposes to hesitate in the middle of each swing to keep the grinding balanced.
That was 1992,  today it is even harder to find hand-type bench grinders, apart from ebay USA at 5$. But low speed grinders are less a problem even if they can be expensive.

After his fine grit wheel he uses fine oilstones with fine cutting oil or even better kerosene. He favors a one handed grip and short strokes.  Small chisels and scrapers get there own stone to minimize damage.

The irons of his planes are impressively thick.  He proposes to have spare plane irons and extra chisels, to avoid interrupting the flow of other work

The story
James Krenov has his own writing style.  Technically I don't have the hand grinder and the thick plane blades, making it difficult to follow his method.

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 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 :).

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.

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.

01 June 2010

French woodworks

I did a short trip to Paris.  Setting foot on the French soil, by stepping out of my car, I was confronted with a Roubo like pick-nick table. On one side there is the massiveness, on the other the legs are not in line with the top nor jointed through the top.  But that's ok,  what makes a good workbench, makes a poor pick-nick table.  For one moment I thought that Chris Schwarz had come over to contaminate the whole country.  But no, this was a one of a kind bench,  all the other tables around me made a more modest use of wood,  half of them even had a concrete base (now concrete, that's an idea for a workbench).

In Paris there is not that much visible woodwork.  An interesting place is the musée des arts et metiers, as you can for example hope to see some Roubo carpentry models there.  But after parking at the Eiffel tower and taking the boat to Notre Dame we did not get further than Beaubourg two blocks short of Arts et Metiers (arts and crafts, although Arts and Crafts translates to Arts et Artisanats). Another time maybe.

Parking place close to the Eiffel tower (that's the breadcrumb picture to get my car back)

 Waiting for the boat to Notre Dame, while the fire brigade is training its recruits.

Some doors facing Notre Dame

The town hall

 High standing (this is art) carpentry at Beaubourg

 All this under the watchful eye of (Lucian) Freud