Instead of having clamp on top..........make a block or metal part which the clamp will slide into. Screw this piece to bottom of table c;lose enough to original table to clamp onto the bottom of it.

Another alternative is T track on bottom of table . Make a bar to cross full length of orig table and use T bolts to attach new table . This also allows repositioning of table.

@Gerald Thank you for the additional options. Not sure I completely picture these. 🤔

There is a "lip" on the bottom of the DP table so might be able to use that if the add-on table had sides that slipped over the DP table.

And, yes, I'm overthinking this! Tired from poor sleep and a few too many "things" going on so that adds to my analysis paralysis. Eventually all the ideas and suggestions will merge into an outcome! Appreciate all the examples and info.

or just make a wood table bigger than the steel table with edges that mate up to the width and depth of the steel. fits snug, held in place by gravity. need a drawing?

think of a hat.

the wood top exactly fits over the steel table. no clamps needed, constrained on all 4 sides, holds in place by gravity alone, no clamps needed. you can easily add tracks for hold downs as needed, and can easily make a replaceable insert for drill thrus.

1 hour ago, DAB said:

or just make a wood table bigger than the steel table with edges that mate up to the width and depth of the steel. fits snug, held in place by gravity.

Had considered that but didn't know if I could get that perfect fit (thus the added insurance of a clamp or two). For most situations, a little movement would not be an issue, but other times it might (e.g., if doing a row of peg holes that need to line up, would want zero play). I could just clamp from the top and that would work in those situations (but then I couldn't sit and overthink this 😉).

I have been looking at the fasteners again, and the setup of this table is a challenge. Little room to slide anything into the DP table slots. These are the measurements.

Starting with some of the prior suggestions, these may be a workable size.

cut plywood say 1" larger than each side (so if the table is 20x14, cut plywood to 22x16, 1" overhang each side. square it up best you can. clamp in place temporarily.

have some 1x1 stock handy, glue and screw it to the overhangs, clamp until the glue is dry, you can also screw from the top. it will fit perfectly.

now you can add another layer of plywood or mdf, that will hide the screws and let you work in a replaceable insert. done in less than an hour (for the glue to dry).

the underlying dimensions of the steel table won't matter, you aren't interacting with them, just the overall table size. or you can make the wood table as big as you like, but still snug up the 1x1s underneath, or make the second layer bigger if you wish.

@DAB very helpful! Thank you.

1/4 x 20 T-nuts and flat head screw along with shop made wooden blocks might work. Couple pieces of plywood for the top.

Sorta adapted several of the ideas into one concept

I really like DABs idea and it could be pulled off if needed . As to slack from measurements just use shims in the cracks. By the way under no circumstance use a round T nut. At some point you might want to renew this table and round will spin in slot.

@lew Great visual. The issue I see is not being able to slide anything in from the side as the slots on the DP table are about 1 1/16 from a raised edge.

@Gerald I wouldn't have thought of that issue with the round T nut. Likely couldn't get it tightened either. 🤦‍♀️

Will try @DAB idea. Hopefully will be able to get moving forward and get some progress pictures.

Appreciate the brainstorming with me.

Got "top layer" plywood cut and shims to raise the t-track are being 3D printed.

Decided on square replaceable backer rather than round given ease of cutting replacements. Offset so I can rotate it four times as it gets chewed up.

Need to decide on cleanest way to cut the square out for the replaceable piece. Thinking to drill corners, jigsaw to cut the sides and then maybe followup with router.

An easy way to get the opening square and precise is to rough cut the opening with a jig saw. Then tape 4 pieces of scrap (double stick tape, though I guess you could pin nail them down if you have a pin nailer) and then flush trim to the pieces with a flush trim router bit. You'll still need to square the corners (use that corner chisel you have). This pic is really small but it's all I could find in a hurry (dinner is one the stove) to give you an idea of how to tape the scrap pieces in place.

@Fred W. Hargis Jr That looks like a doable process. And I laughed at the mention of a chance to use that corner chisel device (now where did I put it😉).

Some progress before I had to go to dental appointment.

Drilled holes, rough cut with jigsaw, used router to clean up.

Tried the corner chisel - ended up final cleanup with an actual chisel!

Printed some drawer glides that I may use under the table to hold it in place.

31 minutes ago, BB1 said:

Drilled holes, rough cut with jigsaw, used router to clean up.

Wow that dentist is ruthless 😂

2 hours ago, lew said:

Wow that dentist is ruthless 😂

Good one 🤣🤣🤣

Was a "redo" on a temporary crown so thankfully no real drilling etc on this visit - just an interruption in my shop time!

Getting things glued up. Too many clamps...or just enough??? 🤔😁

Never seen too many clamps.

and for those who do not have twenty-eleven clamps, you can simply jack your car up, slide your plywood, with glue) under the tire, let the jack down, have some coffee for an hour, jack your car back up and extract your now glued up plywood.

i'm full of dumb ideas......

2 hours ago, DAB said:

i'm full of dumb ideas......

Remember - If it's stupid, but it works, It's not stupid!😁