Blacksmithing
and Cutlery
by Gérard HEUTTE
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Use of threaded axis for folder
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Here is an alternative to folding axis traditionally caulked.
The use of screws allows a removable folding knife and above all to adjust the friction force.
I deliberately leave aside the aesthetic aspect that is very personal and subjective ...
Purists may prefer the caulked axis that are more in line with the traditions !
Principle
The principle is very simple. All is based around the threaded axis. It is a cylinder whose inner
portion is threaded . Two screws enable the mounting and tightening. Here is a diagram of the assembly:
This diagram shows an installation with a counterbore (for "burying" the screw heads).
Parts
The first choice to make is between the metric system (i.e. in millimeters) and imperial (i.e.
in fractions of inches). Although the metric system is supposed to be the reference, the imperial
system is very common because many parts (if not most) come from the USA. But the equivalent in
metric system can be (hardly) found among European suppliers.
Axis
Many models are available. In metric system , the diameter will be 3 or 4mm, the length of
about 10mm and a thread of M3.
Personally, my choice was on stainless axis of 10mm length, 4mm diameter and thread M3.
(see opposite illustration)
Screws
Many screw designs may be used: Button heads or flat heads , length of around 10 or 12mm. The
imprint will be of type Torx or Allen . The material is preferably stainless steel. Of course, all this
will depend on suppliers stock.
The advantage of the button heads is that they can be used for mounting with or without counterbore.
Warning:
> The diameters of the screw heads (more or less standardized) are different for button heads and flat
heads.
> M3 Torx screw heads (button head) are typically 5.8mm in diameter. With an axis of 4 mm (and thus a
4mm hole), the rest surface will be 0.9mm wide. With a 5mm axis, it is reduced to 0.4mm, which is
not enough... In this case, it is required to use screws with large head or baseplate.
Personally , my choice fell on Torx M3x12 button head screws. I shortcut them to desired length
(depending on the thickness of the handle slabs). (see illustration)
Tools
For installation without counterbore , no special tools are required.
For mounting with counterbore, it will be necessary to have the right counterbore cutter:
> Diameter of the guiding pin = diameter of the axis.
> Cutter diameter = diameter of the screw heads.
Of course, no chance of getting standard sizes !!! So it will probably necessary to make one as shown
here
On the opposite picture, the teeth of the cutter are in 90MCV8 steel (machined to the diameter of the
screw heads before hardening). The guiding pin is a brass tube of 4mm diameter.
Advantages and disadvantages
Without considering the aesthetic side, this system has only advantages:
> Adjusting the friction force is very simple. The knife holder can adjust it as he wishes. Furthermore,
in a conventional assembly, the slack increases with time. This system allows an easy remedial.
> This system allows disassembly of the knife, which facilitates cleaning and maintenance.
The only real disadvantage of this system could be cost, but less than two euros is really small
compared to the knife price...
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