Fig. 101. Sewing machine items
When a machine is reasonably tight in all parts, gauges and setting marks may be adhered to for the preliminary adjustments; and then if the machine works erratically, other adjustments must be made. Where no marks or gauges are furnished for the adjustment of the needle bar, it should be so set as to allow the shuttle or hook to enter the bold part of the loop formed from the needle. A good rule is to set the needle bar so that the needle-eye is about 1⁄32 inch below the point of the shuttle M ([Fig. 100 C]) when the latter is up to the centre of the needle groove. But this may have to be varied from 1⁄64-inch to 3⁄32-inch. In boat-shaped and similar shuttle machines, a good rule is to set the needle so that the eye N will pass just below the lower side of the shuttle O as the latter is passing through the loop as in [Fig. 100 D], P, indicating the level of the bed plate.
[II]
MECHANICAL MOVEMENTS
What is meant by this term is that these devices are intended for the transmission of motion. Motion in mechanics may be simple or compound. Simple motions are those of straight translation, which if of indefinite duration must be reciprocating, or what is called oscillating or helical.
Compound motions consist of combinations of any of the simple motions. Perpetual motion is an incessant motion conceived to be attainable by a machine supplying its own motive forces independently of any action from without, or which has within itself the means, when once set in motion, of continuing its motion perpetually, or until worn out, without any new application of external force. The machine by means of which it has been attempted, or supposed possible to produce such motion, is an invention much sought after, but physically impossible.
Fig. 102. Coffee mill and details