5 Clock Mainspring Winder Clamps Clockmaker Repair Tools. Clock Mainspring Winder. This is a new clock mainspring winder. It measures approximately 3 15/16" x 2 7/16" (100 x 62 mm) 4 Mainspring Clamps. This is a new set of 4 mainspring clamps. Use these to hold wound mainsprings. You receive: One mainspring clamp that has an inside diameter of approximately 58 mm. One mainspring clamp that has an inside diameter of approximately 45 mm. One mainspring clamp that has an inside diameter of approximately 34 mm. One mainspring clamp that has an inside diameter of approximately 24 mm. We work hard to update our descriptions and pictures of our merchandise. As part of a process of ongoing innovation by our suppliers, newer versions of the item shown may be shipped before we are able to complete an update. As a result there may be a slight variation in color and design.