Stuck lock nut on shimano deore hub. HELP!

Hi. Hope everyone is well.
I'm trying to service my shimano deore fh-m530 rear hub. Serviced the front wheel no problem, running lovely now. However, the lock nut on the non drive side (rear hub) seems to be stuck, and there's no nut on the same side to apply any counter pressure with a cone spanner. Any advice on how I can get it off so that I can clean and grease the bearings. Any advice welcome. I've scoured the web and can't find anything other than the hub breakdown picture from the shimano website. Thanks!

Can you share a picture? And maybe the hub breakdown diagram you mention?

sure. here's the hub break down.. https://ambringa.cdn.shoprenter.hu/custom/ambringa/image/cache/w1400h900wt1/product/AFHM530AZAL1.jpg?lastmod=-62169987600.1591627937

here's the lock nut in question...

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Heat it up, it'll either have threadlock or corrosion keeping those nuts on, which the heat will help with.

Hard to tell in the pic but does the hollow angle have a hexagonal hole, for a 5mm Allen key? Often, hubs that don’t have opposing nuts on th NDS have that.

If the diagram is accurate, Another possibility is that the metal shield around the cone on the NDS has shifted outboard, covering the interface of the cone that would take a spanner. If that’s the case, some wd40 or a hairdryer and some gentle taps with a hammer and punch might be enough to move the shield inward. Edit- from the pics it isn’t obvious what the issue is.

I think @Adhiero is probably right that the metal dust cap is obscuring the spanner flats on the cone.

You could try holding the drive side locknut and loosen the NDS lock nut away from it? The risk is that the DS loosens rather than the NDS of course. But with a bit of heat and penetrating oil on the NDS it should hopefully loosen first.

Basically, its that outer most bolt that is stuck. Just wont budge. Tried as you suggested with wd40, and as @Alexnharvey suggested with the nut on the other side but still no luck. I've leant it up against the radiator for now, and i'll come back to it later with a hairdryer to see if the heat helps loosen it off.
I don't want to go at it with a hammer just yet, as the cone on the DS is still attached and I don't want to damage the bearings. If I can however get a tool inside the freehub body to grip the cone nut on the DS, then I might be able to get some purchase on that pesky NDS lock nut. I tried with my pliers gripping the DS cone bolt but it keeps slipping.
Also checked already to see if I can slide a 5mm or 4mm inside the axle and there's no hex hole unfortunately :-(. If I can't sort this afternoon I give the LBS or local engineer a ring I think!

Thanks a lot for all of your help and suggestions! I let you know if I manage it :-)

maybe if u don't want to use a hammer u can extend your tool , eg with an old seatpost or pipe, to get more leverage.

I suggest you apply the most heat you can as directly as possible to the nut. Blowtorch, soldering iron, even a cigarette lighter are going to do a lot more than the the radiator or hairdryer.

Keep going with the wd40 if ti's the best you've got. A drop of diesel or acetone (nail polish remover) will help any oil to penetrate into the threads. A little motor oil/3in1 oil and a drop of acetone make a good quick penetrating oil mix.

Edit obviously you need to take care if you are using direct flame around the flammable liquids like acetone or diesel and oil.

I’m no expert but something I would consider doing myself is to screw another nut onto both the stuck NDS and drive side nut to give you a wider surface to get a tool on to without slipping... if you have something that would suit... also, have you tried tightening the NDS before trying to loosen it off? Sometimes works... otherwise why not take the DS nut off and tap the whole axle through to the NDS and out of the hub - then with only the axle and stuck nut left you can soak it in WD40/heat it etc and see if that works 🤷‍♂️

(Obvs also Take the freehub body off)

I don't want to go at it with a hammer just yet, as the cone on the DS is still attached and I don't want to damage the bearings.

Outer nut is seized, got it. For applying heat on that nut, a hair dryer or pouring boiling water over it would stand the best chance. The radiator is going to be relatively slow heat, so the axle inside the nut is given more time to absorb heat and expand as well.

You’ll probably still need more leverage though. Either a vice, a longer tool, a pipe or other extender for the tool you have, a counterforce like a foot or a friend pressing down on the opposing tool... That’s the order of what I would’ve done in the shop if it was needed in a rush. If no rush, fill a cup with 1” of chemical tools like rust remover and put the nut in overnight.

Just to clarify the hammer suggestion: My suggestion is to tap a large flat screwdriver or a pencil-sized punch along the dust cap where I’ve put orange dots and all around. Hopefully the cap isn’t too rusted on, and it should shift in towards the hub enough to expose the cone flats.

If you look at the part I’ve surrounded with a green rectangle, it looks like there’s a 1mm space between the steel ring and the yellow/green spacer on the axle. I think that space is there because the steel ring is a metal dust cap (like @Alexnharvey also thinks and helpfully rephrased), and it’s made its way out and is now covering the spanner flats on the cone. The dust cap isn’t attached to the cone except by a tight fit, and possibly rust in this case.

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If I can however get a tool inside the freehub body to grip the cone nut on the DS, then I might be able to get some purchase on that pesky NDS lock nut

If you have a large Allen key or similar, something I’ve done at home before I had more tools was to fit an Allen key or similar between the cone flats and the inside of the freehub body, immobilising the cone. Then turning a wrench on the NDS to spin the axle and undo the freehub cone all the way. Once the axle is free of the hub you have more options to remove the stuck nut. GL!

Ah! That's a good idea! I'll try that too.
I see what you mean about the dust cap, its wobbling but it wont go further in to expose the cone nut. I think I'll have to take a lesson from this about assuming wheels left at the back of the garage for 8 years are going to be fine. Haha.

Success!
Thank you all for your help and tips! In the end I think the combo of using the lighter to apply some heat as suggested and some more wd40 helped. I had a friend clamp the washer on the NDS to apply some counter pressure, then I twisted it off with an adjustable spanner.
The bearings are absolutely shot, more dust and rust than grease. But thanks to your help I can service it now. Thanks!

Thanks for letting us know. Good job team, glad it worked out, I may have gotten emotionally involved, I need to get out more.