How do I tighten these bolts?

[FlattestWhite]

Sort of DIY related, but about bikes. I have a special bag that attaches to a metal fitting that then slots into the rack on my bike. There are holes in the bottom of the bag that bolts go through to attach it to the fitting. I can’t get the nuts on far enough, and they keep undoing and falling off.

The nuts only seem to go a short way on to the bolt, not enough to tighten it up enough to hold the fitting on to the bag. Googling tells me that they may be lock nuts, and that the plastic bit inside should stop it undoing itself, but it doesn’t - so I suspect I haven’t got them on far enough. But I can’t work out how to do it - it’s already really fiddly trying to hold it all in position. The bolt just spins round. The other end of it has a small hex indent like you use an allen key to tighten, but even if you try to put an allen key in there at the same time, it still just spins or the nut doesn’t move any further (maybe my hands aren’t strong enough to provide the resistance needed). The head of the bolt also fits flush into a plastic piece, so you can’t hold it still with any other tools. So with my fingers, I can only get the nut to go on up to the first few threads, and then it falls off from the vibration of cycling. I can’t tell if I’m not doing it right to start with, or if I’m not strong enough, or need different tools, or if it’s just a badly designed system.

The photo shows the bolt - the plastic piece and bolt go inside the bag, and then the washer and nut go underneath the metal fitting to hold it in place. How do I tighten something like this?! I already need to buy some more nuts as at least one has fallen off, so I could buy something else if there were any more suitable fasteners. they are 5mm in diameter.

Shall wrench/ spanner or even pliers to grip the nut as you tighten should do the trick.

I still just seem to either have the bolt spinning or the nut spinning, even if I try to hold the nut with pliers and turn the allen key, or vice versa. Or nothing moves at all.
Perhaps I just need to take it to a bike shop or something where there are people with stronger hands, but it looks like I should be able to do it myself (assuming that the nuts ARE supposed to go right up to the fitting, which I wasn't 100% sure about??).

the middle photo shows about as tight as I am ever able to get it, with about a cm gap, whereas the bag plus the fitting are only a few mm, so I'm pretty sure it should do up more than that. Even off the bag, though, I still haven't been able to get it done all the way up to the top, even just to figure out whether it was supposed to be like that. It's really awkward holding the disk and bolt inside the bag, and then the fitting, then the washer and nut on the other side, and trying to get the strength to tighten it more, holding it still with one hand and tightening with the other. Doesn't help that I'm not totally sure how it is supposed to look, of course!

Is the nut the right way up?

I think so. I've tried it both ways, but it only goes it really one way.

There are four of these fastenings, one in each corner, and they're all the same.

That is a lock nut so shouldn’t undon by itself once one properly. Check u have the but the right way up , also check u have the right size Allen key as if u have and hold that still whilst turning the nut it shouldn’t spin. If you can’t get it to stop spinning I would ask for help at a shop as you might round of the inside of the Allen key bit so would need a new one.

Those nuts have a nylon insert to stop them undoing, but the first time you use them you are cutting a thread in the nylon which will be a tight fit.
There's no way to do this without a spanner and an Allen key, these are not possible to do by hand. Even pliers are not really the right tool for the job.
If you really can't do it even with the proper tools then either a helpful neighbour, a handyperson or a bike shop would be able to deal with it for you.
Good luck.

thanks both.

sounds like it is probably a matter of strength then, partly because of the awkward position of it all. I'll have another go with a spanner if I can find a small enough one to hold the nut still, especially if I know that it's meant to be really tight the first time and that it's supposed to go on further. I'll double check the allen key size too; I think it's the only one that fitted, but it's on a sort of 'key chain' of keys, without a really solid bit to grip on to, so given that it sounds like it is going to need a fair bit of force, I might need to get a better one.

and after that, I'll take it to the bike shop! I thought they'd think I was very silly for not being able to do it up properly myself

Agree self locking nuts can be hard work. As you can separate everything I’d probably use Allen key + spanner combo to firmly attach to something else which isn’t awkward then undo and put in desired awkward position.

If the keychain has springs holding the Allen keys they are quite easy to remove then you can hold the long side more easily.

Thank you all! Success. Armed with the knowledge that it was meant to take a fair bit of force, and the purchase of an adjustable spanner that could be really tightened but was still small enough to get into the space, I have now managed to get them done up. The allen key shape was still a pain, but I could use it in the end. I found also that doing the rear fasteners first meant that it was easier to hold it together and not quite as awkward (though still a bit of a difficult design, as with one hand in the bag, it's hard to see what you are doing, and the other hand having to hold the bits on the other side!

But I've avoided the humiliation of having to go to a shop and tell them I couldn't do it myself so I'm pleased about that. i think I just hadn't realised how much you have to push, and stopped when it got hard.

Well done !! 😁

Best combo for this is a set of Allen keys plus a compact ratchet socket set.