James, I already filed my application to sit for the PE exam this October, and it was accepted. I had experience in many areas to list, so I chose not to include all of my design experience. I also had several design projects to choose from, and not wanting to include them all I decided that the best approach was to walk the reader through the process of actually designing, building, and calibrating one of these machines. This allows you to impart to the reader the depth and scope of your experience. If I had listed them all it would have the made the application too long. Below is an excerpt from my application to give you an idea of how I approached it. If you have any questions, post them and I will respond.
Maui
EXCERPT
During my period of employment for this endorser I worked on a variety of design projects that resulted in the construction of equipment used for experimental purposes. An example of this is an attachment that was designed and built for a Buehler diamond saw. The standard Buehler diamond saw holds specimens of various geometries in a multi-purpose clamp, and sections these materials with a rotating, thin (0.015”) diamond saw blade. The purpose in designing and building the attachment was to produce circumferential notches in cylindrical test specimens. The fixture was designed to accomplish this by clamping the specimen in a collet assembly, and then rotating the specimen about its longitudinal axis by use of a small, variable speed electric motor and belt. The motor mount was designed with the ability to adjust the belt tension to the appropriate value. The motor, belt, and collet assembly were mounted on a compact aluminum plate which was pivoted about an axle assembly mounted to the top of the saw. The axle was press fit into a set of sealed ball bearings. Various weights were added to one end of the saw attachment to bring the specimen into contact with the rotating diamond saw blade. By carefully adjusting the weight, the pressure on the saw blade could be increased to the desired amount to form the circumferential notch in the rotating specimen.
The design of this attachment was limited by the availability of space for mounting on the existing equipment, the limited budget for the Laboratory, and the available tools and equipment for fabrication. I designed each component of the assembly, and machined each of the components myself. A Bridgeport Milling Machine and a South Bend Metal Lathe were used to fabricate these parts. Mitutoyo micrometers which measured to the nearest 0.0001” and Vernier calipers were used to verify that each component was machined to the required tolerances. The most stringent tolerances that were successfully achieved were on the axle where the ball bearings press fit into position. The tolerances for the diameter at these locations were +0.0003” – 0.0000”.
After completing construction of the saw attachment, the equipment was calibrated in order to establish the depth of the notch which was produced in the cylindrical test specimens. A micrometer was incorporated into the design to control the depth of cut. By adjusting the micrometer to different depths of cut, and measuring the results by running several test specimens, a correlation was established between the micrometer settings and the final notch depth. A curve was plotted from the resulting test data which established the relationship bewteen micrometer setting and notch depth. A least squares curve fitting technique was used to generate this curve. A clear set of instructions on how to use the attachment to produce a circumferential notch of the desired depth were written and, together with this calibration curve, were attached to the saw for reference.
