Finegrain
Diamond
- Joined
- Sep 6, 2007
- Location
- Seattle, Washington
Hi guys,
I'm doing some 1/8" and 3/4" internal NPT threads. Single-form threadmill. I got to thinking that, unless you make a perfectly tapered bore, the upper threads are going to have sharp crests.
I checked MHB and it has a table of allowed thread truncation. The range for 27 TPI is .0012" - .0036", while the range for 14 TPI is .0024" - .0056" (page 18643 in my 28th edition).
There is also some verbiage about these tolerances only applying to high-pressure applications.
So, am I supposed to use a multi-form threadmill in lieu of making a very precise tapered bore?
Thanks, and regards.
Mike
I'm doing some 1/8" and 3/4" internal NPT threads. Single-form threadmill. I got to thinking that, unless you make a perfectly tapered bore, the upper threads are going to have sharp crests.
I checked MHB and it has a table of allowed thread truncation. The range for 27 TPI is .0012" - .0036", while the range for 14 TPI is .0024" - .0056" (page 18643 in my 28th edition).
There is also some verbiage about these tolerances only applying to high-pressure applications.
So, am I supposed to use a multi-form threadmill in lieu of making a very precise tapered bore?
Thanks, and regards.
Mike