I had someone online tell me a few months ago that we (Americans? People with money? Conceited jerks?) don’t need to know how to make things anymore because we can just buy them new. Ahem… unfriended!
Think of a parent sewing their child’s costume for the school play. Think of boy scouts building their Pinewood Derby cars. I can still tell you all about geysers from building one in 5th grade out of clay and a syringe. There is so much to gain by making things with your hands, and I’m not even getting into the ways it is so much better for the environment. My (limited) experience with clocks is that when you are missing a piece or something is broken, the go-to thing is to order a new piece online. There are a few things that can be made in-house by some repairpersons, but gears require more machinery and more knowledge.
As a clock tinkerer, you won’t be surprised to find out that I enjoy making things myself. In college I regularly used the metal and wood shops for projects, but outside of that environment it’s hard to find a machine shop to play in. That’s why I recently joined the Staten Island NYC Makerspace. Below is the view from the front of the shop. Yes, that’s Manhattan and the Freedom Tower you see in the distance.
My first project is, most definitely, Lori’s clock.
For new readers (Welcome!), Lori’s clock is a 1932 Sessions electrical mantel clock that is downright gorgeous. Unfortunately it is about half a century out of electrical code. What do I mean? Basically it was a serious fire hazard and that if anyone had plugged it in, things could have ended badly. Thankfully Lori has lent me the clock to tinker with. My goal is to get it up and running after a few sessions in the shop.
I’m replacing the outlet with a 12V DC battery, and replacing the two old motors with two new motors that will run off the battery. The motors also have control knobs to finely tune their RPM, since one of them will be responsible for the actual time-keeping of the clock. My first order of business is to 3D model the two gears I’ll need to make in order to connect the motors to the clock.
There are a number of 3D modeling softwares on the market, but the one preferred by most people I know is SolidWorks. The downside is that it’s really only commercially available. I have a license through my school, but it’s only good for one year. Another option for hobbyists, students, educators, small businesses, or anyone who is not a large corporation is Autodesk Fusion 360. It’s free unless you are using it for work-related things at a company that can afford it. Check out their website for more info.
Before starting the modeling, I decided to swing past the shop. I already went in last Wednesday to get the official tour and the approval to fly solo in the shop. Since it has been a few years since I made anything on a mill or lathe I am planning to get some practice in before trying to make the two small gears I need. I had hoped to practice a little bit on one of the mills today with a piece of Ultra-Machinable 360 Brass from McMaster-Carr. Unfortunately various events aligned such that it was not possible (a broken mill, a miscommunication, a last-minute protest, etc.).
For those who haven’t used a machine shop lately, a little primer: a mill quickly spins a bit (like a drill bit) and moves the bit vertically. It’s useful for punching holes, among other things. A lathe is basically the opposite. It is positioned horizontally and holds your piece firmly while spinning the piece at a high rate. While your piece is spinning you slowly use your lathe tool to move inwards from the circumference, slimming your piece down and making the outside cylindrical. Both machines are expensive to buy and maintain.
Since I couldn’t work on the mill, I began doing some measuring for the two gears I will need to make. Gear 1 has to go on the shaft shown below, and its teeth have to line up with the teeth of the gear shown in the image.
Clearly that image is extremely zoomed in. So the question in, how much of a gap is there between the teeth on the above gear? See below. (coin included for size reference).
The above is a close-up of my analog calipers. It’s hard to tell, but they are open very slightly to 0.010″, which is the amount of space between each tooth on the planetary gear that Gear 1 is connection to. Yikes! Is Gear 2 any better? It has to fit through the hole shown below and mesh with the shown gear.
Okay, that’s ever so slightly better…
As you can see, the ends of the teeth on Gear 2 have to be smaller than 0.040″.
Since I’m not sure if this is even possible to machine, I took some time today to measure the smallest mill bits I could find in the shop. Things are a little chaotic there, but I found bits that were 0.020″ and 0.035″ in diameter. Neither is as small as I need for Gear 1, but they may do the trick for Gear 2. For Gear 1 I may need to buy my own mill bit. Realistically, the smaller the mill bit is the more likely it is to break, and I’m not an expert machinist. Thinking that I may buy 2 or 3 mill bits, I did a quick Google search.
I had a brief moment of paralysis when I saw bits for sale for $5000. After recovering, I found a few sellers online that may have what I need. Most promising right now is a tapered mill bit with a nose of 0.004″. The taper should make it less likely for the end to break off, and it shouldn’t affect my work as long as I don’t have to mill anything too deep.
So what happens if I can’t machine these parts? There’s always the laser cutter!
I’ve talked about it some before, but I am really looking forward to using it. I’m a little worried about my material though. The reportedly best material for laser cutting gears (when metal is not an option) is Delrin (polyoxymethylene). Unfortunately, I recently found out that Delrin is highly flammable.
Heh heh… well at least there’s a fire extinguisher right next to it!
Expect a post within a week with the beginnings of 3D models. I’m hoping to get back into the shop Wednesday morning, though I do have quite a full plate between grad school, work at the bakery, working on my iOS app, and protesting the government. To new readers, thanks for checking out my page, and please subscribe if you want to get occasional emails about clocks and physics and machining and DIY-related things.
P.S. Check out Why Make a Blog? for more info about what I do.