Hi I am attempting my first male - female thread cutting procedure on the lathe. Granted working out the external thread's are easier than the internal, being the major is basically the finished size of the bolt. So not much chance of making the bolt to small.
But and there is always a but I do have one big problem on the internal threading.
How the hell do I work out the minor dimension of the thread.
For example if I was cutting a unf 3/4 x 28 tpi then I would not want to bore a hole 3/4 otherwise It's a big boo boo. To big a hole leaves a problem I cant put the material back.
I got a video clip of the 3/4 x 28 example and it states that the minor diameter should be .715 but it does not explain how he came to this number. Granted the major is 3/4 or .750 in decimal.
Surely there has to be a formula for this procedure but I can't find one that an idiot like me can undersatnd, I mean the major dia - 5 * the sqaure root of 3 divided by 8 divided by the pitch was quite sickening for a non mathy like me. so any help would be really helpful
bear in mind that I am not a mathmatician so laymans terms please. Also I come from a metric background and slowly learring the imperial way and the numerous types of threads available so be gentle please :bow:
But and there is always a but I do have one big problem on the internal threading.
How the hell do I work out the minor dimension of the thread.
For example if I was cutting a unf 3/4 x 28 tpi then I would not want to bore a hole 3/4 otherwise It's a big boo boo. To big a hole leaves a problem I cant put the material back.
I got a video clip of the 3/4 x 28 example and it states that the minor diameter should be .715 but it does not explain how he came to this number. Granted the major is 3/4 or .750 in decimal.
Surely there has to be a formula for this procedure but I can't find one that an idiot like me can undersatnd, I mean the major dia - 5 * the sqaure root of 3 divided by 8 divided by the pitch was quite sickening for a non mathy like me. so any help would be really helpful
bear in mind that I am not a mathmatician so laymans terms please. Also I come from a metric background and slowly learring the imperial way and the numerous types of threads available so be gentle please :bow: