1/4" × 28 TPI External (Bolt) Thread Specifications
ASME Unified National Fine (UNF) per ASME B1.1 — bolt/screw dimensions
Applications
Automotive trim
Small engine repair
License plate fasteners
Technical Specifications
Parameter
Notation
Value
Threads Per Inch
n
28.0 TPI
Pitch
P
0.0357 in
Major Diameter
d
0.2490 in
Pitch Diameter
d2
0.2258 in
UNR Minor Dia (Max)
d1_max
0.2065 in
Allowance
es
0.0010 in
Tolerance Class
Class
2A
Thread Height
H
0.0309 in
Thread Depth
h3
0.0219 in
Crest Width
f / (P/8)
0.0045 in
Root Width
r / (P/4)
0.0089 in
Tap Drill
Drill
0.2143 in
Related Thread Sizes
1/4" × 20 TPI (UNC)
1/4" × 32 TPI (UNEF)
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