[OP]
Contributor
I’m planning on building a coffee table using four maloof joints to connect the legs (always wanted to try the joint). I was thinking about how to ensure the top stays flat and may have a great (or potentially stupid) idea.
what about basically using a sliding dovetail, but planing it flush after the fact? I would otherwise do breadboard ends but I think that might look silly with the maloof joints.
is this a good idea or would the dovetail not add the amount of stability I’m looking for?
Contributor
You don't mention the size of the dovetail. But if it's just the dovetail and it's around 1/2" thick, you'll get absolutely not gain any strength. You also don't mention the width of the coffee table, but if it's no wider than 2', I see zero issues with the solid wood unless you do something wrong in the glue up and you don't use improperly dried lumber. Quarter sawn or rift sawn is the most stable.
Contributor
I think most every woodworker has had that idea.
I can share my experience with long sliding dts. They are difficult to get right especially when one is along the grain and one across the grain.
Don’t be too worried about a coffee table bowing slightly.
Now if the bow or cup is so bad you cannot set a drink without spilling your boards were not dry enough for service.
Good Luck
Aj
I believe what would give rigidity against a top cupping or bowing is the shoulder of the male dovetail and the board above the shoulder. By planing the board and shoulder away you are removing the vast majority of the member that would resist the movement you seek to control.
here is a bench I constructed with Maloof joints. The sides of the drawer box are set into the bench top with sliding dovetails. I used this joint simply to join them but they would serve the purpose you envision.
https://sawmillcreek.org/showthread....10#post3146410
Contributor
I have seen that on the back of a church pew but the tail was steel.
Member
It’s not an unusual technique but I don’t think it will work on a panel over 1/2” thick.
If you’re going to do it, do a tapered dovetail.
Personally outside of steel braces I don’t think there’s much you can do to prevent cupping, many think breadboards will, but they have their limits, too.
If cupping happens, it’s because of moisture imbalance or improper drying. Carefully select and acclimated lumber minimizes the issue.
Contributor
Well seasoned lumber that has been milled correctly should be flat enough for a coffee table. You may be over thinking this one.
Moderator
How thick is the top? Maloof joints are usually on pretty thick slabs like chair seats. An sd might be superfluous or would have to be thick to make a difference. Just pick well seasoned wood that has favorable grain for stability and skip the as.
If you use a breadboard, you would cover one side of the maloof joint so you’d lose something aesthetically.
Last edited by Prashun Patel; 12-05-2021 at 6:47 AM.
Member
Sliding dovetails are a fantastic way to keep tops from warping. They can be tapered (many videos of ways to accomplish this) or you can simply do a non tapered. Here is how to do a nontapered joint. Cut the male and female parts so they just begin to fit together. Use a side rabbet plane to remove small amounts off the batten and continue to fit together. Suggest taking shavings off only ONE side of the batten. This will go quickly since you are taking off such small amounts. Put glue on last inch of the batten to secure in the female part of the joint. I believe this method of doing a sliding dovetail is as fast as a tapered variety.Originally Posted by Andrew Hughes
Moderator
Also, the sliding dovetail works to resist cupping if the dovetailed batten is relatively thick. By planing it flush, you'll have something thinner than the top that will not resist any force exerted by the top.
Member
I've used sliding dovetails for this type of application and they work but are fussy. Not sure how big of a top you are planning but the difference in a perfectly fit dovetail and one that's too loose or tight is tiny especially across some width. I've used c-channel with elongated holes drilled in it and routed the legs of the "C" into the bottom of the top for these types of scenarios with good success. You can also do nothing beyond attaching the top and see what happens. It'll probably be fine as others have said. Good luck
Contributor
James, how thick will the table top be? If around 40-45mm, then I doubt that you will need any reinforcement. It will come down to the stability of your wood choice.
If the top is thinner, say 25-35mm, you do not have much meat to play with. Adding a tapered sliding dovetail can beef up the top, but there are a few design factors to follow. I would make the joint half the thickness of the top. Do not plane it flush - that would remove all the strength you are seeking. Instead, aim to make the batten thickness about twice that of the top. This will not be seen from above. Taper the ends or make them stopped, ending about 50mm inside.
This is an example I did for a entrance hall table. In this case the sliding dovetail was to house a batten to add to the thickness of the carcase since it needed to house morticed legs.
And glued into the socket. Note that only the first third is glued. The rear is free to move ...
The joint gets its strength from a tightly fitting dovetail.
The bases have been shaped to reduce their impact ...
Regards from Perth
Derek
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