Need a stronger alternative to T nuts

[Pete Givens]

Hi guys,

I built an upholstered bed recently:

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I'm pretty happy with how it turned out, but I have a major problem with the legs. I bought some tapered wooden mid-century style legs with a 5/16" threaded rod. To attach them, I used the hammer-in T nuts. I'm not sure if it's because of the soft wood (I used dimensional pine) or just a limitation of the product, but they are nowhere near strong enough. As soon as I screwed the legs in I found that I could wiggle them with not much force. Thinking it might be the pine, I cut small blocks of BB plywood and put the T nuts into that, but it isn't much better, if any. I've been sleeping on it and it's fine, but I know that it couldn't take any lateral force whatsoever...the first time I try to drag the bed out off the wall the T nuts will rip right out. So I need to rethink the leg attachment. Should I be looking at the screw in type of T nuts? I'm sure they are stronger but I wonder how significantly stronger they are. Or something different entirely? I was thinking maybe of using the female end of a sex bolt? What do you guys use to attach threaded rod legs onto heavy furniture?

[Pete Givens]

Here's the upskirt shot 320095

[Gerry Grzadzinski]

T nuts need to go into the opposite side of the wood, so that they are pulled into the wood on the other side when you tighten the leg.
They won't work at all if you are pounding them into the side with the leg.
You'll need a threaded insert for that.

[Dan Keeling]

Could you drill a larger hole and epoxy in a threaded rod coupler?

[Kent A Bathurst]

T nuts need to go into the opposite side of the wood, so that they are pulled into the wood on the other side when you tighten the leg.
They won't work at all if you are pounding them into the side with the leg.
You'll need a threaded insert for that.


Exactly. The T-nut is on the other side of the wood from the bolt. They will never hold doodly-squat if used the other way - but you already knew that, eh? I use a forstner bit of the nut flange dia to create a shallow hole, then use the point hole left for a brad point bit of the bolt diameter for the through-hole. Should work fine.

Threaded inserts work fine also. BUT - Lessons learned: The proper way to insert them is to drill the hole, then insert a hex bolt no longer than the insert's length into the insert, snug it down, and use a wrench/socket to screw the insert into the hole.

Those slots on the end of the insert that look perfect for a big screwdriver? Those are just bait for the uninitiated. Don't do it that way.......the insert self destructs. Took me fewer than 5 ruined inserts to figger this out, BTW. But not very many fewer.

You can use a hex bolt of any length, if you put on double nuts to create a lock stop at the top of the insert........ you just need to avoid the bolt protruding and blocking the insertion.

EDIT: Also - what is a "sex bolt"? Where do you get them? Sounds a bit risque. :D

[William Adams]

“Sex bolt” is an informal term for a Chicago screw (or post and screw).

[Pete Givens]

T nuts need to go into the opposite side of the wood, so that they are pulled into the wood on the other side when you tighten the leg.
They won't work at all if you are pounding them into the side with the leg.
You'll need a threaded insert for that.

Wow I can't believe I didn't realize that :o. That makes a lot more sense than the way I was trying to do it..

[Pete Givens]

Could you drill a larger hole and epoxy in a threaded rod coupler?

Is that the same as the threaded insert Kent mentioned, or something different?

[Pete Givens]

Threaded inserts work fine also. BUT - Lessons learned: The proper way to insert them is to drill the hole, then insert a hex bolt no longer than the insert's length into the insert, snug it down, and use a wrench/socket to screw the insert into the hole.

Those slots on the end of the insert that look perfect for a big screwdriver? Those are just bait for the uninitiated. Don't do it that way.......the insert self destructs. Took me fewer than 5 ruined inserts to figger this out, BTW. But not very many fewer.

You can use a hex bolt of any length, if you put on double nuts to create a lock stop at the top of the insert........ you just need to avoid the bolt protruding and blocking the insertion.


Thanks!! I will take that advice if I go the threaded insert route. I would definitely have destroyed a few and been back on here with another post about how worthless those are...;). Now that I understand that I was using the t nuts backwards, I think I'll just install them on that correct side and see how it works.

[Kent A Bathurst]

Cool....

THe hole for the threaded post should be the same size as the post...you might have to screw it in through the wood.....you don't want a lot of "wiggle room" in there.

Which is why threaded inserts may work better for you - the post can't wiggle, and you can get them in lengths like 1" or whatever..much more thread-to-thread contact. Plus - you can put them into your existing holes, because you will need to drill the holes out to accept them.........

On the backwards T-nuts..........I could not figure out why they would not hold the first time I used them. Welcome to the club......... Always looking for new members, Pete - ;)

[Kent A Bathurst]

Is that the same as the threaded insert Kent mentioned, or something different?


Nope. DIfferent critter. Conceptually the same, but I would go with the inserts instead.

[Gene Takae]

Could you drill a larger hole and epoxy in a threaded rod coupler?


This is my favorite technique as well. I usually grind a few notches on the corners to give the epoxy a better "bite" Also be careful not
to allow any epoxy to get into the threads. I have never had luck with threaded inserts.

[Curt Harms]

This is my favorite technique as well. I usually grind a few notches on the corners to give the epoxy a better "bite" Also be careful not
to allow any epoxy to get into the threads. I have never had luck with threaded inserts.


Embedding a coupling nut is a clever idea. I wonder if it'd make sense to drill the thru hole the size of the threaded piece then counterbore for the O.D. of the coupling nut. That'd give a little bit of a shoulder for the coupling nut to rest against. When I've been concerned about getting epoxy in threads I pack the nut's threads with paste wax.

[Pete Givens]

Any of these methods is fine with me, I'm just wondering what the absolute strongest will be? T nuts properly installed, or the threaded insert/coupling nut idea? I'd like to be able to drag the bed across carpet if I ever needed to move it by myself.

[Brian Holcombe]

I've always seen those type of legs bolted solid to a plate and the plate attached with four bolts to the frame.

Anything can wiggle loose on a bed….

[Pete Givens]

I've always seen those type of legs bolted solid to a plate and the plate attached with four bolts to the frame.

Anything can wiggle loose on a bed….

Can you link me to a product? I haven't found any hardware like that, though I really don't know what to search for.

[Peter Quinn]

Try these. http://www.globalindustrial.com/p/fasteners/Threaded-Inserts/thread-inserts-for-wood/5-16-18-insert-for-soft-wood-flush-851618-25?infoParam.campaignId=T9F&gclid=CLG2p-2SwscCFZYWHwod2qEJuQ

you could use t nuts or barrel bolts but that would generally require a corner block behind the primary frame made of hardwood securely fastened to the main frame. This has the nice effect of setting the legs back a bit so you don't catch them with bare feet.and stub toes. There is a special tool for installing he threaded inserts with the slots on he top, and as Kent mentioned that tool is definetly not a screw driver! These inserts have deep coarse threads to hold them in soft wood, add a little 5 minute epoxy on install....not coming loose under normal sleeping/sock changing use.

[Pat Barry]

Interesting thread. Those legs come with those threaded rods are actually using something termed hangar bolts - a machine thread on one side and a wood screw that drives into the wooden leg. I wondered why they don't make a similar screw with wood threads on both sides. Guess what, they do! Its called a dowel screw. Home Depot sells them. They are about a buck a piece and come in various sizes. No insert or T bolt required. Just drill a hole in the wooden frame and twist in the leg with the dowel screw and you are done. Google dowel screw (http://catalog.hangerbolt.com/category/dowel-screws)to see what I mean

[Pete Givens]

Try these. http://www.globalindustrial.com/p/fasteners/Threaded-Inserts/thread-inserts-for-wood/5-16-18-insert-for-soft-wood-flush-851618-25?infoParam.campaignId=T9F&gclid=CLG2p-2SwscCFZYWHwod2qEJuQ

you could use t nuts or barrel bolts but that would generally require a corner block behind the primary frame made of hardwood securely fastened to the main frame. This has the nice effect of setting the legs back a bit so you don't catch them with bare feet.and stub toes. There is a special tool for installing he threaded inserts with the slots on he top, and as Kent mentioned that tool is definetly not a screw driver! These inserts have deep coarse threads to hold them in soft wood, add a little 5 minute epoxy on install....not coming loose under normal sleeping/sock changing use.

Is that the link you meant to post? That takes me to threaded inserts, i was expecting some kind of mounting plate.

[Pete Givens]

On the backwards T-nuts..........I could not figure out why they would not hold the first time I used them. Welcome to the club......... Always looking for new members, Pete - ;)

I need to rename this thread "How not to use T nuts and other musings" :o

[Peter Quinn]

Is that the link you meant to post? That takes me to threaded inserts, i was expecting some kind of mounting plate.

Yes, that is the link I intended. They are longer and deeper than most t nuts, they have coarse threads to grab soft wood adequately, that's about as much purchase as you can get in pine. They also make "surface mount t nuts" with screw holes to secure them, not sure they resist much more lateral load than what you have now.

one thing did in the past was to take some 1/4" X1"X3" steel bar stock. Drill and tap the center for the threaded post, drill and counter sink the four corners for #10 wood screws, then mortise these into the frame in question, screw them down, not going anywhere. If you have a decent drill press and a basic understanding of machining metal they are fairly easy to fabricate. You might have to peel back the upholstery a bit to set the bars....I call them mending plates.....could probably surface mount but the mortises make them rock solid.

[Greg R Bradley]

The ones with "screw holes" are not "surface mount tee nuts". They still need the flange to go on the back side. Actually they are called Brad Hole Tee Nuts and are an alternative to the ones with barbs. There are also different styles and numbers of barbs according to the type of wood. The other main variation is Hurricane Tee Nuts which have a mild reverse screw to locate on the inside of the hole in the wood.

In all three cases, the brad, barb, or reverse screw ONLY stops the tee nut from rotating. The flange on the back provides most of the strength along with some possible additional location by the barrel.

[Pete Givens]

I picked up some threaded inserts from Lowes today. They are only about an inch deep, so I'm going to install two in each hole. Progress pics to come tonight.

[Pete Givens]

Success!

I installed the threaded inserts. Fortunately, the hole I had drilled for the T nuts seemed to be the perfect size. I loaded up two in each hole since they were fairly short. Way stronger now! Thanks for everyone's help!

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[Jeff Ramsey]

Have you considered barrel nuts?

http://www.amazon.com/BARREL-FURNITURE-BOLT-SLOTTED-14MM/dp/B006ZLKOOU
https://en.wikipedia.org/wiki/Barrel_nut
http://www.beckson.com/bb.html

[Kent A Bathurst]

Success!

I installed the threaded inserts. Fortunately, the hole I had drilled for the T nuts seemed to be the perfect size. I loaded up two in each hole since they were fairly short. Way stronger now! Thanks for everyone's help!

He shoots!! HE SCORES!!!

Our work here is done, gentlemen.........off into the sunset. :D


How's that for mixing completely unrelated metaphors/references?

[Allan Speers]

Man, this thread went from "funniest question of the year" (and we've all been there) to a really useful collection of info.

Whooda'thunkit?

[Kent A Bathurst]

Man, this thread went from "funniest question of the year" (and we've all been there) to a really useful collection of info.

Whooda'thunkit?

blind hogs & acorns, monkeys & typewriters & shakespeare..........you know - that kind of sheer dumb luck. Has to happen every so often, no?

[Pete Givens]

Thanks Kent, you da real MVP.

[Bruce Wrenn]

Those slots are for use with a driver made for that brand of threaded inserts, not a screw driver as you found out.

[Roger Feeley]

You could drive the t-nut into the end of short dowel with a hole in it. Then glue the dowel into a hole in the leg with the t-nut trapped at the bottom of hole. Now the t-nut is pulling against the dowel.

[Kent A Bathurst]

Those slots are for use with a driver made for that brand of threaded inserts, not a screw driver as you found out.

I did not know the first half. Makes sense. I definitely learned the second half. Thanks, Bruce. Been 15 years since that fiasco..........never to late to learn.

[Joe Kieve]

To answer Kent's question: Sex bolt....http://www.mscdirect.com/browse/tn/Fasteners/Bolts-Screws-Cap-Screws/Bolts/Sex-Bolts-Binding-Posts?navid=12108778
We used to use them to attach door closers.

[Pete Givens]

Definitely and I appreciate all the responses! I would have expected this to go more like "YOU'RE INSTALLING THEM BACKWARDS NEWB" /thread.