Shafts #

Rod vs. shaft #

In engineering parlance, a rod means a round stick and a shaft means a really round stick.

If you look at a 6 mm diameter steel rod like McMaster 8920K22, you’ll find it costs around $9 per meter, can be undersized up to 0.05 mm, and has no straightness specification.

Compare that to a 6 mm steel shaft like Mcmaster 1482K64. The shaft costs around $40 per meter, can only be undersized by 0.01 mm, and has a straightness specification of 0.03 mm per 300 mm of length.

Generally, we buy rods unless we need to make something spin. For spinning stuff, we use shafts.

How to attach stuff to shafts #

1. Press fit #

2. Set screws #

3. D-shafts #

4. Keys and keyways #

5. Tapered hubs #

6. Clamping shaft couplings #