Need help with a bolt/threaded insert type connection - Woodworking Talk - Woodworkers Forum
 
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post #1 of 19 Old 04-24-2013, 04:26 PM Thread Starter
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Need help with a bolt/threaded insert type connection

I'm an architect with basic carpentry experience, and I need to come up with a removable stair railing connection. The railing will be in place 99% of the time but will need to be removed for moving furniture up and down the stairs. I would like to use a bolted connection, connecting a plate attached to the balusters with a sloped top plate of the wall. But since the underside of the connection will be concealed, I need some type of fixed threaded insert. I would prefer that the insert be set into underside of the bottom plate rather than the top side, to avoid any chance of the bolt ripping the insert out with it if too much force is put on it. Basically I just want something that will act as a nut and washer normally would in a typical connection.

I've attached a sketch showing the basic layout. The red line is where the two pieces will separate.

Thanks in advance for any help!
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post #2 of 19 Old 04-24-2013, 05:23 PM
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something like this?
http://www.mcmaster.com/#tee-nut-inserts/=mgqwza

John

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post #3 of 19 Old 04-24-2013, 06:24 PM Thread Starter
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Originally Posted by jschaben View Post
Yes, exactly. Now my question is, how would the threads work with the bolt? I think those are meant to be driven from the same side as the bolt. So what happens when the bolt and the insert are driven from opposite ends?
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post #4 of 19 Old 04-24-2013, 06:46 PM
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Quote:
Originally Posted by porculator View Post
Yes, exactly. Now my question is, how would the threads work with the bolt? I think those are meant to be driven from the same side as the bolt. So what happens when the bolt and the insert are driven from opposite ends?
Tee nuts can be threaded from either end. They work better when the pull forces the prongs into the wood. Threaded inserts might also work.




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post #5 of 19 Old 04-24-2013, 09:59 PM Thread Starter
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Excellent, thank you. I found some hammer-in threaded inserts at Home Depot and experimented with those. They wouldn't hold their shape even in softwood and the bolts wouldn't make it all the way through. I think the tee nuts will probably be the way to go.
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post #6 of 19 Old 04-25-2013, 12:43 AM
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Quote:
Originally Posted by porculator View Post
Yes, exactly. Now my question is, how would the threads work with the bolt? I think those are meant to be driven from the same side as the bolt. So what happens when the bolt and the insert are driven from opposite ends?
Those are designed to be driven in from the opposite side, just like your artwork.
Those sound like the ones you got from home depot and, yes, the metal is on the soft side so it isn't uncommon for the prongs to deform. I've been known to nip off the prongs and butter the underside of the t-nut with epoxy. It really can't go anywhere with the bolt installed. The prongs are primarily there to keep the nut from turning when the bolt is being tightend and hold the nut in place while the bolt is being installed. The epoxy accomplishes both nicely.
Length of the bolt needs to be at least the thickness of both pieces of the assembly minus about half the barrel length of the t-nut. This should allow the assembly to be tightened without the bolt protruding out the bottom.

John

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post #7 of 19 Old 04-25-2013, 09:18 AM
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+1 on the T nut's being rather soft steel.

C'man gave a link for brass threaded inserts.

Rockler sell steel threaded inserts. Harder/stronger steel than the T nuts.

http://woodworking.rockler.com/hardw...readed-Inserts

If you do use the T nuts, it looks like you want this to be flush, I would drill a recess hole for the top with a Forstner bit, otherwise the top will be proud despite attempts to drive it flush with a hammer - at least that was my experience.
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post #8 of 19 Old 04-25-2013, 11:14 AM
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Quote:
Originally Posted by Dave Paine View Post
+1 on the T nut's being rather soft steel.

C'man gave a link for brass threaded inserts.

Rockler sell steel threaded inserts. Harder/stronger steel than the T nuts.

http://woodworking.rockler.com/hardw...readed-Inserts

If you do use the T nuts, it looks like you want this to be flush, I would drill a recess hole for the top with a Forstner bit, otherwise the top will be proud despite attempts to drive it flush with a hammer - at least that was my experience.
I have pretty good luck with tee nuts. Never twisted one. For installation, I use a Forstner bit first that will clear the head of the nut's diameter, and drill to about a heavy 1/16" or more to get the head either flush or recessed. The pilot point of the Forstner bit will make a center for the hole for the correct size drill bit. Tee nuts come with different length barrels.






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post #9 of 19 Old 04-26-2013, 06:52 PM
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I had a problem staircase that was difficult to move furniture because of the balustrade. I solved it by making the whole balustrade removable with heavy bolts into the stair stringer. It worked well but it was a staircase with a landing so the removable balustrade was in two sections. Each set of balustrade with its railing and balusters could be removed temporarily. This would only work on some staircase designs. There are several ways to disguise the bolts.
Good luck.
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post #10 of 19 Old 04-27-2013, 12:08 PM
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Are these what you are looking for? http://www.mcfeelys.com/search/t+nuts

They are called "T-nuts". They are available in many hardware stores and maybe even the "big boxes". The other choice are "Theaded Inserts" but the T-nuts will be much more secure and can be tighted more without pulling out.

Howie..........

Last edited by HowardAcheson; 04-27-2013 at 12:11 PM.
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post #11 of 19 Old 04-27-2013, 12:18 PM
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Quote:
Originally Posted by HowardAcheson View Post
Are these what you are looking for? http://www.mcfeelys.com/search/t+nuts

They are called "T-nuts". They are available in many hardware stores and maybe even the "big boxes". The other choice are "Theaded Inserts" but the T-nuts will be much more secure and can be tighted more without pulling out.
I'm just curious...did you read any of the previous posts before responding?





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post #12 of 19 Old 04-28-2013, 10:33 AM
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Do you have access to the back side of the wall? T nuts must be installed with the T and prongs op the screw coming in. I would recommend a threaded insert. They can be installed any time in the construction process and only require one hole. I also find their threads to be longer and more precise.

T nuts would have to be installed out of phase with normal construction procedure. Inserts can go in when the trim man installs the rail.

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post #13 of 19 Old 04-29-2013, 06:03 PM
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>>>> I'm just curious...did you read any of the previous posts before responding?

Nope, when I'm traveling I bulk download thread responses, prepare my responses and then upload them in a batch. Could be a couple of days with no contact with a forum between download and response.

Is there a problem or are you just being a skutch?

Howie..........
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post #14 of 19 Old 04-30-2013, 06:52 AM
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Quote:
Originally Posted by HowardAcheson View Post
>>>> I'm just curious...did you read any of the previous posts before responding?

Nope, when I'm traveling I bulk download thread responses, prepare my responses and then upload them in a batch. Could be a couple of days with no contact with a forum between download and response.
Bulk downloading threads and batch responding...that's a good one, I'll have to remember that one. But, you still have the ability to agree or disagree with a post. Doesn't sound very polite to ignore what's been posted, to restate the same post, or repeat the same information.




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post #15 of 19 Old 04-30-2013, 10:00 PM
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Quote:
Originally Posted by HowardAcheson
Are these what you are looking for? http://www.mcfeelys.com/search/t+nuts

They are called "T-nuts". They are available in many hardware stores and maybe even the "big boxes". The other choice are "Theaded Inserts" but the T-nuts will be much more secure and can be tighted more without pulling out.
Howard
I think t nuts will be hard to install. Granted they will have more strength but they would have to be installed when there was access.

Al

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post #16 of 19 Old 05-02-2013, 05:00 PM
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I'd recommend these Screw in Threaded Inserts. Pre drill with the recommended drill bit then use a flat bladed screw driver to screw em home about 1/4" counter sunk. I've used em in All kinds of wood and never had a problem except with particle board. If you use a bit of 5 min epoxy on em at the time of install they'll be there for good.


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post #17 of 19 Old 05-02-2013, 05:13 PM
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Quote:
Originally Posted by MissionIsMyMission
I'd recommend these Screw in Threaded Inserts. Pre drill with the recommended drill bit then use a flat bladed screw driver to screw em home about 1/4" counter sunk. I've used em in All kinds of wood and never had a problem except with particle board. If you use a bit of 5 min epoxy on em at the time of install they'll be there for good.
I agree. Skip the t nuts. I've seen them split the wood. I like to run the inserts in with a bolt and nut driven with a socket wrench.

Al

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post #18 of 19 Old 05-02-2013, 07:08 PM
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Just a consideration here.... since it is a stair railing, which will have some sideways force, Do you think that there would be any chance of the threaded insert loosening up?

I think if it were me, and I have access to install the T-nut, that might be a better way to go.... harder for it to be loosened up/pulled out. The flange on the t-nut would provide better holding power. However, if you cannot attach the t-nut to the backside, the threaded insert would be way to go, installed like Al said, with a threaded bolt and nut attached to the threaded insert, and driven with a socket wrench, so as to try to insert it as straight as possible.

just my 2 cents... now I'm broke.

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post #19 of 19 Old 05-02-2013, 08:06 PM
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Quote:
Originally Posted by thegrgyle
Just a consideration here.... since it is a stair railing, which will have some sideways force, Do you think that there would be any chance of the threaded insert loosening up?

I think if it were me, and I have access to install the T-nut, that might be a better way to go.... harder for it to be loosened up/pulled out. The flange on the t-nut would provide better holding power. However, if you cannot attach the t-nut to the backside, the threaded insert would be way to go, installed like Al said, with a threaded bolt and nut attached to the threaded insert, and driven with a socket wrench, so as to try to insert it as straight as possible.

just my 2 cents... now I'm broke.
A threaded insert will never loosen. If you can picture how a stair rail is installed and when in the construction process. It's plain to see you would not be able to install a t nut. T nuts don't have threads and require pounding them in from the back side. If you were installing a handrail you will be one of the last workers on the job site. You will be installing at trim. The wall will be drywalled and painted.

If the t nut didn't have something behind it it would wiggle back and loosen. That's another problem with t nuts they only have hold when pulled not pushed. Also there threads are shorter and not as tight on fit.

Al

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