Kitchen worktop clamps - I feel that I'm missing something?

[julianf]

This is for my own kitchen, not a commercial job -

We have beech block counter top from Wickes. 29mm thick.

I need to join this at the corner. I've routed the joint in an acceptable way to me, and will consider adding biscuits also, but I just don't understand the clamps.

The pack from, I think, Screwfix rhat I have are 20mm "deep".

So, if I position these on the center line, the wood above them will only be 4.5mm thick?

I found another random clamp in my workshop that measures 16mm which seems better (leaving 6.5mm above, if I put it on the center line) but I still am doubting if I'm understanding this correctly.

The joint in question is the one below. It's not 90 degrees, if that makes any difference at all.

I have a router and a biscuit jointer, but no router jigs (however I can cnc cut a jig from alloy if it's considered essential)

Thank you.

 

[Doug B]

Something’s amiss with your corner post, as for the worktop clamps just don’t let them fully into the thickness of the worktop. If you’re concerned about them sticking down into the cupboard below trim them with an angle grinder.

 

[julianf]

Something’s amiss with your corner post, as for the worktop clamps just don’t let them fully into the thickness of the worktop. If you’re concerned about them sticking down into the cupboard below trim them with an angle grinder.

So it's not required to put them on the center line then?

I had some vision of the joint bowing if the force was offset, but I guess that probably won't happen?

The post is in the wrong place. It needs to be on the other side, and a 6" wine rack style thing in the hole. It's position is from an earlier test layout.

Thank you.

 

[julianf]

Ps

What thickness of wood would you suggest I should keep above the clamp?

Or is it really just a case of clamping on the lower edge?

 

[julianf]

I've found a Q&A with trend where the advice is to cut 28mm deep recesses in a 40mm top, for use with their 16mm clamps.

Ie they are advising to run the clamp on the center line.

Which seems sensible. I'm just unsure of the protocol for my 29mm worktop?

 

[DBT85]

You got any spare bits kicking around you can play with?

The bolts are long enough that it shouldn't be a major issue if rather than insetting them 20mm they are only inset 15mm. That force is getting transferred through the remaining material in a cone shape just like a normal clamp

The hole you make also doesn't need to be perfect. I once had to drill one out using nothing but a spade bit on a drill and it worked out fine. A complete pain in the backside to do it that way though mind!

 

[weekend_woodworker]

I joined some bits of oak work top in a similar way to make a desk top for my daughter longer. I used a template and cut just deep enough so the bolts didn’t stick out the bottom. I used my router to cut some biscuit slots so the surfaces lined up nicely. It seems to be perfectly sold like that.

 

[julianf]

You got any spare bits kicking around you can play with?

The bolts are long enough that it shouldn't be a major issue if rather than insetting them 20mm they are only inset 15mm. That force is getting transferred through the remaining material in a cone shape just like a normal clamp

The hole you make also doesn't need to be perfect. I once had to drill one out using nothing but a spade bit on a drill and it worked out fine. A complete pain in the backside to do it that way though mind!

Sorry, I think you might be mis understanding my problem.

It's not the thickness to the joint that I'm worried about. It's the remaining material on top of the metal.

Ie between the top of the work surface and the void cut into it below.

(Thank you regardless!)

 

[DBT85]

Sorry, I think you might be mis understanding my problem.

It's not the thickness to the joint that I'm worried about. It's the remaining material on top of the metal.

Ie between the top of the work surface and the void cut into it below.

(Thank you regardless!)

That's what I mean, if you cut a 20mm hole in 29mm worktop you've got 9mm left but your bolts will sit flush with the underside. Just cut them 15mm deep and it'll work fine.

You seemed concerned that if the bolt was not on the vertical centreline of the joint that it would cause a problem. My point was that owing to the length of the bolt, the clamping action is radiating out in such a way that the bolt being set lower down would not cause a problem, while giving you now 14mm of material left on the top. If the bolt was shorter and therefore the clamping distance is shorter then the cone of pressure eminating from the clamping action does not become as large.

If you're happy with onyl 9mm thickness on top then set the bolts in the full 20mm. Don't worry about them being on the vertical centreline.

 

[Doug B]

So it's not required to put them on the center line then?
.

Well unless you’re willing to have a very thin section above the bolt you’re not going to be getting the bolt in the centre.
Personally I’d let the bolt in 19mm so it left 10mm above the bolt, if you’ve got a good joint it will pull up nice, it’s not like you’re gluing the joint.
If you are having to apply the sort of pressure with the bolts that causes any bowing you need to be reassessing your joint, the bolts should just nip the two joining surfaces together but not prevent lateral movement, I tend to fit 100mm x8mm dry dominos on the loosest setting to aid alignment & prevent up & down movement whilst still allowing lateral movement.

 

[julianf]

Thank you both. I feel more at ease with the situation now.

Am I right in thinking that I should NOT glue the joint, as the grain directions, hence movement, are not aligned?

I don't have a domino cutter, but I do have a biscuit cutter. Should I add biscuits? Without glue?

Thank you all once again.

 

[Doug B]

No glue on any parts.

 

[Racers]

The bolts only hold the edges togther you don't need much clamping force, a couple of biscuits/dominos are a must.
I slather the joint in danish oil before fitting sealse it up a treat.

Pete

 

[Lons]

I averaged around 10 kitchens a year over 18 years as part of my business plus several of my own over a much longer period the majority of which were standard melamine or hardwood and the rest solid surface and granite. For the wood and chipboard I always installed clamps inset just enough to be flush with underside surface, any deeper and you'll have difficulty tightening them up anyway. They're mainly only to hold the joint together while the glue sets and don't need to be overtightened though I note Pete and others don't use any glue which is fine although personally I've never had a single call back for any of my glued joints cracking or separating. If the joints don't clamp up square that's because they aren't cut properly.
Worktop jigs come with a cut out to enable you to route the correct shape usually for 3 clamps across a standard worktop.

I'd add that I'm not saying there's a right or wrong way just what has worked for me on my own and commercial installations over many years so just my twopennerth from personal experience.

 

[Racers]

On solid wood I oil the worktop before fitting so the glue probbaly wouldn't stick, thats why I use what ever oil I have used.

Pete

 

[DBT85]

Thank you both. I feel more at ease with the situation now.

Am I right in thinking that I should NOT glue the joint, as the grain directions, hence movement, are not aligned?

I don't have a domino cutter, but I do have a biscuit cutter. Should I add biscuits? Without glue?

Thank you all once again.

I've had to partially dismantle a few kitchens before now and if the joint had been glued it would have been a PITA to get that bit of worktop out. There is also just little need. The clamps will hold it.

The biscuits are just there for alignment so again glue isn't doing anything. I never used any but I'll be honest and say I only ever actually needed to do about 5 proper joints. Lons probably did more in a month!

 

[TheTiddles]

I’ve only ever fitted one set of kitchen worktops, however if it was chipboard I’d say glue is essential. The builders who did all the houses here didn’t, water gets in the joint and swells the chipboard up, you then have no choice but to replace them

fasteners on the centreline would be ideal, but they’re only there to pull the joint together, so if you are starting to bend the joint by compressing the material you’ve probably got another problem going on

Aidan

 

[Lons]

On solid wood I oil the worktop before fitting so the glue probbaly wouldn't stick, thats why I use what ever oil I have used.

Pete

Ah right Pete, Whilst I always glued the joints I also treated the hardwood tops first to stop glue sticking on the surface.

 

[planesleuth]

Hello. I have been manufacturing kitchens for 40 years and fitted many a worktop in my time. We didn't generally make the worktops however. Laminated and timber worktops all have their own quirks and the biggest problem prior to jointing is bowing over the width of the joint, that's why we never, ever used biscuits. Always use silicon and not glue because we never found a single worktop that matched its partner in thickness. Even a few thou. out is enough to let standing water in. With reference to your worktops. They are mass produced and thin staved. The likelihood of movement within the timber now and into the future is high, that's why you use silicon with no biscuits. The two surfaces have to be allowed to move and you must be prepared to periodically sand the joint smooth again and re-oil once it has moved. This is the nature of the material and you must accept this. It's all about moisture contents and the original timber selection within the worktop (which will be minimal). The best advice would have been to ensure that the worktops are acclimatised to the room before installation.

 

[Jetset]

I’ve only ever fitted one set of kitchen worktops, however if it was chipboard I’d say glue is essential. The builders who did all the houses here didn’t, water gets in the joint and swells the chipboard up, you then have no choice but to replace them

fasteners on the centreline would be ideal, but they’re only there to pull the joint together, so if you are starting to bend the joint by compressing the material you’ve probably got another problem going on

Aidan

Glue on the biscuits (if any)?