Fire door offcuts - how to join ?

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Stuartgb100

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I have several offcuts from 1 hour fire door blanks.
These are all the same thickness, either 45 or 50mm. Cannot recall at the moment.
They vary from 75 to 250mm in width.
They are approximately 2400mm long.
The construction seems to be 2/3/4mm plywood on both faces,
with a softwood core of small laminated sections.

I plan to use these to make up infeed/outfeed tables for a radial arm saw.

Just wondering how you would joint everything together.

Thanks.
 
I’m certainly no expert here but I think I’d be sandwiching them in between two sheets of 9 or 12 mm ply or mdf - I can’t imagine there is much in the way of solid material to join to. As long as there not varnished or laminated you could easily arrange them close to your dimensions, plenty of pva and anything heavy to place on top- once dry just trim to your desired dimensions.
 
I’m certainly no expert here but I think I’d be sandwiching them in between two sheets of 9 or 12 mm ply or mdf - I can’t imagine there is much in the way of solid material to join to. As long as there not varnished or laminated you could easily arrange them close to your dimensions, plenty of pva and anything heavy to place on top- once dry just trim to your desired dimensions.
Thanks for that.
I was thinking that I could cut a slot in each section - say 7mm wide by 20mm deep, and then machine a long fillet - say 5mm thick and 35mm wide.
Then clamp sections together using heavy weights to keep it all true.
Obviously this would need a true/level bed to work from.
Does that work, do you think ?
thanks.
 
Hi Stuart
I can't see any reason why it won't work, I've laminated sections with loose tongues in that way many times though not fire door offcuts.

There is a proviso. You need to trim down the lengths to make sure the mating surface are trued to 90° otherwise it will be almost impossible to get it flat, you can do that on your table saw but a better finish is using a router. Instead of loose tongues a biscuit jointer if you have one works well also
 
Thanks Lons.
Your point regarding the mating faces is, of course, crucial.
I think I'll trim the faces using my table saw with an 80 tooth new blade.
I should get a pretty smooth finish that way.
I'll also mark each piece with 'F' for the leading end,
and 'T' for the upper face.

When cramping up, I'll make sure that the boards alternate such that the 1st piece has 'T'
facing upwards, the 2nd has 'T' facing downwards.
in this way, there should be a perfect fit, even if the saw blade is not perfectly at 90 degrees to the table.

Cheers.
 
If you alternate them as you describe it's important that you also alternate when you cut the slot otherwise if you're a fraction out you won't get a flat surface.
I don't agree with Jacob, I've done it and it's easy enough, just fiddly the only question is if it's worth the effort. Certainly if you can get hold of some free or very cheap larger offcuts that would always be a better option.
 
Thanks for the replies.
I think that I'll give it a go.
It's only my time, and the offcuts were foc anyway.
I'll machine it all up and then do a dry fit to see how it looks.
Cheers.
 
You could consider kitchen worktop bolts to pull the sections together and then overlay with a thin sheet of mdf.

Good luck.
 
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