JOINERY. 



213 



Johwrr. planes of the bar, and having their distance from one 

 ^p- t -w another equal to the thickness of the said bar. And, 

 consequently the ellipse, which directs the form of the 

 concave edge of the bar, will have its lesser axis equal 

 to the diameter of the interior cylindrical surface, and 

 that which forms the convex edge equal to the diameter 

 of the exterior cylindrical surface. 



The circular bar, or, as it is improperly called, cod 

 br, depends on the developement of the part of the 

 cylindrical surface, formed by cutting a vertical cylinder 

 by a number of horizontal concentric cylindrical sur- 

 faces, which gives the form of the veneers, or thin 

 lice* of wood to be bent in thicknesses. 



The head of the sash depends on the cutting of a 

 hollow cylinder, so that the side contained between the 

 two cylindrical surfaces, that stand upon the exterior 

 and interior sides of the plane of the sash, may be 

 every where perpendicular to these surfaces, and to 

 follow the true shape of the elevation of the window, 

 and thus the angles will be easily moulded. Rut in 

 order that there may be no variation of the mouldings 

 in a circular sash frame, it is necessary that both the 

 radial and circular bars, as well as the head, should 

 be moulded upon the same {principle as a hand rail, 

 viz. by means of face and falling moulds ; the face 

 mould for the radial 'bars will be as before observed, 

 and the falling mould will be a parallel slip of wood, 

 straight in the edges, in breadth equal to the thickness 

 of* the bar. The falling moulds of the other parts 

 mnrt be made according to the developement of the cy- 

 lindrical surface*. 



.HC, Plate CtC XXXVII. is the eleva- 

 tion of the head of the sasb. and A DC the plan rf the 

 same. Bisect the arc ABC in B : draw BF perpendi- 

 cular to AC', cutting the concave side of the plan at 

 D : draw DC parallel to AC, and AG parallel to BF. 

 Bisect the arc AB at 3, and draw 5 c parallel to BF, 

 cutting (>L> at c, and the curve AD at c' : draw the 

 straight line A 3 K : draw AH making any angle with 

 AK, and 3 I parallel to AH: make AH equal t< 

 and N I equal to cc : draw the straight line HIK 

 join BK, and produce BK to L : draw AL perpendicu- 

 lar to BL, and join HL. Divide the arc All into any 

 number of equal parts as here, into 6 : draw 1 a, 2 b, 

 Sc. fcc. parallel to BF, cutting the innide of the bead 

 of the sah at a, A, c,&c. the inside of the plan at a, h. c. 

 tec. and the straight line CD at a, b, c. &c. From the 

 points a, b, c, Sec. draw aa', bb', cc', &c. perpendicular 

 to AL, cutting HL at a', b', c'. &c. and AL at g, k, i, 

 cc.: perpsodJcular to HL draw a'a", W, cc 7 ', &c. 

 Make a'a", t> b ", cV". Ac. respectively equal to ga. A*. 

 sc, &c, and through the points a", b', c", &c. draw the 

 curve "A"r*d"r"./" : draw also the straight line 

 ;, <f, r, parallel to AH, cutting AL at o. HL at r; 

 draw rt perpendicular to HL ; make n equal to qp; 

 draw I.B' perpendicular to HL, and make LB' equal 

 to LB ; join H/, in" and B'f, which will complete 

 the concave edge of the face mould. In the same man- 

 ner, by transferring the perpendiculars between AL, 

 and the convex side AB respectively, to the perpendi- 

 culars upon HL, we khall have the points through 

 which toe convex edge of the face mould must pass, 

 then tracing through the points so found, will com. 

 plete the face mould H. 



To draw the falling mould S, Fig. 2. for the convex 

 side of the rail. Extend the arc AB, Fig. 1. with the 

 divisions to the straight line AB, Fig. 2. and mark the 

 Iktremitie* A, B. and the divisions 1,9,3, tie. Draw 

 the lines AA', 1 a, 2 6, 3 c, &c. perpendicular to AB. 



From Fig. I . transfer the distances GA, aa', bb', cc', &c. Joinery. 

 to Figure 2. upon AA', 1 a, 2 b, 3 c, &c. and draw the ^""X"""' 

 curve A a b c d e B will give one edge of the falling CCCXMV , I . 

 mould S ; the lower edge will be found in the same Figs . z> 3,' 

 manner. 



To find the falling mould T, Fig. 3. for the concave 

 side. From Fig. 1. extend p a, ab,bc, &c. tof, to Fig. 

 3. and place them upon PF, from P to a, a to 6, A to c, 

 &c. perpendicular to PF draw P l,am,b n, &c. From 

 Fig. 1. transfer the perpendiculars q r, ga', h b', i c, 

 &c. to Fig. 3. npon P /, a m, bn, c o, &c. and draw the 

 curve Imnopqr. From Fig. 2. transfer A A', 1 a, 2 b, 

 S c, ice. to Fig. 3. upon a a', b b', c d, &c. and draw the 

 curve a bed e F which gives the upper edge of the 

 falling mould T. The under edge of T will be found 

 in the same manner from the under edge of S. The 

 upper line mnopqr coincides with the top of the 

 stuff, when the mould T is bent round, and the space 

 between the curves a 6 c d e F, and Imn opqr shews 

 the waste of stuff at the acute angle of the piece. 



Fig. 4. shews the application of the face mould R to pjg. 4. 

 the plank ; the plane U shews the upper face of the 

 plank ; the plane V the edge ; and the plane \V the 

 lower face of the plank ; so that the two sides and the 

 edge of the plank shew . as if* they were stretched out 

 in one plane. 



To apply the moulds, in order to square the stuff, 

 that is, to make it stand ever the plane, and opposite to 

 its elevation, when set up in due position : Apply the 

 mould first to the top of the plank at U, so that the 

 chord line of the concave arc or the mould may coin- 

 cide with AB, the edge of the plonk, then draw the 

 form of the mould upon the plane U ; let g be one of 

 the extremities of the chord ; draw g k perpendicular 

 to AB, cutting the arris line CD at A ; make the angle 

 Eg i equal to the angle LHA, Fig. 1. and the angle 

 ikfm the plane \V equal to LYF, Fig. 1. make hf 

 equal to A i, and draw j e parallel to CD. Then ap- 

 ply the mould to the plane W, so that the face may 

 coincide therewith, and the chord with the line CD, 

 and the point that was at g may now coincide with /'; 

 then draw the form of the tno ild upon the plane W ; 

 proceed to cut out the head in the same manner as di- 

 rected for a hand rail. 



The mould X, Fig. 1, U the mould for the radial 

 bars, traced from the plane below ; Fig. 5. shews the Pig. 5. 

 method of applying it to the plane, which is exactly 

 the same as if it were a hand rail. 



Fig. 6. shews the method of tracing the veneers of Pigs. 6, T, 

 the cod or circular bar. Fig. 7. is the concave veneer. 8, 9. 

 Fig. 8. the convex veneer. Fig. 9. is the method of 

 forming the edges of the veneers, which are to be cat 

 out to their thickness afterwards. 



flWr*. 



Mrs and hand-rails are most important branches in Stain, 

 joinery ; but before we enter upon their construction, 

 it will be useful to point out some of the leading prin- 

 ciples, without regarding the materials of which stairs 

 arc constructed. 



The breadth of steps in general use is from 9 to 12 

 inches, or about 10 inches at the medium. In the best 

 staircases, the breadth ought never to be less than 18 

 inches, nor more than 18. It is a general maxim, that 

 a step of greater breadth requires less height than one 

 of less breadth : thus a step of 12 inches in breadth will 

 require a rise of 54 inches ; which may be taken as a 

 standard bv which to regulate those of other dimen- 

 sions; so that multiplying 12 inches by ;.{,, we should 



