How to Turn a Broken Plastic Gear Into a Free Steak
Introduction: How to Turn a Broken Plastic Gear Into a Free Steak
Welcome to "How to get a Free Steak out of a Broken Plastic Gear 101"!
My father-in-law is the best grandfather in the world and a wonderful part of my family, but occasionally he conspires with his equally old and technology-challenged friend to make my life difficult. In their latest episode of “I bet Matt can fix this” (that’s me), they volunteered me to make replacement gears for an ancient machine used to make the little equally spaced holes found within kitchen cabinets for selecting where the shelves are placed. This machine is essentially a drill press with around twenty drills running off of a single drive motor through a series of plastic gears. In this case, a series of broken plastic gears.
I should note that the equipment is obsolete and parts are no longer available, and that custom made replacement gears were quoted at $300 a piece.
Supplies
Micrometer
Protractor
3D Printer
Steak (stay with me... you'll understand)
Step 1: Exhale Loudly With a Smidgen of Disdain
This is a critical step that alerts your enthusiastic parent-in-law that the assigned task may not be as simple as he thought (regardless to the fact that it is or isn’t) and can often be used to gain a quality steak dinner upon completion of said project.
Step 2: Put on Your Thinking Cap
This is the part where you need to realize that the original machine was most likely poorly engineered in the first place (otherwise it would not be broken after the 40 years of the abusive service that it has endured up to this point) and that the internet and a 3D printer are the key to any project’s success. This step may require excessive imagination on your part, as the “machine” was probably engineered just fine, but you should tell yourself anything that you need to hear when a free steak is potentially involved.
Step 3: Take Some Measurements
I used a digital micrometer to properly measure one of the remaining gears for the machine. I found that the gears were 3/4-inch tall and fitted onto a 1/2-inch diameter shaft that was machines flat on two sides (to 3/8-inch wide). The overall diameter of the gear was 1.30 inches. The secondary importance of using a digital micrometer is that this $10 Amazon purchase really impressed all the old dudes that were standing around and watching me. 215
It should be noted that old-school micrometers used a mechanical dial that spun around and around, and they could easily be misread by an unqualified person, but a cheap digital micrometer is accurate and easy to read. Don’t let the old dudes get too close or they may realize this and your cool points will be lost.
Additionally, I brought a protractor to measure the gear angle. In this case, I exercised my fatherly right to borrow from my children’s crafting supplies and was unfortunately only able to find a translucent light red (pink) protractor. This required me to exercise significant discretion during the measurement process to avoid an onslaught of inappropriate comments from these “men”. Fortunately for me, I was able to complete the necessary task without detection. This showed a gear angle of 22.5 degrees.
Step 4: 3D Modeling
My 3D modeling program of choice is Autodesk’s Fusion 360. This is a professional grade program for 3D modeling and design, and Autodesk has made it available, for free, to hobbyists like myself who like to goof around with 3D modeling but can’t justify an annual licensing fee. I am especially grateful for this because I’ve tried to use many other free 3D modeling programs and I found Fusion 360 to be the best balance of available tools and capability for the types of projects I work on.
I also found that Autodesk has a Helical Gear Generator add-on for Fusion 360 (by Hobbyist <PERSON>) that can be downloaded. This function automatically models your gear through a simple pop-up menu that asks for the design characteristics of your gear. To be fair - it has been a few years since my last mechanical design class that discussed gear design and I had to look up lerms like backlash, pressure angle, module… Seriously, I’m a mechanical engineer - I’ve been out of school for 23 years and this is the first time I’ve ever had to use this stuff…
To make a long story short, you choose the number of teeth for your gear and adjust the “module” to fit the gear to the needed diameter (1.30 inches for my project). 737