Reading the Steel Rule

Summary

In this metrology course CMM 118, Brett Logsdon teaches how to read various scales on a steel rule. He covers the standard steel rule with 30-second and 60-force graduations, explaining how to read and reduce measurements. The video also explains the decimal rule with 10 and 100 spaces per inch, and the metric rule with half-millimeter and millimeter graduations. A special mention is given to the symmetric rule, which can be confusing due to its unique graduations. The instructor encourages questions and offers assistance via email or text.

Takeaways

• 📏 The standard steel rule is used for precise measurements and is graduated in 30 seconds and 60 force.
• 🔍 Reading the steel rule involves counting the graduations, which are in 30-second increments for the example provided.
• ✂️ When an even number is encountered, the numbers are halved to reduce the measurement, such as 28 30 seconds becoming 14 16.
• 🔢 The 64 steel rule is more challenging to see but is read in the same manner, with graduation marks every 64th.
• 📐 The decimal rule differs, with 10 spaces between 0 and 1 inch, and measurements are read as fractions or in terms of 'thousandths' of an inch.
• 📉 The metric rule is straightforward, with graduations of half a millimeter on the top scale and whole millimeters on the bottom scale.
• 🔄 The metric scale typically measures to additional decimal places, unlike the inch scale.
• 🚫 A special note on symmetric rules: they may have a different graduation, such as one centimeter instead of ten, and require adding a zero for millimeter conversion.
• ⚠️ A warning is given about metric rules that only have a single number at the end, which should be read as centimeters and have a zero added for millimeters.
• ❓ The instructor encourages questions and offers to answer them via email or text, promoting further learning and clarification.

Q & A

What is the purpose of the lesson on the steel rule?

The purpose of the lesson is to introduce the use of steel rules in the metrology course CMM 118, focusing on how to read and interpret measurements from different types of steel rules.

How is the standard steel rule graduated?

The standard steel rule is graduated in 30 seconds and 60 force, with each increment representing a specific measurement value.

What is the process for reading a measurement that ends on a 30-second mark on the steel rule?

To read a measurement ending on a 30-second mark, one simply counts the 30-second increments until the desired mark is reached, then reads the corresponding number.

How do you handle an even number measurement on the 30-second scale?

For even number measurements, you reduce both the numerator and denominator by half to obtain the final fraction.

What is the difference between reading a 30-second scale and a 60-force scale?

The 30-second scale is read by counting the 30-second increments, while the 60-force scale is not mentioned in the transcript, so it's assumed to be similar but with different graduations.

How is the 64 steel rule different from the 30-second scale?

The 64 steel rule has graduation marks of 64 on the bottom, which means it's graduated in smaller increments compared to the 30-second scale, making it more precise.

What is the significance of the decimal rule in the context of the lesson?

The decimal rule is different from the inch-based rules and is used to measure in tenths of an inch, with 10 spaces between 0 and 1 inch.

How do you read a measurement on the decimal rule that lands between the graduation marks?

For measurements between graduation marks on the decimal rule, you count the spaces and express the measurement as a fraction of an inch, such as 6/10 or 600 thousandths of an inch.

What is the difference between the metric rule and the inch-based rules?

The metric rule is easier to read for those familiar with the metric system, as it uses millimeters and centimeters, with graduations of half millimeters and whole millimeters.

How do you read a measurement on the metric rule?

On the metric rule, you count the graduations as millimeters, with each long mark representing a whole millimeter and the short marks representing half millimeters.

What is a symmetric rule and how is it different from other rules?

A symmetric rule is a metric rule that is graduated differently, often with one centimeter represented by a single number, and the user is expected to add a zero to get the millimeters.

What advice does the instructor give for dealing with unfamiliar or tricky rules?

The instructor advises to be cautious with unfamiliar rules, especially symmetric rules, and to always look for the graduation indicator, such as 'cm', to correctly interpret the measurements.