Jointing woodwork

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Try square usage

The butt joint

A butt joint is formed by joining two pieces of stock without fitting one piece into the other. The pieces so joined may be held together by means of glue, nails, or screws. The glued butt joint is most frequently used when joining two or more boards together, edge to edge, in order to produce a wide panel. The success of such an operation depends on the planing of the butting edges, that is, the edges touching each other. The butt joint may be strengthened by the use of dowels.

When such a panel is to be made up, the stock required should be cut from a rough-stock list which allows the necessary waste for planing. The pieces are placed edge to edge on the bench and arranged so that the annual rings of each end are in opposite directions. The relative position of each edge is marked by lettering the butting edges.

A work face is planed on each piece. The second step is to dress the butting edge of each piece, making each one smooth, straight, and square to the work face. The edges which are marked alike to be joined must be tested by placing them together to see if they fit tightly. The slightest. space between the butting edges will produce a poor joint. Long pieces of stock that are to be joined will produce a more permanent joint if the butting edges are slightly concave.

Of all the joints, the butt joint is the weakest, for it depends for its strength solely upon the glue, screws, or nails used to hold it together. The strength of a butt joint may be increased by the use of dowels.

Before glue is applied to the edges, the work is given a final test by placing a clamp across the center of the pieces and drawing them up tightly. They should fit tightly at the ends so that the boards cannot be moved by pressing on them with the fingers.

Lap joint

Lap joints are formed by one piece of stock extending over another, with a section of each removed to fit them together. The most common lap joints are the end-lap, half-lap, middle-lap, and cross-lap joints.

The end-lap joint

The stock which is to be joined together by means of an end-lap joint is cut and dressed to size. The stock is arranged with the work faces up, and the ends which are to be cut to form the joint should be marked A and B.

The second step is to lay out the length of the cut, which must be equal to the width of the piece that is to set in it. This is done by plating piece B on the work face of piece A, with the edges and ends flush. A knife mark is made on A, keeping the knife as close as possible to the edge of piece B.

Piece B is now placed on the bench with the work face down, and the operation is repeated, using piece A to obtain the required length of the cut. In the third step, a knife line is cut across the work face of A and the second face of B, passing through the knife mark which was made previously. This line is continued half way across both edges.

The fourth step is laying out the depth of the cut with the marking gage. The gage is set for half the thickness of the stock. A gage line is made along each edge, extending from the knife line to and across the end; this must be done on both pieces. The section of each piece to be removed is shaded as shown, and the pieces are placed over one another to check the layout.

The first step in cutting the joint is to make a V-groove across the face of each piece. This is done with a chisel. The purpose of the V-groove is to guide the backsaw and start it flush with the line. The backsaw is placed in the V-groove and the stock is cut to the gage line. The V-groove will only aid in starting the cut at the proper place. The saw must be kept straight and parallel to the vertical knife lines on the edges.

The section to be removed is cut away with a chisel. The greater part of the stock can be cut away by using a mallet to drive the chisel, cutting from the end toward the saw cut. The finishing cut is made at the gage line, using a paring chisel across the grain. The end-lap joint is usually fastened together with glue, screws, or nails. It is strongest when used in such a manner that the force exerted on either member is toward the point where the pieces join. It is of ten used in the construction of frames, instead of the mortise-and-tenon joint.

The half-lap joint

The half-lap joint is laid out and cut in the same manner as the end-lap joint. The length of the cut may be varied to meet special requirements, but in any case the length of the cut must be identical on both pieces.

The middle-lap joint

A middle-lap joint is formed when the end of one piece extends over to join the other at some point between the ends. The stock is cut and dressed to the required size. The pieces to be joined are placed on the bench with the work faces up.

The location of the dado to be cut in piece A to receive piece B can best be established by squaring of the dado across the face. (A dado is a flat groove across the grain of a member) This center line is the center line of the dado and does not necessarily indicate the center of the stock. Across the end of piece B a center line is drawn.

The width of the dado is marked off by placing piece B on the face of piece A so that both center lines coincide. A knife mark is made on the face of piece A as close as possible to the edges of piece B. Knife lines are squared across the work face through these knife marks. They are carried halfway across the edges.

Piece B is laid out as an ordinary end-lap joint, marking off the required length of the cut on the side opposite the work face.

The depth of the cut on both pieces is marked off with a marking gage. The gage is set for half the thickness. Gaging is done from the work face on both pieces. The gage lines on B are on the two edges extending from the end to the knife line as well as across the end. The sections that are to be removed should be shaded, then the pieces placed over one another to check the layout.

The first step when cutting the dado in piece A is to cut V-grooves across the face to guide the saw. Saw cuts are made by placing a backsaw in the V-grooves and sawing down to the gage line. If the dado is wide, several saw cuts can be made within the area of the stock to be removed.

The removal of the stock within the limits of the saw cuts is done with a chisel, working from both edges toward the center. The dado is finished by using a paring chisel or with a special tool which is called a router.

The cutting of piece B to fit in the dado is done in the same manner as described for the end-lap joint.

The middle-lap joint is used when one member or piece of stock is to be fastened to another member at a point between the ends. There is no strain on the fasteners used to hold these members together if the pressure is applied to the edges or the face of the member that is set in the dado. Crosspieces in a frame are frequently joined to the outside frame members by means of this joint.

The cross-lap joint

The cross-lap joint is formed when two pieces cross one another so that the surfaces are flush. They may cross one another at any point and at any angle. The two pieces of stock are cut and dressed to the required size, as previously described.

The first step when laying out a cross-lap joint is to place the pieces with the work face of one up and the work face of the other down. The center of the joint is located and a line squared across the work face A of one piece and the side opposite the work face B of the other. Center lines are also square across one end of each piece from face to face.

The next step is to place piece B on the face of A so that the center lines on the end and face coincide. Knifemarks are made on the face of A as close as possible to the edges of piece B. This establishes the width of the dado that must be cut in piece A to take piece B. The operation is repeated to lay out the width of the dado that is to be cut in piece B to take piece A.

Knife lines are squared across the face of each piece through the knife marks that located the limits of the dado. These knife marks are carried half way across each edge. The depth to which the dado on each piece is to be cut is marked off with the marking gage. The gage is set for half the thickness of the stock and a line is gaged from the work face of each, extending between the knife lines. The cutting of the dadoes to form the joint is done in the same manner as in the middle-lap joint.

Cross-lap joints that are to be made at any angle other than 90 degrees should be laid out with a T-bevel rather than with a trysquare. The method of laying out and cutting such a cross-lap joint is identical to that just described.

Of all the lap joints, the cross lap joint is the strongest. It relies least on the glue, screws, or nails used to fasten the members together. Such a joint will withstand pressures in any direction except one, without depending on the fastener that holds it together.

The rabbit joint

A rabbet joint is formed by cutting a recess along the edge or end of one piece of wood to receive the edge or end of another piece which is cut to fit it. The two pieces to be joined by a rabbet joint are squared to the required size.

The two pieces are placed on the bench in their relative position. Shown is the piece into which the rabbet is to be cut is marked A; the other piece is marked B. The width of the rabbet is equal to the thickness of the stock which is to set in it. This is laid out by placing piece B on the work face of A, with the face of B flush with the end of A. A knife mark as possible to the inside face is made on the face of A as close of B to locate the width of the dado. A knife line is cut across the work face and part way across the two edges, using the trysquare to guide the knife.

The depth of the rabbet is laid out, using the marking gage. (Gaging is done from the work face.) The gage is set for the required depth. The gage line extends across the end and on the two edges from the end to the knife line. The section which is to be removed is shaded. The layout is checked by placing piece B on the shaded section.

A V-groove is made across the face of the stock, using the chisel the knife line. The chisel cut must be made from the section of the stock which is to be removed.

The shoulder cut is made by placing the backsaw in the V-groove and cutting a kerf down to the gage line. The saw should be kept straight and parallel to the lines on the edges.

The rabbet is cut to the required depth with a chisel. The cutting edge of the chisel is placed on the end of the stock, well above the gage line, and struck lightly with a mallet. The rabbet is finished to the gage line with a paring chisel, working from both edges toward the center.

The strength of a rabbet joint is the result of cutting the pieces to be joined in such a manner that the strain is at right angles to the nails or screws used to fasten the members together. This type is often used to reduce to a minimum the amount of end-grain exposure.

The dado joint

The pieces that are to be joined by means of a dado joint are cut and squared to the required size. A dado joint is formed by cutting a recess across the grain of a piece of wood from edge to edge or face to face to receive a second piece. It differs from the rabbet joint in that it has two shoulders, or vertical cuts, while the rabbet which is cut along the edge or end of a board has only one. The two pieces are placed on the bench in their relative positions ; the one in which the dado is to be cut is marked A, the other B.

The center of the dado is located on piece A and a line is squared across the face. A center line is gaged along the end of piece B. Piece B is placed on piece A so that the center lines coincide. Knife marks are made on the face of piece A as close as possible to the faces of piece B to establish the width of the dado.

Knife lines are cut across the faces through the knife marks and part way down the edges. The trysquare is used to guide the knife. The handle of the try-square should be held tightly against the work edge when cutting the lines across the face, and against the work face when cutting the lines across the edges.

The depth of the dado is marked off with a marking gage, setting the gage for the required depth and gaging from the work face. The gage line should extend between the two knife lines on each edge. The section of the stock which is to be removed to form the dado is shaded, and the for accuracy by plating piece B in position. The dado is cut, and as described for cutting the middle-lap joint.

The miter joint

The miter joint is a form of butt joint, differing only in that the pieces which are joined are cut at an angle other than 90 degrees. It is produced by making a bevel cut on the ends or edges of the pieces which are to be joined. It relies for its strength on the fasteners, and is therefore no stronger than the butt joint.

Pieces of equal width or thickness that are to be mitered must have the bevels which are to be joined cut at the same angle.

The angle at which the cut is made is half the angle formed by the two pieces when joined. The stock that is to be used is cut and squared to the required size.

The pieces to be joined by a miter joint are arranged on the bench in their relative positions. A T-bevel is used to lay out the angle at which the miter is to be cut. The T-bevel is set. A line is drawn across the face of the wood, using the bevel. The line is carried across the edge with a trysquare.

The miter, if at the end of the wood, can be cut with a backsaw. The cutting should be done slightly beyond the line to allow for trimming the bevel with a block plane. The angle at which the miter has been cut and planed is tested with the T-bevel.

Miters along the edge or the end of the wood can be cut entirely with a plane, laying them out and testing them

The mortise and tenon joint

The mortise-and-tenon joint is one of the best methods of joining two pieces of wood. It consists of two parts: the mortise, which is a rectangular hole cut into one member; and the tenon, which is a rectangular projection the same size as the mortise, cut on the end of the other member. It is used when joining the end of one piece to the face or edge of another.

The mortise-and-tenon joint has many variations, each of which has a special name: blind, stub, through, open, haunched, keyed, and wedged. Basically, however, the method of laying out and cutting all mortise-and-tenon joints is the same.

The pieces which are to be joined are cut and squared to the required size. The pieces are arranged in their relative positions and marked A and B. The mortise is to be cut into the edge of A, and the tenon is to be cut on the end of B.

The length of a tenon varies from 1/2” to 2", depending on the size of the member into which it is being fitted and on the type of mortise-and-tenon joint that is to be made. The thickness of the tenon is usually one-third the thickness of the stock on which it is cut. Before the actual laying out can be undertaken, the size of the mortise must be determined as well as its distance from the end of the stock.

A center line indicating the center of the mortise is drawn on the edge of the stock. The location of the upper end of the mortise is established by measuring in the required distance from the end and squaring a line across the edge. The length of the mortise is measured from this line. A second line is squared across the stock at this point, establishing the length of the mortise.

The width of the mortise is laid out with the mortise gage set. The tenon is laid out by first measuring off the required length from the end and squaring a knife line around the stock. The handle of the trysquare should be kept against the work edge and work end.

Using the mortise gage without changing the setting of the double pins, mark off the required thickness of the tenon, gaging lines on the end and down the two edges from the end to the knife line. The width of the tenon, which is the same as the length of the mortise, is laid out with the mortise gage. The double pins are set for the required dimension, and the head is set for the distance from the edge that the gage lines are to be made. The gage lines are made across the end and on the faces, extending from the end of the stock to the knife line. The portion of the stock that is to be removed when cutting the mortise and the tenon should be shaded. The lay-out is checked for accuracy.

Cutting the mortise

The mortise can be cut by boring a series of holes within the area that is to be removed. The remainder of the wood is cleaned out with a chisel. Since most mortises are cut relatively deep, the use of a bit to remove the major portion of the stock will make the work considerably easier.

Use an auger bit of the same diameter as the mortise. The stock is held in the vise, and a series of holes are bored within the limits of the mortise. The holes should be bored at the ends of the mortise first. When boring the holes, place the point of the bit on the center line, carefully holding the bit at right angles to the surface throughout the operation. The holes are bored to the required depth of the mortise, which should be about 1/8" deeper than the length of the tenon.

The wood left between the holes is removed with a paring chisel. The chisel must be held perpendicular, with the bevel side toward the center of the mortise. Keep the sides of the mortise straight and do not cut beyond the gage line. Clean the ends of the mortise with a narrow paring chisel.

Cutting the tenon

A V-groove is cut across the faces and the edges to aid in starting the shoulder cuts. The cutting of the groove is done from the stock to be removed toward the knife line. The shoulder cuts are made to the depth of the gage lines, sawing across the faces first and then across the edges.

The tenon must be fitted to the mortise, and should be tested from time to time as the paring of each cheek progresses. The cheeks of the faces are cut with a chisel by a series of paring cuts until the waste is removed down to the gage line. The cheeks on the edges are cut in the same manner.