FOR ANY SIZE THREAD AT ANY PERCENTAGE OF DEPTH
NC/NF INCH & ISO
METRIC
major dia. less thread pitch = tap drill size
Note: thread pitch
=
1.0 inch divided by threads per inch ( t.p.i. )
M 38.5 , 1.5 = 38.5 - 1.5 = M 37 tap drill
The above examples are for 75% thread.
_____________________________________________________
For other
percentages, change the ( .75 ) in the equations below.
(
inch )
Major Dia. less ( 1.299 x .75 )
=
tap drill
t.p.i.
(metric) Major Dia. less ( 1.082 x pitch x .75 ) = tap drill
___________________________________________________________________
FOR
SOCKET HEAD CAP SCREWS
screw dia. + .010 = depth
example: 1/4 in. screw c'bore depth = .260
__________________________________________________
FIND THE DISTANCE ACROSS THE CORNERS
OF A HEX SHAPE
add 15.5% to the distance across the flats
example: 5/8 hex plus 15.5% = .722
_____________________
ACROSS THE CORNERS OF A SQUARE
add 41.5% to the distance across the flats
example: 1" square plus 41.5% = 1.415
Created: 06/16/2001
Last Rev: