What Is a Limit Gauge?
A limit gauge is an inspection tool designed for quick verification of a product’s dimensional conformity. It uses a pair of gauges representing the upper and lower acceptable limits of a product’s dimension. By testing whether a product can or cannot pass through these gauges, its acceptability is determined, making the process efficient for items like screws where dimensional accuracy is crucial.
Applications of Limit Gauges
Limit gauges are essential in mass production for process control, notably in manufacturing screws, but also applicable to various components to control thickness, height, width, and hole sizes. They ensure quality control with minimal measurement variation, suitable for use after thread forming, surface treatments, and during both shipment and acceptance inspections.
Principle of Limit Gauges
The principle relies on the ability of a product to pass through the ‘go’ gauge (street-side gauge) without passing through the ‘no-go’ gauge (stop-side gauge). This method ensures the product dimensions are within specified tolerances, verifying that dimensions do not exceed the maximum limit and are not below the minimum limit.
Types of Limit Gauges for Screws
Screw limit gauges come in various types, each designed for specific applications:
1. Ring Gauge for Screws
Used for inspecting male threads, ring gauges have a threaded hole that the screw must match to pass inspection. The acceptance criteria can include torque considerations, although there are no specific ISO regulations for torque during ring gauge inspection.
2. Plug Gauges for Screws
Plug gauges inspect female threads, similar in use to ring gauges, to ensure the thread fits appropriately.
3. Wear Inspection Gauges
These are used to check the wear on ‘go’ gauges to ensure they remain within acceptable tolerance ranges. Regular checks prevent false acceptances due to gauge wear.
Limit gauges for screws are detailed by standards, including ISO, with considerations for surface treatments like plating affecting screw dimensions. Agreements on gauge handling and acceptance criteria are essential in business transactions to ensure consistency and reliability in quality control processes.