Re: [CAD_CAM_EDM_DRO] 15/16-16 bore size

Mike,
In a ref. (don't remember which one now, maybe
the Machinist Handbook?), I found the following formula for Metric threads:

Metric Tap Drill Size=Size-thread pitch

and for Imperial threads the formula is:

Math formula for tap drill size CUTTING TAPS
Basic Major Dia.– (.0130 X % of Full Thread)/Threads Per Inch =Drilled Hole

Math formula for tap drill size THREAD FORMING TAPS
Basic Major Dia.– (.0130 X % of Full Thread)/Threads Per Inch =Drilled Hole

Hope this helps

Country Bubba







At 08:22 AM 3/3/2009, you wrote:

>That screw thread chart looks good. Does such a chart for metric
>threads down to 0.4 exist. I'm having some difficulty making internal
>and external 0.8mm threads. I don't have a metric set of drills and the
>imperial set I have seems to have sizes that fall unequely in between
>the "correct" size for internal threads. I'm also having problems with
>external threads of the same size. Any tricks for dealing with these
>small sizes.
>
>Mike