MFT table vs 3/8 t nuts

[Jeff C Johnson]

I was thinking about building a MFT style table, but I don't really want to have to worry about using dogs and hold down fasts (none of which I currently have), and was thinking about making a torsion table box but with T nuts under the surface that I can use to attach jigs and other things using 3/8 bolts or threaded rod.

Some friends have told me that's not the way to do it, as no one does it like this. I'm not trying to be original, I just want to build something that works for me and I can make cheap knobs and hold downs. Plus, it might reduce the need for a large side vise (as used with dogs to hold material). I have a vise on another heavy bench that does most all of my vise needs.

Are there things that I haven't thought about here? It seems good to me, but I'd hate to build this and then say to myself "what was I thinking".

I know many will ask, "what do you want to use the table for..." which is a valid query. Basically, I'd use it to


mount jigs such as my pocket hole tool.
Hold 2x4's flat as I square up a frame for assembly
any other material hold down using bar clamps with end cut off and 3/8 bolt welded on (yes, additional work, but I like doing this).
Putting in threaded rod to old material "in the air" for painting/gluing.


Thanks.
Jeff

[Adam Herman]

like a welding table. i find a good welding table has a grid of tapped holes. one problem with T nuts is they only hold tension, not compression, as compression will just push it out. they also, IMO, have a tendency to strip out the little teeth in the wood.

Mcmaster has some different options if you search for nuts. i would try the adhesive or screw mount nuts I think. you could also use several lengths of t track with t nuts in them, dadoed into the top.

[Jeff C Johnson]

like a welding table. i find a good welding table has a grid of tapped holes. one problem with T nuts is they only hold tension, not compression, as compression will just push it out. they also, IMO, have a tendency to strip out the little teeth in the wood.

Mcmaster has some different options if you search for nuts. i would try the adhesive or screw mount nuts I think. you could also use several lengths of t track with t nuts in them, dadoed into the top.


Good point on the compression weakness. I don't see having any compression that could push them out, but it's a good point. Threaded inserts are an option as well.

Also, unrelated to this reply, I also plan on putting a hardboard sacrificial top on it that I can replace as it gets damaged. I have a laser cutter that can make new replacements at any given time. I wish it (lasercutter) was strong enough to cut the thicker MDF of the table, but alas, I'll have to do that part with boring bits.

[Adam Herman]

you mentioned holding things up for finishing, that would be compression on the T nuts.

[Jim Becker]

It was brought up in another thread in the CNC area, but embedded fasteners collect debris quite easily. That's less of an issue for a bench than with a CNC, but still should be considered. I personally prefer the MFT-stye grid of holes. They support both dogs and certain types of clamps very nicely.

[Jeff C Johnson]

True, if just a threaded rod, though I was going to make a through-hole knob to tighten it down to the table to prevent the TR from rotating when attaching stuff to it (in theory). Not even sure if it would make a good holder, just speculation on potential use at this point.

[Jeff C Johnson]

True on the debris, but I think a quick blower would take care of that. Having not really used dogs or hold fasts down that much, I'm designing from a perspective of ignorance. Most times I've tried to hold things down I've used drywall screws directly into the table, so that's probably much of my thought on this idea. Most time I've seen dogs used its been for planing, and I just don't do that very often, but I do have a need to hold down jigs (which dogs would probably work too).

Also, the holdfasts would require me to have more space needed below for the tail, plus they're expensive compared to bolts, rods, etc. Having a laser cutter, I can make knobs very easily, even with the hex pattern of the bolt cut in, though obviously the torque available would be limited to the strength of the wood.

[Tom Bender]

My preference is a split solid top with at least 3" overhang all around for clamping, but you are going in another direction, So staying with your plan to make threaded holes (using inserts)

Go to 1/2" NC, and get high precision threads. The extra cost is minimal but the better feel will be there forever. The faster advance (1/12" per rev vs 1/16") will be nice and the risk of overloading will be less.

Install the inserts from the bottom so they will resist a lot of upward force.

When you want to hold something up, just run a nut and washer on the top.

[Stephen Bandirola]

This looks interesting
https://www.microjig.com/post/the-ultimate-workbench
Anybody use the Microjig Matchfit system?
https://www.microjig.com/products/dovetail-clamps-pro

[Bill Dufour]

I thought you meant tee nuts in a tee slot so you could move it around. As is used on most metal working machines.
Bill D.

[Jeff C Johnson]

Good points. I already have a bunch of 3/8 t-nuts, but if some tear out I can drill out and get 1/2 inch fine thread, which makes sense. Plus, half inch would be easier to notch and weld to the end of a bar clamp (with end removed) for easy down clamping.

The washer/nut thing you describe on the last sentence is exactly my thoughts as well. The main top would be MDF, and 3/4 ply (with t nut) underneath since MDF is flat and 3/4 ply resists tear out. If there was an easy way to have the 3/4 square pieces (4"x4") snap in and be removable, I could use whatever threads I needed provided I had other blocks to put in, but that's probably wayyyy too much work.

A buddy suggested a few aluminum extrusions for normal t bolt attaching.

[Jeff C Johnson]

Oh. no. The kinds with barbs. I get your point, I've used those you describe with 80/20 aluminum extrusion stock.

[ChrisA Edwards]

This looks interesting
https://www.microjig.com/post/the-ultimate-workbench
Anybody use the Microjig Matchfit system?
https://www.microjig.com/products/dovetail-clamps-pro

I use the Microjig Dovetail clamps for quite a few things. I like that Microjig table idea. I have the Whiteside router bit to make the dovetail dado's for the clamps, so I might run a couple of dovetail slots in my homemade MFT top.

[Will Blick]

Dont give up on the MFT hole system. Why?
If u want to make square cuts with track saws, and u can make precision drilled holes, its quite useful for cutting. IF u dont plan on making square cuts on the top...it still incredibly useful top.... and now you dont have to drill the holes with super precision to maintain squarness.

If your fear is having to buy lots of MFT products... well, maybe. First, there is so many products for the MFT, dogs, fences, clamps, stops, side clamping of long boards, etc. So versatile, hence its popularity.

If you check out anchor dogs, such as those sold by axminster tool, as well as other places, you will see, u can make most of the jigs you want utilizing the metal anchor dogs, which are not very costly. Nice clamp down and push clamps might be hard to build, but the BEST ones by Bessey are about $25 each, lesser brands cost less. Fences, stops, etc, can easily be made yourself with the addition of the anchor dogs. Get some ideas looking at some videos and MFT suppliers web site, LV, UJK, TSO, WoodPeckers, ARmor, and others I cant think of right now...