# Screws VS nut inserts



## Woodypk (21 Feb 2021)

Hi guys,

I was going to make a simple oak top (30mm thick) coffee table on a steel frame. I was thinking for attaching the top, I would have some metal "tabs" approx 30mmx30mm that will be slotted to allow wood movement in the correct orientation. 

My question is, could anyone offer any information with regards to using the drill and screw in threaded nut inserts with bolts rather than using regular wood screws?

Has anyone used these for this type of application and had any good/bad results that they can report?

Thanks guys


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## marcros (21 Feb 2021)

I have used the threaded inserts a couple of times for table tops to frames. It works fine and is my current preferred method (although I dont make many items, so dont read much into this). I haven't managed to find anywhere selling the tabs from anywhere though and they strike me as being a useful item. I have done it with a slotted hole in the lower piece. If I were sourcing the tabs, I would use a circular piece so that I could use a forester bit to inset them.


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## marcros (21 Feb 2021)

thinking further, on your steel frame...

what does the base look like? can you drill and expand the holes directly in the steel or is it tubular? Can you make the top of the base a plate and then drill/slot that? I was thinking more about wooden tops and wooden bases when I answered.


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## Phil Russell (22 Feb 2021)

I have recently made some smallish (c 45 x 15cm x 15cm high) oak tables for our cat to feed from (don't ask). I used insert nuts fitted (screwed) into the underside of the oak (18mm thick) to fasten legs. The legs, 30mm diam had more insert nuts in the ends; table top and legs being connected by 6mm studs. Using insert nuts into the end grain of the legs worked well except when I tried a soft wood when the insert nut would not grip enough. Using beech legs was fine. 
As an experiment I did try using pronged T nuts which you hammer in: I did not think they were strong enough.
Cheers, Phil


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## Droogs (22 Feb 2021)

If you are envisioning that the table will be disassembled fairly often then inserting Helicoils (other brands are available) and using machine screws through the metal frame with a washer would be the better way to go. But if it wont be done often then decent wood screws will suffice.


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## Rorschach (22 Feb 2021)

Droogs said:


> If you are envisioning that the table will be disassembled fairly often then inserting Helicoils (other brands are available) and using machine screws through the metal frame with a washer would be the better way to go. But if it wont be done often then decent wood screws will suffice.



Helicoils in wood? I think you are thinking something else. Helicoils are fitted into thread holes in metal to repair damaged threads, not to provide a threaded hole in another substrate such as wood.


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## Woodypk (22 Feb 2021)

marcros said:


> thinking further, on your steel frame...
> 
> what does the base look like? can you drill and expand the holes directly in the steel or is it tubular? Can you make the top of the base a plate and then drill/slot that? I was thinking more about wooden tops and wooden bases when I answered.



Marcros, the base design is if you can imagine, a wireframe cuboid. I'll probably use 25mm or maybe 30mm steel box section. I'm not sure about screwing direct to the frame. 1/ I want to hide the fixings as best as possible and 2/ I think it would be much easier to slot some thin steel plates and weld them on in maybe, 2 pieces per side of the frame so 8 in total. 

The Tabs will be made from 2/3mm plate steel, welded flush to the top of the frame, pointing inwards ( imagine the way the small black picture frame tabs look on the back of a photo frame) with slots in the correct direction to allow movement.

I don't actually envisage it ever coming off, I was just wondering if there is any strength advantages of using say, M8 nut inserts drilled and glued with a dab of Araldite vs regular wood screws.

As Rorschach has mentioned, I've used helicoils in metallic threads but don't know how they'd fare in timber.

Thanks for the input guys


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## Droogs (22 Feb 2021)

Rorschach said:


> Helicoils in wood? I think you are thinking something else. Helicoils are fitted into thread holes in metal to repair damaged threads, not to provide a threaded hole in another substrate such as wood.


Helicoil is the name of the Brand- See below @Rorschach (you really should, stop engage brain and then mouth), might be less embarasssing





__





Heli-Coil® Self-Tapping Screw Thread Inserts for Wood | STANLEY® Engineered Fastening







www.stanleyengineeredfastening.com


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## Woodypk (22 Feb 2021)

Droogs, 

Have you use the helicoil wire type inserts vs the regular screw in nut type inserts? Have you found one to be better than the other?


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## Droogs (22 Feb 2021)

I actually prefer the Helicoils to the "normal" brassy coloured thread inserts, i just feel the are stronger and in wood go in quicker. They must cut in easier. I found that with MDF that it is best to screw in and then screw out and give the hole a quick bit of thin CA and put the insert back in, seems to strengthen the area around the insert a bit better. 
That though may just be in my head


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## Rorschach (22 Feb 2021)

Droogs said:


> Helicoil is the name of the Brand- See below @Rorschach (you really should, stop engage brain and then mouth), might be less embarasssing
> 
> 
> 
> ...



Well there was no need for that. As you can see above, I am not the only one to question you.

I am well aware of the helicoil brand, I have never seen those wood inserts for sale though, where do you buy them?


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## Droogs (22 Feb 2021)

UK distributor is Rivetwise, i apologise for being a bit shirty - not a good day


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## Cooper (22 Feb 2021)

Droogs said:


> disassembled



Sorry to be a pedant but what happened to dismantled? First we lost railway stations for train stations, there seems to be no end. 
Cheers
Martin


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## Droogs (22 Feb 2021)

@Cooper The army only taught me to assemble, they had gone metric by the time I joined up, so trade training never covered how to mantle


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## Rorschach (22 Feb 2021)

Droogs said:


> UK distributor is Rivetwise, i apologise for being a bit shirty - not a good day



Thank you.

Looking at Google it seems they are not as common as the normal threaded inserts or t-nuts that you see. I couldn't find them for general sale but I did see the website you mention so maybe they are more of an industrial rather than retail item? Are they any good? Do you know what makes them different to their inserts designed for metal?


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## Droogs (22 Feb 2021)

They seem to be steel to me and have a sort of more flattened diamond /rhomboid cross-section and are at a true 60 degree V to give wood the best amount of material in the thread for strength. I get them from Rivetwise after being given some a few years ago, can't remember how much they were. But as I mentioned they seem to need a bit of help re the thread inside of MDF, they have a tendency to just pull the mdf apart rather than just pull out if the panel is yanked . I think the brass coloured ones are designed more for MDF whereas these are defo for use in solid wood. I use them for removable veneered solid edged panels that need to be taken off of internal steel frames in custom PC/Printer integrated desk builds for servicing, component replacement etc.


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## Rorschach (22 Feb 2021)

Droogs said:


> They seem to be steel to me and have a sort of more flattened diamond /rhomboid cross-section and are at a true 60 degree V to give wood the best amount of material in the thread for strength. I get them from Rivetwise after being given some a few years ago, can't remember how much they were. But as I mentioned they seem to need a bit of help re the thread inside of MDF, they have a tendency to just pull the mdf apart rather than just pull out if the panel is yanked . I think the brass coloured ones are designed more for MDF whereas these are defo for use in solid wood. I use them for removable veneered solid edged panels that need to be taken off of internal steel frames in custom PC/Printer integrated desk builds for servicing, component replacement etc.



Good to know for the future. Cheers.


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## Cabinetman (22 Feb 2021)

The oak that I was fastening into was about an inch and a quarter thick but this was a seriously heavy piece of furniture, more on here, search under the word Behomoth. Ian


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## Cabinetman (22 Feb 2021)

I could have done with those Droogs, handy to know about.


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## Jos7000 (23 Feb 2021)

Woodypk, I'm intrigued as to why you want to use metal tabs fastened to the underside of the top and then fasten these to the frame. Would it not be just as strong and easier to drill the box metal in a size suitable for the bolts and then widen the lower side to facilitate the head of the bolt to pass through (and a socket to tighten it) thus hiding the bolt?


Disassemble = to take apart with a view to being able to reassemble. 

Dismantle = take apart often by brute force without a requirement to put back together.


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## Jonm (23 Feb 2021)

Jos7000 said:


> Disassemble = to take apart with a view to being able to reassemble.
> 
> Dismantle = take apart often by brute force without a requirement to put back together.


Interesting, I have always used them interchangeably. I looked up the origin of dismantle as follows
*dismantle (v.)*
1570s, "deprive or strip of fortifications or equipment, raze, destroy, tear down," from French desmanteler "to tear down the walls of a fortress," literally "strip of a cloak," from des- "off, away" (see dis-) + manteler "to cloak," from mantel "cloak" (see mantle (n.)). The literal sense, "deprive of dress, strip" (c. 1600) is archaic or obsolete in English. Related: Dismantled; dismantling.

So the origin of the word is to take apart and destroy. However with use it’s meaning has changed somewhat but the implication is that the item will not be put back together ie dismantled railway, car dismantler etc.

So full marks to Droogs for his careful choice of words.


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## Jos7000 (23 Feb 2021)

I would be more concerned with the likes of bicycle to bike, friend to m8 (worse still m9). Then there is the replacement of English with Americanisms, my dad used to get really angry about it, I never understood why, until I reached a similar age. You may hate me for this one day, but, American films (not movies) or TV shows, the use of the word stat, it's in everything and double negatives, grrr.
Rant over


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## Ollie78 (23 Feb 2021)

You could try something like buttonfix type fittings. Instead of welded tabs bolt the button part to the metal frame with tapped holes and countersunk machine screws. Then router the top to accept the female part if the connection. Then the top is fitted by placing on and sliding to the side. 

Ollie


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## recipio (23 Feb 2021)

Threaded inserts are tricky to use. I find that a 10 mm hole is optimal for hardwood and 9mm for softwood. I made a pair of sidetables once that required a 12.5 degree splay in the legs and simply set some threaded rod in the legs with epoxy resin.Worked fine.


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## Woodypk (24 Feb 2021)

Jos, 

The tabs aren't fastened to the underside. They're welded to the frame.

I had thought about drilling a clearance hole for the screw/bolt head and a smaller hold to keep the screw/bolt head captive inside the box section but thought it might look a bit weird having the holes through the frame on show. And also perhaps slightly more awkward to properly slot these holes to allow for movement across the table top.

It might not though... I do make most of my decisions on the job, half way through a project so who knows what I'll end up with!


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## Woodypk (24 Feb 2021)

Ollie78 said:


> You could try something like buttonfix type fittings. Instead of welded tabs bolt the button part to the metal frame with tapped holes and countersunk machine screws. Then router the top to accept the female part if the connection. Then the top is fitted by placing on and sliding to the side.
> 
> Ollie


Ollie, I'll check these out...


recipio said:


> Threaded inserts are tricky to use. I find that a 10 mm hole is optimal for hardwood and 9mm for softwood. I made a pair of sidetables once that required a 12.5 degree splay in the legs and simply set some threaded rod in the legs with epoxy resin.Worked fine.


Recipio, 

I think for this particular application, it should be much harder than drilling pilot holes. I'm just going one step further than fitting a nut insert into the hole with this method...
If I end up using it.

For something that I don't want to take apart, I'd definitely reach for the domino.


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## MARK.B. (24 Feb 2021)

One easy and very very cheap way of doing it would be to cut suitable sized slots on the inside edge of the frame , then using a couple of off cuts and a screw make swiveling tab;s that fasten to the top and swivel into the cut out slots , that should hold it firmly in place / is easy to remove if needed and wont be seen


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## TheTiddles (24 Feb 2021)

30mm of oak is absolutely loads of material to take a wood screw, a handful will be plenty to pick up the table and swing it around by the top. Threaded inserts are for things where a narrow tapped thread is weak, you’re not in that situation
Aidan


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## Sgian Dubh (25 Feb 2021)

Woodypk said:


> My question is, could anyone offer any information with regards to using the drill and screw in threaded nut inserts with bolts rather than using regular wood screws?
> 
> Has anyone used these for this type of application and had any good/bad results that they can report?


What you are proposing is overthinking and overengineering on a grand scale. Create your holes or slots in the metal 0.5 mm wider than the widest shank diameter of a woodscrew, e.g., 4.5 mm slot for a no 8 (4 mm dia) screw, or 5 mm slot for a no 10 or ~4.5 mm dia screw. Use a roundhead wood screw (for its flat underside) and fix directly into the wood. Incorporating threaded inserts into your solution is just so much unnecessary faff for no appreciable gain. Slainte.


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## Woodypk (25 Feb 2021)

Thanks for the replies guys. 

I had thought going the way of the woodscrew would be absolutely fine. It seems like for this project, it's probably more than suitable. 

Cheers guys


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