This section is from the book "A Treatise On Architecture And Building Construction Vol2: Masonry. Carpentry. Joinery", by The Colliery Engineer Co. Also available from Amazon: A Treatise On Architecture And Building Construction.
The portion r s then butts against the rib at v c, and the whole is secured in place by the pressure of the stiles of the sash against the outer ends of the horizontal bars.
The mortising of the horizontal bars into the stiles is effected in precisely the same manner as into the vertical bar, the molded portion being coped and the solid central part let into the mortise.
59. On the side elevation (b) is seen at a" a round hole, \ inch in diameter and § inch deep, bored in the sides of each sash just above the middle, to receive the knot of the sash cord which is to extend over the pulleys to the balance weights in the weight box. A groove is cut 1/2 inch wide and 1/2 inch deep at c" b" for the cord to lie in, from the top of the sash to c"; and a hole 3/8 inch in diameter, bored from c" to the 7/8-inch hole at a", as shown by the dotted lines c" a", holds the cord in place, and prevents the knot from slipping out of the hole at a".
At k" I" on this side elevation (b) is shown a portion of the parting bead in its position relative to the sashes. It will be readily seen that, as the meeting rails of the sashes extend beyond the interior and exterior faces of the upper and lower sashes respectively, the beveled portion of these rails must be notched out on the ends to fit around the parting bead.
60. When all the parts of a sash are made - stiles, rails, vertical and horizontal bars - the whole frame is drawn together with bench clamps, and then wedges dipped in glue are driven in on each side of each of the tenons b'. The mortises are made 1/2 inch wider on the outside than on the inside of the stiles, to make room for the wedges, which are driven until the joint is closed tight. Holes 1/4 inch in diameter are now. bored through each mortise and tenon b' and each dovetail joint, and wood dowels dipped in glue are driven through the joint to secure it, as shown at w' in the elevation (c). When the clamps are removed from the sashes, the faces are smoothed and made ready for fitting into the frames.
61. Sashes should always receive one coat of paint before they are glazed, in order to prevent the wood from absorbing the oil from the putty with which the glass is fixed in place, and thereby rendering the putty brittle and inadhesive.
In glazing the sash, the rabbet is first prepared, by spreading a thin layer of putty along the glass bearing, to form a cushion, against which the panes of glass are first partly secured, by means of small triangular pieces of tin, called glazing brads, which are driven into the wood against the face of the glass. Putty is then spread in the rabbet to form a triangular fillet, and permanently hold the glass in place. This putty extends to the outside of the rabbet and up the face of the glass to within 1/16 inch of the daylight opening. The back putty which has squeezed out between the pane and the glass bearing is then scraped off flush with the daylight opening, and the sash is then set aside to await its second coat of paint.
If a pane of glass is curved slightly, it should be placed with its convex face to the weather, and, if warped so that its surface is not even, it should not be forced to a full bearing in the rabbet, but permitted to lie naturally in place, and any unevenness should be taken up in the bearings by back puttying - that is, the space between the glass and the bearing face of the rabbet is filled with a thin layer of putty, against which the uneven surface of the glass may rest.
62. To fit and hang the sash in the window frame, it is first necessary to remove the stop-bead and parting strip, and then fit the upper sash so that it slides easily between the pulley stiles. It is then secured in place by means of a couple of wood blocks nailed under it; the parting strip is replaced, and the lower sash is then similarly fitted. The lower rail of the sash is then planed off until the meeting rails rest snugly together, as required.
In providing weights for the sashes, the pair for the upper sash must be at least half a pound heavier than the weight of the sash, while for the lower sash the weights must be at least half a pound less than the weight of the sash. This half-pound excess in the upper weights and in the lower sash tends to keep the sashes close and tight against the window head and the sill.
To hang the sash, the pockets must be opened by unscrewing and removing the covers. The sash cords are carried over the pulleys by means of a piece of light but strong string, which has been previously forced over the pulley and drawn down within the box with a lead weight, called a mouse, small enough to go over the pulley sheave, but heavy enough to carry the string. The sash cord is then made fast to the weight, and, with the top sash resting equally on the sill, the weight is pulled up to the pulley, and the cord is cut off just long enough to permit a knot to be tied at the required point. By the use of metallic cord grips, knots on the ends of the sash cord are not required, but care must be taken to have the grip of a size to properly fit the cord. When both weights for the upper sash are thus attached, the sash is removed from the frame far enough to permit the cord to be pushed down through the groove and the hole seen at g" h", Fig. 28, and a knot is tied to prevent it from pulling out. When both weights and cords are thus attached, the sash is replaced in the frame, pushed up and down a few times to test its efficiency, and the lower sash is then hung in a similar manner. When the sashes are both hung, and are found to slide satisfactorily, the stop-bead is replaced and secured, and the pocket is closed and screwed up tight, to prevent the cover from catching on the lower sash.
63. Hinged sashes are, as previously mentioned, divided into two general classes; namely, those hinged at the sides, and those hinged at the top or bottom. The first named are usually hung in pairs, closing at the center with rabbeted meeting stiles in much the same way as a pair of folding doors, and are called "French casements," from the country of their origin.