The Contact Screw

The contact screw runs through the upper binding post. It makes contact with the
front spring. The point where this contact screw makes contact on the front spring will
change a machine’s performance. It is an important co-factor in the setting and adjusting
of the distance the armature bar will travel (the stroke), by, among other things, acting
as a limiter for the front spring, so it must be tightened or loosened in conjunction
with the tension on the spring(s)

Once again, the bend in the rear spring will control the distance the armature bar /
front spring assembly will potentially travel this is called the “stroke”. The gauge of the
front spring will dictate at what rate of speed the armature bar assembly will travel
(bounce) when moving from the coil to the contact screw, in direct relation to the tension
applied to the rear spring. Tightening the contact screw will lessen the distance
the armature bar will travel and increase the speed of it’s movement. Changing the
angle of contact will also make a difference. Pivoting the contact screw to make contact
farther back on the front spring will reduce the distance the armature bar will travel
even more–shortening the stroke, increasing the tension put on the front spring resulting
in a non functional machine. Let’s explain. Tightening the contact screw or moving
the contact screw’s point of contact back without adjusting the spring tension will retard
the function of the machine in the same way:
Shortening the stroke- this lessens the distance the needles will protrude from the tip of
the tube, and in effect may limit potential needle penetration…solid color requires
slightly more needle penetration at greater force than shading…but the stoke should be
the same in either application.
Another result of a compromised stroke by tightening the contact screw is the versatility
and performance of the machine. A machine that can shade smoothly, needs flex in
the front spring. When the screw is tightened, it pushes down on the front spring,
decreasing the flex margin the spring already has and increasing the upward tension
against the contact screw. A machine with this much tension would not be able to shade
smoothly or consistently.
Shortening the front spring and moving the contact screw’s contact point farther back
on the front will do the same– reduce stroke and cause too much tension for the new
stroke change.
Let’s review. The loss of distance (tightening the contact screw or adding more of an
upward bend in the front spring) will also limit the stroke and reduce the potential needle
penetration. It is crucial that potential needle depth is not sacrificed. The less needle
that penetrates, the lighter the color will be, the lighter the line will be (unless using a
single needle). Loosening will do the opposite, again, the potential needle penetration is
affected.
A larger stroke will require more tension on the rear spring to compensate for the distance
the armature bar will travel (See illustration p. 52).
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Material
Silver is recommended first and foremost–sterling is excellent. Brass or even copper are
fine. Steel or even stainless steel will work but are not recommended. When operating,
a machine undergoes friction in several areas, the most obvious is where the contact
screw connects with the tip of the front spring. A groove in the front spring may appear
over time in the specific area that the front spring connects with the contact screw; this
is normal wear and tear but the time it takes to develop varies according to the material
the contact screw is made from. A steel screw will burn hotter and holes in the front
spring will appear sooner. It is important to monitor spring wear and replace when necessary.
This is the reason we recommend silver first, followed by brass, copper, steel and
stainless steel. Silver does not wear a hole in the front spring at as fast of a rate as the
other metals do.
Understanding Screw Threads
Contact screws as well as securing screws may be metric but are commonly standard. 8-
32 is the most frequently used screw in the tattoo machine assembly. It can be found on:
binding post screws, coil securing screws, contact screws, armature bar / spring assembly
screws, spring saddle screws and tube vice screws. This does not mean that any other
screw type cannot be used. Let’s talk about the number 8-32. This number does NOT
mean 8/32” of an inch, it is not a measurement on a ruler. In these numbers used to
describe screws, for example 6-32, 10-24 and 8-32, the first number indicates the size of
the screw’s diameter, or inside diameter of it’s corresponding washer so a #6 screw will
fit a #6 washer…the second number is the number of threads per inch this particular
screw has. So, on a 10-24 screw- the screw is a #10 which has 24 threads per inch on it.
Re-Tapping a stripped #8 hole with an 8-32 tap. A tool which is very easy to use.
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Tap and dye sets are available to rethread screws and to “tap” (re thread the hole).
It is common for inexperienced artists to put a metric screw in a standard hole and vice
versa and stripping out the already existing threads on a frame or binding post. That’s
why an understanding of these numbers is important. This is a simple task, these tools
are worth the investment.
Contact
The more surface contact, the better the function, the longer the life of the front spring
the better the performance of the machine. This may be achieved by filing the contact
screw or bending the spring until maximum surface contact between the flat section of
the screw and the front spring is achieved, this may involve and extra bend inthe front
spring.
Contact screw maintenance
Carbon build-up is common on the flat surface of the contact screw, so occasionally filing
or lightly sanding the tip of the contact screw to remove the carbon build-up is recommended,
but only remove the carbon build up, do not remove screw stock. Too much
stock removed will result in having to re-tune the machine.
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Securing the Contact screw
The contact screw is located on the upper binding post. The most highly recommended
material for this screw is silver. Silver is a soft metal and can be bent easily or have the
threads damaged easily. A securing screw is commonly used to secure the contact screw
in place once the machine is tuned. It is extremely important NOT to damage the contact
screw because it will limit future tuning of the machine. If the securing screw is
metal, a small acrylic ball or a piece of an o-ring can be used in between the end of the
securing screw and the threads of the contact screw. If the threads are damaged on the
contact screw, it will not be able to turn when adjusting or fine tuning the machine. Also
recommended are nylon or plastic screws for use as securing screws.
Another perfect example of careless maintenance. The contact screw is pitted at the surface
contact area with alot of carbon built up inside that pit. The threads are becoming
stripped due to the lack of thread protection inside the binding post, In this case, the
securing screw was being tightened directly against the threads of the contact screw
without any thread protection in between them.
It is not necessary to use a screw as a ‘contact
screw’, a simple cylindrical rod made from brass or
any other recommended metal can be used, provided
that it fits snuggly into the drilled hole in the
upper binding post. These rods can be purchased
in brass at any hardware or hobby shop. A thread
protector, is not necessary, (but recommended to
absorb vibration) so any metal screw can be used
because there are no threads to ruin.