TheTiddles
Established Member
Yes it will, that’s one of the failure modes for threaded inserts. Using a nut means you don’t have to have a screw just the right length
Aidan
Help me out of this situation! Broken insert
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Aidan
TheUnicorn
Established Member
yeah, did think that might be one benifit of the additional nut, save finding exactly the right bolt, also I can see that by being able to keep the pressure on with a second spanner whilst unscrewing the whole assembly could be a benifit, but that seems to be something I've added into the mix (possibly incorrectly).
Seems like the whole design is pretty flawed, quite aside from the failing of the metal (more cheese gromit), as soon as you you go to unscrew the internal bolt you are always going to be simultaniously (potentially at least) unscrewing the fixing from the wood, the addition of a sprung washer might lessen the likelyhood of overtightening the bolt into the insert.
I would have thought a spiked t nut or a hanger bolt would be a better option most of the time
This is not the best video, but it demonstrates the procedure. The second nut doesn't do anything, and it's too bad he is using pliers instead of spanners, but the procedure works.
Inspector
Nyuck, Nyuck, Nyuck!
Primitive graunch artist!
Pete
Pete
novocaine
Established Member
If you tighten the bolt to the top you will turn the insert inwards. If you righten a nut agaist it with a bolt set in then you wont. Why make life harder yourself by winding the insert in? you also wont get the bolt torqued up on the insert as it will want to wind in and when you hit the bottom the bolt head will then tighten just a shade more and you wont be able to wind it back out without bringing the insert out.
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novocaine
Established Member
I've always used screwfix. hears a story.....
once upon a time inserts didn't come with hex heads in them, you had to wind them in with the bolt and nut method already described by multiple people, it was wonderful, it supported the insert all the way though and provided a nice spread load instead of point loading the very tiny edge of a driving head, it let them use a cheaper but still suitable material.
Then the manufacturers saw an idea, and they thought the idea was good, they'd put a driving head in to the insert, how hard could it be, then people would have the option of installing the insert in to hard woods the old fashion way with the bolt and nut and in to soft wood and man made boards with the driver head, it might mean a change in materials but gosh darn it, it would be worth it to have a product out before anyone else.
But the evil accounts dept. witch didn't like this idea, it was an extra process, it would cost 0.000000001p and the different material, that had cost implications too, per insert and that cost couldn't be passed on to the consumer because cousin frank over the hill would copy their idea and not add that cost on, instead choosing the lower their 400% profit margin to 400%. So she cast a spell on the instructions and removed the traditional fitting technique, this save 0.0000000001p on the price of print, and she didn't bother contacting the materials supplier to ask about better materials, why change this one, it would be fine, it's only an insert and it's not meant for really nice work.
At first it didn't seem to matter, people still used the old ways and the company prospered, but as newer and younger folks starting using the inserts the old ways got forgotten, "it's got a driving head, why would I need to do that" and so the story goes, "these fittings are made of cheese", "these fittings aren't fit for purpose", "it's ruined my love piece of quilted maple".
so heed the tale folks, occasionally, just occasionally, the old ways do make sense.
once upon a time inserts didn't come with hex heads in them, you had to wind them in with the bolt and nut method already described by multiple people, it was wonderful, it supported the insert all the way though and provided a nice spread load instead of point loading the very tiny edge of a driving head, it let them use a cheaper but still suitable material.
Then the manufacturers saw an idea, and they thought the idea was good, they'd put a driving head in to the insert, how hard could it be, then people would have the option of installing the insert in to hard woods the old fashion way with the bolt and nut and in to soft wood and man made boards with the driver head, it might mean a change in materials but gosh darn it, it would be worth it to have a product out before anyone else.
But the evil accounts dept. witch didn't like this idea, it was an extra process, it would cost 0.000000001p and the different material, that had cost implications too, per insert and that cost couldn't be passed on to the consumer because cousin frank over the hill would copy their idea and not add that cost on, instead choosing the lower their 400% profit margin to 400%. So she cast a spell on the instructions and removed the traditional fitting technique, this save 0.0000000001p on the price of print, and she didn't bother contacting the materials supplier to ask about better materials, why change this one, it would be fine, it's only an insert and it's not meant for really nice work.
At first it didn't seem to matter, people still used the old ways and the company prospered, but as newer and younger folks starting using the inserts the old ways got forgotten, "it's got a driving head, why would I need to do that" and so the story goes, "these fittings are made of cheese", "these fittings aren't fit for purpose", "it's ruined my love piece of quilted maple".
so heed the tale folks, occasionally, just occasionally, the old ways do make sense.
novocaine
Established Member
second nut is acting as a lock nut to the first, basically increasing the surface area of the thread to increase the amount of friction.
Phil Pascoe
Established Member
No, the bolt would undo, there being nothing to stop it doing so. A locked nut wouldn't - you're using the spanner on the bolt, not the nut that does the locking, The insert and the nut become one single entity, the bolt pulling the whole thing out.
You could of course superglue the bolt in, when it wouldn't.
TheUnicorn
Established Member
thankyou, that really makes sense, it is the fact that the thread of the bolt can stay static, whilst still applying pressure with the nut that makes the difference
thankyou mike, I did understand the technique, I was just getting a bit caught up on some of the technicalities, novacaine's explaination about the static thread got me over the final hurdle
Terrytpot
Established Member
Problem is direction of rotation..screwing the bolt in tightly also tightens the insert into the wood so that when you reverse direction it may only unscrew the bolt and not the insert as well. If there’s enough insert left proud that you can lock off on with a nut then you can unscrew with a bolt and locknut using 2 wrenches.
TheUnicorn
Established Member
well, I now understand the benefit of the nut, however in principal if you tighten a bolt right in, and then start backing the bolt out, surely which ever surface of the the insert, ie the internal or external thread, has the weaker grip, will be the point of movement? Seems like a design that is always going to be prone to failure, over tighten the insert and you crush the grain of the wood and so it spins, or overtighten and the cheese metal buckles, undertighten and you have a wobbly chair leg or whatever you are screwing in. They obviously look nicer (cleaner look) than a T nut, but I would have thought the T nut is mechanically stronger
TheUnicorn
Established Member
yes I personally think that two spanners / wrenches (same thing I think?) offers the most control, maintaining pressure on the insert with clocked pressure, removing the insert with anticlocked pressureProblem is direction of rotation..screwing the bolt in tightly also tightens the insert into the wood so that when you reverse direction it may only unscrew the bolt and not the insert as well. If there’s enough insert left proud that you can lock off on with a nut then you can unscrew with a bolt and locknut using 2 wrenches.
novocaine
Established Member
It would if he actually tightened the nut with his spannerpliers.
yer, ok, a fair comment. I apologies.
I might not have bothered watching the video beyond the first 10 seconds (had to stop, the screams of mechanical sympathy were louder than the video)
sometimewoodworker
Established Member
it could for putting the insert in, but even then it’s not ideal, but for extraction it probably will not.
TheUnicorn
Established Member
why would a bolt without a nut not do the job or putting the insert in place perfectly well? I obviously now recognise my error in the method of removing it (that does need a nut). As the insert buckled with the allen key, as it was designed, I can't see what other option there is?
novocaine
Established Member
Because you'll torque the bolt as you tighten the insert in. Get to the bottom then find it wont come undone and instead it will wind the insert back out. It takes more torque to wind in than it does to back put.
TheUnicorn
Established Member
so how do you put the thing in then?, or is that another nut bolt combo situation?
