As an engineer, I do a lot of sketching and drafting. It helps to have a nice pencil for the job, and I have a $50 mechanical drafting pencil that is a joy to use. Erasers are another matter. Most people make due with those terible bricks of low quality rubber that just move graphite around on the page instead of picking it up after a few hours of use. I prefer to use Pentel retractable erasers, since they have a small area, they wear quickly, always leaving fresh, clean rubber for actually erasing. A few years ago, Pentel made a really horrible decision and redesigned their erasers. They created a lovely new feature; the clip/slider is attached to the eraser by about 1 square millimeter of cheap plastic, meaning it almost immedately breaks off, rendering the eraser useless.
After going through half a dozen erasers in 5 months, I decided to take matters into my own hands, and build my own. For this project, I created a CAD model. I initially planned on only creating a new aluminum body for the current eraser mechanism. However, after trying this out, I was dissatisfied with the feel and reliability of the resulting product. So I designed a new eraser latching mechanism, and machined it out of brass. The finished product is shown below. Also in the pictures are my nice drafting pen, and a craptastic Pentel eraser which was the motivation for this project.
Solidworks Rendering of the Latch Mechanism (withouth the springs).
New matching set of aluminum eraser and aluminum pencil.
My eraser next to the inspiration for this project, a Pentel eraser.
All the parts to the eraser latching mechanism. The carriage (bottom middle) has a hole for the eraser, and a slot for the latching mechanism. Two springs in the slot provide upward force that secures the latch. The pen clip screws into the latching mechanism. When you press down on the pen clip, the latching mechanism disengages from the slots on the main body, allowing you to slide the eraser in and out. When you don't press down on the pen clip, the latch is engadged and the eraser is secure. The mechanism is simple, and works amazingly well. The best part, it doesn't make those horrible clicking noises when you use it.
All the parts in this project were machined by hand on a lathe and a mill, the entire project took about 20-30 man hours.