46 —
M
achinist
c
alc™
P
ro
fractional Thread Size
Find the available Internal and External Thread characteristics
for a 1/4-28 screw.
KeySTROKe
DISPLAy
g *
ALL CLeARed
1. Verify Thread Class is set to 2B:
g b
(Thread Class)
INT 2b
2. Enter the Thread Size:
1 / 4 t
SIZe
1/4 –
INCH
3. Enter the TPI and store the final Thread Size:
2 8 t
THReD
SIZe
$
1/4 –
28
INCH
4. Find the available Internal Thread characteristics:
t
(Cut Tap Drill Size)
TAP
DRILL SIZe
3
t
(Roll Tap Drill Size)
R-TAP
DRILL SIZe
5.9
MM
t
(Close Fit Drill Size)
CLOSe
DRILL SIZe
f
t
(Free Fit Drill Size)
fRee
DRILL SIZe
H
t
(Min. Internal Pitch Diameter)
PTCH-
SIZe
0.2268
INCH
t
(Max. Internal Pitch Diameter)
PTCH+
SIZe
0.2311
INCH
t
(Min. Internal Minor Diameter)
MINR-
SIZe
0.2110
INCH
t
(Max. Internal Minor Diameter)
MINR+
SIZe
0.2200
INCH
t
(Min. Internal Major Diameter)
MAJR-
SIZe
0.2500
INCH
5. Switch to Thread Class 2A and find the available External
Thread characteristics:
g b b
(Thread Class)
eXT 2A
t
THReD
SIZe
$
1/4 –
28
INCH
t
(Rod Size for Thread Cutting)
ROD
SIZe
0.2500
INCH
t
(Rod Size for Cold Forming)
CfORM
SIZe
0.2239
INCH
t
(Max. External Pitch Diameter)
PTCH+
SIZe
0.2258
INCH
