This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
These embrace the class of most uninteresting hardware - so commonplace as hardly to demand attention; but they play, after all, a large part in modern construction, and have had the greatest influence in the evolution of the now almost extinct trade of joinery, as understood a hundred years ago.
By reference to the cut of the "Jefferson" nail (Fig. 3), it will be seen that it is a wedge more adapted to splitting all wood through which it is driven than to make the parts more secure. It was the successor of the oak pin of Colonial days, and was used in much the same way. After the parts were most carefully fitted together, holes were bored only slightly smaller than the nail, and the latter was driven in to secure the close contact of the parts, which, indeed, were already fitted so nicely that they would cling together with a very slight binder.
Fig. 4 is the end of a timber taken from the Capitol, which shows how the splice joint was made; this was a joiner's fit, which took very little to complete the union. Through all the work of joinery- illustrated by this close fitting - the same principles extended, so that the use of nails of the Jefferson type was very limited.
Screws, except in very crude forms, were seldom used. Fig. 3 shows bolts and a nut of the same period taken from the Capitol trusses. It will be noted that in order to make their use possible, the parts must have been accurately fitted.
With modern machinery for making nails and screws, came a revolution in carpentry work. The old mortise-and-tenon timber frame gave way to the balloon frame. Joinery died a natural death, as it was found much cheaper simply to lay the pieces together and drive spikes or nails until the whole was solid. In many instances the use of spikes or nails was carried to extremes - in fact, their use became reckless; and so important is their place in construction work, even to-day, that it is a by-word, that "any man is a carpenter who can drive a nail." But the man who can select the right nail or screw, and drive it where it is needed, and in the right way, is a rare man.
Fig.4. End of a Piece of Old Timber from Capitol, Washington, D. C, Showing Former Method of Making Spliced Joint.
From the strictly practical standpoint, nails and screws may be divided into two classes - First, those used in construction work only; second, those used in construction work so exposed as to require consideration of the appearances they present.
For the first, round wire nails are now used almost exclusively. The older cut nail is wedge-shaped, with two rough sides, which make it hard to drive and which tear the fibre of the wood; the wedge shape, moreover, permits these nails, after they are once started, to be more easily drawn out. The wire nail is smooth, does not tear the wood, and is more easily driven than the wedge; and, on account of being of the same diameter throughout, it holds firmly even after being started in withdrawal.
A nail should never be driven clear through any woodwork so that the point appears, unless it is clinched, in which case a wrought-iron or "clout" nail is required; the wire nail is too hard to be easily bent and clinched. A nail driven clear through so as to expose the point unclinched will not hold so well as one shorter with the end buried.
In the frame, it is not the number of nails that tells, but their careful placing in such parts and at such points as to keep the building stiff. Nails should be grouped to afford the largest efficiency. In nailing the boarding onto a frame, for example, it is necessary to put two nails in each board to each stud. One nail would be sufficient to secure the boards; but, as there is bound to be a slight shrinkage drawing the edges of the boards apart, if the frame is not otherwise securely braced, a strong wind will rack the structure out of plumb until the edges of the boards touch again, the single nail in each board allowing a swing which would have been effectually stopped by two.
The smallest nail competent to accomplish the purpose should be used, on account of the greater ease with which it can be driven; the difference in effort required to drive ten thousand 20d nails and an equal number of 16d's is a very material item in expense.
When strength is obtained by doubling timbers and in trusses, holts and nuts with large washers should be used to the exclusion of nails, as a sudden jar or a slight shrinkage of the wood will prevent the nails clamping the parts closely together, and this separation or loosening of the joints materially reduces stiffness and strength.
The use of wrought-iron nails can with great profit be extended. For instance, after a house is boarded up and building paper put on, in placing the exterior finish boarding, of whatever nature it may be, if the nails are clinched on the inside, the contact will be so close as to prevent the opening of cracks between the layers, and in cold weather the nails will not "draw" and allow the joints to open.
Where nails must be used in finished surfaces, all questions of general construction must be dropped, and only such nails used as are absolutely necessary to secure the members in place; and special attention should be given to selecting nails with such heads as will not disfigure the finish. Wire nails of very small diameter and with heads only slightly larger in size, are now made; and it is remarkable how firmly these hold the parts in place. These nails, carefully driven and with heads set below the surface of the finish, leave a small mark that can be readily hidden with putty colored to match the tone of the wood. Wherever possible, nails should be put in the quirks or concealed places, rather than in plain surfaces where the last blow of the hammer is apt to leave a round indentation in the wood. A careful carpenter in good work can place his finish so that it can be either nailed or screwed in place from the back, or the nails or screws placed so that the heads will be covered or in inconspicuous places. In purely constructive work, screws (unless as bolts) are little used except in special finish, such as mantels and other cabinet-work put together and finished complete before being set in place.
When it is necessary to provide for the shrinking and swelling of the wordwork, round-head screws with washers can be used. Fig. 5 illustrates such a screw, A being the washer; B a long slot, and C the screw; this arrangement allows movement with the screw sliding on the washer.
When it is necessary to use screws in finished surfaces, the treat-ment should be exactly the reverse of that governing the use of nails.
Fig. 5. Round-Head Screw with Washer.
There are many forms of screws on the market, with well-tormed heads, finished in lacquer, blued, or plated (it is necessary to have some finish to prevent rust). A variety of typical forms are shown in Fig. 6. The custom of starting screws with a hammer - in fact, driving them three-quarters of the way in - should not be allowed; a screw with a battered head or not driven in straight, disfigures the work; when started by the hammer, one or both of these conditions generally prevail.
Fig. 6. Typical Forms of Screws.
Fig. 7. Strap Hinge.
Screws which show should have heads of pronounced shape, spaced regularly - in fact, made a feature in the design.