Major Diameter Before Threading

A thread micrometer,:cry:, Mike you give great advice on tool making or machining but I tell you the advice you give on tools is always hard on the wallet:D I know you are a "buy once,cry once"- kind of a man but I must admit I have had zero regrets listening to your advice and recommendations.
I'll work on a thread mic next.:encourage:
Actually I need two don't I, one metric and one imperial.

The cheap way to go is to buy a three wire set. They are accurate. I just don't like them because I always drop one or two of them. Yes, yes, I know how to use wire/putty/etc, etc. I just don't like them, and then I have to do a calculation to get the info I need. A thread mic is direct reading and takes a few seconds to figure out where I am.

You do not need a Tesa thread mic. A Shars-quality set will do fine and no, you don't need an Imperial and Metric set. The anvils with the Imperial set will also measure metric, although you'll need to convert inches to mm. You can also buy these in Metric if you prefer to work in those units.

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You can get by with the 0-1" mic for most work. If you go bigger then buy a bigger one. This is the equivalent of the Fowler/Shars tool: https://www.amazon.ca/Accusize-0-00...=1504044906&sr=8-1&keywords=thread+micrometer

Sorry about the wallet hit, Ken. We, as members of the HM community, are duty-bound to get other guys to buy stuff! :)
 
I've designed lots of threads over the years, they all are cut to specific tolerances. Most can only be cut on CNC machines.
In my shop for any 60 degree vee thread, I leave the OD a couple of thousandths big. Doing this allows for deburring of the thread flanks with file and a little polishing with emery to make the threas look pretty. Once done, the OD is generally right on size.



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In my shop for any 60 degree vee thread, I leave the OD a couple of thousandths big. Doing this allows for deburring of the thread flanks with file and a little polishing with emery to make the threas look pretty. Once done, the OD is generally right on size.
Great tip Ken, thanks.
 
Just interested but 4gsr could explain what you mean by most can only be done on the cnc. Other than a manual machine not having the right pitch in the thread box why couldn t a manual machine cut a thread a cnc could?
 
Just interested but 4gsr could explain what you mean by most can only be done on the cnc. Other than a manual machine not having the right pitch in the thread box why couldn t a manual machine cut a thread a cnc could?
Imagine a thread with a variable pitch or lead that changes from start to end. A thread with a variable depth to it. A thread with a taper that changes from end to end. Just a few examples of threads that can't be cut manually. And most CNC machines can't cut them either!
 
Interesting. I ve made variable screws on screw machines but a wood to metal thread and tapered threads on a manual lathe with the taper attachment. To change actual pitch. Not possible on a manual machine. Learn something everyday. Thanks for posting!
 
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