18. Hammer. The carpenter’s hammer is used principally to drive or withdraw nails.
The various trades have hammers made specially for their needs; thus we have machinists’, roofers’, upholsterers’, stonecutters’, and other hammers, but the claw hammer shown in the sketch is the one commonly used by workers in wood.
Fig. 42. The Claw Hammer
The head a (Fig. 43) is of steel, with the face b specially hardened so that it may not be dented by the nails. Notice the length of the handle h. This length did not simply happen. Had it been intended to hold the tool in the position shown at A, the handle would not have been made so long. The proper position is that shown at B. Position A is frequently taken by beginners, and should be studiously avoided.
Fig. 43. Using the Hammer
A nail may be withdrawn with the claw, and be kept straight for further use by a little care. Having started the nail slightly, place a small block of wood under the hammer head, as shown at C. Should the nail be an unusually long one, the size of the block may be increased as the nail comes out.
Fig. 44. Common Forms of Nail Punch, or “Set”
In driving nails care must always be taken not to mar the surface of the wood by striking the nail head after it has become even with the surface, as this produces a depression and ruins any fine surface.
If it is desirable to sink the nail head below the surface, a nail punch, or set, is used. This is always necessary when the surface is to be planed after the nailing.
19. The Mallet. The mallet might be described as a hammer with a wooden head, and is used whenever we wish to deliver a blow which shall be less concentrated than that of the hammer. It is used in certain kinds of heavy chiseling, such as house framing, and gives a blow which does not shatter the tool handle as a hammer would.
Fig. 45. The Mallet
The use of the mallet is well illustrated by the making of a mortise-and-tenon joint, the chisel and mallet being used to cut the opening known as the mortise, as shown in Fig. 46.
20. Screw-Driver. The screw-driver is perhaps the most common of household tools, and is probably abused more than any other. The handle is usually flattened so that the hand may grip it more tightly, but occasionally a round or fluted handle is seen.
Patent spiral screw-drivers have come into use in recent years, but where considerable force is required the brace and screw-driver bit are more effective.
Fig. 46. Cutting a Mortise
21. Sandpaper. “Sandpaper is the last resort of a poor workman.” This statement has been made by many teachers to many thousands of students, and is true in many cases; but there are certain kinds of work where sandpaper, if properly used, is allowable.
Fig. 47. The Screw-Driver
It must always be kept in mind that a surface which has been sandpapered has become “gritty,” i.e. the fine sand has come off and is more or less imbedded in the wood. Consequently sandpapering must not be done until all tool work has been finished, as the grit will take the edge off the best tool, and the finer the edge the more quickly will it be ruined.
Fig. 48. An Exercise involving the Use of Sandpaper
Again, a sandpapered surface is always a scratched surface, and the finest of scratched surfaces cannot compare with the perfectly smooth, satiny surface produced by a sharp plane. However, there are many places where neither the plane nor spokeshave can be used, and here it is allowable to use sandpaper after the tool work has been carried as far as practicable.
Fig. 48 is a case where sandpaper may be used with propriety. The bevels in this lesson are to be chiseled and then sandpapered with a sandpaper block,—the block in this case being simply a small piece of wood with square edges, about which the sandpaper is fastened closely.
Curved articles, such as the hammer handle, must dispense with the block, the sandpaper being held in the hand.
22. Squaring up Stock. This term simply means to reduce a piece of sawed or rough lumber to one having smooth, flat sides at right angles to each other, and of definite length, breadth, and thickness (see Fig. 49).
Fig. 49. The Successive Steps in squaring up Stock
First. Straighten one face with fore plane, jack plane, or jointer, and smooth with smoothing plane. This face, called the working face, becomes the basis from which all the other sides are squared.
Second. Plane one of the adjoining edges and make square with the working face. This edge, known as the joint edge, must be thoroughly tested throughout its entire length with the try-square, and must be square with the working face at every point.
Third. Set marking gauge at required width and with gauge block against the joint edge, gauge a fine line on working face.
Fourth. Plane down second edge to gauge line, just drawn, squaring the edge with working face.
Fifth. Set gauge to required thickness and gauge line on both edges from working face.
Sixth. Plane face parallel to working face down to the two gauge lines. This gives the required thickness. It only remains now to secure the required length.
Seventh. Square knife line around the four smoothed sides with knife and try-square as near one end as possible, carefully observing the precautions given in Chapter II.
Eighth. From the line just drawn, measure the required length along edge of working face and square a line on the four sides at the last point, as at first end.
Ninth. Block-plane first end to knife lines. If the second line is more than an eighth of an inch from the end of block, saw to the knife line with backsaw, and block-plane smooth and square.
The above method should always be followed in preparing stock for laying out the exercise.
23. Laying Out. Let it be assumed that the exercise to be executed is the middle lap joint shown at A, Fig. 50.
Fig. 50. Successive Steps in laying out and making a Middle Lap Joint
First. Square up stock, leaving ends rough.
Second. Lay off the length of each piece, in this case 4½ inches, with an eighth of an inch between for sawing, as at a.
Third. Square all the lines around four sides.
Fourth. Saw to end lines and block-plane ends.
Fifth. Lay off width of opening in piece No. 1 and square lines across face and halfway down on both edges.
Sixth. Measure length of lap on No. 2, square the line across bottom and halfway up the sides. Gauge the horizontal lines ll from working face.
Seventh. Saw pieces No. 1 and No. 2 apart and block-plane ends.
Eighth. Saw to the lines, chisel, and fit the pieces.
Although the above is the method of laying out a typical joint, each problem will require special treatment and here the student will be guided by his instructor.
24. Securing Parts. Many articles made of wood consist of several pieces fastened together.
When two pieces are fitted together the surfaces of contact are called a joint. There are many kinds and shapes in joinery, and usually some extra fastening is required to hold the pieces together. These aids are glue, nails, and screws; while on heavy construction still others, such as wedges, pins, and dowels are used. The first three are commonly used in small work.
Fig. 51. The Hand Screw
Glue is of two kinds, fish and animal. Both are made from refuse matter,—animal glue being manufactured from such products as bone, horn, hoofs, and hide.
The dry glue in the form of chips must be dissolved in water and heated, being applied while hot. Liquid glues sold in cans ready for use are now very common and require no heating.
In making a glued joint it is usually necessary to hold the pieces tightly together until the glue has set, or hardened, and as this takes some time, hand screws built on the principle of the vise are resorted to. Fig. 52 shows two pieces glued together and fastened in a pair of hand screws. Care must always be taken to keep the jaws of the latter parallel. At a this is shown done properly, while at b is shown a careless method which, of course, will spoil the joint.
Fig. 52. Method of using the Hand Screw
In gluing on the end grain a preliminary, or sizing, coat of glue must first be made to fill up the pores, which act very much like a sponge. This coat should be allowed to dry, or partially dry, before applying the final coat; otherwise the pieces will be held weakly, if at all. Beginners are inclined to use too large a quantity, and this tendency should be avoided.
In some cases nails are used together with the glue, as at the corners of picture frames. It is customary in this instance to nail in only one direction, as shown in Fig. 53.
Fig. 53. Miter Joint at Corner of Picture Frame
25. Nails. The nails in common use are of two kinds, cut and wire.
Two views of a cut nail are shown in Fig. 54, a being the side view and b the front view. Notice that in the front view the sides converge like a wedge, while in the side view they are parallel.
Fig. 54. Use of Cut Nails
Care must always be taken that the point does not enter the wood as shown at c, as the wood will be split by the wedge action; d shows the proper method.
Steel wire nails are now in general use. They are made from wire and are consequently round in section, with a comparatively sharp point. There are two distinct kinds, named flat head and bung head.
Flat-head wire nails, as the name implies, have thin, flat heads, which prevent the nail from being driven beneath the surface.
Bung-head wire nails, or brads as the smaller sizes are called, have very small heads, which allow the nail to be sunk below the surface. This is done by means of the nail punch, or set, and is necessary when the surface is to be planed after the nailing.
26. Screws. Screws are much used, and allow the pieces to be readily taken apart. They are divided into two classes, flat head and round head, and are of steel or brass. Steel screws are either blued or bright. Bright screws are polished and blued screws are produced by treating the bright ones with heat or an acid.
Fig. 55. Methods of using Screws
Fig. 55 shows a flat-head screw at a and a round-head at b. Flat heads are used for the more common work where it is desirable to have the screw head flush (even) with the surface or below it, while round heads are used where this is not necessary. In the latter case round heads are used partly because they are more ornamental. Flat heads must always be flush or below the surface, and in all but the softest woods it is necessary not only to bore a hole for the screw, but also to countersink it with a countersink bit in order that it may receive the head. Two methods of fastening with flat-head screws are shown in Fig. 55.
Sketch A shows the two pieces of wood in position, the hole bored in upper piece (only) and countersunk; B shows the screw in position. In this case the screw head is visible. It is occasionally desirable to hide the screw entirely. Sketch C shows the hole prepared for the screw; D shows the screw in position and a circular wooden plug driven in over it. The plug is then leveled with the surface and the screw completely hidden.
Fig. 56. The Difference between Perspective and Mechanical Drawing
27. Mechanical Drawing. A mechanical, or working, drawing is quite different from a pictorial drawing such as an artist produces. The artist’s drawing represents objects as they appear, while the mechanical drawing represents them as they really are. Things in nature do not look as they are. For example, when we stand on a railroad track the rails appear to converge until they seem to meet in the distance. We know that this is not the case, that the rails are really everywhere equally distant. The optical illusion of the rails meeting at the horizon is called perspective. Mechanical, or constructive, drawing takes no account of perspective. In Fig. 56 a is the perspective representation of a track, while b shows a track by mechanical drawing.
In a working drawing more than one view is necessary to show the true shape of an object.
In Fig. 57 is shown the mechanical drawing of a cylinder,—the front view, as its name implies, being the image it would make in a mirror held before it vertically, and the top view the image it would make in a mirror held directly over it horizontally.
Fig. 57. Mechanical Drawing of a Cylinder
Fig. 58. Mechanical Drawing of End Lap Joint
Occasionally three views are necessary. Fig. 58 a shows the front, top, and side views of an end lap joint. The complete working drawing of this joint, with all the necessary dimensions, is shown at b.
Fig. 59. Drawing Board showing T Square and Triangles in Position
In making drawings of this kind the greatest accuracy is required and special instruments are necessary.
The drawing board on which the paper is fastened must be perfectly flat, with one of its edges straight.
Fig. 60. The T Square
The T square is used for guiding the pencil or pen when drawing horizontal lines.
The two triangles t t (Fig. 59) are used for drawing vertical and oblique lines, and a pair of compasses is needed for circles and arcs of circles. Each triangle contains one right angle, the one on the left being known as a thirty-sixty triangle because the two remaining angles are thirty degrees and sixty degrees respectively. The one on the right is called a forty-five-degree triangle because it has two forty-five-degree angles.
The position of T square and triangle when drawing vertical lines is that shown in the sketch, the line being drawn from the T square upward. Horizontal lines are drawn from left to right.
The rule used in mechanical drawing is called a scale, and should not be used for drawing lines. Its purpose is measuring.
Fig. 61. The Triangles used in Mechanical Drawing
In making a drawing the first step is to determine the spacing. The size of the paper may be measured, the number of views are known, and also the size of each. The views should be so arranged that the spaces between will be in good proportion. It is a good plan to make first a free-hand sketch, putting on dimensions and figuring the spaces before beginning actual work on the mechanical drawing. Fig. 62 at a shows a free-hand sketch of a single dovetail joint, and b the mechanical drawing complete.
Fig. 62. Drawings of a Single Dovetail Joint
All dimensions must be given, and as far as possible they should be so placed as not to interfere with the clearness of the drawing. Neat, small arrowheads and plain, clear figures add to the general appearance, just as does careful lettering in titles and all printed words.
A drawing which is made the exact size of the object represented is known as a full-sized drawing; but for large objects such a method would necessitate large and unhandy sheets of drawing paper. It is customary in such cases to make what is called a scale drawing.
A scale drawing may be half, quarter, or eighth size, and the fact is printed under the title in smaller letters, thus: ½ inch = 1 inch, or ¼ inch = 1 inch.
Other scales may be used. In map making, for example, a sixteenth of an inch may represent one, ten, or even a hundred miles. Whatever scale is used, however, the dimensions must always give the exact size of the object represented.