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RE: pitch diameter

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It is aluminum. For steel, you can just follow the allowables per gauge thickness of metal… which can be pulled directly from the ITWBuildex or Hilti (or…) catalogs.

Maybe there is one that addresses aluminums of various alloys and tempers that I’m just not aware of.  If you (or anyone) know of one, I would be forever grateful. 


The aluminum design guide requires calculation of the thread stripping area of the base material, but provides no help on the matter.  The formulas I’ve found require the use of the maximum pitch diameter (or was it minimum…) but I can’t find a resource that states ANY pitch diameters for self tapping screws – only machine, ANSI and ISO…



is the only site I’ve found with any such information on tek/kwik-type screw dimensions, but it doesn’t include the apparently elusive “pitch” diameter.  I typically just take the average between the major and minor diameters and call it a day… but if I’m going to be so exact in these calcualtions, I’de rather be 100% correct versus “approximately exact”


And more than anything, I plan on eventually (big word) building this all into canned excel/VBA calculations, and I don’t see much purpose in being generic when being precise is just as easy once computers are factored into the picture.




From: Andrew Kester [mailto:akester(--nospam--at)]
Sent: Tuesday, July 07, 2009 5:30 PM
To: seaint(--nospam--at)
Subject: re: pitch diameter



What do you need to know all that for? I have done a lot of light gage design, what am I missing?


CFSEI should have the answers to your light gage, I mean, cold formed steel questions....


On that note, why must "they" keep changing the names of perfectly good terms? What changed?


Light Gage >> Cold formed

Slab on grade >> slab on ground (which sounds less technical)

pour concrete >> place/pump concrete

is it wood, is it timber?

wood sheathing can be plywood or OSB....


Sorry about the tangent.


Andrew Kester, P.E.