Slotted Truss Head Machine Screws, UNC manufactured in A4 Stainless Steel (ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80) are dimensioned to ASME B18.6.3. The sections below give the mechanical and physical properties of the grade, its behavior in corrosive and elevated-temperature service, and the full size table.
Why Choose A4 Stainless Steel for Slotted Truss Head Machine Screws, UNC
Specified for marine, coastal and chemical applications. For slotted truss 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 Truss Head Machine Screws, UNC in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Comparable Grades
For Slotted Truss Head Machine Screws, UNC, the alternative stainless grade is A2 (304). A2 (304) covers general indoor and outdoor service. A4 (316) adds molybdenum, which is what buys the chloride resistance for marine and de-icing-salt exposure. Where strength matters more than corrosion, plated alloy steel in class 8.8 or 10.9 is the swap to make.
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 Truss Head Machine Screws, UNC Available in A4 Stainless Steel
| Size | Pitch P (in) | Head diameter dk (in) | Head height k (in) | R (in) | J (in) | T (in) | Length range l (in) | Reference standard |
|---|---|---|---|---|---|---|---|---|
| #0 | 0.013 | 0.131 | 0.037 | 0.087 | 0.023 | 0.022 | 1/16"~1 1/2" | ASME B18.6.3 |
| #1 | 0.016 | 0.164 | 0.045 | 0.107 | 0.026 | 0.027 | 1/16"~1 1/2" | ASME B18.6.3 |
| #2 | 0.018 | 0.194 | 0.053 | 0.129 | 0.031 | 0.031 | 1/16"~2 1/2" | ASME B18.6.3 |
| #3 | 0.021 | 0.226 | 0.061 | 0.151 | 0.035 | 0.036 | 1/8"~2 1/2" | ASME B18.6.3 |
| #4 | 0.025 | 0.257 | 0.069 | 0.169 | 0.039 | 0.04 | 1/8"~4" | ASME B18.6.3 |
| #5 | 0.025 | 0.289 | 0.078 | 0.191 | 0.043 | 0.045 | 3/16"~4" | ASME B18.6.3 |
| #6 | 0.031 | 0.321 | 0.086 | 0.211 | 0.048 | 0.05 | 1/8"~4" | ASME B18.6.3 |
| #8 | 0.031 | 0.384 | 0.102 | 0.254 | 0.054 | 0.058 | 1/8"~5" | ASME B18.6.3 |
| #10 | 0.042 | 0.448 | 0.118 | 0.283 | 0.06 | 0.068 | 3/16"~8" | ASME B18.6.3 |
| #12 | 0.042 | 0.511 | 0.134 | 0.336 | 0.067 | 0.077 | 1/4"~8" | ASME B18.6.3 |
| 1/4" | 0.05 | 0.573 | 0.15 | 0.375 | 0.075 | 0.087 | 3/8"~10" | ASME B18.6.3 |
| 5/16" | 0.056 | 0.698 | 0.183 | 0.457 | 0.084 | 0.106 | 1/2"~10" | ASME B18.6.3 |
| 3/8" | 0.062 | 0.823 | 0.215 | 0.538 | 0.094 | 0.124 | 1/2"~12" | ASME B18.6.3 |
| 7/16" | 0.071 | 0.948 | 0.248 | 0.619 | 0.094 | 0.142 | 3/4"~12" | ASME B18.6.3 |
| 1/2" | 0.077 | 1.073 | 0.28 | 0.701 | 0.106 | 0.161 | 3/4"~12" | ASME B18.6.3 |
| 9/16" | 0.083 | 1.198 | 0.312 | 0.783 | 0.118 | 0.179 | 3/4"~12" | ASME B18.6.3 |
| 5/8" | 0.091 | 1.323 | 0.345 | 0.863 | 0.133 | 0.196 | 3/4"~14" | ASME B18.6.3 |
| 3/4" | 0.1 | 1.573 | 0.41 | 1.024 | 0.149 | 0.234 | 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.
