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Dial Spring Scale with Tare Screw: Fray & Pigg, 1881
John S. Fray and Horace Pigg of Bridgeport, Connecticut, patented this weighing scale in 1881, US 243,539. A dish sits on the standard of a frame hung on two pairs of cross-arms, so it moves straight up and down. A coil spring on a right-angle lever carries the load, and a rack on the frame turns a pinion carrying the pointer round the dial. To take up the tare, a screw rod through the front of the case moves the lever's lower end. Because the spring hangs vertically from the lever's horizontal arm, the adjustment is more sensitive and the bearing surfaces fewer.
Intermediate
Workshop process
Instructions
1
1
Case and frame
Case and frame
Make the upright case with removable front and top. Cast or otherwise form the frame with a standard that passes up through the top to the weighing dish, and pivot it on upper and lower cross-arms whose other ends pivot to the back of the case.
Materials for this step:
Scale Casing1 piece
Scale Frame with Cross-Arms1 piece
Weighing Dish1 pieceTools needed:
Screwdriver Set2
2
Spring and lever
Spring and lever
Pivot the right-angle lever at the back of the frame. Hang the coil spring from its horizontal arm and connect the spring's lower end to the frame by a screw, so the tension can be regulated.
Materials for this step:
Right-Angle Lever1 piece
Scale Coil Spring1 pieceTools needed:
Screwdriver Set3
3
Rack and dial
Rack and dial
Journal the pinion in a bracket so its front end passes through the dial plate and carries the pointer. Pivot the rack bar to the frame and keep it in mesh with a light spring, so the frame's descent turns the pointer.
Materials for this step:
Rack Bar and Pinion1 piece
Scale Dial and Pointer1 pieceTools needed:
Screwdriver Set
Precision Tweezers Set4
4
Tare screw
Tare screw
Pass the tare rod horizontally through the front of the case into a threaded opening in the lever's lower end, so turning it sets the pointer to zero with the container on the dish.
Materials for this step:
Tare Screw Rod1 pieceTools needed:
Tap and Die SetMaterials
8- 1 piecePlaceholder
- 1 piecePlaceholder
- 1 piecePlaceholder
- 1 piecePlaceholder
- 1 piecePlaceholder
- 1 piecePlaceholder
- 1 piecePlaceholder
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Tools Required
3- Placeholder
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