8" NSK Yellow Dial Verneer Calipers . Reading 0.200/rev. Direct rack & pinion.
$ 44.88
Description
Very nice NSK Japan Dial caliper with direct rack & pinion drive. Excellent working condition with sharp inside tips and clean jaws. Will slide all the way out and back without hopping the needle! If you ever wondered about why these dial calipers can have 0.100/rev or 0.200/rev reading (like this one.) Let me explain. When these dial calipers first came out in the 1970's, they were made to read 0.200/rev by using a very simple straightforward single pinion gear directly attached to the needle on the dial and a rack located on the bottom of the groove in the caliper. This direct method rack/pinion almost never "hopped" the gear track. Now, customers were confused by the double reading and wanted a single 0.100/rev model! Manufactures put a 2:1 reduction gear between the pinion and the needle on the dial so it would now read 0.100/rev. Now you had to have a small gear on the dial needle engaged with a large gear stacked on top of small gear engaged with the rack. Unfortunately, this arrangement increased the error in reading and also produced "backlash" in the gear train to make the needle "bounce" when measuring. To solve this problem, makers added a "shock proof" method that was actually quite complicated involving a stacked intermediate gear and a watch spring to alleviate the backlash. A much more complicated assembly that required "temperamental" adjustming and ultimately more likely for the rack to pinion to hop the track. They also had to move the rack to the top of the slot in the track. I have gone through quite a few of these 0.100/rev dial calipers (like Starrett & Mitutoyo brands) and they tend to "hop" the rack and the needle moves out of position. But, my original double reading that I purchased in the 1970's has never hopped the rack. And every one of the double reading calipers I find, are still reading with the needle TDC on the dial. So, I really like these 8" models with the double dial that I can feel confident that it's still reading correctly.
