Material specification page for button head socket cap screws, unc in Property Class 8.8 Steel. Covers the grade designation (ISO 898-1 property class 8.8), corrosion and magnetic behavior, comparable grades and their trade-offs, and the sizes available to ASME B18.3.
Why Choose Property Class 8.8 Steel for Button Head Socket Cap Screws, UNC
The workhorse medium-carbon alloy class for structural joints. For button head socket cap screws, unc, this matters when requires plating (zinc) for corrosion protection is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 898-1 property class 8.8 |
|---|---|
| Magnetic response | Magnetic |
| Service temperature | commonly limited to approx. +300 °C; confirm against the coating and the load |
| Corrosion characteristic | Requires plating (zinc) for corrosion protection |
Corrosion Behavior in Service
Carbon and alloy steel button head socket cap screws, unc require a coating for corrosion protection. Zinc plating (with or without passivation) is the most common; hot-dip galvanizing is used for outdoor structural service; black-oxide is mainly a tarnish-prevention finish for tool-room use.
Comparable Grades
For Button Head Socket Cap Screws, UNC, class 10.9 or 12.9 is the comparable strength step. Move up when the joint preload approaches the proof load of the current class; move down when the joint is over-specified. For corrosion-critical service, switch to stainless A2 or A4.
Sizes of Button Head Socket Cap Screws, UNC Available in Property Class 8.8 Steel
| Size | Pitch P (mm) | b (mm) | da (mm) | Head diameter dk (mm) | Hex socket s (mm) | t (mm) | r (mm) | Head height k (mm) | Length range l (in) | Reference standard |
|---|---|---|---|---|---|---|---|---|---|---|
| #0 | 0.318 | 6.096 | 1.646 | 2.896 | 0.889 | 0.489 | 0.061 | 0.838 | 1/16"~1/2" | ASME B18.3 |
| #1 | 0.397 | 7.417 | 2.003 | 3.531 | 1.27 | 0.699 | 0.074 | 1.02 | 1/16"~1/2" | ASME B18.3 |
| #2 | 0.454 | 8.738 | 2.359 | 4.166 | 1.27 | 0.699 | 0.087 | 1.201 | 1/16"~1" | ASME B18.3 |
| #3 | 0.529 | 10.066 | 2.718 | 4.775 | 1.587 | 0.873 | 0.101 | 1.384 | 1/8"~1" | ASME B18.3 |
| #4 | 0.635 | 11.379 | 3.072 | 5.41 | 1.587 | 0.873 | 0.114 | 1.565 | 1/8"~2" | ASME B18.3 |
| #5 | 0.635 | 12.7 | 3.429 | 6.045 | 1.984 | 1.091 | 0.127 | 1.746 | 3/16"~2" | ASME B18.3 |
| #6 | 0.794 | 14.021 | 3.786 | 6.655 | 1.984 | 1.091 | 0.14 | 1.928 | 1/8"~3" | ASME B18.3 |
| #8 | 0.794 | 16.662 | 4.499 | 7.925 | 2.381 | 1.31 | 0.167 | 2.291 | 1/8"~3" | ASME B18.3 |
| #10 | 1.058 | 19.304 | 5.212 | 9.169 | 3.175 | 1.746 | 0.193 | 2.654 | 3/16"~3" | ASME B18.3 |
| #12 | 1.058 | 21.946 | 5.925 | 10.414 | 3.572 | 1.965 | 0.219 | 3.018 | 3/16"~3" | ASME B18.3 |
| 1/4" | 1.27 | 25.4 | 6.858 | 11.1 | 3.969 | 2.183 | 0.254 | 3.493 | 3/16"~4" | ASME B18.3 |
| 5/16" | 1.411 | 31.75 | 8.572 | 13.894 | 4.763 | 2.619 | 0.318 | 4.366 | 1/4"~4" | ASME B18.3 |
| 3/8" | 1.587 | 38.1 | 10.287 | 16.662 | 5.556 | 3.056 | 0.381 | 5.239 | 1/4"~5" | ASME B18.3 |
| 7/16" | 1.814 | 44.45 | 12.002 | 19.431 | 6.35 | 3.493 | 0.445 | 6.112 | 3/8"~5" | ASME B18.3 |
| 1/2" | 1.954 | 50.8 | 13.716 | 22.225 | 7.938 | 4.366 | 0.508 | 6.985 | 1/2"~5" | ASME B18.3 |
| 5/8" | 2.309 | 63.5 | 17.145 | 25.4 | 9.525 | 5.239 | 0.635 | 8.731 | 3/4"~5" | ASME B18.3 |
| 3/4" | 2.54 | 76.2 | 20.574 | 27.94 | 11.113 | 6.112 | 0.762 | 10.477 | 3/4"~6" | ASME B18.3 |
Dimensions are independent of the material: every size above is available in Property Class 8.8 Steel.
Custom manufacturing · Made to drawing
Need this screw in a grade that is not listed?
Grade 8 8 Steel is one of the grades the catalog describes. Material and finish are usually what drives a special — a grade the standard part is not stocked in, or a coating chosen against a salt-spray figure instead of a default. Made by cold heading or warm forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
