Thanksgiving break is nearly upon us, and the student body is desperate to extend their week-long break into something even longer. But classes are still in session! There are still amazing and exciting things to learn!
And we have toys to give away!
Annual tradition to encourage our introductory physics to stick around: problem session prizes. Puzzle games, fidget spinners, stretchy rubber toys, and some other unidentifiable plastic oddities that came in the variety packs. It’s a literal grab-bag of eye-searingly bright toys.
Need to connect one thing to another? You have options. Somanyseeminglyendlessoptions. And, yes, digging through all of that will reveal treasures upon treasures, from more head drive styles than you can imagine ever needing – at least twenty-two – to nuclear-grade duct tape to plain old Elmer’s glue sticks. (We have yet to find a use for nuclear-grade duct tape around here, but glue sticks come in handy sometimes.)
Mechanical fasteners, specifically screws, see a great deal of use around here. Among other benefits, they’re easy to remove. When you spend your days making and modifying things, leaving open the possibility of taking an apparatus apart and swapping in a newer, better piece is reassuring. Sure, it means tapping a lot of holes instead of simply running a bead of adhesive. Trade-offs.
The variety of socket head screws alone can be mind-boggling. You could make an entire career out of just maintaining the ANSI standards on those things. Presumably someone does. Several someones.
For most jobs, alloy steel will do. Strong, inexpensive, and available in every length and thread imaginable. If it’s going someplace where it might get wet, zinc-coated provides corrosion resistance. Or upgrade to 18-8 stainless steel, which isn’t as strong but is more corrosion resistant. If it’s passivated, even more so. Black oxide if you want a matte-black finish; chrome-plated if shiny’s the thing. Silver-plated “have mild lubricity so they thread smoothly.”
New vocabulary word: lubricity.
316 stainless is more corrosion-resistant. A286 stainless are as strong as alloy steel, as corrosion-resistant as 18-8, and so expensive that they’re sold as single screws only. Save those for the next time you’re building an aircraft.
Then there are the other metals, each with special applications. That often includes resistance to corrosion from salt water or other chemicals, and if that’s where you find your project, get ready to do your homework. “Corrosion-resistant” is a big umbrella.
Sometimes you’ll get an even more unusual request: build a gizmo without any metal. Metals, especially ferrous ones, tend to cause trouble when working with magnetic fields, and physicists love them some magnets. Steel’s out. Brass, bronze, and aluminum are nonmagnetic, but are conductive enough to generate potentially disruptive eddy currents in a changing magnetic field. Could present a problem. That leaves plastic.
Plastic. The standard is nylon, which is strong, durable, and light. It may also expand when wet, so watch out for that. Polypropylene is more resistant to various chemicals and doesn’t swell in water, and you can expect to pay for those added benefits. Then there’s PEEK. Polyether ether ketone. Strong. Resistant to a whole array of chemicals. Happy up to 500° F. At several dollars per screw, you’ll know when you need one.
