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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 Author Profile Mail author Edit

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

Posted by: BJH ® 11/08/2003, 12:54:08 Author Profile Mail author Edit

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... Good luck, BJH

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