floating shelf - too wide

an electric plane?

Router?

If you are going to install this into an alcove I would recommend making a 45 degree cut at each of the back two corners. The corner of the two walls is likely to be slightly rounded especially if papered. The triangular piece cut out means that you will not struggle getting the last 1cm gap closed up to the back wall. It also gives the opportunity of running cable up the corner.

Have you put a set square on the back wall to see if the adjacent wall(s) are actually at 90 degrees. If not you may not need to take off a parallel 2mm strip. You may have to taper one or both sides.

I have 4 shelves in alcoves either side of a chimney breast and each are labelled for their unique position as they are not interchangeable. Old

Can you try a surform?

What have you already got?

My weapons of choice would probably be:

powered plane - controlled removal of material to a set depth, and it does not care what it is made out of.

Table saw

circular saw used against a guide (either just a square held against the edge of the board, a batten clamped to it, a sawboard[1], or even a track saw)

router, with (preferably) a straight edge or with its own fence (but extended to make sure you don't lose control at the ends of the cut.

Then if getting a bit more rough and ready (and it would not be uk.d-i-y without it), and angle grinder with a flap disk on it[2].

If you want a hand tool option, then use a fine tenon saw and the "knife wall" technique. Mark the cut line with a knife, not a pencil, repeat several times until you have a deep score. Now on the waste side place a chisel a mm away from your score line - angle it at about 45 degrees with the blade flat on the surface. Now bump it. It should cut toward the knife score and chip out a wedge. Work your way along until you have a notch the full width. Now using that notch to guide the saw, carefully start sinking the cut across the full width.

Looks a bit like an IKEA type product which probably means there is not much substance to it. For 2mm I think I would try a decent sander.

what about a flat bed mouse sander?

On 02 Nov 2023, SH wrote

Good god - surely the RSPCA have banned them?

and gorilla tape too!!

Conventional orbital sanders don't really have the removal rate to do it quickly - but I guess it would work at a push. A random orbit would be better - but unless you spend lots on a very good one, they are tricky to use on narrow edges IME.

If it's an alcove and plastered then chip out a slot in one of the walls, or both.

I can't work out why you want to heat it with an electric iron?

How much are you trying to get off it?

I'd be inclined to saw it with my Japanese pull saw but you'll probably expose the "guts" of the shelf, this won't matter if it's up against a wall of course

I would carefully gouge a 2mm slot into the plaster, after using a stanley knife to make two clean cuts into the plaster as far apart as the thickness of the shelve. Then simply use polyfilla or whatever to make good.

After using a laser measuring device, I found I needed to remove a further 4mm.

I have a WorkMate but have sold most of my power tools. They would have been too cumbersome for this anyway.

I plan to make a kind of frame of 38mm x 12mm to slip over the shelf leaving 4mm to the edge. I can nail or screw it in place from beneath to stop it slipping and then use my £6 chinese saw.

Thaks for concentrating my mind. :)

Alan