TopThread™ and TopGroove™ Hardware TopThread and TopGroove Toolholders and Boring Bars clamp screw clamp shim screw insert shim insert size and style clamp clamp screw shim shim screw NG-1L CM-109 S-304 – – NG-2R CM-182 S-310 – – NG-2L CM-183 S-310 – – NG-2R CM-74 S-310 – – NG-2L CM-75 S-310 – – NG-3R CM-184 S-412 – – NG-3L CM-185 S-412 – – NG-3R CM-72 S-412 – – NG-3L CM-73 S-412 – – NG-3R* CM-78 S-412 – – NG-3L* CM-70 S-412 – – NG-4R CM-72 S-412 SM-420 SL-344 NG-4L CM-73 S-412 SM-420 SL-344 NG-5R CM-80 S-352 – – NG-5L CM-81 S-352 – – NG-6R CM-120 S-412 SM-416 S-111 NG-6L CM-121 S-412 SM-416 S-111 NG-8R CM-144 S-422 SM-419 S-112 NG-8L CM-145 S-422 SM-419 S-112 NG-8R** CM-144 S-422 SM-427 S-111 NG-8L** CM-145 S-422 SM-427 S-111 TopGroove relief grooving NU-3125R CM-72 S-412 – – NU-3125L CM-73 S-412 – – NU-3125R** CM-72 S-618 – – NU-3125L** CM-73 S-618 – – *25mm diameter boring head. **Boring head. widia.com F37