by Danny Staple

Machine bolts in robot building

Some handy robot kits and parts come with machine bolts (screws) and nuts.

These are handy if you don’t have the exact size needed but are often flawed in two major ways.


First they are often Nylon. That makes them cross thread easily. Be really careful not to over tighten these.

It is helpful in that these threads can be cut to size, but be careful not to leave a rough edge that would make it hard to thread the nut on.

I generally prefer metal bolts, and get a selection of thread lengths so I do not need to cut them.

Bolt head types

The next issue with these are the heads. Supplied bolts often come with a flat head. These are frustrating and will slide out a lot when you screw them.

The next common type are cross heads and posi heads. They aren’t quite the same, but they do still torque out, with the added problem of damaging the heads of the screws or screwdrivers.

My preferred type have a hex socket head. These do not slide out like a flat head, or torque out like a cross/posi. They are a little pricier, but I consider it worth it for the removal of frustration when maintaining or building a robot.

Example parts

Pimoroni have some lovely n20 motor brackets. These fit over n20 motors, and with two bolts, secure the motors nicely to a chassis.

The nylon bolts are suitable in that they keep the cost down, and are easily clipped to length. I’m not sure if these nylon type could be done with hex, but pozi would be an improvement.

What I use

I use a hardware kit with a selection of thread sizes and lengths, hex head machine screws, with nuts and washers.