Threads and Threading - Sportpilot.info

METRIC SCREW THREADS M PROFILE 1789
Fig. 3. External Thread Design M Profile with No Allowance (Fundamental Deviation)
(Flanks at Maximum Material Condition). For Dimensions see Table 3
d 3 max rounded
root minor dia.
;;;;
r
min =
0.125P
;;;;
;;;;
Point of
intersection
d 3 min minor dia.
Machinery's Handbook 27th Edition
;;;;
r
min =
0.14434H
min truncation
Basic M profile
Upper limiting profile
for rounded root
(See notes)
Fig. 4. M Profile, External Thread Root, Upper and Lower Limiting Profiles for
r min = 0.125 P and for Flat Root (Shown for Tolerance Position g)
Notes:
1) “Section lined” portions identify tolerance zone and unshaded portions identify allowance (fundamental
deviation).
2) The upper limiting profile for rounded root is not a design profile; rather it indicates the limiting
acceptable condition for the rounded root which will pass a GO thread gage.
3) Max truncation
H
Td2 = --- – r ⎛
min 1 – cos 60° – arc cos⎛1– ------------ ⎞ ⎞
4 ⎝ ⎝ 4r ⎠ ⎠
min
where H=Height of fundamental triangle
r min = Minimum external thread root radius
T d2 =Tolerance on pitch diameter of external threasd
P
4
0.125P
0.5 T d2
0.5 es
Point of
intersection
Rounded root
max truncation
(See notes)
d 2 basic pitch dia.
0.5 es
H
4
d 1
d 1 max flat root
minor dia.
Copyright 2004, Industrial Press, Inc., New York, NY