The combined ratchet and hand feed in Hiscox figure 1380 uses a hand screw running inside a worm-wheel nut. A ratchet indexes the worm shaft for small automatic feed increments. Turning the hand screw directly relative to the nut gives quicker manual adjustment. The ratchet and worm reductions combine to produce the small automatic feed.
Actuator motion note for Combined Ratchet and Hand-feed Gear
For a separate machine-positioning task, a linear actuator may provide controlled push-pull motion. Its stroke, speed and end positions must match that task; it does not reproduce the ratchet, worm and screw feed ratios shown here.
With leverage, force is traded against travel. A bracket change that improves force can also increase required stroke, slow the output motion, or move the actuator into a poor mounting angle.
Sketch a proposed actuator linkage at the start, middle, and end of travel. At each position, check the line of action, required force, available clearance, and whether the actuator rod remains close to axial loading.
- Map actuator stroke to the actual output travel before choosing a model.
- Check for binding, changing leverage, and peak load near the ends of travel.
- Decide whether timed motion is acceptable or position feedback is required.
For a FIRGELLI design review, calculate the load case with the FIRGELLI actuator force calculator and plan the switching or controller arrangement with the linear actuator wiring diagram generator. If an actuator or cylinder is already installed, the linear actuator replacement finder helps keep the comparison tied to real dimensions.
Combined Ratchet and Hand-feed Gear Interactive Calculator
Compare fine automatic feed through a ratchet and single-start worm with direct hand-screw adjustment. Change the counts, screw lead and operating mode.
Equation Used
- Single-start worm.
- No missed teeth, backlash or slip.
- Specified screw/nut restraint in each mode.
- Not a self-locking or load-capacity calculation.
Single-start worm. Nut is restrained axially; automatic mode holds screw rotation, manual mode holds nut rotation. Illustrative timing and tooth profiles.
Fine ratchet feed and direct hand adjustment
In automatic mode, the pawl carrier rocks through the selected number of ratchet teeth. The wheel and its worm shaft advance on the working stroke and hold while the pawl returns. The rigid pawl is lifted clear for the return in the schematic; the engraving does not establish its detailed spring or release geometry. A single-start worm then turns the worm-wheel nut by one revolution for each Z worm-shaft revolutions. With the hand screw held against rotation, the nut’s small rotation moves the screw axially.
In manual mode, the nut and automatic train are held stationary and the hand screw turns inside the nut. One relative screw revolution advances one screw lead. The selector changes the assumed holding condition for the calculation; it does not operate a modeled clutch.
The animation separates a face view of the ratchet, a plan view of the worm-wheel nut, and a front view of the screw. These are synchronized views of one drive, not three independent mechanisms. Tooth forms, support bearings and the holding restraint are schematic. The source establishes the arrangement but does not specify tooth counts, thread hand, pawl dimensions or exact operating timing.
Where a combined feed is useful
A small indexed feed can accompany a recurring machine stroke, while direct hand adjustment brings the tool or work into position more quickly. Hiscox places this device among mill and factory appliances. The two operating modes illustrate that division between fine feed and positioning.
The entered tooth counts and screw lead are illustrative design values. They are not dimensions for a particular shaper or planer.
Feed through two reductions
Let n be teeth picked up per cycle, N the ratchet tooth count, Z the worm-wheel nut tooth count, and L the screw lead. For the single-start worm shown, the automatic feed is:
a = (n/N) × (1/Z) × L
The ratchet and worm advance 360n/N degrees per cycle; the nut advances 360n/(NZ) degrees. Manual adjustment advances L per relative hand-screw revolution. At f cycles per minute, the selected mode’s average feed rate is its travel per cycle multiplied by f.
The general signed screw relation is x = L(θs − θn)/(2π), using a consistent positive direction for the screw and nut angles. Automatic playback holds θs fixed and rotates the nut oppositely; manual playback holds θn fixed and turns the screw. Feed direction in the drawing is an illustrative choice of thread hand.
Worked feed example
With one tooth picked up on a 40-tooth ratchet, a single-start worm driving a 40-tooth nut, and a 0.4 in/rev screw lead, the automatic feed is 0.00025 inch per cycle. The worm shaft turns 9°, while the nut turns only 0.225°. At 60 cycles/min, average feed is 0.015 in/min.
A direct hand-screw revolution instead advances 0.4 inch: 1,600 times the automatic increment. At an entered rate of 60 hand turns/min the geometric feed rate is 24 in/min. That comparison is not a recommended manual operating speed.
What the model includes and leaves open
The ratchet advance, worm reduction, relative screw rotation and axial feed are linked exactly by the entered counts and lead. The worm is single-start. If a real mechanism has a multi-start worm, a different wheel arrangement or additional gearing, its ratio must be accounted for separately.
The model assumes complete tooth pickup, no lost motion, a nut held axially in bearings, and the appropriate member restrained against rotation. It does not infer that a worm is self-locking. Actual back-drive resistance depends on its geometry and friction.
Playback is slowed for inspection; entered cycle rate changes the feed-rate result. Ratchet return is a prescribed smooth motion. Pawl spring, holding restraint, thread profile and bearing proportions are explanatory rather than manufacturing drawings. Axial travel uses a labeled one-lead scale, so the small automatic increment can be compared with direct manual travel.
Combined feed questions
Why is the automatic feed so small?
A ratchet step first turns the worm shaft, and the worm-wheel reduction makes the nut turn more slowly. Both reductions multiply to give the small feed per cycle.
Does the ratchet directly rotate the hand screw?
No. The ratchet drives the worm-wheel nut while the screw is restrained against rotation.
Why does manual mode advance much farther?
It turns the screw directly relative to the held nut, giving one lead per hand revolution.
What happens when the operating rate is zero?
The calculated average feed is zero and automatic playback stops. The mechanism remains visible, and the cycle control can still inspect its positions.
Is the worm assumed self-locking?
No. The holding condition is explicit and is not a self-locking guarantee.
Primary construction reference
Hiscox, Mechanical Movements, Powers, Devices and Appliances, printed page 334, figure 1380. The caption identifies the hand screw turning in the worm-gear nut for quick adjustment. The single-start worm, entered counts, motion timing and viewing projections are stated reconstruction choices.
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