Old desk restoration-Help needed.

[JJ1]

I'm currently repairing an old 1950's Oak desk which I use as a desk for my computer. So far I've repaired all the drawers, and refinished the desk with some Osmo Polx Oil.

Unfortunately, the desk top is in quite a bad way and I've decided to make a new one. I've purchased a sheet of 19mm crown cut oak veneered mdf for the desk top and I plan to add 26mm thick, 60mm wide solid oak edges, (as were used on the existing top). I'm intending to use loose tongues to attach the oak edging. I've bought a 6.4mm groover for my router.

My first question is; Is it ok to use 6mm MDF for the loose tongues, instead of the ply tongues often used?


Do I have to be concerned with where to apply glue and tongues or is wood movement of the edges not an issue. Please excuse my poor illustration, but in the image above, the light purple is where I am intending to use a loose tongue. Does that look right? Should I also insert a tongue (dark purple) to attach and glue the short and long edges together or will that prevent the short sides from expanding and contracting across their width?


Any help and advice would be really appreciated as I've not attempted anything like this before and I'd like to try and do the best job I can. Not to mention the fact that what started out as a desk costing £20 has now cost me a small fortune by the time I've bought 4 long Bessey clamps, oak veneered mdf, solid oak, groover router cutter, Osmo oil, etc :shock:

 

[Phil Pascoe]

"what started out as a desk costing £20 has now cost me a small fortune by the time I've bought 4 long Bessey clamps, oak veneered mdf, solid oak, groover router cutter, Osmo oil, etc :shock:"
You're lucky - I looked at a few bits of wood when i was about eleven and it cost me bloody thousands. :lol:

 

[JJ1]

You're lucky - I looked at a few bits of wood when i was about eleven and it cost me bloody thousands. :lol:

LOL

 

[BearTricks]

I did the same with a mid century danish sideboard. Someone had clearly bought it to upcycle, done a terrible job and then dumped it at the charity shop. When we bought it it was a fiver, and the label on it said "thing".

After buying a new sander, chisels, clamps, some nice wood to replace the top and some stain it cost me twenty times what I paid for it just to make it look acceptable. At least the TV isn't on the floor now.

 

[MattRoberts]

My first question is; Is it ok to use 6mm MDF for the loose tongues, instead of the ply tongues often used?

Are you referring to loose tenons, such as biscuits or dominos? I'll assume you are, in which case MDF is not a good material for any loose tenon joints. You ideally need a hardwood. Biscuits and dominos are often made from beech.

If you are referring to a long thin tongue across the whole length of the joint, I don't know why it would be loose as opposed to a tongue in the oak and a groove in the ply?

Do I have to be concerned with where to apply glue and tongues or is wood movement of the edges not an issue.

No, not really. If your centre panel is veneered ply, you don't need to worry about it moving. The oak edging may have some small movement, but it will always be outward from the centre of the table and therefore should be more or less even across all edging

Please excuse my poor illustration, but in the image above, the light purple is where I am intending to use a loose tongue. Does that look right? Should I also insert a tongue (dark purple) to attach and glue the short and long edges together or will that prevent the short sides from expanding and contracting across their width?

I would recommend concentrating on joining the edging to the centre ply, and not to each other (so light purple but not dark purple). That way the overlapping edging is free to expand, but still attached firmly to the inert centre panel)

 

[custard]

My first question is; Is it ok to use 6mm MDF for the loose tongues, instead of the ply tongues often used?


Do I have to be concerned with where to apply glue and tongues or is wood movement of the edges not an issue. Please excuse my poor illustration, but in the image above, the light purple is where I am intending to use a loose tongue. Does that look right? Should I also insert a tongue (dark purple) to attach and glue the short and long edges together or will that prevent the short sides from expanding and contracting across their width?

You don't have to be concerned with movement, MDF doesn't move and 60mm wide lipping is too narrow to cause problems.

MDF tongues are no where near strong enough for your purposes, try snapping a piece with your hands and you'll understand why, you need a decent quality ply tongue.

The biggest potential problem is 60mm Oak lipping on a veneered MDF top. MDF doesn't have a lot of structural integrity where as Oak has plenty. Think about it this way, sooner or later someone will sit on the edge of the desk, their weight will bear down on the edge of the Oak lipping (which cantilevers out in space), the lipping therefore acts as a 60mm long lever transferring that load to where the lipping is attached to the MDF top. That's the big problem that needs to be designed out.

You should think about the following options,

1. Adjusting the dimensions of the top to make sure the lipping rests directly on the legs and top rails to provide support. Looking at the photos this might already be the case, but double check because if it's not the case the desk won't survive long.

2. If t's not the case then reduce the width of the lipping significantly so it doesn't offer so much leverage.

3. Or, use a deep, strong, plywood tongue

Good luck!

 

[JJ1]

Are you referring to loose tenons, such as biscuits or dominos? I'll assume you are, in which case MDF is not a good material for any loose tenon joints. You ideally need a hardwood. Biscuits and dominos are often made from beech.

If you are referring to a long thin tongue across the whole length of the joint, I don't know why it would be loose as opposed to a tongue in the oak and a groove in the ply?

I didn't have wide enough pieces of oak for the edges, hence wouldn't have had enough width to cut a tongue from that. Originally I was going to buy some biscuits and a biscuit cutter for the router but decided a 6.4 mm Groover would be a better and easier option. It'll also be useful to have for any future projects.

No, not really. If your centre panel is veneered ply, you don't need to worry about it moving. The oak edging may have some small movement, but it will always be outward from the centre of the table and therefore should be more or less even across all edging

OK, got it.

Please excuse my poor illustration, but in the image above, the light purple is where I am intending to use a loose tongue. Does that look right? Should I also insert a tongue (dark purple) to attach and glue the short and long edges together or will that prevent the short sides from expanding and contracting across their width?

I would recommend concentrating on joining the edging to the centre ply, and not to each other (so light purple but not dark purple). That way the overlapping edging is free to expand, but still attached firmly to the inert centre panel)

Will do.


Many thanks for your help, it's much appreciated

 

[JJ1]

Hi Custard,

Thank you very much indeed for your help and advice.
You raise some important points that I hadn't considered and would certainly have caused me issues with the strength of the joint, especially as I was considering making the desktop a little longer and wider than it was originally. As it is, it's the solid edges which are supported by the frame of the desk. If I had of gone ahead with making the top larger, then the edges would have been weak and unsupported as you pointed out. Phew! Good job you mentioned that.
I will go ahead and use ply for the tongues as you advise.

 

[Jacob]

A suitable case for Fablon. Fill the lifted bits and just stick it on.
Or - plane edges square, stick on faced ply or formica to cover the whole area and then stick a thin facing edge all round.

I quite like cheapo furniture like this and it's a challenge to up-cycle as it was built to a very low standard all round.

 

[JJ1]

A suitable case for Fablon. Fill the lifted bits and just stick it on.
Or - plane edges square, stick on faced ply or formica to cover the whole area and then stick a thin facing edge all round.

I quite like cheapo furniture like this and it's a challenge to up-cycle as it was built to a very low standard all round.

It's a bit late now Jacob as I've already bought everything for a new top


Formica?? I'm trying to make it look better, not worse :? Fablon?? I'm not sure sticky backed plastic was quite to my taste for this old, oak desk, but each to their own :roll:

 

[MattRoberts]

Of you don't have a domino, I'd personally get the wolfcraft dowel master and dowel the edging on. Much stronger than a tongue and groove in this instance

 

[JJ1]

I have a dowelling jig but I'm not confident of getting completely accurate positioning of the dowels. I would need quite a lot for the long edge and it would only take one of them to be a fraction out and I'd be stuffed. I did consider dowels originally but with no side to side margin for error, I dismissed it in favour of false tongues.