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Short screws and bolts are those with a length-to-diameter ratio equal to or less
than 5. Long screws and bolts
have a length-to-diameter ratio greater than 5 but less than 10.
Special processing is normally required for bolts with a ratio
greater than 10 in order to minimize the extremity-to-center
thickness ratio.
Tables 1.1
and 1.2
indicate the recommended
electroplating process for each size of externally coarse (UNC)
and fine (UNF) threaded fasteners for all thickness classes in
Table 2. For externally threaded fasteners with UNS and UN
thread series, rack-plating is recommended. For internally
threaded fasteners barrel-plating is generally suitable.
Note 1 — Barrel-plating process (B) and rack-plating process (R).
| Diameter (D),(in,) | Length(L) L ≤ 5D |
5D < L ≤ 10D | 10D < L ≤ 20D | 20D < L ≤ 30D | L > 30D |
|---|---|---|---|---|---|
| 1⁄4 | B | B | B | B | R |
| 5⁄16 | B | B | B | B | R |
| 3⁄8 | B | B | B | R | R |
| 7⁄16 | B | B | B | R | R |
| 1⁄2 | B | B | R | R | R |
| 9⁄16 | B | B | R | R | R |
| 5⁄8 | B | B | R | R | R |
| 3⁄4 | B | R | R | R | R |
| 7⁄8 | R | R | R | R | R |
| 1-4 | R | R | R | R | R |
Note 1 — Barrel-plating process (B) and rack-plating process (R).
| Diameter (D),(in,) | Length(L) L ≤ 5D |
5D < L ≤ 10D | 10D < L ≤ 20D | 20D < L ≤ 30D | L > 30D |
|---|---|---|---|---|---|
| 1⁄4 | B | B | B | B | R |
| 5⁄16 | B | B | B | R | R |
| 3⁄8 | B | B | B | R | R |
| 7⁄16 | B | B | R | R | R |
| 1⁄2 | B | B | R | R | R |
| 9⁄16 | B | B | R | R | R |
| 5⁄8 | B | R | R | R | R |
| 3⁄4 | R | R | R | R | R |
| 7⁄8 | R | R | R | R | R |
| 1-4 | R | R | R | R | R |