Clearance for glue joint in large wooden disk puzzle?

[Perry Holbrook]

I'm working on the design of a round dining table top using ambrosia maple cross cut disk from a tree about 24" in dia. The table is 41" in diameter. I cut the wafers 3" thick about 2 years ago and they are reasonably dry now. The table top will look pretty much like a jigsaw puzzle of 26 irregular shaped pieces ranging in size from 20" to 4". I have the layout drawn for cutting the pieces with my CNC router. Now I need to offset the cut lines inward a small amount to allow for the glue joint and any other clearance needed to get a fit that is not too tight or loose.

Any idea on what kind of gap I should leave between each piece, I'm thinking around .05 I've not decided on the glue type but it's going to be too big to glue in one attempt.

In case you are wondering, I'll use the CNC to true up the outside edge and flatten the top after the glue up. Also, just for information, none of the disk split while drying and only have radial hairline cracks that will fill easily, probably with epoxy, maybe colored.

The base will be welded steel and I am considering putting a steel ring around the outside edge of the top. The chairs will be steel and maple.

Thanks,
Perry

[Jamie Buxton]

A .05" glue line is pretty big. I'd be aiming for .01" or less. But I don't know all what you're doing to fit all those pieces together. What precision does your CNC router offer? Can you cut to .01"?

[Perry Holbrook]

I can cut to .01 and I think my spindle is square to the table in both x and y planes. But with 3" thick material it will have to be perfectly square cuts to the bed on all cut surfaces. I think you are right that .05 is too big.

Perry

[Jamie Buxton]

I can cut to .01 and I think my spindle is square to the table in both x and y planes. But with 3" thick material it will have to be perfectly square cuts to the bed on all cut surfaces. I think you are right that .05 is too big.

Perry

Ah, I missed the part that pieces are 3" thick. Perhaps you can cut the pieces so they are tight near the surface of the table, but have more wiggle room lower down? For instance, if you cut the parts upsidedown, you could offset the bit for 2 1/2" of cut, and cut the last 1/2" to be exact?

[Perry Holbrook]

That may work, thanks

Perry

[Sam Puhalovich]

Perry ... I think that what your looking for is .005 ... 5 thousandths ... gap.
Actually a little less.
Rail-and-stile door cutters are sized to cut a 'space' that will allow a dollar-bill to fit into the dry joint.
That makes for a perfect 'mate' when the glue swells-up the mating area.
I don't see your table situation any different.

[Perry Holbrook]

Really, that small. But that is actually what I was wondering about. Thanks

[Jamie Buxton]

Do you have to use the full thickness of the cookies in the table? Could you cut them down to say 3/4" thick, and then cut your parts from that? You'd have less worry about whether you're going to get perfect fit for the entire height of the parts.

[Perry Holbrook]

Thought of slicing them, but resealing 20" irregular shaped disk creates a real challenge. Plus when it's in the house and I'm showing it off, saying it's 3" solid will be more impressive :)