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Workshop Wednesdays – Lapped Dovetail Joint with Mitred Top


Monday 9 July 2018

I don't know how many 'through' dovetail joints I've cut before being able to claim any degree of proficiency at this skill. This was followed by mastering a 'through mitred' dovetail. The third was a 'lapped' dovetail joint.

All pretty standard stuff so far but requires much practice to get them right. However, it seemed that there was something missing from my repertoire – a 'lapped mitred' dovetail. I'm sure this had been done before but I couldn't find any record of such a thing in my collection of woodworking manuals.

I wanted a joint like this even though a 'through mitred' dovetail makes a very attractive finish when, for example, making a box where the apex runs into a mitred detail across the top. However, there are often times when a lapped dovetail joint looks smarter for a particular design, but is let down by not having a mitre. So after many days of experimenting, I came up with a solution and would like to share the outcome with readers who, like me, never tire of learning new tricks.

As this is very much a decorative joint it's important the faces of any components that are to be seen should not be heavily scored with a marking gauge or knife. A light mark, however, can be removed with a plane afterwards.

STEP 1

Start with marking out the tails on the side pieces, as if they were drawer sides, with spacing for a thicker pin at the top. Mark as many tails as you like using whatever method you prefer for spacing. For this example, I started 5mm from the bottom – A – and 7mm from the top – B.

STEP 2

Lightly mark the outside face and mark normally around the bottom and normally on the inside face. Do not mark the top edge. Usually when marking for a lapped dovetail the tails are about 3mm shorter than the thickness of the timber to allow for the 'lap', but in this case mark to the full thickness – you will see why in due course!

STEP 3

Mark your cut lines for the tails with zero thickness at the thin end. These will increase in size later when the tails are shortened.

STEP 4

Now mark the end of the front piece for the 'lap'. If the timber is between 10 and 16mm thick then make it a 3mm lap. Do not extend the line to the full width of the component. Stop 6mm short of the top and bottom edges – C and D.

STEPS 5 & 6

Now back to the tail piece. Mark 3mm – or the same thickness as the 'lap' – in from the ends of the tails and trim them back to the line, starting at the bottom. Do not cut off the top small tail. I make this cut on a bandsaw, using a sliding mitre attachment set at 90° with a stop on the fence to avoid any possibility of cutting off the top tail.

STEP 7

You can now mark out for the pins and remove the waste in-between, except for the top pin. This will be mitred from the outer face corner and not cut square.

STEPS 8 & 9

To do this use a mitre gauge or sliding bevel to mark from the baseline scribed on the inside of the box – E – to the external corner on both pieces – F. Cut a little proud of the mark and trim with a chisel to establish a good fit.