Marking using “Method of Two” and “Method of Three”

Both methods are irreplaceable when you have to divide a certain linear space into a number of smaller equal spaces. This operation doesn’t pose any threat or difficulty if a value of each space is a whole number. Say, you need to line up 20 marks with a distance of 10 mm between them. No problem. You will just lay down a ruler and place a mark every 10 mm, preferably without moving the ruler.

When you have to deal with non-round numbers, such technique will not be effective. Any attempt to lay down the ruler and draw marks with a distance between them described by a number with 2-3 digits after the comma will lead you to a mistake in overall distance. A smallest mistake in representing a complex value of the smaller space along with significant number of divisions will create a phenomena known as a Combined Mistake, which was discussed in a separate article.

Division using “method of two” and “method of three” will eliminate the very possibility of a combined mistake, help you to mark your material or component with maximum accuracy and preserve the value of the main overall distance. Both methods require you to reverse the technique of linear marking and to start from greater distance dividing it equally, piece by piece. Using these methods you don’t have to be concerned anymore about accurate representation of complex values of each particular smaller space – all you have to represent is a quantity of spaces. As a result of accurate equal division values of the smaller spaces will be kept automatically.

Combined (Cascading) Mistake

In most cases a model maker does not have to be deadly precise. A tolerance for single part or element might vary from 0.5 mm (0.020″) to 1mm (0.040″). A tolerance may be even bigger for larger models and components.  Considering that a minimal reasonable thickness of an element and a wall limit usually should not be less than 0.5 mm (at least model maker has to try to keep it that way), you don’t have to worry very much about a single mistake. Let’s emphasize the word “single” in this last phrase, because there is a treacherous phenomena known as a “combined” mistake, which must not be underestimated nor overlooked.

A combined mistake is a summary of series of single mistakes in self-repeating elements lined up to create a whole part or element.  A single mistake alone might be sometimes microscopical, which often makes it very difficult to compensate for. That single mistake, however, multiplied by number of self-repeating elements is resulting in a combined mistake in overall dimension, which might be quite significant and compromise the whole part, element or an entire model. A combined mistake is like a snow ball – the greater the number of self repeating elements, the more significant a combined mistake will be.

Measurement Systems and Bridging Between MMGS and IPS Systems

The MMGS (millimeters, grams, seconds) or metric system became universal and was accepted all around the globe. No doubt, it is simple, handy, decimal by nature and use decimal fractions. Millimeters are small units, easy to visualize and reflect acceptable for model making tolerance. I personally love millimeters as main measurement units and train my crew to think in millimeters as well.

Truth is, however, that the main measurement system in the United States is traditional IPS (inch, pound, second). We can argue endlessly about convenience of this system, advantages, disadvantages and reasons why Americans are holding onto this system. This argument is not relevant and article is not about it. IPS system in the United States does exist, it’s alive, used every day and will be in active use for a while. It is a fact that has to be accepted.

Professional model maker working in USA or with US specialists must comprehend in both measurement systems and operate freely with metric and non-metric units. Bridging between MMGS and IPS is surprisingly simple. There is no a slightest reason to feel confused or frustrated, there are only a few numbers to remember.

1″ (1 inch) = 25.4mm (25.4 millimeters)

1mm (one millimeter ) = 0.040″ (forty thousands of an inch)

And that’s simply ALL you have to know! Remember these values and you will be comfortable with both systems from now on.