In Fig. 2795 let b represent the centre of the bend curve, the line c representing one end, g the other end, h the inner and j the outer arc of the bend. Let it be determined to build up the bend in five pieces, as shown at 1, 2, 3, 4, 5, which represents an end view of the half pattern. Templates are then made for each of the pieces 1, 2, &c., being formed as denoted by the oblique lines, whose dimensions slightly exceed the half circle e of the pattern, to allow wood for dressing up. To find the curve for these pieces, set the compasses to a radius from b to the outer corner of piece 1, and draw the arc k. Set the compasses to the radius from b to the inner corner of piece 1, and draw the arc l, and the space between these two arcs, which space is marked 1 t, is a template for the curve of piece 1. By a similar process applied to pieces 2, 3, 4 and 5 similar templates for their respective curves are obtained; and selecting timber of a proper thickness, we mark out the respective curves from these templates, which may be of thin board or of stiff paper. In putting these pieces together the lower ones are set to lines forming a plan of the bend, being set a little outside the lines to allow wood for truing the pieces to shape after they are put together. The lower pieces are temporarily fixed to the board on which the plan is marked, and the upper ones fastened to the lower by glue, the joint surfaces of each line being planed true previous to being glued. It is a great assistance, however, to cut out two half circles, representing the ends of the pipe, and to place them on the board to build upon. When a bend of this kind occurs in a covering for a pipe that is exposed to view, it is necessary, for the sake of appearance, to have the pieces composing the bend to correspond with those on the straight part of the pipe, as shown in Fig. 2796. The part a would be got out in staves, as described for the pattern of a pipe. The bend b would be also got out as described for that figure for a bend, save that the number of staves for the bend would equal the number on the pipe. But in this case each stave should be fitted to its fellow by pins, or its edge fitting into dowels on the edge of its fellow; thus one edge of a stave would have the dowels and the other the pins; the whole, when finished, being bound together by metal bands, as shown in the figure.
The patterns for a globe valve, such as shown in section in Fig. 2797, would be made as follows (which is taken from “The Pattern Makers’ Assistant”):—
“The flanges vary in shape; but as a rule small valves are provided with hexagons and large ones with round flanges suitable for bolting to similar flanges to make joints. For small valves, say up to 2 inches, the pattern is usually made with the hexagons cut out of the solid, but for sizes above that, they should be made in separate pieces, as shown in Fig. 2798, and screwed to the pattern, so that in case of necessity they may be removed, and flanges substituted in their stead. In Fig. 2799, we have a perspective view of the finished pattern; and Fig. 2800 represents the pattern as prepared, ready to receive a flange or hexagon as may be required. A globe valve pattern should be made in halves, as shown in Fig. 2801, the parting line of the two halves being denoted by a b. To make this pattern, we first prepare two pieces of wood so large that, when pegged together, the ball or body of the pattern can be turned out of them, and long enough not only to reach from p to p, in Fig. 2799, but also to allow an excess by means of which the two pieces may be glued or otherwise fixed together. These two pieces we plane to an equal thickness, and then peg them to retain them in a fixed position, taking care, however, that the pegs do not occur where the screws to hold the flanges will require to be. We also place two pegs within a short distance of what will be the ends of the pattern when the excess in length referred to is turned off. We next prepare, in the same way, two more pieces, to form the two halves of the branch, shown at b, in Fig. 2801, for which, however, one peg only will be necessary. These pieces must be somewhat wider than the size of the required hexagon across the corners, that is, supposing the hexagon is to be solid with the branch; otherwise we must make them a little wider than the diameter of the hub of the flange, or of the round part of the hexagonal pieces. Their lengths must be such as to afford a good portion to be let into the ball or body of the pattern (as shown by the dotted lines in Fig. 2800), which is necessary to give sufficient strength. The two pieces must be firmly fixed together, and then turned in the lathe.
“During the early stages of the turning, or, in other words, during the roughing out, we must occasionally stop the lathe and examine the flat places on the body; for unless these places disappear evenly, the work is not true, and one half will be thicker than the other, so that the joint of the pattern will not be in the middle. It was to insure this that the pieces were directed to be planed of equal thickness, since, if such is the case, and the flat sides disappear equally and simultaneously during the turning, the joint or parting of the pattern is sure to be central. If the lathe centres are not exactly true in the joint of the two pieces, they may be made so by tapping the work on the side having the narrowest flat place, the process being continued and the work being trued with the turning tool at each trial until the flat places become equal. By this means, we insure, without much trouble, two exact halves in the pattern, which is very important in a globe valve pattern on account of the branch and other parts, not to mention the moulding. Having turned the body of the pattern to the requisite outline, and made, while in the lathe, a fine line around the centre of the ball where the centre of the branch is to come, as shown in Fig. 2800 by the line a, we make a prick point (with a scriber) at each crossing of the line a and the joint or parting of the pattern. We then mount the body upon a lathe chuck, in the manner shown in Fig. 2802. A point centre should be placed in the lathe and should come exactly even with the line a. In Fig. 2802, v v are two V-blocks made to receive the core prints. These Vs are screwed to the lathe chuck, and the pattern is held to them by two thin straps of iron, placed over the core prints and fastened to the Vs by screws. If the chuck and centre point run true, the V-blocks are of equal height, and the core prints are equal in diameter, the prick point opposite to the one placed to the centre point will run quite true; and we may face off the ball or body to the required diameter of branch, and bore the recess to receive the same. We make the holes in the flanges of the same size as the core prints; but we should not check in the print, because, if a flange with a different length of hub were substituted, it would be a disadvantage. To obtain the half flanges, we take a chuck and face it off true in the lathe; then, with a fine scriber point, we mark the centre while the chuck is revolving. We then stop the lathe, and, placing a straight-edge to intersect the chuck centre, we draw a straight line across the chuck face. We then take two pieces suitable for the half flanges, and plane up one flat side and one edge of each piece. If the flanges are not large ones, they may be planed all at once in a long strip. We place the pieces in pairs, and mark on each pair a circle a little larger than the required finished size of flange. We then fix each pair to the chuck, with the planed faces against the chuck, and the planed edges placed in contact, their joint coming exactly even with the straight line marked on the chuck face, and we may then turn them as though they were made in one piece and to the requisite size.
“In Fig. 2803 we have a representation of one half of a suitable core box, the other half being exactly the same, with the exception that the position of the internal partition is reversed. To get out this core box, we plane up two pieces of exactly the same size and length as the pattern, and of such width and thickness as will give sufficient strength around the sphere, allowing space for the third opening. After pegging these two pieces together, we gauge, on the joint face of each, lines representing the centres of the openings and the centre of the sphere. We then chuck them (separately) in the lathe, and turn out the half sphere. We next place the two halves together, and chuck the block so formed in the three positions necessary to bore out the openings; or if preferred, we may pare them out. The partition (a, in Fig. 2803) follows the roundness of the centre hole, and is on that account more difficult to extract from the core than if it were straight and vertical. When, however, the partitions are of this curved form, the pieces of which they are formed are composed of metal, brass being generally preferred. Patterns have in this case to be made wherefrom to cast these pieces, and they may be made as follows: First, two half pieces are turned; each is then cut away so as to leave the shape as shown at a in the same figure, and is then fitted into the spherical recess in the core box, letting each down until both are nearly but not quite level. The two wing pieces are then fastened on, and this pattern is complete. When the pieces are cast, they must be filed to fit the core box, and finished off level with its joint face, a small hole being drilled in the centre, and a pin being driven through the piece and into the box to steady the corners. We then saw the pieces in halves with a very fine saw.
“If the partition, instead of following the roundness of the valve seat, is made straight, the construction of the core box is much more simple. In this case, a zigzag mortice is made clear through each half of the box, its size and shape being that of the required partition. Fig. 2804 represents a half-core box of this kind. A piece of wood a is fixed, as shown, to the partition, to enable the core maker to draw it out before removing the core from the box. The mortice for the partition should be turned out before the half-spherical recess, the mortice being temporarily plugged with wood to render easy the operation of turning.
“In very large valves (say 10 or 12 inches) a half-core box is generally made to serve by fitting the two half partitions, shown at a, in Fig. 2803, to a half-core box, and keeping them in position by means of pegs, a half-core being made first with one and then one with the other in the core box. It is often necessary to form a raised seat in the body of an angle valve, such as shown in Fig. 2805, which represents a section of such a body. It is shown with flanged openings, though in small valves hexagons to receive a wrench would be substituted.
“Fig. 2806 is a plan of half the core box necessary for forming the raised seat. From this construction, it will be seen that the large core, though solid with the branch core, is not solid with that forming the hole in the seat and the part below it; therefore the core prints on the body pattern must be left extra long to give sufficient support in the mould for the overhanging cores. The loose round plug p, is made of the size of the outside of the seat and fitted to the box. The part outside the box is a roughly shaped handle to draw it out by. The diminished part d is a print, and into the impression left by it is inserted the core made in box shown in Fig. 2807. The print d is of the same diameter as the hole in the seat; and the print on the pattern is of the size of the increased diameter below the seat. Large angle valves are made with half a core box by making a branch opening in the box right and left, a semicircular plug being provided. Two half-cores are made with the plug, first in one and then in the other branch opening. The plug p should be in this case only half round.”
For finding the lengths of the sides of regular polygons, scales, such as shown in Figs. 2808 and 2809, may be used, the construction being as follows:—
Draw a horizontal line o p, Fig. 2809, and at a right angle to it the line o b. Divide these two into inches and eighths of an inch, and draw lines meeting the corresponding divisions on o p, o b. From the point o draw the following lines: A line at 551⁄2 degrees from line o p, which is to serve for polygons having 9 sides; a line at 521⁄2 degrees to serve for polygons having 8 sides; a line at 49 degrees for polygons having 7 sides; a line at 45 degrees for 6 sides; a line at 40 degrees for polygons having 5 sides. It may be added, however, that additional lines may be drawn at the requisite angle for any other number of sides.
The application of the scale is as follows:—
The point o represents the centre of the polygon; hence from o to the requisite line of division on o b represents the radius of the work. From the line o b to the diagonal line (measured along the necessary horizontal line of division) is shown the length of a side of the polygon. From the point o, measured along the line having the requisite degrees of angle, to the horizontal line denoting the radius of the work, gives the diameter across corners of the polygon. The diameter across the flats of a square being given, its diameter across corners will be represented by the length of a line drawn from the necessary line of division on o b to the corresponding line of division on o p. A cylindrical body is to have six sides, its diameter being 2 inches, what will be the length of each side? Now, the radius of the 2-inch circle of the body is 1 inch; hence, find the figure 1 on line o b and measure along the corresponding horizontal line the distance from the 1 to the line of 45 degrees, as denoted by the thickened line.
A body has six sides, each side measuring an inch in length, what is its diameter across corners? Find a horizontal line that measures an inch from its intersection of the line o b to the line of 45 degrees, and along this latter to the point o is one-half the diameter across corners.
Example 3.—It is desired to find the diameter across corners of a square whose side is to measure 3 inches. Measure the distance from the 3 on line o p to the 3 on line o b, which will give the required diameter across corners.
This scale lacks, however, one element, in that the diameter across the flats of a regular polygon being given, it will not give the diameter across the corners. This, however, we may obtain by a somewhat similar construction. Thus, in Fig. 2808, draw the line o b, and divide it into inches and parts of an inch. From these points of division draw horizontal lines; from the point o draw the following lines and at the following angles from the horizontal line o p:—
| A line at | 75 | ° | for polygons having | 12 | sides. |
| „ | 72 | ° | „ | 10 | „ |
| „ | 67 | 1⁄2° | „ | 8 | „ |
| „ | 60 | ° | „ | 6 | „ |
From the point o to the numerals denoting the radius of the polygon is the radius across the flats, while from point o to the horizontal line drawn from those numerals is the radius across corners of the polygon.
A hexagon measures 2 inches across the flats, what is its diameter measured across the corners? Now, from point o to the horizontal line marked 1 inch, measured along the line of 60 degrees, is 15⁄32 inches; hence the hexagon measures twice that, or 25⁄16 inches across corners. The proof of the construction is shown in the figure, the hexagon and other polygons being marked for clearness of illustration.
Let it be required to make a pattern for a section of pipe such as shown in section and in plan in Fig. 2810, which is from “The Pattern Maker’s Assistant.” This pattern would be made to mould, as shown in the section, lying horizontally, and must therefore be made in two halves, the line of joint for the two halves being along a b in Fig. 2811.
“The body a and the branch b would be made separate from the flanges, and would be reduced in diameter at the ends to receive them. To form a, take two pieces of timber, say three inches longer than the length of a, including the core prints, and measuring a little more than half the diameter of the pipe one way, and a little larger than the full diameter of the pipe the other way, and glue them together at the ends for a distance of 11⁄2 inches, which will serve to hold them while turning them in the lathe.
“The pieces may then be turned in the lathe to the required diameter. During this turning, however, it is essential to insure that the joint of the two pieces be exactly in the centre, otherwise one half of the pattern will be (when the halves are separated) thicker than the other.
“The ends are then turned down to receive the flanges, the reduced diameter being necessary so as to leave a shoulder for the flanges to abut against to keep them true, or at a right angle to the axial line of the body. The branch is turned up in the same way, and the flanges are then turned and put on.
“The end of the branch may be cut to fit the circumference of the body as follows:—
“Set a bevel square to an angle of 45°. Take the halves of the branch apart, and rest the stock or back of the bevel against the end face, and let the blade lie on the joint face, and mark two lines a b in Fig. 2812, which lines must just meet in the centre of the branch at the end. Cut away the angular pieces c and d down to the lines a b. This performed on each half will leave them when given a quarter turn as shown in Fig. 2812, and the curve shown by the junction of the horizontal with the vertical shading lines is the curve for the end; hence the surface covered with the horizontal lines requires to be cut away.
“When this is done on both halves the branch will fit to the body, as shown in Fig. 2813, in which a is the body and b c the two half branches. For a temporary pattern the branch may be fastened to the body with a few screws; but for a permanent pattern it should be glued also, which is done as follows:—
“Lay one half of the body a, Fig. 2813, on a board, with the flange overhanging to be out of the way, and clamp it there; lay the branch also on the board, and draw it firmly up to the body by clamps, while also clamping it flat down to the board, as shown in Fig. 2814. This will insure that the joint faces are true with one another, that is, lie in the same plane. Paper should, however, be placed between the joint faces and the board to prevent them from becoming glued to the board, and the edges, therefore, from breaking away. The second half can be put together as the first one, paper being put between the two to prevent them from being glued together; and to further strengthen the joint, let into each half a piece of hard wood p, Fig. 2815, and put in the screw shown at a.
“Suppose now that the diameter of the branch had been smaller than that of the body of the pattern, then the length of curve necessary on the branch end to let it abut fairly against the cylindrical pattern body may be found as follows:—
“Draw on a piece of board the line a b, Fig. 2816, and from any point c mark a semicircle equal in radius to that of the radius of the body of the pattern, draw the line e parallel to a b, and distant from it to an amount equal to the radius of the branch, then from the junction of e with the semicircle as at d, mark the line f at a right angle to a b. Let it now be noted that the semicircle a g represents half the pattern body, and e d f b the branch; hence from f to g is the length of the branch end that will require to be curved to fit the circumference of the body, while it is also the length to be added to the distance the branch requires to stand out from the body. To draw the curve on the end d f g of the branch the gauge or marking instrument, shown in Fig. 2817, is employed. The branch p is placed in V-blocks (Fig. 2818), resting upon a plane surface. The gauge consists of a stand e carrying a vertical bar a; upon a is the closely fitting cross-tube carrying the arm c, which in turn carries the marking pointer d, which is set distant from the centre of the bar a to the amount of the radius of the piece of work or the cylinder is to fit against.
“If the branch required to stand at an angle to the body, as in Fig. 2819, the marking may be performed by the same gauge and in the same manner, but the axial line of the branch must be set, when marking one side, at an acute angle to the axial line of a, and at an obtuse angle to a when turned over to mark the other side, which may be done in each case by raising one of the V-blocks until the branch lies in either case at the same angle to a as it will require to stand to the body on which it is to fit.
“When the body is much larger in diameter than the branch, a hole may be bored in the former to receive the end of the latter, by giving to the branch end a stem, as in Fig. 2820, and then cutting in the body a recess for the branch end and its additional stem. This recess may be cut out in the lathe, chucking the body as in Fig. 2821.
“Should it occur that one end of the T is of larger diameter than the other, one chucking V must be deeper than the other, and we may find their respective depths by the following process:—
“Draw line a b, Fig. 2822, which line represents the chuck face. Let point c represent the centre of the lathe. Mark line c e and set a pair of compasses to the radius of the body of the pattern at the centre of the branch location. Then take a radius from c and about 1⁄16 inch up from line a b, and with this radius we mark on the line c e the point e. From this centre we mark the two arcs having radii corresponding to the unequal diameters of the pattern at the location where the chucking V’s are to be placed. We then draw tangent lines to each of these arcs, and thus obtain the correct depth of V necessary to hold the axial line of the pattern parallel to the lathe chuck.
“The core box would, unless the pattern were a small one, be built up in courses, as shown in Fig. 2823. The box would be drawn in plan, and end and side views drawn as shown, so as to draw in the half circle representing the bore of the half-core box and mark off the courses as from 1 to 6. These courses need not be of equal or of any particular thickness, but may suit that of any suitable timber at hand. Courses 1 and 2 should extend over the whole outline of the box, while the pieces 3 and 4 are made in width to suit the curvature of the core as shown, and to extend the full length of the box. The pieces 7, 8, 9, and 10 are of the length of the branch, and are made in width to suit the curvature of the branch core. If the branch core were a short one it could be cut out of the solid; but in any event, the grain of the wood should be as shown, and the holding pieces at g and h should be employed.”
Chapter XXXV.—WOOD WORKING MACHINERY.
The machines employed in wood working may be divided into 7 classes as follows:
1. Those driving circular saws.
2. Those driving ribbon or band saws.
3. Those driving boring or piercing tools.
4. Those employing knives having straight edges for surfacing purposes and cutting the work to thickness.
5. Those employing knives or cutters for producing irregular surfaces upon the edges of the work.
6. Those employed to produce irregular surfaces on the broad surface of work.
7. Those employed to finish surfaces after they have been acted upon by the ordinary steel cutting tools.
CIRCULAR SAWS.
The thicknesses of circular saws is designated in terms of the Birmingham wire gauge, whose numbers and thicknesses are shown in Fig. 3078, where a Birmingham wire gauge is shown lying upon two circular saws, which show the various shapes of teeth employed upon saws used for different purposes.
The teeth numbered 1 are for large saws, as 36 inches in diameter, to be used on hard wood. Numbers 2 and 5 are for soft wood and a quick feed. Numbers 3 and 4 are for slabbing or converting round logs into square timber. Number 6 is for quick feeds in large log sawing. Numbers 7, 8, 9 and 10 are for bench saws, or, in other words, saws fed by hand or self-feeding saws. Number 8 is known as the “London Tooth,” because of being used in London, England, on hard and expensive woods. Number 9 is the regular rip-saw tooth for soft woods. Number 10 is the Scotch gullet tooth. Number 11 is for either cross-cutting or rip sawing by circular saws used on soft woods. Number 12, is for large cross-cut saws; the flat place at the bottom of the tooth prevents the teeth from being unnecessarily deep and weak. Number 13 is for cross-cutting purposes generally. Number 14 is for rip sawing on saws of small diameter. It is also used for tortoise-shell, having in that case a bevel or fleam on the front face, and no set to the teeth.
The following table gives the ordinary diameters and thicknesses of circular saws and the diameters of the mandrel hole:
| Diameter. | Thickness. | Size Mandrel Hole. |
|||
| 4 | inch. | 19 | gauge. | 3⁄4 | |
| 5 | „ | 19 | „ | 3⁄4 | |
| 6 | „ | 18 | „ | 3⁄4 | |
| 7 | „ | 18 | „ | 3⁄4 | |
| 8 | „ | 18 | „ | 7⁄8 | |
| 9 | „ | 17 | „ | 7⁄8 | |
| 10 | „ | 16 | „ | 1 | |
| 12 | „ | 15 | „ | 1 | |
| 14 | „ | 14 | „ | 1 | 1⁄8 |
| 16 | „ | 14 | „ | 1 | 1⁄8 |
| 18 | „ | 13 | „ | 1 | 1⁄4 |
| 20 | „ | 13 | „ | 1 | 5⁄16 |
| 22 | „ | 12 | „ | 1 | 5⁄16 |
| 24 | „ | 11 | „ | 1 | 3⁄8 |
| 26 | „ | 11 | „ | 1 | 3⁄8 |
| 28 | „ | 10 | „ | 1 | 1⁄2 |
| 30 | „ | 10 | „ | 1 | 1⁄2 |
| 32 | „ | 10 | „ | 1 | 5⁄8 |
| 34 | „ | 9 | „ | 1 | 5⁄8 |
| 36 | „ | 9 | „ | 1 | 5⁄8 |
| 38 | „ | 8 | „ | 1 | 5⁄8 |
| 40 | „ | 8 | „ | 2 | |
| 42 | „ | 8 | „ | 2 | |
| 44 | „ | 7 | „ | 2 | |
| 46 | „ | 7 | „ | 2 | |
| 48 | „ | 7 | „ | 2 | |
| 50 | „ | 7 | „ | 2 | |
| 52 | „ | 6 | „ | 2 | |
| 54 | „ | 6 | „ | 2 | |
| 56 | „ | 6 | „ | 2 | |
| 58 | „ | 6 | „ | 2 | |
| 60 | „ | 5 | „ | 2 | |
| 62 | „ | 5 | „ | 2 | |
| 64 | „ | 5 | „ | 2 | |
| 66 | „ | 5 | „ | 2 | |
| 68 | „ | 5 | „ | 2 | |
| 70 | „ | 4 | „ | 2 | |
| 72 | „ | 4 | „ | 2 | |
Circular saws are sometimes hollow ground or ground thinner at the eye than at the rim, to make them clear in the saw kerf or slot with as little set as possible, and therefore produce smooth work while diminishing the liability of the saw to become heated, which would impair its tension. They are also made thicker for a certain portion of the diameter and then bevelled off to the rim.
This is permissible when the work is thin enough to be easily opened from the log by means of a spreader or piece that opens out the sawn piece and prevents it binding against the saw.
The shingle saw, shown in Fig. 3079, is an example of this kind, the saw bolting to a disc or flange by means of countersink screws.