Custom Screw Material & Strength Selection Workflow

1. State the function before the alloy

Separate the load-bearing function from locating, adjustment, electrical contact or a passage. State the environment, mating metals and cleaning conditions. A screw used for an optical adjuster may have a different priority from a clamp in an outdoor housing, even when the outline looks similar.

2. Keep strength values attached to their basis

Identify whether the quoted number describes stock material or a finished fastener class. Record grade, temper or heat-treatment condition, product form and the applicable specification. Do not transfer a stock tensile figure directly to the assembled load capacity. Thread engagement and the mating component can govern the connection.

Requirement	Route to investigate	Question to resolve
Specified steel fastener property class	Carbon/alloy steel or suitable 10B21 route	Which material and final condition meet the ordered class and verification?
Corrosion exposure with a stainless preference	SUS304 / SUS316 and the applicable finished requirement	Which environment, mating metals, strength and galling controls apply?
Low mass with a machined shape	Named aluminum alloy and temper; titanium only where justified	What thread engagement, wear and surface conditions are required?
Electrical or thermal contact	A specified copper grade; brass only where appropriate	What conductivity, contact finish and mechanical acceptance are needed?
Adjustment and custom turned details	A grade-specific steel, stainless or brass option	How do wear, contact, thread fit and manufacturing economics compare?

Requirement

Route to investigate

Question to resolve

Specified steel fastener property class

Carbon/alloy steel or suitable 10B21 route

Which material and final condition meet the ordered class and verification?

Corrosion exposure with a stainless preference

SUS304 / SUS316 and the applicable finished requirement

Which environment, mating metals, strength and galling controls apply?

Low mass with a machined shape

Named aluminum alloy and temper; titanium only where justified

What thread engagement, wear and surface conditions are required?

Electrical or thermal contact

A specified copper grade; brass only where appropriate

What conductivity, contact finish and mechanical acceptance are needed?

Adjustment and custom turned details

A grade-specific steel, stainless or brass option

How do wear, contact, thread fit and manufacturing economics compare?

3. Review surface and assembly effects

A coating can alter dimensions and friction. Stainless, titanium and other combinations may need an assembly-specific galling review. Lubrication or a coating change must be coordinated with the assembly process rather than added after a torque requirement has been agreed. High-strength steel surface processing also needs a hydrogen-risk assessment for the actual route.

4. Approve evidence and changes

Specify material documentation, final mechanical requirements, dimensional acceptance and any coating or functional checks needed for the order. Agree who approves an alternate grade or condition. Sample approval should identify the exact material and process revision so a later substitution is visible.

Illustrative comparison

For a screw retaining an outdoor cover, compare a specified stainless solution with a coated-steel solution against the same environment, joint requirements and acceptance plan. Do not select solely from color or a single nominal strength number. The review should resolve corrosion, engagement, friction, visible condition and required records before a final quotation.

Reference and related topics

BSSA: galling resistance of stainless steels ↗ explains why the mating pair and contact conditions matter. The material pages provide grade- and condition-specific strength references.

Grade, condition and joint.
Make the choice together.