Category Archives: Metrology

Measuring Countersink Angle Using Gage Balls

This post will cover how to measure a countersink angle using gage balls. Figure 1 shows how a countersink is normally specified on an engineering drawing. I frequently use countersinks in my wood and metal working hobbies. In addition, using gage balls to measure the countersink angle provides a good example of how to apply basic geometry concepts to a practical problem.  I use this example in my role as a volunteer adult math tutor at our local library. Continue reading

Posted in General Mathematics, Metrology | 2 Comments

Shotgun Bore Diameter Math

I have been doing some metalwork lately that involves using units of "gauge". You will find the term gauge used in the measurement of wire, metal thickness, and pipe bore diameter. This quaint, but confusing, measurement system is slowly falling out of favor (example, sheet metal thickness gauge). Continue reading

Posted in Metrology | 3 Comments

Measuring a Chamfer Angle Using Gage Balls

One metrology operation I have had to perform a number of times is measuring a chamfer angle precisely – Figure 1 shows today's example. Many items are chamfered – even in electronics. For example, edge connectors on printed circuit boards often need to be chamfered to ensure that they do not damage the connectors they are being inserted into. Continue reading

Posted in Metrology | 2 Comments

Tapered Side Angle Measurement

I thought I was done with my metrology review when I encountered an excellent set of discussions at the Hobby-Machinist web site. They advertise themselves as "The Friendly Machinist Forum" and all signs indicate that is true. In addition to excellent tutorial discussion, there are some excellent metrology discussions on that site, and I want to document a few of the examples that are shown there. Continue reading

Posted in Metrology | 2 Comments

Another Angle Measurement Using Roller Gages Plus Error Analysis Example

While I covered angle measurement in a previous post, that approach can be difficult to apply for acute angles. The approach presented in this post works well for acute angles, but will not work for obtuse angles.

As part of this post, I will also demonstrate how to perform a tolerance analysis on this approach. The tolerance analysis is important in understanding the level of accuracy required in your linear measurements to achieve the desired angle accuracy. Continue reading

Posted in Metrology | 1 Comment

Measuring Round-Over Radius Using a Roller Gage

This blog post shows how to measure the radius on a rounded corner (a.k.a. bullnose) using a roller gage. I saw this method being used on this web page, and I wanted to document it here for future reference. Continue reading

Posted in Metrology | 1 Comment

Bore Diameter Measurement Using Gage Balls

I am continuing to work through the metrology examples on this web page as part of junior machinist self-training. Today's technique shows how to use gage balls to measure the bore diameter of a cylinder (Figure 1). You can measure a bore diameter using a micrometer, but I have concerns that I might be measuring along a chord instead of a diameter – this error would result in too small of a result. The gage ball approach should eliminate that type of error. Continue reading

Posted in Metrology | 5 Comments

Angle Measurement Using Roller Gages

I am continuing to work through some basic metrology examples – today's example uses roller gages to measure the angle of a drilled hole (Figure 1). The technique discussed here uses two roller gages and a plug. The plug must fit the hole snugly (i.e. no backlash) as it will provide the surface that we will be measuring. Using this approach assumes that you need a very accurate measurement of a hole's angle as rough measurements can be made using a protractor. Continue reading

Posted in Metrology | 2 Comments