6.2 Use a 1.6
mm drill bit and drill only the rear most pinhole, using the spring as
guide. Remove the vise-grips and fit a pin in the hole you just drilled.
Holding the spring, liner and blade in position, scribe a mark on the
liner along the bottom of the spring, as indicated in the sketch.
Fig 6.2
6.3 Remove the
blade and pivot pin. You now need to drop the spring to a minimum of 0.7
mm to 1 mm maximum past the scribed mark on the liner. Do this by
measuring the distance from the mark to the top of the liner and adding
0.7 to 1 mm. Use your Vernier as a jenny calliper to mark the spring
position. This is done to put a load on the spring so it will press down
on the back square when the knife is open.
6.4 Move the
spring to the new position and clamp in place (the rearmost pin must still
be in place) Drill the remaining pinholes using the spring as guide.
6.5 Remove the
blade and spring from the liner. Fit the two liners together with the
pivot pin in place and clamp. Using the one liner you have just drilled as
guide, drill the pinholes through the other liner as well. Remove the
clamp and de-burr the pinholes.
6.6 You now
need to cut a relieve around the pivot pin on the inside of the liners.
The depth of the relieve should be about 0.02 mm, its radius the distance
from pivot hole to round end.
The purpose of
the relieve is to prevent the liner from scratching the ricasso area of
the blade when opening and closing.
Hand sand the
outside edges of the relieve, leaving the inner raised area flat, and
finish the inside of the liner to 400 grit.
Below is a
picture of the setup I use to polish liners. A piece of angle iron, ground
flat on one side, clamped in a table vice. The liner is held in place with
a vice grip (a piece of leather protects the liner)
I use 303
stainless steel or bronze for bolsters. As I have said previously, brass
has no class. It tarnishes to a dull dirty looking yellow. Bronze on the
other hand, tarnishes to a lovely antique brown. Another option is to use
Damascus for bolsters. I cover the use of Damascus in a separate chapter.
You will note
that on all the drawings the bolsters have sloping shoulders. This is
called a dovetail and besides looking quite neat, it helps to hold the
covers (handle material) in position. I use a jig, which clamps the
bolster material at a precise angle. This is placed on the rest of my disk
grinder. By holding the jig steady and pressing against the disk I get the
angle required. The handle materials are done in the same way.
Here is a
picture of the jig and two dovetailed bolsters.
7.1 Measure the
width and length of the bolsters from the photocopied design and cut two
pieces from the bolster material, slightly oversize.
7.2 Grind all
the sides of the bolster clean, paying particular attention to the inside
(liner side). Grind the inside flat on the platen using a 180 grit belt,
then touch on a disk grinder fitted with a 180 grit sheet or on a sheet
stuck to flat surface. Sand at a different angle, this will clearly show
any high spots that must be removed. I prefer to use a disk grinder, as it
is quite easy to rock the bolster on a flat surface, giving it a slight
convex.
7.3 File or
grind the shoulders, where it abuts against the covers, square and flat.
Check with a small engineer's square and straightedge. Remove any burrs
that may have formed.
Alternatively,
file or grind dovetails. If you do not have a jig, clamp the bolsters
together with a vice grip. The inside of one should be on the outside of
the other, they should form a "step". Now grind or file both at an angle
at the same time. Make sure that you keep the filed surface flat. When you
are finished, release the clamp and turn the bolsters inside inwards and
you will have a perfect, symmetrical dovetail.
7.4 Fit the two
liners together with pins in place. Fit the bolster alignment clamp where
the covers and bolster meet.
7.5 Clamp one
bolster in position with a vice grip. Spot mark the pivot pinhole with a
3.2 mm drill and remove. Do the same with the other bolster.
7.6 Drill the
pivot holes through with a 3.2 mm drill and de-burr.
7.7 Fit one
bolster with the pivot pin on the still assembled liners and drill a blind
hole from the liner side into the bolster using a 1.6 mm drill. The depth
of the blind hole in the bolster should be 2 to 2.5 mm.
(you may fit
more than one pin if you prefer)
7.8 Do the same
to the other bolster. This pin will ensure that the bolster is glued on
exactly the correct spot, as the alignment clamps will be removed when
gluing. It will also be peened to further strengthen the joint.
7.9 Scribe the
bolster outline along the liner with pins in place.
7.10 Profile
the bolsters on a 60-grit belt. Touch the bolster insides on the disc
grinder to make sure they are flat.
7.11 To fix the
bolsters to the liners you need to have the following ready:
A piece of
angle iron, (one side machined flat and a 1.6 mm hole drilled in the
centre.) A Vice-grip, glue (Pratley 123), a 1.6 mm pin, and a 3.2 mm pin.
Clamp the angle iron in the bench vice, smooth side on top.
Fit the 1.6 mm
pin through the hole and drop the liner (outside on top) over the pin. Fit
the 3.2 mm pin through the pivot hole on the bolster. Apply the resin to
the bolster inside, the hardener to the liner.
(A piece of
waxed paper between the angle iron and the liner will keep the two from
sticking)
Align the 1.6
mm pin with the blind hole in the bolster and the pivot pin with the pivot
pinhole in the liner. DO NOT let the bolster touch the liner. When the two
pins are in their appropriate holes in the liner and bolster, press the
two together and immediately put on the vice -grip, clamping the angle
iron, liner and bolster together.
Wait about 5
seconds then remove the pivot pin from the top and the 1.6 mm pin from the
bottom, else they will be glued in position as well. Use a Stanley knife
blade to scrape away any excess glue from the shoulder where the handle
covers will touch the bolsters. Wait about 3 minutes before releasing the
vice grip. Repeat the process with the other bolster and liner. Fit a pin
to the blind hole, cut off with a side cutter and peen. Grind or file
level with the surface of the liner. IMPORTANT: see step 7.13!!
7.12 Fit the
blade, spring and liners together with the blade in the open position,
using temporary pins. I fit the pivot pin and rearmost pin first. The next
two pins I grind to a point as the spring will be put under load and does
not align with the holes in the liner. You will note that the pinhole in
the spring is slightly higher than the hole in the liner. The next to last
pin is tapped through, then the final pin
7.13 Put a
sharp 60-grit belt on the belt grinder, using the same diameter wheel as
the one you used to hollow grind the blade. There is a trick involved in
grinding bolsters that have been glued to the liners: YOU MUST KEEP THE
TEMPERATURE AS LOW AS POSSIBLE. If you are not confident, do not peen the
pin in the blind hole. Also, do not peen if you plan to do file work on
the liners or fit Damascus bolsters. See the chapter on using damascus.
Shape the
bolsters with the 60-grit belt. Run along the spine of the knife,
levelling the bolsters, blade, spring and liners. Hollow grind the blade
to the correct edge thickness. Quench the blade frequently to prevent it
from tempering. Close the blade, level and shape the front of the
bolsters. Follow with 180 grit, reopen, polish bolster sides spine and
blade hollows. Change to a 400-grit belt, and repeat. Do the same with an
A30, A16, and old A16 except for the spine. Disassemble the knife; remove
any burrs that may have formed on the liner edges as well as the shoulders
of the bolsters.
7.14 By now you
would have noticed that the knife does not close properly. The edge might
be sticking out above the liners; the spring is not level with the liners
when the knife is closed. To correct this you need some patience, a bit of
luck also helps.
Put a 400 grit belt on the
vertical platen and set the horizontal rest so it at 90 degrees to the
platen. You need to remove material from the kick to drop the blade into
the slot. If the spring is still above the liners when the knife is closed
you need to remove material from the corner where tang front and round end
meets as well. This will cause the blade to rise. Be careful, remove a
little material, put the blade, liner and spring together with the rear
most pin in place on the spring and check how much the spring needs to
drop and where you must remove some more material. You may note that when
open, the spring drops slightly past the level of the run up on the blade
if only the rear most pin is in place. A piece of grit got between the
square back and the spring when you shaped the bolsters and polished the
blade. This can be corrected after final assembly. You need to get the
spring to drop to this exact level when the blade is closed. Work on the
400 grit up to the point where you only need to remove about 0.05 to 0.1
mm and switch to a 1200 grit belt for the final finishing. You might want
to assemble the knife, fitting all the pins and see what the spring does
under load before moving on to the 1200 grit belt.
