Merrow MG-3U Industrial Sewing Machine For Emblem Edging. The Merrow MG-3U sews a tight decorative edge on emblems and patches. The MG-3U stitch is renowned for its consistency, coverage, and uniformity. The Merrow MG-3U is a 3-thread industrial sewing machine that is meant for putting a decorative edge on emblems and patches. It makes a 1/8″ to 3/16″ stitch at a standard rate of 28 SPI (though this can be decreased or increased to 20 or 40 SPI respectively), yet even while running at 5500 RPM still operates under 90 dbA.