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Marking Out Wooden Coffee Tables' Corner Joints.
MARKING OUT THE MORTISES
MARKING THE MORTISES
DIAGRAM SHOWING RAIL & TENON
MARKING THE MORTISES
SETTING UP THE MORTISER
- With the legs cut to final length, they are laid out on the work surface with one outside face downwards and the other one towards you. A roofing square cramped to the bench is quite useful for making sure they are lined up properly, (see picture on the right). If one was setting up to make hundreds of the same table legs, it would only be necessary to mark out one leg, or a template leg for mortising. As I am only making one table at a time, it is hardly worth setting stops on the mortiser to cut the mortises on one face, and then resetting them to cut the mortises on the other face, so I mark out as below, and cut to my marks.
- One of the rails is lined up with the top of the legs and a pencil mark is made at the line of the bottom of the rail. A pencil mark is then made about 4mm up from the the bottom of the rail, and marked across the four legs with a square. I've reproduced the diagram from the JOINTS page on the left, so that you can see what this mark is for. It represents the end of your mortise cut. If you were to cut the mortise right up to the depth of the rail, firstly you would have to be incredibly accurate with each cut, so as not to leave any visible gap, and secondly, you would be unable to cut the mortice slightly longer than the tenon to leave a bit of 'wriggle' room when fitting the tenon. The last line to be marked across the legs, is the start of the haunch, which you calculate by using the 1/3 - 2/3 ratio as shown in the diagram. Once this is done, the two lines representing the end of the mortise and the start of the haunch are squared off onto the other back face of each leg.
- If you are making a table with the rail flush with the outside face of the legs, then your mortice gauge has already been set up to mark the tenons and you can use it without adjustment, to mark out the mortices between the pencil lines you have already marked on the leg for the length of the mortise, working as usual from the outside face. If you're using the more traditional design of having the faces of the rails set back slightly from the faces of the legs: make a pencil mark on top of one leg at the distance in that you want the face of the rails to come, then line your tenon test piece up with this mark and mark the tenon postion on the top of the leg. Next take your mortise gauge, slightly loosen the screw holding the stock, and tap one end on the bench until the two pins correspond with the two marks on the top of the leg. Tighten the stock, and mark the mortice on one of the legs with the gauge. Once again, if you are cutting the mortises by hand, you will now need to use the gauge to mark out each mortise on every leg. If you're using a mortiser, you only need to mark one mortise on one leg. (see MARKING THE MORTISES image on the right: this is not a typical example in that the legs in this case are going to be curved outwards: the mortise gauge is still set from the outside faces but the hatched area marked on the top of the leg will be cut off with the bandsaw after mortising, to give a new face).
SETTING UP THE MORTISERTo facilitate the setting up of the mortiser, I like to mark the mortise (using the gauge) on to the top of the legs as well as on the back faces. It is easier to see if the box chisel is lined up properly by sliding the leg up to the chisel and viewing it against these lines (see the image bottom right). The outside face of the leg goes against the fence, which you then adjust until the chisel is in line with your gauge marks. Then you can also use these markings to set your depth stop for the depth of cut, and have a suitably sized off-cut of wood to slide in under the stop to make the shallower cut for the haunch.
Researched & written by Nick at TheCoffeeTable.co.uk - Copyright © TheCoffeeTable.co.uk - Telephone: 01420 474862