Both metric (M6, M8, M10) and Whitworth (1/4", 5/16", 3/8") threads are common in furniture manufacturing. They look alike but are not interchangeable.
| Metric (ISO) | Whitworth (BSW) | |
|---|---|---|
| Unit | millimetre | inch |
| Thread angle | 60° | 55° |
| Pitch | in mm (1.25 mm for M8) | threads per inch (18 for 5/16") |
5/16" and M8 are almost the same diameter, but forcing a metric nut onto a Whitworth bolt damages the thread and weakens the joint. Check the label ("M" means metric) or use a thread gauge. See our nuts.
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