Classifying Bolts / Machine Screws
Unified Thread Standard (The US standards for threads per inch)
| Major diameter (inches) | Threads per inch | ||
|---|---|---|---|
| Coarse (UNC) | Fine (UNF) | Extra fine (UNEF) | |
| #0 = 0.0600 | 80 | ||
| #1 = 0.0730 | 64 | 72 | |
| #2 = 0.0860 | 56 | 64 | |
| #3 = 0.0990 | 48 | 56 | |
| #4 = 0.1120 | 40 | 48 | |
| #5 = 0.1250 | 40 | 44 | |
| #6 = 0.1380 | 32 | 40 | |
| #8 = 0.1640 | 32 | 36 | |
| #10 = 0.1900 | 24 | 32 | |
| #12 = 0.2160 | 24 | 28 | 32 |
| 1/4 | 20 | 28 | 32 |
| 5/16 | 18 | 24 | 32 |
| 3/8 | 16 | 24 | 32 |
| 7/16 | 14 | 20 | 28 |
| 1/2 | 13 | 20 | 28 |
| 9/16 | 12 | 18 | 24 |
| 5/8 | 11 | 18 | 24 |
| 3/4 | 10 | 16 | 20 |
| 7/8 | 9 | 14 | 20 |
| 1 | 8 | 14* | 20 |
Bolt Types
| Type | Picture |
|---|---|
| Thread Cutting Bolt | |
| Carriage Bolt | .jpg/200px-Carriage_Bolt_(PSF).jpg) |
| Set Screws |  |
| Eye Bolt | |
| J-Bolt | |
| U-Bolt |  |
| Shoulder Bolt | |
| Elevator Bolt | |
| Sex Bolt | |
| Mating Screw | |
| Hanger Bolt |
Bolt Head Styles
| Name | Abbreviation | Profile | Top |
|---|---|---|---|
| Hex | HH, HX, HHMB |  |
|
| Washer Head | WH | ||
| Flat | FH |  |
|
| Pan | PN |  |
|
| Button | BH |  |
|
| Round | RH |  |
|
| Truss | TH |  |
|
| Oval | OH, OV |  |
Bolt Materials
| Material | Abbreviation | Distinguishing Features | Picture |
|---|---|---|---|
| Zinc Plated | Z | ||
| Stainless Steel | SS | Usually not magnetic | |
| Galvanized | G | Chalky dull appearance | |
| Chrome | C | Very shiny appearance | |
| Bronze | B | Golden / bronze color |
Hex Bolt Grades
Steel Hex Bolt Grades
Note, if the bolt is blank and doesn't have a manufactuer marking on this list. It's best to assume that it doesn't meet any specification. If it has a manufactuer marking that's on this list than it probably meets the grade 2 specifications.
Specification BodySpecificationGradeMarkingMartensitic SAE J429 1 No SAE J429 2 ASTM A307 A SAE J429 5 No ASTM A449 1 SAE J429 5.2 Yes ASTM A449 2 SAE J429 7 No SAE J429 8 No SAE J429 8.2 Unknown ASTM A354 BD No| SAE | 1 | No | place | SAE J429 grade 1 |
Stainless Steel Hex Bolt Grades
AlloySpecification BodySpecificationMarking
303, 304, 304 L, 305, 384, XM1, 18-9LW, 302HQ, 303Se
ASTM F593CBolt Drive Styles
| Drive Type | Abrevation | Picture |
|---|---|---|
| Hex | HH, HHMB | |
| Square | SQ |  |
| Phillips | PH |  |
| Slotted, Straight Blade | SL |  |
| Combination (Philips + Slotted) | ||
| Hex Socket | HEX |  |
| Torx | TRX |  |
| One way |  |
|
| Robertson | ROB |  |