12-12-2016, 05:23 AM
Hi Sean,
I'm not really sure what you are looking at.
A thread gauge will tell you the pitch of the thread, not the diameter of the fastener, as there are multiple sizes that use the same pitch thread (M6x1, M10x1, 1/4-20, 1/2-20 etc). You need to measure the diameter of the male thread to establish the correct size. It may be a little undersize, which can cause confusion. For example, a M8x1.25 bolt may have a diameter between 7.78mm and 8.00mm. This is where having the correct thread gauge is important, as that will generally tell you whether to expect an inch or metric fastener (not always though...).
I'm guessing that your lathe will be using UN (60°) or British Whitworth (55°) threads.
I'm not really sure what you are looking at.
A thread gauge will tell you the pitch of the thread, not the diameter of the fastener, as there are multiple sizes that use the same pitch thread (M6x1, M10x1, 1/4-20, 1/2-20 etc). You need to measure the diameter of the male thread to establish the correct size. It may be a little undersize, which can cause confusion. For example, a M8x1.25 bolt may have a diameter between 7.78mm and 8.00mm. This is where having the correct thread gauge is important, as that will generally tell you whether to expect an inch or metric fastener (not always though...).
I'm guessing that your lathe will be using UN (60°) or British Whitworth (55°) threads.
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