I bought one of those, the write up sounds good, but it is a long way out, about 0.5mm over the length of the 300mm rule on the standard 90/45deg stock. With a little bit of fettling I'm sure it could be made right though.
I bought one of those, the write up sounds good, but it is a long way out, about 0.5mm over the length of the 300mm rule on the standard 90/45deg stock. With a little bit of fettling I'm sure it could be made right though.
That's around 1 1/2 thou per inch (*), which is close to grade 'B' accuracy (which is 1 thou per inch IIRC). Given that some fixed engineering square are only grade 'B', I'd say that your combo square is working as well as should be expected.
But you probably don't really need a 45degree square. The inside surface is usually the reference face, so you should be using a 135 degree square looks just like yours but obtuse rather than acute, available at all good engineering suppliers.
That's interesting BugBear, my squares are all reasonably accurate then. I never realised that a square could be that far out and still be considered square. To me that seems quite a bit out when I am using it. I'll have to check a bit harder on the spec next time I buy one.
That's interesting BugBear, my squares are all reasonably accurate then. I never realised that a square could be that far out and still be considered square. To me that seems quite a bit out when I am using it. I'll have to check a bit harder on the spec next time I buy one.
If you consider the size of the machining error at the two points where the rule is actually fitted to the head, you'd be amazed that even this accuracy you find so disappointing is achievable.
