Fasteners & Hardware
We use two bolt sizes for almost everything on the robot. Knowing which one to grab and what nut/locking method to pair it with covers 90% of what you need to know about hardware.
Bolts
#10-32
Light-duty connections: sensor mounts, electronics, polycarbonate panels, thin brackets
0.196" (#9 drill, or 13/64" drill as a second-choice)
1/4-20
Structural connections: mechanism mounts, gearbox attachment, frame joints, anything load-bearing
0.257" (17/64" drill)
Both sizes use socket head cap screws (the kind you tighten with a hex key).
Stick to these two sizes across the entire robot. Mixing in metric, 8-32, or other sizes means more tools, more bins, and more confusion at competition. The only exception is hardware that comes with COTS parts (some motors and sensors use M3 or M4 bolts).
Nuts and thread-locking
Nylock nuts
The default for everything. The nylon insert prevents the nut from vibrating loose. If you're not sure what nut to use, use a nylock.
Blue Loctite (242)
Use on bolts that thread directly into a tapped hole (where there's no nut). One small drop on the threads before threading in. Holds the bolt in place but you can still remove it with a normal wrench.
Red Loctite (271)
Permanent. You need a heat gun to remove it. Only use this on bolts you never want to come out, like a setscrew in a hub that absolutely cannot slip.
You don't need both Loctite and a nylock nut on the same bolt. If you have a nylock, the nylon insert already prevents loosening. Loctite is for when you're threading into a hole and there's no nut.
Shaft retention
If a shaft can slide, it eventually will. Every shaft needs something holding it in the right position.
Shaft collar
Clamps around the shaft with a set screw
Easy to install and adjust. Good default choice for most shafts.
Bolt through the end
A bolt threads into a tapped hole in the end of the shaft
Very secure. Works well for shaft endpoints.
Snap ring / e-clip
Sits in a groove cut into the shaft
Low profile and lightweight, but needs a pre-cut groove and can be annoying to install.
Check every shaft in your design and make sure it has something retaining it. If a shaft doesn't have a collar, a bolt, or a snap ring on it, it will slide out of position during a match.
Other hardware worth knowing about
Rivets
Rivets are permanent fasteners that don't need a nut on the back side. You insert the rivet through a hole, squeeze the rivet gun, and it clamps the parts together. They're lighter than bolts and can't vibrate loose.
We rarely use rivets because we disassemble and reassemble frequently during the season, and rivets are permanent (you have to drill them out to remove them). However, they're useful for joints that are truly permanent, like attaching a bellypan to the frame when bolts aren't working.
If you do use them: 3/16" aluminum blind rivets are the FRC standard. Drill the hole to 3/16" (not oversized). Use at least two per joint so the parts can't rotate.
Heat-set inserts (for 3D prints)
If you need to bolt into a 3D printed part and want it to survive being tightened and loosened multiple times, use heat-set inserts. These are small brass threaded inserts that you push into a hole using a soldering iron. The heat melts the surrounding plastic, and when it cools the insert is locked in with strong metal threads. Common sizes: M3, M4, or #10-32.
Standoffs
Hex standoffs are threaded on both ends and create a fixed gap between two plates. Common use: stacking plates at a set distance. Buy them in standard lengths (1/4", 1/2", 3/4", 1") and keep them stocked.
Shoulder bolts
A shoulder bolt has a smooth, precision-diameter section between the head and the threads. This makes them useful as pivot pins for small mechanisms. The smooth section spins freely in a bearing or bushing while the threaded end clamps into the frame.
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