This section is from the book "The Manufacture Of Boots And Shoes: Being A Modern Treatise Of All The Processes Of Making And Manufacturing Footgear", by F. Y. Golding. Also available from Amazon: The Manufacture Of Boots And Shoes.
The machines for turning lasts are chiefly of two kinds - one, the copying lathe, that copies from a pattern last a similar sized one; and the other sort are accurately constructed machines, that enable . the other sizes in a "set" to be turned from one model. The degree of accuracy with which this is done is surprising - the correct pitch, spring, and shape is preserved throughout the set. An illustration of a machine of the latter type is given in Fig. 83. A block as it leaves this machine is illustrated by Fig. 84. The other machines used are band saws, drilling machines, finishing machines, etc.
Lasts may be either "rights and lefts "or" straights." When they are made so that they are symmetrical on either side of a last, they are "straights ;" but when made with an outside and inside joint they are "rights and lefts."
Fig.83. Gilman's Last Turking Machine.
Pitch is given to a last to accommodate the heel of the boot or shoe to be made thereon. It is the elevation of the back portion of the last from the line that would pass tangentially through the position of the joint. As the height of the heel is increased so the "pitch is made greater, and following, the waist is hollowed more to facilitate the building of a square heel. In Figs. 90, 91 the amount of elevation of the seat of the last above the line below is the pitch P.
Spring is the term used to denote the elevation of the toe of the last from the line that would pass through the joint basis S in Figs. 90 and 91. It is regulated by the kind of boot and firmness of the sole. If the substance of the sole be light, very little spring is required, if other things are equal; and on the other hand, stout soles require a greater amount of spring in the last. The reason for this is because, if spring is not provided in the stouter goods, the boots when worn will "turn up at the toes" and, as a consequence, wrinkles will be formed across the front of the shoe which are unsightly and uncomfortable.
The spring for an average last would be about 1/2 in.; a shoe last having another in. A scale of "last spring" may be constructed, and for convenience may be measured from the level surface upon which rests the last, the seat not being raised. The basis for such a scale would be, men's, 1 in., and would be subdivided upon the plan illustrated in Fig. 58.
Other than the spring actually required for the material and substance of the boot, there is an allowance made for the fact that in high heels the "line of contact" is more forward, and consequently the fore part of the shoe is relatively shorter, preventing the full elasticity and bending of the foot. A high-heeled boot - such as a Louis does not need so great a spring in this sense as a boot with a low walking heel. The rule may be condensed thus Low heels - longer forepart - more spring.
High „ shorter „ less „
Sometimes the term "spring" is used to describe the hollowness or arch of the waist, the term" dead" being applied when the waist is flat.
Drop, or Dead Waists are the terms used relatively to denote the style of waist of the last. If the last be placed on a stand so that the bottom is uppermost, then by placing a straight edge from tread to seat, a last would be said to be drop waist when the distance between the straight-edge and last is great, and on the other hand dead when near to the edge. The correct shape of the waist is important; first, because of the building of the heel, and secondly, to enable a correct fit to be obtained across the heel of the boot.
The Classifying of Lasts may be done in several ways, according to the kind - as block, sectional, etc.; or as boot, shoe, etc.; or as machine-sewn, welted, hand-sewn, etc. The former is preferable, as the others may be classed as subdivisions.
Comb Lasts are lasts made all in one piece, without having any block cut. They are used for making " needle and thread "work, sewrounds, and slippers, and during use the place of the usual block is taken by a "fitting" or "shover."
Block Lasts are lasts that have a block cut so as to permit of the last being drawn from the boot. Blocks are cut in various shapes, according to taste or work; but the ideal cut is one that allows of its withdrawal and insertion with as little tendency to injury to the goods being made as possible.
Sectional Lasts are of various patterns, many of which are protected by patents. Their use is intended to mitigate the risks from breakages and alteration of shape of the goods during manufacture, and the principle is to be recommended as a correct one. See Fig. 85, 85a.
The Easy Exit last is a well-known device of this sort, and is illustrated by Fig. 856. The last is in two portions, which are locked by a spring that is released by a key. The men's lasts sometimes have a block as well.
The Arnold hinged last is another variety of sectional last, and is illustrated by Fig. 86. It requires no key and has no loose parts that may be misplaced.
The Miller last is illustrated by Figs. 87 and 88. It is a neat and compact arrangement requiring no key to loosen it.
The Brining last is illustrated by Fig. 89. It consists of two portions fastened together by a cord, one end of which raises a spring. In the iron lasts the top of the spring is liable to catch in the upper during withdrawal.. If this were remedied it would be a serviceable last.*