Elm slab table with glass insert? Where to go from here?

[Arlowtis]

I posted a while back about an elm slab I purchased with concerns about dying times and cracking. The major concern was the pith still very much intact in the slab. 

I ended up taking it to a local sawmill and having it ripped in two, kiln dried, and planed. It went from 3+ inches to 2.5 but ultimately that's an ok swap with the potential air dry time and quality. 

Now my plan is to fasten the two sections to two continuous iron legs with appropriate slots on the plate to allow for movement, and seat a piece of glass 1/4" deep in the center. I wanted to outline my plan for you guys and see if you'd do things differently as I'm now totally in uncharted territory. 

The two pieces have been sanded, though not finished, to remove all roughness and splintering. When I put them together, the center line isn't totally flush so I am concerned about getting the glass to fit equally on both pieces, in terms of depth. But my plan is to:

-order the glass in dimensions that will allow for 2-3" floating in the center and 1" resting on each side of the table

-sand the table a little further to a softer texture then bolt to the legs with the 2-3" gap. 

-route (slightly deeper than?)1/4", 1" wide on each side of the gap

-seat the glass to check for fit then sand down any minor imperfections

It feels like that might be "too easy" or "too good" to be true though. Am I way off base? Also, there are several small cracks throughout the table, I assume these should be filled to prevent food from getting stuck inside...but would that need to be done before further/final sanding and routing? 

Lastly - if anyone knows anything about glass, how likely is it that a piece of tempered glass at 6-7" x 72 3/4" will warp? Would it be smarter to get annealed glass and put a safety film on it? 

Thanks in advance! 

[wtnhighlander]

I think you are on the right track with your routing plan.

As for the glass, tempered is pretty tough, and isn't likely to warp. Although I would consider a piece thicker than 1/4" for aesthetics, since the slab is so thick.

(you mentioned routing 1/4 deep, so I assume the mention of 3/4 thick glass is a typo. If it isn't...Awesome!)

[Martin-IT]

take a look at this video, something similar to want you want to do:

 

[elrodk]

If your slabs are flat and straight enough on the top side you can adjust on the underside to fix the misalignment. Just route a mortise to the appropriate depth on the underside of the high piece. If there is a twist or uneven thickness it could get tricky. Best bet would be to plane or drum sand the top pieces to a consistent thickness. If this is not feasible, you could route (or chisel) a mortise for all the base attachment points a little deeper than needed. Shim everything level between the base and the tops. The shims will be hidden in the mortise and covered when the base is attached. The mortise will need to allow for cross grain movement.