TPI
Units & Measurements abbreviation · Engineering Unit
| Stands for | Threads per inch |
|---|---|
| Categories | Units & Measurements |
TPI stands for Threads per inch, an engineering unit abbreviation.
The number of thread crests per inch along a screw or bolt, the US way of specifying thread pitch. A 1/4-20 bolt has a quarter-inch diameter and 20 TPI, the standard camera tripod screw.
Example: Order 3/8-16 bolts, coarse thread, 16 TPI, in grade 8 steel.
Usage notes
Metric threads give pitch in millimeters instead, so an M8 × 1.25 bolt has 1.25 mm between crests. US threads come in coarse (UNC) and fine (UNF) series. TPI also rates saw blades, where it means teeth per inch and higher numbers give smoother cuts.