Material specification page for slotted oval head machine screws, unc in A4 Stainless Steel. Covers the grade designation (ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80), corrosion and magnetic behavior, comparable grades and their trade-offs, and the sizes available to ASME B18.6.3.
Why Choose A4 Stainless Steel for Slotted Oval Head Machine Screws, UNC
Specified for marine, coastal and chemical applications. For slotted oval head machine screws, unc, this matters when superior, including marine and chloride environments is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80 |
|---|---|
| Magnetic response | Largely non-magnetic |
| Service temperature | approx. -200 °C to +400 °C, subject to the property class and the joint |
| Corrosion characteristic | Superior, including marine and chloride environments |
Corrosion Behavior in Service
A4 (316) adds 2–3% molybdenum to the A2 (304) composition, which dramatically improves resistance to chloride-pitting corrosion. For Slotted Oval Head Machine Screws, UNC in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Comparable Grades
For Slotted Oval Head Machine Screws, UNC, the alternative stainless grade is A2 (304). Choose A2 (304) for general use and A4 (316) wherever chlorides are present; the molybdenum in A4 is the whole difference. Remember that stainless is the corrosion answer, not the strength answer — for load, look at class 8.8 or 10.9 instead.
Using Stainless Fasteners in Aluminum
The galvanic couple here runs the wrong way: aluminum is the less noble metal, so it corrodes and the fastener does not. What governs the rate is the ratio of areas — a large anode and a small cathode is a tolerable combination, the reverse concentrates the attack into thin material around the hole. An isolating washer plus sealant breaks the circuit; where that is impractical, match the fastener to the substrate.
Sizes of Slotted Oval Head Machine Screws, UNC Available in A4 Stainless Steel
| Size | Pitch P (mm) | Head diameter dk (mm) | A_mean (mm) | Head height k (mm) | C (mm) | J_min (mm) | T_mean (mm) | Length range l (in) | Reference standard |
|---|---|---|---|---|---|---|---|---|---|
| #0 | 0.318 | 2.845 | 2.642 | 0.889 | 0.533 | 0.406 | 0.699 | 1/16"~1 1/2" | ASME B18.6.3 |
| #1 | 0.397 | 3.48 | 3.264 | 1.092 | 0.635 | 0.483 | 0.876 | 1/16"~1 1/2" | ASME B18.6.3 |
| #2 | 0.454 | 4.115 | 3.886 | 1.295 | 0.737 | 0.584 | 1.041 | 1/16"~2 1/2" | ASME B18.6.3 |
| #3 | 0.529 | 4.75 | 4.496 | 1.499 | 0.838 | 0.686 | 1.206 | 1/8"~2 1/2" | ASME B18.6.3 |
| #4 | 0.635 | 5.385 | 5.118 | 1.702 | 0.94 | 0.787 | 1.372 | 1/8"~4" | ASME B18.6.3 |
| #5 | 0.635 | 6.02 | 5.74 | 1.905 | 1.041 | 0.889 | 1.549 | 3/16"~4" | ASME B18.6.3 |
| #6 | 0.794 | 6.655 | 6.35 | 2.108 | 1.143 | 0.991 | 1.702 | 1/8"~4" | ASME B18.6.3 |
| #8 | 0.794 | 7.925 | 7.582 | 2.54 | 1.321 | 1.143 | 2.032 | 1/8"~5" | ASME B18.6.3 |
| #10 | 1.058 | 9.195 | 8.826 | 2.946 | 1.524 | 1.27 | 2.375 | 3/16"~8" | ASME B18.6.3 |
| #12 | 1.058 | 10.465 | 10.058 | 3.353 | 1.727 | 1.422 | 2.705 | 1/4"~8" | ASME B18.6.3 |
| 1/4" | 1.27 | 12.116 | 11.671 | 3.886 | 2.007 | 1.626 | 3.15 | 3/8"~10" | ASME B18.6.3 |
| 5/16" | 1.411 | 15.164 | 14.643 | 4.851 | 2.515 | 1.829 | 3.962 | 1/2"~10" | ASME B18.6.3 |
| 3/8" | 1.587 | 18.212 | 17.615 | 5.842 | 2.972 | 2.057 | 4.775 | 1/2"~12" | ASME B18.6.3 |
| 7/16" | 1.814 | 19.304 | 18.733 | 5.664 | 3.099 | 2.057 | 4.877 | 3/4"~12" | ASME B18.6.3 |
| 1/2" | 1.954 | 20.701 | 20.066 | 5.664 | 3.327 | 2.311 | 4.978 | 3/4"~12" | ASME B18.6.3 |
| 9/16" | 2.117 | 23.673 | 22.987 | 6.604 | 3.81 | 2.591 | 5.804 | 3/4"~12" | ASME B18.6.3 |
| 5/8" | 2.309 | 26.67 | 25.908 | 7.569 | 4.293 | 2.946 | 6.604 | 3/4"~14" | ASME B18.6.3 |
| 3/4" | 2.54 | 32.639 | 31.75 | 9.449 | 5.232 | 3.327 | 8.204 | 1"~14" | ASME B18.6.3 |
Dimensions are independent of the material: every size above is available in A4 Stainless Steel.
Custom manufacturing · Made to drawing
Need this screw in a grade that is not listed?
A4 Stainless Steel is one of the grades the catalog describes. Head form and drive can be specified to the assembly rather than to a standard: a larger bearing face, a security drive, or a socket sized for the tool already on the bench. Made by cold heading or warm forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
