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Re: Pitch Diameter

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AAMA TIR A9-91 "Metal Curtain Wall Fasteners" Table 4 has various max. and min. pitch diameters for different thread types.

On Mon, Jul 6, 2009 at 6:30 PM, Richard Calvert <RichardC(--nospam--at)> wrote:

Does anyone know of a resource for min and max pitch diameters of self tapping screws (i.e. TEK Screws)?

ITWbuildex doesn’t provide any of this information, so for my calculations of Asn per the ADM05 (ref. Eq. I always use the external thread stripping area formula as found here:

and the values for the various diameters from


and then use the ave. between T-max and t-min as my value for the min pitch diameter… which I understand to be a decently close estimate for tightly spaced threads, but self-tappers are slightly loose…


even better, would anyone happen to know of a better formula than the one I’m using?


Richard Calvert, EIT 

Project Engineer


Lindemann Bentzon Bojack

Architects & Engineers

290 Citrus Tower Blvd, Suite 200, Clermont, Fl. 34711

tel: 352.242.0100 ext.141 fax: 352.242.0302

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