I need to tighten an unfamiliar nut! It’s to secure a heating element to a boiler so I can brew some beer at the weekend.

It looks like this, and I think it’s called a KM8 locknut:

locknut

Anything cheap-ish I could pick up from screwfix or B&Q on the way home?

Google would suggest you need a KM8 locknut tool.

A loose bearing BB wrench should do the job if you know someone you can borrow from.

Otherwise the tool you need is called a hook spanner.

Yeah, I tried that and found a socket for near £100…I’m not likely to need the tool again, so hoping to handle it for a fair bit cheaper.

Seems I might be able to do it with something called a hook wrench for <£20, but confirmation of what I need would be awesome.

I’m coming across different names for what I think might be the same thing and getting a bit confused 🙂

Cheers neilwheel – are hook spanners one-size-fits-all, or do I need a specific size?

Part Tool pin spanner should do it, either the red or green handle versions. You might have to bend the legs in a bit to make it work.

you can get c spanners which are hinged to adapt to different sizes but looking at your image id either mod an old socket to fit or use a pair of point nose pliers or god forbid tap it round carefully with a punch. If you are careful you’ll be fine.

piece of wood with two stout nails knocked in at the distance of the notches cut head of nails file ends square, may do it

Cheers neilwheel – are hook spanners one-size-fits-all, or do I need a specific size?

Sized by the diameter of the fitting.

you could also try a punch and hammer to tap the lockring to tighten it

Awesome, thanks all. Think I’m getting one of these:

http://simplybearings.co.uk/shop/p210437/SKF-HN8-9-Hook-Type-Lock-Nut-Spanner-58-65mm/product_info.html

I loved the nails-in-wood suggestion…this thing is sealing a hole at the bottom of a pot that’s holding liquid at a rolling boil for 90 minutes, however, and I’m a bit nervous of doing it wrong…oh, and it holds a 2.4kw element in place as well 🙂

It’ll be nice to have the tool handy in case I need to service it down the line also!

Have you checked the size of the fitting?
That seems too big for what you need. If the curve of the throat is too shallow, the tool will roll off before you can get a decent bite.

hinged c spanner

this might do the job

As mav12 said, punch and hammer, just don’t hit it too hard!!

To make it work properly it should have an MB8 Tab washer to work with it (but will only work if the male thread has a groove down it length).
Tighten nut up so one of the slots lines up with on of the tabs, then knock the tab down in to the slot to create a lock.

Good point on the size of the fitting. I had convinced myself the nut size reference is KM8 – I’ll measure the actual nut size later so I’m sure

aroyalnit – Member
Anything cheap-ish I could pick up…

C spanners / Hook wrenches are often included in motorcycle toolkits – used to adjust the pre-load of the rear suspension.

Pin spanner is the correct tool. Depending on how tight it needs to be a pair of tight angled internal circlip pliers would do.

I did some measuring, and bit the bullet on the tool I linked to. I now have a non-leaky boiler, and a brew day going ahead as planned on Sunday 😀

Thanks all!