To mitre or not to mitre. . .???

[Maceman]

Please can I have some good advice??!!!

I have fitted my ikea kitchen and have always planned to have a chippie fit the worktops for me. I now have various people suggesting different approaches.

The worktops are IKEA Numerar Birch Block 38mm thick. The kitchen is U shaped and requires to joins.

I bought enough worktop to join diagonally across the corners, but everyone I've spoken to has said not to do it and to join at 90 degrees.

One camp are saying to fully mitre the joins and bolt together.

The other camp are saying to just butt the tops together, bicuit and screw from underneath.

I have booked someone to come next Monday to mitre them, but could cancel and go with someone else.

Please, please, please can someone tell me which is best???

Thanks!!

Maceman

 

[joe-90]

The best way to do it is the way Ikea do it.

If you look at the worktop you will see that it has a very fine bevel.
For the female cut you use a circular saw (good one) to just cut off the bevel (using a straight edge for guidance), or a router if you have one. It's just a thin sliver.

Then using a very sharp chisel you cut into the end of the sawcut at 45 degrees. This gives you are very slim female mitre cut (just 2 - 3 mm depth).

For the male section you literally just par off the corner at 45 degrees to match the female section.

You end up with a very tiny mitre joint.

Then I'd biscuit ( to stop the cupping) and screw plates underneath (not china ones, mind)

 

[Scrit]

Then I'd biscuit ( to stop the cupping) and screw plates underneath (not china ones, mind)

And in time the joint would fail as you are trying to joint end grain and long grain - so I'd advise against using glued biscuits and instead use loose ones with conventional joiners which will allow the joint to move. All surfaces must be thoroughly sealed (oiled) before assemvly and a bead of silicone will seal the joint as well. Trade joiners tend to allow for wood movement to avoid expensive call-backs in the future

Scrit

 

[joe-90]

Then I'd biscuit ( to stop the cupping) and screw plates underneath (not china ones, mind)

And in time the joint would fail as you are trying to joint end grain and long grain - so I'd advise against using glued biscuits and instead use loose ones with conventional joiners which will allow the joint to move. All surfaces must be thoroughly sealed (oiled) before assemvly and a bead of silicone will seal the joint as well. Trade joiners tend to allow for wood movement to avoid expensive call-backs in the future

Scrit

Where does it say glue in the post I made?

Read what's there - not what you think is there.

 

[big-all]

Then I'd biscuit ( to stop the cupping) and screw plates underneath (not china ones, mind)

And in time the joint would fail as you are trying to joint end grain and long grain - so I'd advise against using glued biscuits and instead use loose ones with conventional joiners which will allow the joint to move. All surfaces must be thoroughly sealed (oiled) before assemvly and a bead of silicone will seal the joint as well. Trade joiners tend to allow for wood movement to avoid expensive call-backs in the future

Scrit

Where does it say glue in the post I made?

Read what's there - not what you think is there.

heeelllooo joe hows it going

you are of course right you did not say glue
but to be fair to scrit he didnt have a go at you he just suggested an appropriate action for the situation as he read it albeit slightly wrongly

i wished i made as few "reading" errors as scrit

 

[Scrit]

Joe

If you screw plates underneath you will NOT allow the wood to expand and contract UNLESS you either use undersize screws with round heads(so that they are loose in the hole) OR you file-out the holes to make them oval/oblong OR you can find flat plates with oval slots already punched in them (I can get right angle ones from loads of places, but not flat ones - unless I resort to using a hammer to flatten angle plates.....). With respect you OMITTED to mention this in your response.

As to not reading what is there, dude, by implication wooden dowels and wooden biscuits are designed to be used with and are NORMALLY used with (i.e. by default unless OTHERWISE stated) GLUE to make a permanent bond, therefore to mention using biscuits you would be taken by most woodworkers as IMPLYING the use of glue. When giving instructions in an assembly shop to trained joiners/assembly workers the OMISSION of glue would always be SPECIFICALLY STATED. You were not specific and OMITTED to mention this exception to normal practice, whilst I did specifically state GLUED BISCUITS. Happy now?

The use of a loose spline and conventional worktop fasteners allows the joint to move with time, although I generally use a fixed (flat repair type) plate as well under the front of the joint. I've installed several dozen hardwood worktops this way over the last 8 or so years and I've yet to have a joint fail.

Another question is this - exactly how will two or three biscuits stop cupping? If the worktop is acclimatised before installation, properly sealed and correctly attached to the carcasses (using sliding screws or wooden buttons (as in a traditional hardwood table) how or why will it cup?

Scrit

 

[davecooper]

Can I hijack this post a little as it is very close to my situation. I have just joined my worktops and was forced into using a full corner mitre because access to the clamps would have been near impossible with a straight joint in either direction. I used biscuits but still have a very small level difference in the middle (less than the thickness off a sheet of paper), but the front and back are perfectly flush. Is this common with this type of joint and is it ever likely to become a problem?

 

[joe-90]

Joe


Another question is this - exactly how will two or three biscuits stop cupping? If the worktop is acclimatised before installation, properly sealed and correctly attached to the carcasses (using sliding screws or wooden buttons (as in a traditional hardwood table) how or why will it cup?

Scrit

They may not be fastened correctly. 3 or 4 biscuits glued one side only will help stop the cupping (if they are not fastened correctly). This is DIY forum - the people fixing worktops are not time-served tradesmen. They want a bit of help to get a decent (if not perfect) job. This isn't the place to be pedantic.

 

[Scrit]

I used biscuits but still have a very small level difference in the middle (less than the thickness off a sheet of paper), but the front and back are perfectly flush. Is this common with this type of joint and is it ever likely to become a problem?

That sounds as though your worktop material is slightly bowed across the width. I reckon that fully one in three of the laminate worktops I've installed are cupped across the width and/or warped in some way and lower-price solid wood worktops appear to fare little better (IKEA, are you listening?), however, with solid wood you do at least have the option of planing/scraping or as a last resort even belt sanding to get the joint level. I try to orient the bow so that it is upwards, leaving just a single high spot to get rid of) and I carry a block plane, a couple of scrapers and a belt sander in my installation kit to deal with this in much the same way as I would true-up a mortise-and-tenoned door. You need to work with the grian away from the joint taking very fine shavings - for this a block plane with an adjustable mouth is really the best tool, although a cabinet scraper (much cheaper) will do an excellent if somewhat slower job. If your joint is dipped in the middle then I'm afraid there's little you can do to correct it.

BTW, did this bow occur after you'd installed the top, or was it apparent at the time you installed?

Scrit

 

[Scrit]

They may not be fastened correctly. 3 or 4 biscuits glued one side only will help stop the cupping (if they are not fastened correctly).

Explain, please. My limited professional experience is that a good many worktops are cupped across the width at delivery - the thinner the top the more likely they are to be bowed - and that providing they are acclimatised to the house and properly sealed they will not move substantially in service. That being the case it can be easier to orient the worktops in such a way that the bow is upwards leaving the installer with only one high spot to deal with (rather than two which you'll get if the bow is downwards). This high spot can be taken down in a variety of ways (see my previous post)

Oh and another reason for using a loose spline instead of a biscuit is that a biscuit is made from compressed, super-dry beech. This means that they will tend to swell in the presence of moisture (plentiful enough in a kitchen) and lock the joint, even without glue being present. They can also "telegraph" through to the surface as a lozenge shaped depression if you are unwary enough to glue in place then sand the surfaces almost immediately - the moisture in the PVA glue can cause the wood fibres to swell, you sand away then the moisture is absorbed and the fibres return to their original shape leaving a "shadow" depression on the surface. Not common, but it does happen......

This is DIY forum - the people fixing worktops are not time-served tradesmen. They want a bit of help to get a decent (if not perfect) job. This isn't the place to be pedantic.

And you'd know all about that, dude. Ask an experienced tradesman or craftsman how to do a job and if he/she chooses to tell you they'll like as not tell you how to do the job correctly rather than how to bodge it. I fail to see how knowing how to do a job properly and explaining is pedantic - or are we going to have another interminable MDF argument here?

Scrit

 

[mr_mike]

Hello Scrit

Did you receive my email ? Just wondered if you knew a good supplier
for Mafell....am after an AD160 planer/thicknesser in the New Year...

Thought you might be the man to know !?

Apologys all for hijacking the post

 

[davecooper]

BTW, did this bow occur after you'd installed the top, or was it apparent at the time you installed?

Scrit[/quote]

It was apparent straight away at the time of installation. Had I known then I would only have biscuited the ends and probably used some sort of plate underneath to pull the centres flush. Still, I can live with it, its just that annoying feeling that I could have done a better job as I am sure many DIYers know. Just out of interest, will this ever become a problem?

 

[joe-90]

or are we going to have another interminable MDF argument here?

Scrit

Chill out fella. Never use MDF.

The guy wants a simple and easy way to sort out his worktops.

 

[Scrit]

Never use MDF.

Go back to knitting the fog, dude......

 

[Scrit]

It was apparent straight away at the time of installation. Had I known then I would only have biscuited the ends and probably used some sort of plate underneath to pull the centres flush. Still, I can live with it, its just that annoying feeling that I could have done a better job as I am sure many DIYers know. Just out of interest, will this ever become a problem?

The only way I've ever seen to counteract this effectively is to rout a stopped dovetail housing (i.e. a dovetail shaped trench or groove) across the underside of the worktop from the rear (stopping short of the front) with a stair trenching bit then make-up a dovetail-section hardwood batten to insert into the housing from the back - a bit extreme for my tastes, but used in some modern solid pine furniture from Austria and appears to work well (see the books by Franz Karg if you are interested).

I suspect that the thinner worktops such as Ikea and Screwfix's 28/30mm ones are more prone to this than the 38/40mm ones such as Junckers, et al. As I said the best thing with these thinner tops is to let them acclimatise for a day or two before installing, then instal with the bow (if any) uppermost and proud, at least then you stand a chance of planing/scraping/sanding the high spot out. If you try too hard to stoip timber moving it has a tendency to do things like split, so I'm not in favour of constraining it too much. I'd also make sure that everything is sealed thoroughly, too. At this stage your worktop is probably too far gone to correct, but I'd say that it will probably not get any worse with time providing you sealed the faces/edges properly (you did give it 3 or 4 coats of oil before assembly didn't you?) and give it the occasional feed of oil

Scrit