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Identifying the size of my Bolt or Screw
With so many thread types across metric and imperial it can be confusing, even to us experts. It can look like M5 but why doesn’t a M5 nut wind on? Is there a way to tell if I don’t have a thread tool. You can most of the time with ideally a digital vernier, next best is a ruler or tape measure. Start off by measuring the outside of the thread, then click on the dropdown and select the range your measurement falls within. This will give you a selection of possibilities. You need then to identify the thread type. if you fastener has a marking on the head, refer to the bolt identification chart, once identified, and now you have narrowed down the size, you know need to work out the thread. Is a metric or imperial, is it coarse or fine?
Outside diameter of the thread
Metric Coarse
Metric Fine
Metric Extra Fine
UNC
UNF
BSW
BSF
BA
Screw Gauge
You know the size screw but want to cross check the diameter. Select the size from the dropdown to see the closest match.
You can multiselect to compare sizing
| Screw Type | Thread Type | Outside Diameter of Thread |
|---|
