Quote of the Day
Of course her kids come before you! Hell, her kids come before her.
— I saw this on Pinterest, but I once heard a manager say something similar to an employee. I always work to keep my priorities properly set – family is first.
Introduction
Figure 1:Round-Over Radius Measurement Example.
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.
You might wonder why an electrical engineer is so interested in mechanical metrology. Unfortunately, I regularly deal with issues involving precision mechanical measurement. For example, I just left a meeting where we discussed flatness issues with connectors that have been reworked onto printed circuit boards. We have discovered that a mounting problem introduced an angle on a connector that results in failures at a specific temperature. This type of precision work justifies the granite slab and metrology gear that I keep in our workshop.
In this post, I will work through the basic geometry associated with this measurement and will work an example.
Analysis
Definitions
Figure 2 shows the key variables in the problem. The blue circle represents the radius of the round-over that we wish to measure. We can derive an expression for the radius R in terms of h1, H, and D1 by applying the Pythagorean theorem to the red-legged right triangle.
Figure 2: Definitions of Terms.
Derivation
Figure 3 derives an expression for the radius of the round-over.
Figure 3: Derivation of Round-Over Radius Formula.
Example
Figure 4 shows how I computed the round-over radius for the example of Figure 1. The formula and the scale drawing agree.
Figure 4: Worked Figure 1 Example.
Conclusion
I plan on using this measurement method on a project very soon. I have one more metrology example to work through and it will include determining the level of accuracy (i.e. tolerance) of these measurements.
Pingback: Another Angle Measurement Using Roller Gages Plus Error Analysis Example | Math Encounters Blog