My crank consistently loosens and i don't feel like hassling the lbs anymore to tighten it so i'm wanting to purchase the tool. What's it called thanks

Depends, what kind of crankset is it?

And maybe you should actually solve the problem and find out why it keeps loosening in the first place.

Depending on the crank, you use either a socket wrench or an allen wrench to tighten it. Take off the dust cap and look at the bolt. I don't know if different tools are used for the really fancy high-end cranks, but a socket wrench or allen key is fine for most.

If the crank arm is consistently loosening, then you have an undiagnosed problem. Tightening it whenever it gets loose is fine, but it will never stop happening unless you fix the underlying problem.

If it's this, you just need an 8 mm allen.


If it's this, you need a socket wrench.


But as relyt was saying, this doesn't really solve anything permanently if your crank arm keeps loosening.

Torque Wrench.

Have the LBS, if you can't do it your self, clean the threads of the bottom bracket spindle, and apply Loc-tite to the bolt before installing it.

If you have a tapered BB then most likely the crank interface is buggered which is causing the continued looseness.

Or a 7mm allen (!) if it happens to be one of a couple '80s Campagnolo cranks w/self-extracting bolts.

Typically 14mm, but some (Campagnolo in particular) will require a thin-wall 15mm socket, a pipe socket, or Campagnolo's own spoon-shaped remover to clear the remover threads.

Pipe socket:


-Kurt

Mine doesn't look like either (stock Huffy MTB). The cranks are curved coming out of the bike. There's a hex nut around the base where the crank (non-drive side) comes out. Would an adjustable wrench or channel-lock pliers work?

Neither crank is loose, but if you hold onto both pedals with your hands, you can 'wobble' them side to side.

you need a 15MM thin wall socket . your problem is your crank arms ,they are make of a soft metal and need replacing . the hole in the arms are enlarging and that why they keep coming lose on you . I have see allot of this around here because people buy chap bikes.

To be clear, it sounds like you have a one-piece ("Ashtabula") bottom-bracket/crank. Does yours look like the right-most picture? https://sheldonbrown.com/gloss_bo-z.html#bottom

Edit: Rico_SPD, just noticed you are not the OP. If you have a one-piece system, the replies in this thread won't really help you. Check out: https://sheldonbrown.com/opc.html

Whether directed to Rico or the OP, I would not suggest, with the information given, that the hex is 15mm. Most of them are 14mm, with the exception being Campagnolo and some of the other high-end components of the '70s and '80s.

One other thing I figured would be wise to add:

Some '80s Campagnolo cranksets with the following remover assembly utilize 7mm allen keys. Beware - 7mm keys are hard to come by. Reasonably easy to grind an 8mm down to fit snugly in the 7mm socket though.



-Kurt