Plane or sand MDF alcove shelves

victor2

I think I'd go for cutting into the plaster as already suggested. You're only talking a few mm.

Don't know how relevant it is, but MDF, like timber, will expand and contract slightly due to temperature changes, so a bit of room for that would have to be allowed too?

DanDare999

greensalad said:

DanDare999 said:

greensalad said:

DanDare999 said:

How do you plan to reduce their size?

Cut to the smallest dimension across the alcove or scribe to fit?

Just sand or plane down the edges to remove the required mm. No scribing because the backs are already wide enough as the alcove tapers a few mm, it’s about 750 at the front and as much as 755 at the back. The shelves are exactly 750. So I only need to lose enough mms to slide them in. I was going to just take off a little on each side, concentrating on the front half of the sides, and keep sliding them in to check until they fit.

I was going to just take off a little on each side
 If you're not scribing then why?

Because they don't fit?

DanDare999 said:

How do you intend to deal with any gaps?

Not look too closely

I meant way risk damage to both sides, I bit off one side will do it.

Not going to bother with a bit of caulk and a touch up paint job?

greensalad

DanDare999 said:

greensalad said:

DanDare999 said:

greensalad said:

DanDare999 said:

How do you plan to reduce their size?

Cut to the smallest dimension across the alcove or scribe to fit?

Just sand or plane down the edges to remove the required mm. No scribing because the backs are already wide enough as the alcove tapers a few mm, it’s about 750 at the front and as much as 755 at the back. The shelves are exactly 750. So I only need to lose enough mms to slide them in. I was going to just take off a little on each side, concentrating on the front half of the sides, and keep sliding them in to check until they fit.

I was going to just take off a little on each side
 If you're not scribing then why?

Because they don't fit?

DanDare999 said:

How do you intend to deal with any gaps?

Not look too closely

I meant way risk damage to both sides, I bit off one side will do it.

Not going to bother with a bit of caulk and a touch up paint job?

Yeah I was trying to decide whether to caulk it or not. The veneer is oak and the alcove is painted a brown colour, so the caulk would be white unless I can manage to neatly paint it. I'll probably see how bad it looks before I decide. Shelves are going to have a bunch of stuff on anyway so it might not be noticeable to bother. 

Bendy_House

greensalad said:

Bendy_House said:

Mike has two good ideas - use the safest tool, a belt sander, or set the shelf in to the wall, assuming it's plaster skim, for example.

For the first, I just tried a Facebook Marketplace for belt sanders, and there's a barely-used Bosch not too far away for £40, and probably haggleable on that. If you don't already have one, they are great tools. Used carefully, and with the shelf held securely so it cannot shudder, this would remove the required mm or so very easily.

For the latter idea, if you scribe and dig out a slot in the wall, then place a strip of masking tape on the top-end of the shelf before positioning it, fill in the slot over it, sand when dry (masking tape protects the shelf), and if you then gently run a sharp knife flat against the filled wall on to the masking strip on the shelf, you'll be able to peel away the visible masking tape neatly, leaving a hidden strip buried under the filler. That make sense?

If belting, obviously belt backwards away from the front edge in case you burst the veneer forward.

Thank's I've bitten the bullet and ordered a belt sander on a Black Friday deal. I had a look at secondhand, but at the moment I have no car so going to collect anything is impossible. So I've bought a cheapie Einhell one. My snobbery about high quality tools has tempered a bit recently, as I've had some good wins with cheap tools for one-off jobs. I'm still happy to spend a bit more on something that I know will get a tonne of use, but for a job like this a £35 cheap tool will probably get me there fine. What grit sandpaper should I be using on MDF? I'll do it outside obviously and wear a mask.

It's thick board, so you'll likely need quite coarse - even 80 grit. Clamp the shelf down well so it cannot move, with just a couple of inches protruding over whatever it's on, mark a crisp thin line to indicate what needs removing - from what you say, it's a mm or two at the front, tapering back to zero just a couple of inches back from there? BOTH ends are 'squint'? Ie, you are going to remove a mm or two from both ends? Only remove where needed!

Fire up the baby, and bring it in to gentle contact with the shelf end. Keep it flat (don't 'rock' this baby). Keep it moving gently (unless the sander's sole plate is long enough to do the whole section you need to remove - good chance?) Keep the sander under control - hold it securely - and keep a steady eye on what you are doing. Remember, sand away from the front edge, or you risk lifting/cracking the veneer on the front. 

It should work. :-)