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4-40 Self Tapping Hole Diameter
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Posted by: rob

11/07/2003, 18:03:42

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Does anyone know the suggested diameter for a 4-40 Self Tapping Pan Head Screw going into hard steel?



Rob


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self taping / thread rolling
Re: 4-40 Self Tapping Hole Diameter -- rob Post Reply Top of thread Forum
Posted by: RKimball

11/08/2003, 15:43:09

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Good answer, however I have some concerns with the hard steel comment.

Remember you need several points of hardness less in the work than in the self taping/forming screw or tap. ... or you are going to break and/or seriously weaken many screws in the product.

-randy-




** The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, don't fail to listen to suggestions. -randy-


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Re: 4-40 Self Tapping Hole Diameter Agree
Re: 4-40 Self Tapping Hole Diameter -- rob Post Reply Top of thread Forum
Posted by: BJH

11/08/2003, 12:54:08

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Rob,

Recommended hole size for a 4-40 thread rolling screw for 70% thread engagement into steel is .1006" (#39 or # 38 drill).

Note: Pilot hole sizes for thread forming srews tend to be a little larger than pilot holes for self-tapping screws.

If you indeed have a self-tapping screw, then I would recommend starting with a pilot hole near .096" (i.e # 41 drill).

Camcar-Textron has a very informative website...check out their link...http://www.textronfasteningsystems.com/camcar/PDFS/taptite.pdf

Good luck,

BJH







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