(New) Coffee Table Gallery
Marking up the position of the shoulder line for the tenon that will be cut into the end of two of the table's rails.
Measurement to +/- 0.1mm. This possible by ensuring the rule is flush with the squared end of the rail, parallel to it's sides and ensuring the pencil is sharp.
Squaring a line through the measured position of the shoulder.
Notice how the engineer's try square is held to ensure the line is drawn at exactly 90 degrees to the rail's side. Three fingers, one finger, thumb. You should be able to pick the rail and square up with one hand if you're holding the square properly.
Using a Mortice gauge to scribe the width of the tenon. The gauge spurs have been set to the width of the chisel to be used remembering that no two chisels of a particular named width are likely to be the same. Notice how the gauge is held - three fingers, one finger, thumb and the spurs are trailing as the gauge is pushed forwards.
The marking gauge, used to scribe the length of the tenon, is similar to the mortise gauge (and held the same way) but it only has one spur.
It can be set very accurately by 'feeling' the spur into the etched mm. mark on a steel rule and then bringing the stock up to the end of the steel rule before tightening the thumbscrew
A dovetail saw is used to remove material quickly cutting on the waste side of the marking gauge line.
The saw is positioned accurately using the thumb as a guide to saw against.
A solid 'reference' for the saw is provided pressing the the thumb and first finger against the wood.
To remove the 2mm of material needed on from each side of the tenon a 25mm bevel edged chisel is used.
The pairing action needed is a satisfying skill once mastered and relies on holding the chisel correctly and referencing it by resting the index finger on the vice and maintaining firm pressure with the thumb.
The mortise is chiselled out using the chisel the mortise gauge was set to and will fit between the marked 'tramlines exactly.
The chiselling is started with 'concertina' cuts about 3mm deep remembering to start with the flat side of the chisel about 1.0mm inside the line which allows the wedging action of the cut to drive the chisel up to the line.
Subsequent passes can be much deeper - 7mm to 8mm if you are mortising softwood. Check you are cutting absolutely vertically and when you're removing waste work from the middle to the outside of the mortise. Turn the chisel over so the bevel is running parallel to the bottom of the cavity and don't lever against the mouth of the mortise.
Check the depth of the mortise periodically and keep chiselling until the depth measured in all areas is one or two millimetres deeper than the tenon that will be fitted into it. Don't worry about the surface at the bottom of the mortise - getting the depth right is all that matters. If the mortise is a little short pair it back to the freshly knifed line by hand.
This mortise is the work of a student who hadn't cut one before attending the class.
The process takes about half an hour even or shorter if you are heavy handed with the mallet once you have established the accuracy of the cavity with your initial run of 3mm cuts.
The finished mortise and tenon joint.
Having learnt how to mark up and cut a mortise and tenon joint accurately by hand, the remaining three joints are cut by machine.
Here one of the remaining mortises is being cut using a mortiser.
The tenons are cut to width using a bandsaw and...
......to length using a second, smaller, bandsaw.
The waste is sawn to the shoulder line by hand.
The four completed mortise and tenon joints are glued and held under pressure using sash cramps to produce two identical leg components.
These are then jointed with dowel joints which are accurately drilled using simple jigs that could be copied at home. The joints are glued in place rather than held with with scan fittings as in the photo.
The coffee table top is made from 19x144 redwood planks which are butt jointed at each end to give an outside length 584mm.
Safe working practices are taught alongside every new skill and this machine is no exception.
Safety goggles, ear protection, dust extraction, knowledge of safety features built into the machine, safe working practices and close supervision mean that the benefits of the process can be enjoyed without fear.
A simple template is used to mark the positions of the two biscuit joints that will strengthen each butt joint.....
....and a line is squared through each point to line up the biscuit jointer precisely.
The biscuit jointer cuts a cavity for the biscuit with a small circular saw blade that is partially exposed when the tool is pressed against the workpiece. (Note mitre joints are no longer used)
The end grain now looks like this.
These plywood strengtheners aren't essential as the biscuited butt joints are more than strong enough. They are added to teach the process of screwing and gluing which is common practice in wooden constructions.(plates will be at 90 degrees rather than 45)
The display cavity is created using a mitred frame that is glued, clamped and then 'rub jointed' on to the underside of the table top. Once dry, the bottom surface is planed flush to accommodate the plywood bottom