making "beech" (etc) block counter top - gluing and clamping

[julianf]

This sort of stuff -

Im wanting to make some sheets out of smaller bits of reclaimed mahogony. So ill prep all the parts, but then im wondering how its clamped and glued?

I cant think (in a production environment) that each strip is glued end to end, then thicknessed, before all the strips are glued? Im thinking that they must all be done together, but then you need multiple clamps in the (if youre looking at the photo above) horizontal plane, and then a few in the vertical also.

How would you advise i do this? Im not wanting to make massive sheets or anything, but i may as well do it in the most sensible way.

 

[doctor Bob]

you will need to finger joint all the end grain to end grain joints otherwise it will just pull itself apart.
Block tops are mass produced on expensive machines.

https://www.youtube.com/watch?v=PPpV707hY6o

 

[julianf]

Thank you.

I just went and looked in my own kitchen... certainly no finger joints on the worktop there. But that's kind of a red herring really. Im not wanting to make kitchen counter top, i was just using that as an example.

I made a test part a while back with the majogony blocks. I guess my parts will be somthing like 160mm x 50mm x 20mm thick, and ill be wanting to make them into "sheets" no larger than about 300mm x 600mm x 20mm.

Im hoping that the(relatively) stable nature of old mahogony will make my life a bit easier. My test part seems pretty strong.

 

[Phil Pascoe]

You'll probably be able to see the finger joints if you look at the edge - they won't show on the surface.

 

[julianf]

...i know. I could take a photo, but, really, as i said, thats a red herring anyway. I was using it as an example.

It was suggestions as to clamping that i was after.

 

[rafezetter]

...i know. I could take a photo, but, really, as i said, thats a red herring anyway. I was using it as an example.

It was suggestions as to clamping that i was after.

It may well be that the outer run of the worktop uses blocks with no finger joints as they are somewhat ugly.

As for clamping I think you might struggle a bit as small blocks tend to slip around with glue on them, keeping them properly aligned so you don't end up having to do a lot of planing to bring the top (at least) flat again isn't an easy ask.

I have heard of a tip where sprinkling salt into the glue surface just before placing the two glued faces together helps reduce or even eliminate that tendancy to slip, but I've never tried it myself to verify this - apparently the salt provides enough mechanical grip to stop slipppage.

Other way would be to make a box frame larger than the size you need, laid out on a known flat surface that's been waxed and cut the pieces to fit, and use a caul across the width to clamp row by row.

It'll be right messy too

 

[dzj]

Once I had some time on my hands and a lot of off cuts, so I glued them all up in 2 x 0.3m panels. Pine/ Spruce...Not much to look at, but worked well for shelves, dividers and such. Utilitarian stuff.
No finger joints, just staggered, glued and clamped. I used a melamine particle board (covered with plastic wrap) to layout all the glued up pieces. I also attached a batten along one edge to align the pieces and also to help clamp everything together.
2 opposing surfaces of the off-cuts were planed (for glue up), the other 2 surfaces were just off the table saw. When the glue dried, I ran the whole panel through the thicknesser.

 

[julianf]

For want of a better plan, i could weld up a quick frame, and tap two faces for M8 bolts or similar.

But then ill end up with the parts bowing up if i put too much pressure on them.

I saw little point in normalising the thickness of each part prior to gluing, as im only really interested in one face, and ill need to thickness off some at the end. I figured id just loose more and more stock if i started thicknessing the faces too early, but maybe that would be the way to do it - that way i could put a plate on the whole thing and weight it down before tightening up the frame screws.

Maybe im over thinking this, and i could just use some of those light weight clamps, like the IRWIN etc. ones. I only have metal ones here, and theyre just so unweildy for small jobs.

Above is an example. The purple line is what im wanting as my finished part. The blue lines are my blocks (i said 50x150, but i think 40x190 will work better, and thats what is in the preview.


I want to do a few of these. Similar, but not identical designs.