Geoff's Woodwork

for Students of Woodwork                                          
Basic Setting Out -2

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1.   From Basic Setting Out 1, you should now have the frame as follows:
  • cut to overall size,
  • shoulder joints marked out,
  • waste divided between the ends,
  • arranged in the required layout with joints identified,
  • face marks facing in the right direction

2.   We now want to gauge the width of the mortise and tenons.     The thickness of the tenons should be approx. one third of the width of the material to be jointed.     From this select the nearest mortise chisel to this size.  This may be a hand chisel or a machine hollow chisel  depending how you propose to cut out the mortise.    Larger joints are sometimes drilled out by a series of holes, with an auger or flat bit  to cut down on labour.   Use a drill only if you have nothing else available because it will require further  trimming to convert to square and get a reasonable accurate joint.  Very large mortises rule otherwise.

3.   Take your Mortise Gauge to the Chisel you have selected and set the points as close to the thickness of the chisel as you can determine.   If you cannot get gauge to exact chisel width then edge slightly on the smaller size rather than larger.   This way the tenon will fit inside the machined mortise.   If the tenon is gauged slightly larger it will not fit at all or will be too tight and need trimming.   The joint should be loose enough to adjust and fit without driving all the adhesive out.   If the joint has to be hammered home, it is too tight.  On the other hand it should not be so loose to allow excessive movement away from its original shoulder positions.  Most good adhesives will easily ‘gap-fill’ up to say 1 to 1½ mm’s

4.   To find the centre of the edge of the timber:

  • estimate a first setting,
  • with the stock against the face edge, make a trial mark with the two points
  • using the same setting, mark from the other side,
  • you will now see two sets of doubled marks,
  • the centre is between the two marks.

Adjust the gauge and retry.   When the points coincide from opposite sides, the gauge is correctly centred.

5.   To use the gauge you should hold the timber firmly in your hand or in a vice.    The gauge should be forced against the face side with the points of the gauge ‘trailing’ in order that they should not ‘dig-in’.

Do not press too deep at first otherwise the points tend to follow the grain of the timber and it will be difficult to gauge a straight line.  Better to make two or three attempts until you reach the right amount of depth.  A sharp pencil following the scribed lines will improve the sighting.

6.   Scribe the mortise and tenon gauge lines between the full shoulder lengths and where there is a corner joint, all the way through the waste area to the end.

Where, on the corner joint there is to be a ‘haunch’ continue the scribed lines down to the depth of the haunch, say 12 - 15 mm down.   The exact amount can be marked across in the next stage.   Remember, failing to haunch a corner mortise and tenon causes the joint to ‘break-out’ and the joint is then ‘open’ or ‘bridled’.    Remember to scribe both edges and to keep the stock of the gauge always against the ‘face mark’ otherwise a ‘step’ will occur in the joint and cause ‘winding’.

Tenons are scribed between the full shoulder lines and down the end grain to meet with the other side.   This allows you to saw down the end grain with a tenon saw.

Treat all members similarly with the gauge and when complete return the gauge to the tool box.    Place all timbers in their positions and then consider the next stage.

7.   The joints at the corners that are to be haunched are diminished (made smaller) across the face edge and opposite side.  Avoid where possible marking across the face (other than the shoulder lines) because it can create confusion.

However, note that small marks are made at the edges to allow the transfer of the marks around the timber.

Very often Joiners use a chisel of the correct width or thereabouts to gauge the widths and depths of haunches or other ‘cut-backs’.  This provides a quick measurement but be sure to use a sharp H2 pencil when marking cutting lines and a softer HB pencil for other markings.     Be careful to use the same chisel when using this technique.  All chisels are not always standard sizes.

The mortise should also be ‘cut-back’ on the inside of the joint where a groove or rebate reduces the width of the tenon.

Note also in the illustration opposite, that the depth of the haunch has been made on the end grain of the mortised member.

The shoulder of the tenon may require extending on the face side if a rebate or other moulding is to be  prepared.

Lay out all the members in their appropriate positions to check that all is correct and contemplate you next move.
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Last uploaded  21st September 2003