Extra large threaded inserts

[bertv]

Those Misumi seem to be quite sturdy. I think I would use them upside down (possibly having to drill through and tap) — from a mechanical standpoint better and from esthetics’ also (sink them in).

 

[Daver]

Hi Ed,

An interesting engineering challenge you've cooked up.
I'm late to the party but I join the chorus in supporting Bob D.'s original suggestion. Exactly what came to mind when reading through the various ideas preceding it.
I agree with Steve1. I think the greater the area you can achieve (the larger the plate) relative to the nut, the better you are. For that reason, I like the video game plates better than the Misumi(s).
I would be inclined to Forstner drill a hole for the nut and then mortise the plate in. To be clear, the nut would be up inside the table top and the underside of the plate would be flush with the underside of the table top.
Depending on how flush a connection you can achieve between the plate and the top of the leg, you might even use a wide/fender-washer sized piece of fairly thin rubber on top of the leg.
If the client has an issue with seeing (from underneath) any of the plate outside of the leg dimension, I would just paint the steel something close to the color of the wood and sell them on the strength aspect of it.

Good luck with it!
Dave

 

[harry_]

Am I missing something here?

If the legs are 3" in diameter and fully wound into whatever so they are fully seated against the top, the amount of force necessary to bend even a 1/4-20 would cause whatever to tear out/off the table top long before you could achieve a bend in the in the leg connector.

 

[travisj]

Am I missing something here?

If the legs are 3" in diameter and fully wound into whatever so they are fully seated against the top, the amount of force necessary to bend even a 1/4-20 would cause whatever to tear out/off the table top long before you could achieve a bend in the in the leg connector.

I agree.  A quick although possibly inaccurate google search showed 1/4 all thread of having a 1,600# shear strength.  That said, appearance can be more important than fact in the customer’s eyes (beefy = better).

Sent from my iPhone using Tapatalk

 

[Steve1]

The 1/4-20 stud is not going to shear.  But if you put a sideways load on the leg, you are creating a lever that is trying to pull the insert out of the table top.  If you are using the Rockler style insert that is being held in with three screws, perhaps #4 or #6, can you generate enough force to pull the insert out? ---- yes, easily.

 

[Svar]

Steve1, you are correct. How the fitting is attached to the table top is much more important then the bolt thread size. Hence, it must be a flanged fitting rather than external threaded insert. 3/8", as in the Rockler flange in the OP post is perfectly adequate. This is why commercially available leg connectors have wide pates for plenty of screws and 5/6 - 3/8 central hole threads.

 

[Gregor]

As the material of both the top and the legs is way thick enough: Why not simply use one 14mm Domino edge connector per leg (spread anchor in the top, cross anchor access hole in the legs oriented toward the center of the table which should make it invisible from the outside unless you actually crawl under the table) with two additional smaller dominos (glued only in the legs, lose fit to the top) next to the connector to make alignment quick and easy when attaching the legs?

Should the legs be swapable for different height ones I would think about a way to add a hex key holder (similar to how it's solved for the one in the TS 55 handle) to the top of one leg in each set, so the key will be stored in the currently unused set - for it to always be at hand when actually changing the legs...

 

[Cheese]

As the material of both the top and the legs is way thick enough: Why not simply use one 14mm Domino edge connector per leg (spread anchor in the top, cross anchor access hole in the legs oriented toward the center of the table which should make it invisible from the outside unless you actually crawl under the table) with two additional smaller dominos (glued only in the legs, lose fit to the top) next to the connector to make alignment quick and easy when attaching the legs?

Should the legs be swapable for different height ones I would think about a way to add a hex key holder (similar to how it's solved for the one in the TS 55 handle) to the top of one leg in each set, so the key will be stored in the currently unused set - for it to always be at hand when actually changing the legs...

I like it... [big grin]  An "All Festool" approach to the problem. Now that's thinking outside of the box.  [cool]

 

[Bob D.]

Am I missing something here?

If the legs are 3" in diameter and fully wound into whatever so they are fully seated against the top, the amount of force necessary to bend even a 1/4-20 would cause whatever to tear out/off the table top long before you could achieve a bend in the in the leg connector.

I agree.  A quick although possibly inaccurate google search showed 1/4 all thread of having a 1,600# shear strength.  That said, appearance can be more important than fact in the customer’s eyes (beefy = better).

Sent from my iPhone using Tapatalk

Except the 3/8 rod is not in shear in this configuration, it is in tension (but not all of it applied along the axis of the rod). And the rod will not be the limiting factor, it will be the connection to the table top whatever that is. A threaded insert will not develop much strength in wood, even a hard wood. It's limited by the small contact area of the OD of the insert and a thread depth that is probably less than .125", so very little grip area. I think if that threaded rod which is connected to the leg is threaded into a plate or flange with three or four #12 screws and length as long as possible depending on the thickness of the table top or larger screws would be better.

 

[shanegrilah]

This is too late but I modeled my floor pipe flange idea in CAD just to see what it would look like. Model is made using common components that should be available from a big box store. Pipe flange diameter is not critical because it can be screwed to the bottom of the table top or set into a pocket for concealment. The top of the table leg needs to contact the flange before the tapered thread seats fully but that can be adjusted with depth control of the counterbore for the pipe cap. The pipe cap is the traditional domed variety but flat ones that have a smaller OD can be found. Lag bolt is a 3/8" and a socket should clear before the nipple is thread locked in place. Parts are easier to get if you don't have a welder and probably more robust than a small insert.

Regards,
Shane

 

[ear3]

Received everything I've ordered by now.  I haven't done actual tests yet, but from the looks of them it seems like the Misumi are definitely the way to go.  Really beefy steel, with an 1/8" flange, and a body that totals 1" in depth. -- sort of like the flanges they make for acme screws, but in a a more manageable size. Thanks again for all the recommendations, and especially [member=65451]Steve1[/member] for the Misumi.  Will post pics of how it works out once I complete the project, which is probably still a couple of months away since the client doesn't need the table until April.