Bolsters are two pieces of material, usually metal, fitted between the
blade and handle on a full tang knife.. The purpose of bolsters is to
strengthen (to bolster) the tang, thus preventing the handle scales from
coming loose if the knife is flexed.
Materials commonly used for bolsters are:
stainless steel, (usually one of the 3xx series steels such as 303 or 308),
bronze (most makers use bearing or phosphor bronze, I prefer silicon
bronze),
brass (brass has no class),
nickel silver or one of the cupro-nickel alloys,
damascus,
mokume,
wrought iron,
and on investment and fine art knives sterling silver or even a gold alloy
(12 or 18 carat) may be used.
Bolsters are also useful surfaces for applying embellishments such as
engraving, inlays and etchings.
How to fit bolsters to a fixed blade knife
With a bolster alignment clamp (basically two parallel bars fitted with
guide pins and screws at both ends) in place, clamp the one bolster against
the bar.
Lightly and carefully drill into the bolster through the blade tang. You
only need to drill about half to one mm deep.
Remove the bolster from the blade, and drill each hole all the way through
After drilling a hole, remove the burr at the bottom before drilling the
next hole.
Repeat the clamping, lightly drilling, drilling through and deburring for the
other bolster.
Lightly sand the inside of the bolsters, using a flat surface as backing
for the paper. I use a piece of leftover gravestone granite. Change the
sanding direction and sand lightly
The inside of the bolster should have a crosshatch pattern from corner to
corner if is completely flat.
Use loose pins and trace the top and bottom of the blade on each bolster
Mark the blade side of the bolster as well. Using whatever tools you have
to cut close to the lines. Not on the lines.
Fit two short pins to hold the bolsters together and finish the front face
to 1200 grit. If you are using steel, you can now proceed in applying a mirror
finish if necessary.
Lightly ream each hole using a tapered reamer or a small round file like I
am using on the picture above.
Cut pins, using materials that will match the colour of the bolster
materials. TIG welding rod works great. (You might need to anneal the pinning
material. Be sure to sand the pinning with 800 grit paper to remove all the
oxides after annealing)
Peen the pins using soft blows with a small hammer, when they have set, you
can use a larger ball peen hammer to make sure that the pins completely fill
the tapered holes.
See also the section on
fitting bolsters in the article "Making
a small side knife" for more on fitting bolsters.
Other pages of interest: Metals for
fittings and Properties of Metals
