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Re: Advice on 5/16 -27 pipe tap & die

Posted: Mon Jul 18, 2011 9:46 am
by 10 Wheeler Rob
The 5/16-27 thread is for 1/16" standard wall pipe, where the 5/16-40 threads are used on thinner wall brass and copper tubing. If you making fittings either will work, but you can put a larger bore thru the -40 thread.

Rob

Re: Advice on 5/16 -27 pipe tap & die

Posted: Tue Jul 19, 2011 3:59 am
by Greg_Lewis
Rob has answered your question above. The finer thread leaves more wall thickness on the part, and you can use it with thinner tubing. Also, it's more to scale and looks better if it should show. Some modelers use straight threads on everything, relying on various types of goop to seal them. I have built up a collection of 40 tpi taps and dies (from Victor Machinery) and I use this thread for things other than piping, too. Seems like a good model-builder's thread. (Barry Hauge (Superscale) uses a 56 thread on some of his injector fittings.)

Also, I'd suggest you set up some sort of thread standardization system before you get too far along. Decide now what threads you will use throughout your project and stick to that. I recommend the finer threads in most cases, except perhaps into cast iron, for the reasons above. I didn't do this and my engine has every thread in the book from 00-90 to 1/2-20 including all the coarse and fine and special ones too. Such a mix slows things down when coming back to something done months or years ago and now lost to memory.

Re: Advice on 5/16 -27 pipe tap & die

Posted: Wed Jul 20, 2011 10:07 am
by applejak_2000
Greg,
Thanks for the reply. That's a very good point about every sort of thread being on the model. Right off the top of my head the threads run from 2-56 through 3/4-16. Which is why I just bought a big Greenlee tap and die set. Of the sizes on the prints, it seems that there is a significant amount of 8-32. I'll have to go through the prints and see what I might want to change in terms of the pipe threads that show.