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Preparing the bottom surface of the chisel.
Introduction.
Probably the most time consuming job when getting a chisel ready for fine cabinet making is working on the bottom
surface. A chisel, like timber is rarely flat when it arrives from the manufacturer, some are convex whilst other are
concave, and I don’t mean just a small amount.
The Lie-Nielson chisels arrived the in the best condition requiring a small amount of work, whilst the Japanese chisels
were well out of shape.
Utter basics. So what I am aiming for when working on the bottom surface.
a in the case of a Japanese chisel, some of the hollow is still present.
b completely flat across the chisels width.
c fractionally concave along the chisels length.
d I am also aiming to get rid of the manufacturers machine marks and eventually replace these with a mirror like
finish on my 8000 grit Japanese water stone.
FtBtm01a
my reference 12mm complete chisel 020.jpg
Introduction.
Probably the most time consuming job when getting a chisel ready for fine cabinet making is working on the bottom
surface. A chisel, like timber is rarely flat when it arrives from the manufacturer, some are convex whilst other are
concave, and I don’t mean just a small amount.
The Lie-Nielson chisels arrived the in the best condition requiring a small amount of work, whilst the Japanese chisels
were well out of shape.
Utter basics. So what I am aiming for when working on the bottom surface.
a in the case of a Japanese chisel, some of the hollow is still present.
b completely flat across the chisels width.
c fractionally concave along the chisels length.
d I am also aiming to get rid of the manufacturers machine marks and eventually replace these with a mirror like
finish on my 8000 grit Japanese water stone.
FtBtm01a
my reference 12mm complete chisel 020.jpg
How do I check for
flatness (fractionally
concave) in the chisels
length?
I used one side of my 150mm
(6”) engineers try-square
that I have checked with my
engineers straight edge and
found to be perfectly flat. I
marked this with red marker
pen so there would be no
confusion as to which side
of the try-square I was using.
flatness (fractionally
concave) in the chisels
length?
I used one side of my 150mm
(6”) engineers try-square
that I have checked with my
engineers straight edge and
found to be perfectly flat. I
marked this with red marker
pen so there would be no
confusion as to which side
of the try-square I was using.
This surface is then regularly used during the ‘flattening’ process. I place the bottom of the chisel in contact with this
surface with a light source behind. My light source of preference is daylight, simply by looking out of my workshop
window, or in the evening having a fluorescent lamp at the back.
During the flattening process I am aiming to form a CONCAVE SURFACE so that I can see a glimmer of
light around the centre point, with the ‘heel’ and sharpened end of the chisel, in contact with the flat
surface of the try-square.
I have highlighted the above paragraph simply because it is the key in the process of preparing the chisel bottom. It
needs to be fractionally concave in the chisels length, and the bottom surface will require regular checking especially
when using the very course glass paper in the initial process.
surface with a light source behind. My light source of preference is daylight, simply by looking out of my workshop
window, or in the evening having a fluorescent lamp at the back.
During the flattening process I am aiming to form a CONCAVE SURFACE so that I can see a glimmer of
light around the centre point, with the ‘heel’ and sharpened end of the chisel, in contact with the flat
surface of the try-square.
I have highlighted the above paragraph simply because it is the key in the process of preparing the chisel bottom. It
needs to be fractionally concave in the chisels length, and the bottom surface will require regular checking especially
when using the very course glass paper in the initial process.
FtBtm03a
Equipment required for forming the fractionally concave bottom surface.
To form the initial fractionally concave surface I use an off-cut 40mm (1. 9/16”) thick that was left over when fitting a
new top to some kitchen base units. This was checked with my engineers straight edge and found to be perfectly flat.
I then secure a strip of 80 grit glass paper with cramps. The width of the strip is around ½ the chisel’s length.
To form the initial fractionally concave surface I use an off-cut 40mm (1. 9/16”) thick that was left over when fitting a
new top to some kitchen base units. This was checked with my engineers straight edge and found to be perfectly flat.
I then secure a strip of 80 grit glass paper with cramps. The width of the strip is around ½ the chisel’s length.
FtBtm04a
because the images are not as clear when using this deep green surface, I have taken all the photographs using a
piece of light coloured plywood.
piece of light coloured plywood.
Forming a fractionally concave surface on the chisel bottom.
My method of approach will depend on the width of the chisel.
1 Removing the convex bottom surface on chisels that are 3mm(1/8") wide and up to 9mm(3/8”)wide.
I position the chisel so that is centred on the glass-paper, with pressure being exerted by a couple of fingers as shown.
Keeping the ‘heel’ and tip off the chisel off the glass paper, the chisel is moved in the direction shown.
and slowly moved along the glass paper, checking ever dozen strokes or so on the side of the try-square, so that you
form that fractionally concave surface.
If I was working on a batch of chisel I would certainly add some protection to my finger because otherwise they would
end up rather tender. This 3mm(1/8") wide chisel took around 6 minutes to remove the convex surface and give me a
fractionally concave surface.
My method of approach will depend on the width of the chisel.
1 Removing the convex bottom surface on chisels that are 3mm(1/8") wide and up to 9mm(3/8”)wide.
I position the chisel so that is centred on the glass-paper, with pressure being exerted by a couple of fingers as shown.
Keeping the ‘heel’ and tip off the chisel off the glass paper, the chisel is moved in the direction shown.
and slowly moved along the glass paper, checking ever dozen strokes or so on the side of the try-square, so that you
form that fractionally concave surface.
If I was working on a batch of chisel I would certainly add some protection to my finger because otherwise they would
end up rather tender. This 3mm(1/8") wide chisel took around 6 minutes to remove the convex surface and give me a
fractionally concave surface.
FtBtm 05a.JPG
FtBtm08 6aJPG
and use around
45mm of the
glass paper.
45mm of the
glass paper.
FtBtm03a
A key part of the
process is
checking after a
dozen or so
strokes until you
obtain that
fractionally
concave surface.
process is
checking after a
dozen or so
strokes until you
obtain that
fractionally
concave surface.
2 Removing the convex bottom surface on chisels that are wider than 9mm(3/8”)
Holding the handle very lightly, and pressing firmly with two fingers, I push the chisel in one direction only, keeping the
'front edge' and heel of the blade off the glass paper.
As before regularly check on the engineers try-square how the operation is progressing. Unlike working with the
narrow chisels, this can be a time consuming process. The aim again is to get that fractionally concave surface in the
blades length.
Holding the handle very lightly, and pressing firmly with two fingers, I push the chisel in one direction only, keeping the
'front edge' and heel of the blade off the glass paper.
As before regularly check on the engineers try-square how the operation is progressing. Unlike working with the
narrow chisels, this can be a time consuming process. The aim again is to get that fractionally concave surface in the
blades length.
FtBtm 7a.JPG
3 Japanese chisels.
If you own a Japanese chisel you will be aware that on purchase or regular grinding and sharpening, the flattened
area of the chisel near the front end will become unusable because if you kept grinding away you would end up in the
hollowed out area.
The image below shows the bottom of one of my Japanese chisels. The pencil is resting on the flattened area
If you own a Japanese chisel you will be aware that on purchase or regular grinding and sharpening, the flattened
area of the chisel near the front end will become unusable because if you kept grinding away you would end up in the
hollowed out area.
The image below shows the bottom of one of my Japanese chisels. The pencil is resting on the flattened area
FtBtm 8a
and the same chisel after it has been
worked on.
FtBtm9
worked on.
FtBtm9
and the same chisel
after I have exposed
more metal at the
front end.
Probably around
6mm(1/4")
after I have exposed
more metal at the
front end.
Probably around
6mm(1/4")
Increasing the useable area at the front end of a Japanese chisel.
Starting with Japanese chisels that are between 3mm(1/8") and 9mm(3/8”) wide.
The way to resolve this situation is to is ‘re-flatten’(fractionally concave) the bottom and expose more metal at the front
end. For my narrow chisels I will be aiming to remove most of the hollowed area so that I never have to repeat the
process again.
With the wider chisels, because this process takes much longer, I am looking at an area of metal at the 'front edge'
that is in the region of 6mm(1/4”) long.
I secure a strip of 80 grit glass paper that is around 75mm(3”) wide to the flat surface. Notice that the width of the
glass paper is wider than used in the previous process.
And the chisel is moved in the direction of the arrow so that that ‘heel’ remains on the glass paper and finger pressure
is at the front end.
Starting with Japanese chisels that are between 3mm(1/8") and 9mm(3/8”) wide.
The way to resolve this situation is to is ‘re-flatten’(fractionally concave) the bottom and expose more metal at the front
end. For my narrow chisels I will be aiming to remove most of the hollowed area so that I never have to repeat the
process again.
With the wider chisels, because this process takes much longer, I am looking at an area of metal at the 'front edge'
that is in the region of 6mm(1/4”) long.
I secure a strip of 80 grit glass paper that is around 75mm(3”) wide to the flat surface. Notice that the width of the
glass paper is wider than used in the previous process.
And the chisel is moved in the direction of the arrow so that that ‘heel’ remains on the glass paper and finger pressure
is at the front end.
FtBtm10
I also allow the
chisel to overlap the
edge like this.
chisel to overlap the
edge like this.
FtBtm11
FtBtm03a
As a reminder a
key part of the
process is
checking after a
dozen or so
strokes to check
that the bottom
surface is
fractionally
concave.
key part of the
process is
checking after a
dozen or so
strokes to check
that the bottom
surface is
fractionally
concave.
Now sometimes I find that the concave surface has been removed and therefore I return to using a strip of glass paper
that is around ½ the width of the chisel then resume the process.
that is around ½ the width of the chisel then resume the process.
And for chisels over 9mm wide.
Again finger pressure near the front
end of the chisel and pushed in the
direction of the arrow.
FtBtm12
Again finger pressure near the front
end of the chisel and pushed in the
direction of the arrow.
FtBtm12
And for chisels
over 9mm wide.
Again finger
pressure near the
front end of the
chisel and pushed in
the direction of the
arrow.
over 9mm wide.
Again finger
pressure near the
front end of the
chisel and pushed in
the direction of the
arrow.
FtBtm13
I also allow the
chisel to have it
'front edge' off the
glass paper.
chisel to have it
'front edge' off the
glass paper.
Having obtained the desired length of
metal at the front end of the chisel, I
want to replace the deep scratches left
by the 80 grit glass paper that were
parallel to the cutting edge, with ones
that are running parallel to the length
of the blade by moving it in the
direction of the arrow.
FtBtm14
metal at the front end of the chisel, I
want to replace the deep scratches left
by the 80 grit glass paper that were
parallel to the cutting edge, with ones
that are running parallel to the length
of the blade by moving it in the
direction of the arrow.
FtBtm14
Having obtained
the desired length
of metal at the
front end of the
chisel, I want to
replace the deep
scratches left by
the 80 grit glass
paper that were
parallel to the
cutting edge, with
ones that are
running parallel to
the length of the
blade by moving it
in the direction of
the arrow.
the desired length
of metal at the
front end of the
chisel, I want to
replace the deep
scratches left by
the 80 grit glass
paper that were
parallel to the
cutting edge, with
ones that are
running parallel to
the length of the
blade by moving it
in the direction of
the arrow.
Summary so far.
1
All the chisel will either have been bought with a fractionally concave bottom surface, or I have formed one using the
methods described.
2
The Japanese chisels have had the cutting edge increased at their front end
1
All the chisel will either have been bought with a fractionally concave bottom surface, or I have formed one using the
methods described.
2
The Japanese chisels have had the cutting edge increased at their front end
The next task is to
remove the deep 80 grit
scratches formed in the
previous operations, and
to work on the chisels that
arrived fractionally
concave.
For this I used 70mm(2
¾”) wide 240 grit 'wet and
dry' paper and I only
move the chisels in one
direction irrespective of
the width of the chisel. As
before firm pressure is
exerted at the front end.
remove the deep 80 grit
scratches formed in the
previous operations, and
to work on the chisels that
arrived fractionally
concave.
For this I used 70mm(2
¾”) wide 240 grit 'wet and
dry' paper and I only
move the chisels in one
direction irrespective of
the width of the chisel. As
before firm pressure is
exerted at the front end.
FtBtm15
and its not long even on the wider chisels that the deep 80 grit marks are replaced with 240 grit marks.
Having reached this stage with the glass paper and 240 grit 'wet and dry' paper I now revert to my Japanese water
stones.
Having reached this stage with the glass paper and 240 grit 'wet and dry' paper I now revert to my Japanese water
stones.
FtBtm17.JPG
Firstly the 800 grit stone
I secure my 800 grit water stone in my sharpening station, form a slurry with the 1200 grit stone, mark a pencil line
around 15mm(5/8”) from one edge, and position the chisel as shown
I secure my 800 grit water stone in my sharpening station, form a slurry with the 1200 grit stone, mark a pencil line
around 15mm(5/8”) from one edge, and position the chisel as shown
and the aim is to move the chisel in the direction shown below the complete length of the water stone with firm finger
pressure on the front end of the chisel.
pressure on the front end of the chisel.
FtBtm018.jpg
The whole process is then repeated on the 1200 and 8000 grit water stones.
with the finger or thumb pressure exerted as before at the front of the chisel like this
with the finger or thumb pressure exerted as before at the front of the chisel like this
It does not take long before the 240 grit marks are replaced with finer marks from the 800 grit stone. As a reminder
once I have travelled twice along one edge, that edge of the stone is not used again until flattened.
In this case the stone is rotated 180 degrees and the opposite edge used in a similar manner. The stone is then
flattened as described in the chapter Water stone maintenance
once I have travelled twice along one edge, that edge of the stone is not used again until flattened.
In this case the stone is rotated 180 degrees and the opposite edge used in a similar manner. The stone is then
flattened as described in the chapter Water stone maintenance
FtBtm019.jpg
or this
ending up with a mirror like finish on the bottom surface that is fractionally concave.
FtBtm021.jpg
A few notes.
My first experience of using and owning a quality chisel was when I purchased some Japanese laminated chisels, both
the ‘striking’ type and a couple of the paring chisels. They are superb but required a serious amount of work removing
metal before they were fit for dovetailing.
A few years down the line, Lie-Nielson brought to market a chisel in the European style. Instead of a blade length of
around 60mm for the Japanese chisels the Lie-Nielson’s were in the region of 90mm , and in a similar price range. I
purchased two of these and they match the quality of the Japanese chisels
They still however require the excess metal at the sides of the chisel removing before they are suitable for removal of
the waste between the 'tails' of a dovetail joint. All of this can be seen in the images on this web site.
In 2008 I purchased some bevel edge chisels manufactured by Blue Spruce Toolworks from USA. Unlike all other
chisels that I am personally aware of, they are designed for the removal of the waste between the tails. They are
made from A2 steel and match the quality of the two previous brands.
Having spend so much time over the years on the Japanese and Lie-Neilson chisels to get them suitable for dovetailing
I have no desire to do so with the introduction of the Blue Spruce bevel edge chisels. The are superb.
My first experience of using and owning a quality chisel was when I purchased some Japanese laminated chisels, both
the ‘striking’ type and a couple of the paring chisels. They are superb but required a serious amount of work removing
metal before they were fit for dovetailing.
A few years down the line, Lie-Nielson brought to market a chisel in the European style. Instead of a blade length of
around 60mm for the Japanese chisels the Lie-Nielson’s were in the region of 90mm , and in a similar price range. I
purchased two of these and they match the quality of the Japanese chisels
They still however require the excess metal at the sides of the chisel removing before they are suitable for removal of
the waste between the 'tails' of a dovetail joint. All of this can be seen in the images on this web site.
In 2008 I purchased some bevel edge chisels manufactured by Blue Spruce Toolworks from USA. Unlike all other
chisels that I am personally aware of, they are designed for the removal of the waste between the tails. They are
made from A2 steel and match the quality of the two previous brands.
Having spend so much time over the years on the Japanese and Lie-Neilson chisels to get them suitable for dovetailing
I have no desire to do so with the introduction of the Blue Spruce bevel edge chisels. The are superb.
