Should multiple measurements be taken of the same part or piece when measuring with a steel rule?

Answer: Yes, it is recommended that two identical measurements be obtained before a measurement is recorded. This may require taking an identical measurement two or more times. While we recognize that there is often pressure to work quickly, assuring accuracy in measurement is critical to the manufacturing process and will actually save time in the long run. The old adage is to "measure twice and cut once," and this adage is good advice for the manufacturing worker.

Can fractional steel rules be used to measure at a tolerance level closer than 1/64"?

Answer: No. As a general guide, 1/64" is the closest tolerance level that can be achieved using a steel rule. While some workers may claim that they can achieve greater accuracy, they are increasing the possibility of a costly error if they push a measurement device beyond its intended tolerance levels.

Are metric rules more accurate than English measurement rules?

Answer: No. The measurement system used is not a factor in measurement accuracy or error. Accuracy is determined by the careful attention to detail and consistent application of accepted processes followed by the worker. While it is true that some rules may have finer graduations than others, within a given level of graduation, the two systems of measurement can achieve identical accuracy.

What is the most common source of error when making measurements with steel rules?

Answer: Probably parallax. This is the failure to have your eye or eyes directly lined up parallel to the relevant graduation mark when you observe the alignment. If you are at an angle, the measure will appear different than it really is.

What are the other sources or error?

Answer: There are a few common errors that often make measuring with a steel rule less simple than it should be. One is the failure to record the measurement accurately. This occurs when the measurer thinks one measurement, but writes a different value down. This occurs when the worker is tired, trying to hurry, or is not focused on the task at hand.

Another common error is the failure to precisely line up the graduation mark with the exact appropriate location on the piece being measured. If a finer graduation needs to be used, it is better to take the time to change rules or rule edges rather than estimate the distance between graduations.

A third source of error is confusion on the worker's part resulting from switching from inch to decimal to metric systems. This can only be solved by extended practice using each system, and being careful to note the appropriate system and use it carefully.

How do I take care of a steel rule?

Answer: Like other precision measurement devices, steel rules must be treated with respect and care.  They should be wiped clean after each use. They should also be lubricated from time to time to protect their surfaces. They should be stored carefully in a location that protects them from foreign objects. If they are bent or damaged in any way, they should be turned in to the quality assurance department for calibration or disposal. Follow these guidelines concerning steel rules:

1. Never use a rule to open cans.
2. Never use a rule as a screwdriver to loosen screws.
3. Never use a rule to clean chips in tight comers.
4. Take as good care of a rule as you would an expensive measuring tool.

Are there safety guidelines for the use of steel rules?

Answer: Yes, very important ones. First, they should never be used to measure a moving piece or part. Doing so risks damage to the steel rule and injury to the worker taking the measurement. They should also be located in a consistent place so they do not interfere with machine operations after the measurement has been taken.

How well do I need to be able to read a steel rule?

Answer: The processes used to gain measurements from a steel rule are the same processes that are used for many other measurement devices in manufacturing. The system of having variable lengths of graduation lines, and being able to add the indicated numbers and fractions (or decimals) together to gain the exact measurement, is a fundamental process for the manufacturing worker. Its importance cannot be overstressed! A successful manufacturing worker must be able to perform these fundamental processes quickly, accurately, and consistently. The beginning worker must practice these processes until they can be accomplished with a high degree of accuracy and ease.

Do I have to convert all fractions to "proper" fractions?

Answer: Yes. All fractions must be stated in their proper form. For example, 4/16" must be converted to 1/4"; 16/32" must be stated as 1/2".

Is the metric system really going to replace the English system?

Answer: Maybe/Maybe not. Until one system becomes a standard for measurement, the machinist needs to be able to work comfortably with both systems.