The thickness of the tenon should be around one third of the thickness of the stile, but should be set finally to match the width of the nearest available size of chisel. The width of the tenon should not exceed five times its own thickness, which in turn will determine whether a single or double tenon is used. But if the joint is positioned at the top of the stile, it is usual to divide the tenon width into three parts two for the tenon and one- for the haunch (fig. A). Where the frame of which the joint is a part is to take a panel of some sort and is grooved, the haunch forms part of this. Otherwise, it is customary to make a groove to match a secret haunch (fig. 13 below).

A: This more complicated haunched stub joint is at the top of the stile. If you get confused when marking out, shade in the waste areas in pencil.

B: A marked out plain through mortise and tenon joint ready to be cut. The lines marking the mortise and corresponding tenon width are made with a mortise gauge.

C: Initial marking out on both the stiles and rails is best done with the relevant pieces of timber cramped together. Mark the waste first, then the rail width.

Where the rail is wide (over about 75 mm) it is usual to employ a double tenon. In this case, you can either divide the rail width by four and take each tenon width as one quarter (fig. G) or divide it by three and make the distance between tenon centres one third of the rail width.

G

If you are making a stub tenon joint, the depth of the mortise should exceed the length of the tenon by 2 mm.

The gap allows for excess glue that might otherwise force the joint apart as soon as it has been assembled. When you are cutting the mortise for a stub tenon, make sure that there is at least 4.5 mm of wood between it and the outer edge of the stile.

When marking and cutting a mortise at the end of a stile, it is customary to leave excess waste material known as a horn between 25 mm and 35 mm is usual on a standard sized door frame.

The horn helps stop the stile from splitting as the mortise is cut and also protects the frame in transit to its final position, where the waste is trimmed off.

[edit] Marking Up a Simple Frame

If you are making a framework that incorporates joints at the ends of stiles, do not forget to allow for the extra length taken up by the horns when you compile your cutting list. Rail lengths for a framework are normally taken as the overall width of the frame, allowing you plenty of waste material. But if you are using through mortise and tenon joints, add on 12 mm to the overall frame width, this gives you 6 mm waste on each end to be removed when the joint is finally 'cleaned up'.

With your timber to hand, test each piece for true and mark on face sides and face edges (see measuring & marking). Lay the pieces out as they will appear in the finished frame, face edges inner­most and face sides uppermost. Designate and mark the stiles 'left' and 'right', and the rails 'top' and 'bottom'. You can also mark the joints A-A, B-B and so on, though the marks should be on waste wood that will be removed later.

Next, place the stiles side by side on the bench, face sides uppermost and face edges outwards, and cramp them together with a small G cramp. Remember to place off cuts between the jaws of the cramp and the work piece to protect the latter from becoming bruised (fig. C). With a try square, marking knife and rule, mark off one waste end or horn, whichever is appropriate on both pieces. Follow by marking the finished lengths of the stiles. The material left represents either waste or another horn.

Your next job is to mark the positions of the mortises and, if you are making a wedged joint, the 'wedge room' on either side of them. Again, use the try square, marking knife and rule, but score deeply only those areas that are to be cut. Mark very fine lines on the rest of the timber. If you are making a through tenon joint, separate the stiles and mark around them individually. Start at the face edge and work around the timber so as to end up, at the edge below it. Make fine lines at each edge of the work piece to enable you to continue around it without having to score across the whole surface. When you have finished marking the stiles, cramp the rails in the same way and mark off the overall lengths. Do not forget to add an extra 12 mm waste if you are making through mortise and tenon joints. This will be planed off when the joint is assembled.

Mark the lengths of the tenons as described above, together with the haunches where necessary (figs C and A above). Finally, separate the rails and continue the lines right around each work piece.

[edit] Marking The Mortises

1. To mark out a tenon, the mortise gauge must be set to the nearest convenient chisel size. Adjust the pin spacing as necessary.

2. To find the middle of a piece of timber with a mortise gauge, try it from both sides until you get the pin marks to match up.

3. After you have marked the tenon on the rail and mortise on the stile, reset the gauge and mark out the tenon width.

4. Use a conventional gauge to mark out where the haunch will be cut. Make sure that you have set it to the correct width.

At this stage, you are ready to mark the widths of the mortises on each stile. By far the easiest way of doing this is with a mortise gauge (fig. 1), a tool similar to a marking gauge but with an adjustable scribing pin in addition to the standard fixed one. You are well advised to go to the trouble of buying or borrowing a mortise gauge, rather than trying to 'make do' with existing tools.

Start by releasing the set screw on the stock and adjusting the distance between the pins to match the width of the chisel you are using to cut the mortise out. Next, you must adjust the stock so that the distance between it and the moveable pin allows you to centre the pins on the timber.

To check this, place the stem of the gauge flat on the work piece with the stock face to the face side, then roll the gauge until the pins make indentations in the surface. Repeat the operation from the side opposite the face side. If the two sets of marks co­incide, the pins are centred and you can tighten the stock. If they do not, adjust the stock until they do.

With the pins centred and the stock back against the face side, roll the gauge away from you to mark the mortise widths on the stiles (fig. 2). Keeping the gauge on the same setting, mark around the rail ends to give you the necessary width of the tenons.

If shoulders or haunches are in­cluded in the joints, reset the gauge to the appropriate dimensions and mark them out with the stock against the face edge (fig. 3). Use an ordinary marking gauge to mark the depth of the haunch to be cut across the end of the stile (fig. 4).

If you must use an ordinary marking gauge instead of a mortise gauge, always work from the same face side and edge resetting the gauge for each mark you make.

[edit] Cutting The Mortises

H

• Cramp the work piece securely to a solid part of the bench.
• Drive the chisel into the marked out mortise to dislodge a deep wedge of waste. Use three separate strokes of the chisel.
• Work in a series of small chops from the centre of the mortise to one end, removing waste as you go.
• Turn the chisel around and work back to the other end in the same way.
• For a stub (blind) mortise, wrap a piece of tape around the chisel blade to give you the required depth. Continue removing waste in the same way then trim all sides.
• For a through mortise, continue chiselling until you get half way through the wood then turn the work­ piece over and restart the mortise from the other side.

5. The saw cuts for the haunch groove are best made with a dovetail saw, but if you do not have one, use an ordinary tenon saw.

6. After you have made the saw cuts, chisel out the waste wood in the groove with an appropriately sized bevel edged chisel.

7. The easiest way to start off large mortises is to drill a series of holes within the confines of the marking outlines on the stile.

8. Afterwards, remove the rest of the waste wood with a mortise chisel, held as shown and used in the correct sequence.

Where necessary, the 'wedge room' outside the mortise must also be chiselled.

Line up your chisel on the appropriate line with the bevel point­ing towards the centre of the mortise.

Chop downwards at an angle of about 85° to finish the wedge room 3-5 mm from the end of the mortise.

For a haunch groove, you need to make two saw cuts: one to the waste sides and one to the depth of the groove (fig. 5).

You can use a tenon saw (hacksaw) for these, though if you have one, a dovetail saw is easier to manage.

Once you have made the cuts, remove the waste with a suitably sized bevel edged chisel (fig. 6).

When cutting large (over 12 mm wide) through mortises, you can save yourself a great deal of hard work by drilling a series of overlapping holes before you start chiselling.

The bit should be slightly smaller than the width of the mortise (fig. 7).To avoid splintering the wood, drill through from one side until the tip of the bit just breaks the surface of the other.

At this point turn the work piece over and finish the holes from the reverse side. Use wide and narrow mortise chisels or heavy firmer chisels to remove the rest of the waste.

[edit] Cutting the Tenons

The procedure for cutting a simple tenon is the same as that for cutting the pin in a halving joint (see Constructing Halving Joints).

Make the longitudinal cuts first, then the cross cuts, cutting to the waste side of the line at all times (figs 9 to 12). Afterwards, clean up the tenons with a bevel-edged chisel.

Where a rail is too long to place vertically in the vice, arrange it at an angle, parallel to the bench and firmly clamped.

Many craftsmen prefer this set up for all tenon cutting, so it is worth trying in any case.

9. On large section timbers, use a panel saw or crosscut saw to make cuts with the grain. Make sure that the timber is well supported.

10. Crosscutting, such as cutting ' away the shoulders around the tenon can be done with a dovetail or tenon saw and a bench hook.

11. Make angled cuts with the work piece once more secured in the vice. Here, the secret haunching above the tenon is being cutaway.

12. Take extra care when you cut out the final pieces of waste. Even at this stage, a slip can still ruin the finished joint.

13. The finished rail, showing the sloped secret haunch that will become invisible when inserted into its matching slot on the stile.

14. When making a double joint, use a coping saw to cut away the waste between tenons. Take care not to stray outside the marked lines.

15. Assembly of all mortise and tenon joints is made easier if you first bevel away the edges of the waste on the tenons with a sharp chisel.

Haunched tenon:

Make the longitu­dinal cuts as normal, but remember that one will be shorter than the other to allow for the haunch itself. After­wards, cut the haunch, the cheeks and finally the shoulders.

Double tenon:

To remove the space between double tenons, first make the longitudinal cuts. Remove the waste with a coping saw (fig. 14), then saw off the cheeks and the shoulders. As with all tenons, clean up the finished cuts with a chisel.

[edit] Assembling Non-Wedged Joints

• When you have cut all the joints, assemble the frame in a dry run (without glue) to check the fit.
• The joints should require no more than light tapping with a ham­mer and an off cut of timber (to protect the work) to get them to interlock.
• If greater force is needed, dismantle the frame and make small adjust­ments.
• While the frame is together, set out whatever cramps are necessary and cramp up the frame without adhesive.
• Check that it is square by measuring the diagonals, which should be equal in length.
• Tidy up the inside surfaces of the frame with a finely set plane and glass paper.
• You can, if you wish, apply a finish to the inside edges of the frame timbers at this stage.
• But mask off the mating surfaces of the joints first to keep them clean for when you apply the glue.
• Finally, glue and sash cramp the joints, using off cuts of timber to protect the work pieces.
• Wipe off any excess adhesive while it is still wet.

[edit] Wedged Joints

16. On a through wedged joint, the wedges are tapped in as far as they will go then the waste on the tenon is trimmed off.

• Cut wedges for the joints from off cuts of waste wood.

• Do this as carefully as possible, since you cannot test them in a dry run with the tenon in place.

• Make adjustments to the widths of the wedges where necessary, then glue and cramp up the assembly.

• In the case of a through wedged joint, drive the wedges in once the tenon is in place in its mortise (fig. 16).

[edit] Finishing

When the joints are thoroughly dry, remove the cramps. Cut off all the waste horns, pieces of wedge, through tenon ends with a fine saw, cutting no closer than 1 mm to the work. Afterwards, use a finely set plane and glass paper on a sanding block to complete the finish.