Dial Gauge: Logan, 1883

John Logan of Waltham, Massachusetts, patented this dial gauge in 1883, US 283,627. A gauging bar slides lengthwise through guides in a case with a graduated dial. A chain fixed to the bar is wound round the arbor that carries the pointer, so when the bar moves the chain unwinds and turns the pointer. The pointer's end moves much further than the bar, which makes the reading very delicate. A spring on the arbor winds the chain back and returns the bar to zero. A jaw on the case and a jaw on the bar make it a caliper; a slender rod beside the bar's other end makes it a depth gauge.

高级

Workshop process

说明

Case and dial

Make the case with the graduated dial, with tubular guide projections at opposite sides for the gauging bar.

此步骤所需材料：

带刻度盘的百分表表壳1 个

Arbor, chain and bar

Pivot the arbor carrying the pointer at the dial's centre. Pass the gauging bar through the guides and connect it to the arbor by a chain fixed to the bar and wound round the arbor.

此步骤所需材料：

指针轴与指针1 个

测杆1 个

细链1 个

所需工具：

精密镊子套装

螺丝刀套装

Return spring

Connect a spring between the arbor and the case so that it turns the arbor to wind the chain and draws the bar back to the zero position.

此步骤所需材料：

轴复位弹簧1 个

所需工具：

精密镊子套装

Jaws and depth rod

Fix a jaw on the case and a matching jaw on the bar; when they touch, the pointer reads zero. Fix a slender gauging rod beside the guide at the other end, in line with the bar's end at zero, for measuring depths.

此步骤所需材料：