T-nuts are as the title says, a nut with a “T” cross-section. This means they can be used in a T-slot for retaining and fixing parts.

T-nut in a T-slot

The T-nut fits in a T-slot and so has to be made to certain dimensions.

Below I have labelled the dimensions of a T-nut and in the table I have given some of the common sizes.

T-nut dimensions
Slot Size B [mm]Thread AC [mm]D [mm]E [mm]F [mm]
8M6 x 1.01061419
10M6 x 1.01161622
10M8 x 1.251161622
12M10 x 1.51371722
14M10 x 1.51692229
14M12 x 1.751692229
16M12 x 1.751692529
18M16 x 2.019112932
20M16 x 2.025143238
22M20 x 2.525143538
27M24 x 3.029184151

I have found that in the model making arena the T-nut dimensions are not that accurately followed. Sometimes a mix of T-nuts and threads is actually rather useful.

double threaded T-nuts

Double T-nuts that I made from mild steel for my low profile vice project.

These are 12mm T-nuts and I have threaded them for 6mm and 8mm.

long T-nuts for rotary table

Long T-nuts that I made to extend the working diameter of the rotary table.

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