Researching single point threading on lathe

[Jon K]

So I understand the idea here... one thing I don't see often discussed is prepping for the thread. What size do you turn to? The same size you would need for a tap or die? IE., if I am going to put a 3/8-16 thread on a shaft, how do I know what OD to have the shaft start at?

Thanks all

 

[Tony Wells]

If you don't want to look up the actual limits for each thread size, just use the nominal major diameter, or a couple of thousandths under that, but never more. For example, a 1"-8 UNC-2A you could start at 1.000/0.998 and come out just fine.

Here's a handy chart covering the standard series of threads.

http://server2.smithy.com/media/pdf...s Size-Unified and American Screw Threads.pdf

 

[Tom Griffin]

Jon,

There are charts galore with the precise information, but basically the major diameter is the nominal size of the thread. In other words, the major diameter of a 3/8" thread should be about .375. The smaller diameters are less obvious. basically a #10 is .188", a #8 is .157" and a #6 is .137". You should invest in a Machinery's Handbook. It will provide all the info you'll need to cut any thread imaginable, even threads of your own design.

Tom

 

[Jon K]

Thanks guys! I will be trying my hand at chopping threads... i mean cutting threads... I mean crashing lathes... oh brother.

 

[PurpLev]

Thanks guys! I will be trying my hand at chopping threads... i mean cutting threads... I mean crashing lathes... oh brother.

hmm... sounds like you're on the right path

as mentioned above, there are reference lists of major and minor diameters for cutting threads.