The Contact Screw
" Lie back and dream of me, red death to set you free we'll turn the screws to make you die..."
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)-(see "Spring Tension Test, Ball System" p. 59, 60, 61). 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).
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.
Contact screws as well as securing screws may be metric but are commonly standard. 832 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.
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.
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.
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.
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