[pianotech] Of Chisels

[John Delacour]

At 10:11 +0100 09/10/2010, David Boyce wrote:

>Speak to me of chisels, folks.Ê
>
>What makes them able to take a good edge or not?Ê
>
>Over the years I've bought "bargain" chisels, and sharpened them to 
>what felt like a good edge, only to find that they wont cut wood by 
>hand unaided but have to be battered with a mallet.  it daunts one's 
>confidence.  The other day I was enlarging a mortice in the  front 
>door of my mother's house so as to fit a new lock, and as ujsual was 
>struggling with a cheap chisel.  Then I dug out a couple of my late 
>father's old chisels, very churned-up at the tip, but  a decent make 
>(Marples) and sharpened them, to find that they cut well.
>
>What is the difference in the metal?  Why don't some cut even though 
>they feel sharp to the finger?

Hello David,

Let me speak to you as Yorkshireman to Scot.  The best chisels were 
made in Sheffield in the days when the Sheffield steel makers had the 
monopoly of the iron from the best of the Swedish mines and when the 
steel for cutting tools such as chisels was still produced in small 
quantities in crucibles.  Some people now call this "crucible steel" 
but it was then called "CAST STEEL".  Incidentally this was also the 
steel used for the making of piano wire which excelled over modern 
wire in several important respects.  The whole history of the Swedish 
mines and the Sheffield steel industry is fascinating and explains a 
lot about the difference in quality between the old tools (and wire) 
and the new.

I have collected my many chisels over the years and very soon in the 
process got a sense of what I was looking for.  The best chisels are 
stamped "CAST STEEL" and will have the name of the Sheffield maker 
stamped on them.  There are one or two handfuls of outstanding 
makers:  Ward, Robt. Sorby, I Sorby, Ibbotson, Brades spring to mind. 
In the case of Robt. Sorby you need to be sure they are from the 
early period because the name on a later chisel will not spell the 
same steel or quality.  Most of the great makers did not survive 
after the cast steel age, so a Ward will always be excellent.  I have 
one Marples that seems to be from the old era but others I have are 
post-war and not so good.  I think Marples was fairly late on the 
scene and their tools were not as good as they pretended to be.  Same 
tale as R. Sorby.

One way you can tell good cast steel is from the way it rusts, which 
is hardly at all unless you abuse it.  As time passes it will develop 
a blue-black smooth patina.  You will notice if you look at the 
strings on a piano, such as Bechstein, strung with the old Poehlmann 
wire that is has not rusted in the way that modern wire and inferior 
makes from the past do.

Look in the junk shops for the above names.  You can also find them 
on Ebay but you can expect to have to pay a fair price for them.  The 
besy of them will have a boxwood handle.  I have bought a lot of my 
chisels in bad condition and worked them up myself.  The best thing 
for the initial grinding of the bevel is the old-fashioned 
agricultural 2-foot wheel.  Once I have the angle I sharpen by hand 
on Chinese water stones of decreasing coarseness finishing with a 
Belgian coticule.  For the final edge on paring chisels I buff them 
quickly on the buffing wheel.  This is cheating, of course, but you 
win!

I'll have a look tomorrow to see which other names have slipped my 
memory.  I also have a list of my favourite Sheffield razor makers, 
but the trade was very specialized and the lists are different.

JD