The Shop > Wood & Stuff
3-way joint for box frame.
raynerd:
Hi guys
For my clock case, I want to make a "frame" from wood and my design will be, at a very simplified level, a box frame. If you can imagine, at each corner there will be 3 piece of wood mating at one joint.
I`ve been doing some practice at lap joints and a comb/box joints but neither of these will be good for a 3 ways joint. I`ve been told to use a lap joint and then a mortice and tenon joint for the third joint. Is this the easiest way?
Chris
Jasonb:
Its teh easiest but you will see end grain on the two lapped timbers.
The ideal is a 3 way secret mitre but very complicated and not really practical on a small display case.
I would first run a groove to take the glass in all the timbers, mitre the top ones and then form an "L" shaped tennon on the end of teh vertical corner ones to fit up into the groove. If you are not sure I'll do a sketch. This big case that I have just done for a modelboat is similar in construction but used studs & nuts instead of tennons as it needed to be flat packed for transport.
Another way is to use "L" profile corner posts that are set back a little from the mitred top and simply slip into the glass groove, used that method for one of my this model although the top is solid the method will work with a glazed top
J
spuddevans:
I think we need to have a little more info, or perhaps a rough sketch of what you are wanting to construct. If I understand correctly, you are wanting to build an open fronted box, ie, two sides, a top and a bottom and a back, and perhaps have the front glazed?
What sort of wood are you using?
--- Quote from: craynerd on October 15, 2011, 03:10:19 AM --- I`ve been told to use a lap joint and then a mortice and tenon joint for the third joint. Is this the easiest way?
--- End quote ---
I wouldnt have said that a mortice and tenon joint is the easiest way, it could look very nice, but perhaps not as nice as joining the sides to the top/bottom with dovetails, but that is more difficult than the mortice and tennon joint.
There are a number of ways of doing this, the easiest way is to just butt the sides to the top and bottom and glue&screw them together and then pin the back on to hold the whole thing square.
A slightly harder way, but better would be to attach the sides to the top and bottom as above, then using a router, make a rebate around the inner edge of the rear of the top/sides/bottom assembly, just slightly deeper than the thickness of your backing material, then cut the backing piece to be slightly smaller than the rebated opening (to allow for movement of the wood in the sides/top/bottom) and pin in place.
One of the finest looking would be to dovetail the sides to the top and bottom, and then rebate the rear to accept the back piece, but dovetailing is not the easiest method to do.
I would say not to glue the back into the sides/top/bottom assembly if you are using real wood (ie not MDF or chipboard/plywood) as when it moves with moisture changes the back will not allow the movement and will cause distortions and even splitting. It is better to just pin the back in place with a few small brads (tiny nails).
That's just my rambling thoughts, a lot may depend on how comfortable you are with working with the brown stuff and what equipment you can get your hands on to help you.
Tim
Swarfing:
Chris the easiest method i know is to use two dowels? just 4 holes to drill, insert dowels with glue and clamp. All you need to worry about is your holes are centre and your ends are square.
Jasonb:
Spud, it will be glazed on 5 sides and teh "box" is justy a timber frame to cover the edges of the glass, no point in doing all that work on a clock and only being able to see it from the front. Though a mirror for teh back panel is sometimes used.
J
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