Threading prep question.

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Wino1442

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Hi all.... I have drilled and bored a hole to an inside diameter of 20mm and then threaded it. I now need to make a threaded plug to go into this opening. I'm wondering....do I make the diameter of the plug the same as the opening that it's going into or should I make it slightly larger so I can sneak up on a nice fit when I thread it? Thanks
 
Wino1442 said:
Hi all.... I have drilled and bored a hole to an inside diameter of 20mm and then threaded it. I now need to make a threaded plug to go into this opening. I'm wondering....do I make the diameter of the plug the same as the opening that it's going into or should I make it slightly larger so I can sneak up on a nice fit when I thread it? Thanks
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If you make the plug the same diameter as the hole you bored the plug will simply fall into that hole you will need work out your thread depth and add that to the hole you have bored and then cut your threads on the plug after you have machined it to correct diameter .Im no ecpert but it may have been easier to make the plug first then do the threaded hole .hope this small bit of info helps
Regards Moper
 
I'm thinking 20mm + 2 X thread depth. This will probably not let the plug in but you can take exceptionally light cuts and try the nut after each pass.
As you can tell my threading is trial and error, but by checking the fit after each pass I get fairly good results. There has been a lot of discussion recently about thread cutting, a lot of good info in the thread.
Have a good day
Ray
 
If it's a standard metric thread the major diameter of the male threaded plug you want to make should be printed on a chart somewhere
 
Do not be embarrassed by having to "cut and try"; that is how quite a lot of threading is done. If you start with the OD a small amount oversize, when the threads come up sharp but still do not fit, you can file the crests down a bit and cut some more until it fits, and as Bob said, the fit is on the flanks, not the crest (or root). As has been suggested above, making the plug first and boring the nut to fit is the way to go about it.
 
There are some folks on this platform that try to take it to a much higher technical level, I'm sure you have seen them, Bob ----
 
Thank you all for the replies...I will keep pluggin along. Hopefully I won't have to make this part too many times until I get it right....but I guess that's all part of the learning process.
 
Practice and experience are perhaps the best ways to learn, but a LITTLE book learning is of value too.
 
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