Clamping mitred carcasses. Any tips on closing the gap?

[flanajb]

I have just made a small bathroom cabinet using 18mm birch ply and mitred the sides together. I used a domino to joint it up, but I really struggled to get it to pull together tightly and there is a gap. I used cascamite so should be ok, but what is the trick and can you get this to work with just sash cramps?

 

[Steve Maskery]

Mitres are tricky o clamp up. I'm not sure that sash cramps are the right type of clamp. You need to get pressure directly across the joint.
One way is to use parcel tape, it's stretchy enough to pull the boards together.
Another way is to make 4 rebated strips that sit over the corners and strap them together with ratchet straps (like for a car roof-rack). I'm sure others will be along with other ideas.

 

[marcros]

I like this method. I am not a fan of band clamps. https://goo.gl/images/HmHJpW
https://youtu.be/u5xQcO1D5g8

 

[flanajb]

Mitres are tricky o clamp up. I'm not sure that sash cramps are the right type of clamp. You need to get pressure directly across the joint.
One way is to use parcel tape, it's stretchy enough to pull the boards together.
Another way is to make 4 rebated strips that sit over the corners and strap them together with ratchet straps (like for a car roof-rack). I'm sure others will be along with other ideas.

Thanks Steve. On reflection I'd agree that sash clamps are not the correct clamp. The ratchet straps would have definitely been the way to go as like you say the pressure would be acting across the joint rather than 45 degrees to the joint. I suspect 3 of these would have pulled the miter up perfectly :-( Too late now, but a lesson learnt for next time though.

Thanks

 

[flanajb]

I like this method. I am not a fan of band clamps. https://goo.gl/images/HmHJpW
https://youtu.be/u5xQcO1D5g8

That's an interesting approach but I think the ratchet strap idea would have worked a treat.

 

[dzj]

A dry run or two before glueup is also useful. Diagonal rods come in handy too.

 

[Yojevol]

Here's my preferred method:-

45º blocks glued on and carefully removed after the mitre joint is stable.

Brian

 

[peter-harrison]

I use the spring clamps which you put on with a special pair of pliers. If it's a solid wood, unpainted piece I stick scraps of timber next to the joint to protect it. You can get a surprising amount of force to bear on a joint, and can keep adding clamps until they run out. The trouble with using sash cramps apart from the weight and bulkiness is that if you need to rally crank them up, you end up bending the pieces, and then all your angles etc are messed up.

 

[Woodmatt]

I made a home made version of this which works really well https://www.axminster.co.uk/veritas-4-w ... amp-475309

 

[Inspector]

I've used all the methods shown and the temporary blocks glued to the corners with clamps across the corner is the surest method. Similar is to glue those blocks to a piece of plywood or solid that is just short of the length of the sides. Clamp them to the centre each side. Then clamps across each corner. No glue to clean up.

If you are bent on using ratcheting straps then you need something like these to apply pressure where needed.
http://www.leevalley.com/us/wood/page.a ... 3838,55979

Pete

 

[johnnyb]

If you can't see the edges I like joiners dogs(or there painted) with maybe glue blocks if it a deep carcass.

 

[custard]

A lot depends on what materials you're working with. If it's solid timber then pretty much anything goes and temporarily glued on cramping blocks will give the very best result.

However, mitre jointed carcasses tend not to be made from solid timber. MDF or veneered panels are far more common, and for them a glued on cramping block is a non starter as it would risk damaging the show surface upon removal. The best options in these circumstances are either heavy duty and stretchy tape or some kind of webbing strap. The best strap based cramp that I've used for carcasses is the one from Lamello,

https://www.youtube.com/watch?v=Uqm22bDU2Eo

If you're a hobbyist making a one off then the tape based method is perfectly adequate, but it's too slow for production purposes which is where the Lamello or equivalent would be first choice .