Identifying Thread Pitch
The thread pitch can be measured with a steel rule, as illustrated in Figure 44, or a caliper or comparator can be used.
- The thread pitch is the axial distance from one thread groove to the next. By laying a steel rule down the axis of a screw and counting the number of thread crests in a given length, the pitch can be determined by dividing the count into the length.
- In the example shown (Figure 44), there are 5 pitches in 1 in. so the thread pitch is .200 in.
- Note that the number of threads per inch is the reciprocal of the thread pitch. A common mistake is to count the number of threads starting with “one”. This will lead to a one-pitch error.
- Make sure you start with “zero” for the first thread.
- To double-check your pitch determination, check your pitch determined by count against your actual pitch measurement.