Plating & Gauging Basis for Threads
Define the acceptance requirement first—UJEN will select the appropriate plating and inspection route
Plating changes effective thread size, and thread acceptance issues often come from two hidden variables: when you gauge (pre- vs post-plating) and how the finished surface is produced through the plating route. In many supply chains, screws are commonly processed in bulk plating routes suitable for high-volume production, where parts may contact each other during processing. When a requirement demands a defined finished-part acceptance—such as “GO ring gage must pass after plating”—UJEN will evaluate and apply an appropriate process route and inspection method to meet the requirement. Buyers do not need to specify the plating method; simply state the acceptance requirement (for example, post-plating gage pass), and we will align thread allowance, plating control, and inspection routing accordingly. Custom acceptance requirements may affect pricing, MOQ, and lead time.
Why Plating Changes Thread Acceptance
Plating adds material to thread surfaces and changes the effective size. Depending on coating thickness and process stability, a thread that gauges correctly before plating may not pass the same GO gage after plating. This is why the acceptance requirement and measurement basis should be declared in the drawing/RFQ.
Two Measurement Bases You Must Choose
- Pre-plating gauging: thread acceptance is verified before coating
- Post-plating gauging: thread acceptance is verified after coating (GO gage must pass after plating)
Another Variable: Bulk Processing vs Controlled Processing
In real production, screws are often plated through bulk processing routes suitable for high-volume manufacturing. In these routes, parts may contact each other during processing, which can influence surface condition and the “gaging feel” on the finished thread.
When finished-part acceptance is required (for example, “GO ring gage must pass after plating”), UJEN will evaluate and apply a more controlled process route and inspection method to match the acceptance requirement. The objective is not only appearance, but consistent functional acceptance on the finished thread.
Why a GO Ring Gage May Feel Tighter After Plating
Finished threads can feel tighter after plating because coating build adds material, and surface condition can change through processing. In bulk routes where parts contact each other, micro-contact marks or surface disturbance may occur and affect how smoothly a ring gage runs. This does not always show up in pre-plating gauging, which is why the measurement basis should be defined.
What Changes When You Require Post-Plating GO Gage Pass
- Thread allowance strategy may be adjusted to account for coating build
- Plating route may be evaluated and upgraded to a more controlled process (selected by UJEN based on your requirement)
- Plating process control becomes part of dimensional acceptance
- Inspection routing changes (finished-part gaging after plating)
- Yield and inspection effort may change depending on the acceptance target
How to Specify This in Your RFQ/Drawing
Buyers do not need to specify plating methods. Simply state the acceptance requirement and measurement basis. UJEN will select the appropriate process route and inspection method.
- ISO Metric example: M8 × 1.25 - 6H (internal) / 6g (external); basis: pre-plating gauging
- Unified example: 1/4-20 UNC-2A/2B; requirement: post-plating GO ring gage pass
UJEN Practice (Requirement-Driven Process Selection)
UJEN does not require buyers to specify plating methods. Tell us your acceptance requirement—such as pre-plating gauging, post-plating gauging, or “GO ring gage must pass after plating”—and we will evaluate and apply an appropriate process route (including plating approach and inspection method) to meet the requirement.
If no specific acceptance basis is stated, it is commonly handled under a pre-plating gauging basis in many supply chains. When post-plating gage-pass acceptance is required, the process route and inspection routing will be aligned accordingly. Custom acceptance requirements may affect pricing, MOQ, and lead time.
RFQ Checklist (Copy/Paste Ready)
- Standard family: ISO Metric / Unified / Whitworth
- Acceptance language: ISO tolerance class or Unified class (or customer-defined)
- Plating/coating requirement (if any)
- Measurement basis: pre-plating gauging or post-plating gauging
- If post-plating acceptance is required: state “GO ring gage must pass after plating” (UJEN will select the process route)
- Gaging reference (if specified): ISO 1502 (metric) or ASME gages (Unified)