Table top joinery

[kelLOGg]

I have many sweetgum ovals which I have trimmed to assemble like petals of a flower which I need to join together to make a table top base on which I will put a glass top. The diameter of the sweetgum array is a little over 4'. What is the best way to do the joinery? You can see a pic of them in https://raleigh.craigslist.org/search/sss?query=sweetgum+ovals as picture #6. (I still can't upload pics in NCWW).

Dowels cannot be used and I have never used biscuits. Are biscuits a possibility?

 

[JohnnyR]

The most important thing here is the support from underneath. If fully supported there won't be any strain on the joint. Biscuits will work in this situation as will a spline (make sure grain is cross wise) so you don't have to buy a biscuit joiner. I'm not sure how wood expansion is going to affect this.

 

[Rwe2156]

I think you need a good support base (plywood) rather than dowels because they are likely do develop large cracks.

 

[kelLOGg]

There will definitely be a support under the sweetgum. Any joinery technique I will use will be to keep the sweetgum joints tight - not for support.

JohnnyR, thanks for the spline idea. Never done it but it looks like it would be easier to assemble the parts - unlike dowels which I think would be impossible. I could rig up clamps to hold the joints tight while the glued spline sets. It would definitely be cross-grain splines.
Thanks for replies,
Bob

 

[Jeff]

Nice flower petal idea in pic #6. So you've already cut the ovals as pictured? The spline suggestion will work but clamping the pieces together to keep the joints tight may be a problem with the awkward geometry!

 

[kelLOGg]

The ovals in the pic are just practice pieces. I want to get the technique down so I don't screw up nice kiln-dried stock. I tried it with dowels today and that was a clamping nightmare and it would have to be done 2 more times to make all 4 "petals" an assembly. No more dowels for this project. I have decided to cut 1/2" slots for a 6" x 6" x 0.5" spline on my sawmill. It won't be a smooth notch but a spline coated with epoxy should adhere nicely. I can plane the spline for adequate clearance in the slot. More later.
Bob

 

[Jeff]

Bob, keep us posted as you continue to experiment. Thanks.

 

[kelLOGg]

I notched the half ovals today on the sawmill and planed a temporary spline. See pics but don't notice the screw-up.:no: The notch is not centered but that shouldn't matter except that I put one of the "petals" on the mill up-side-down relative to the others. So that petal has its bark in a different orientation from the others. Oh well, this project is a practice run anyway. I plan to make a permanent spline from the spline shown by gluing two pieces of them with the grain opposing so I will get a cross-grain spline. Then I will plane it to the proper thickness which is ~0.5"

BTW, thanks to Danmart77 for helping me with posting pics.

Bob

 

[Jeff]

A start. It would be nice if we could enlarge or zoom on those pics. I can't see much about them.

I don't see a "spline shown" but the pics are tiny.

 

[kelLOGg]

Jeff, My difficulty in posting was that my pics were too big so I must have over corrected. See if the pics in reply #8 are better. Pic ...37b shows the spline (in foreground)

before ​

it is cut to size.

Bob

 

[FredP]

after assembly you could route in some bow ties.:wink_smil

 

[kelLOGg]

Contrasting bow ties would look fantastic. But, frankly, I am not a very accomplished woodworker. I really like making the lumber more than things with the lumber. I am experimenting with these sweetgum ovals to see what's possible in hopes of selling some of the many ovals I have.

Bob

 

[JohnnyR]

Hard to tell dimensions from the pic. but it looks like you went awfully deep. It looks like you made it 5/8" wide which would require no more than 1/2" deep. I'm guessing at this so someone with more common sense can chime in.
'"

 

[kelLOGg]

The spline is about 9" x 9" x 0.5" in its final form and made from black oak. In the pic showing the spline, it has not been cut to length yet. Does that clear anything up?

 

[JohnnyR]

Now I understand the picture! What I was suggesting is a 1" x 1/2" spline the length needed. You would have to glue two quarters together, rout out the spline to join the two halves. In your method, I would be concerned that the Oak would expand/contract at a different rate than the top. I don't know how stable sweet gum is but you could also use a plywood spline if you do it as in the picture. If the table is supported by an apron or otherwise, a thin spline might be safer.

 

[kelLOGg]

I originally thought of using plywood but 1/2" I thought was about 1/32" too thin for the slot. Should a spline fit loosely? What about the effect of the epoxy - won't that fill in the gap making a tight fit? I have not glued the spline yet so I still have choices.

 

[Jeff]

I originally thought of using plywood but 1/2" I thought was about 1/32" too thin for the slot. Should a spline fit loosely? What about the effect of the epoxy - won't that fill in the gap making a tight fit? I have not glued the spline yet so I still have choices.

Use your oak spline. How does the one in your pic fit in the slot.

Don't over-engineer the construction and joinery. Isn't this a test piece? See if it blows apart or falls apart.