The "JG/T 163-2013 Steel Rebar Mechanical Coupler" specifically stipulates the minimum size parameters for rolling straight threaded rebar couplers, steel column coarse straight thread couplers, and steel straight thread couplers. Any steel rebar straight thread coupler with a size below the minimum size table of the national industry standard JG/T163-2013 for rebar connection is considered a non-standard steel rebar straight thread coupler. Conversely, any steel rebar straight thread coupler meeting or exceeding the requirements of the national industry standard JG/T163-2013 is considered a standard steel rebar straight thread coupler.

The qualified standards for rebar coupler are as follows:

1. Coupler are made of international grade 45 steel, with special manufacturing processes ensuring high dimensional accuracy and reliable quality.

2. Capable of connecting HRB335 grade and HRB400 grade ribbed steel rebars ranging from Ф16 to Ф40mm.

3. After testing by the National Center for Quality Supervision and Inspection of Building Engineering, the couplers meet the I-level joint standards specified in JGJ107-2010.

4. Available in standard type, right and left-handed thread type, and reducing type, comprising fifty-two varieties to meet the rebar connection needs for lateral, vertical, and inclined sections in building structures, including same diameter, different diameter, adjustable length, and directional connections.

In conclusion, the JG/T 163-2013 standard for steel rebar mechanical couplers sets stringent requirements for dimensions and quality, ensuring the reliability and safety of rebar connections in construction projects. Adhering to these standards guarantees the structural integrity and performance of buildings.