Thread: To use or not to use biscuits in laminated table top

Last glue up the centre stand from 66x66, thicker on the bottom 300 than the top part. I ran out of glue faaark but had another old bottle down the shed, a bit gluggy but still liquid so hopefully ok

centre glue up.jpg

Do you think they apply much up/down pressure?

Ive some Frontlines and they clamp like crazy.

These scissor ones look excellent.

By simple mechanics, at 45 deg on the scissors, the force will be distributed 50/50 give or take a little friction loss. So with glue-ups below 20mm thick, downward pressure can become an issue. However an extra clamp or two vertically will fix.
Jacko
Ps a detailed dwg of the clamp mechanism would be appreciated

Originally Posted by woodPixel

Do you think they apply much up/down pressure?

Ive some Frontlines and they clamp like crazy.

These scissor ones look excellent.

Yes they do apply good pressure, but like any clamp, if the surface is not exactly flat (i.e. the boards are exactly the same), then they will apply more pressure to the largest board. These were all dressed boards but come from different lengths and I didn't redress them. All it takes is a small grain/splinter of something on the clamps and they become uneven. These will be turned flat though after gluing so my only concern is that the glue holds.

Originally Posted by jacko

By simple mechanics, at 45 deg on the scissors, the force will be distributed 50/50 give or take a little friction loss. So with glue-ups below 20mm thick, downward pressure can become an issue. However an extra clamp or two vertically will fix.
Jacko
Ps a detailed dwg of the clamp mechanism would be appreciated

Yes the angle will affect the clamping force and these will only work for 30-300mm thick. If I was worried about the any lack of force I would drill more holes in the scissor plates to change the angles.

I have no drawings, but the scissor plates are 250 long and from 40x6, and the aluminium blocks are from 50x25. The bolts/thread rods are all 10mm. At the screw arm end that has 2 blocks (can be clearly seen in last photo) the first block (nearest to the handle) is threaded the entire length of block for the threaded rod and threaded side ways to for small bolts to connect the scissor plates. The second block has a 10.5mm hole into a larger vertical hole that locates a nylon nut, this allows the thread to turn but the block stays in the same position relative to the threaded rod (i.e. as threaded rod extends through the threaded first block and moves forward, so does the second block). At the second scissor at the other end, the block has a 10.5mm holes sideways for the bolt between the scissor plates, and therefore can pivot and move vertically but is fixed horizontally. All the scissor plates have nylon washers against all moving surfaces and a number of metal washes to act as spacers to ensure they act in a straight manor and do not bind against each other or the main RHS beams. The two aluminium blocks that apply the pressure must extend beyond the scissor plate otherwise the interfere with the boards being glued up, which in most cases are fine, but in the glue up of the smaller boards I used timber block extensions between the aluminium blocks and the boards.

I hope all this makes sense.

Have a look at the video link I provided above, my mechanisms are similar but just out of aluminium and sizes adjusted to suit my application. The same author also put out a second video showing some improvements although I did not need them for my application.

I used packing tape on all components that came in contact with any glue I did not want to stick, but in hindsight I should have been more careful with the application, as it only takes a fold in the tape to impact on the levels of the timbers. In my case where everything is turned and surfaces made level, it will not impact at all, except some glue lines may vary in thickness but hopefully not noticeable.

I will be leaving these glue ups for at least a week before turning them to ensure the glue os fully set. The last glue up is 264x264 square and 600mm long so it will take time for the glue to set in the middle. The turned shape will vary from 250 down to ~100 and so even some of the inner joints will be exposed.

I placed the glue-ups on top of each other for the photos. Nothing turned as yet, I have to wait ~ a week to ensure the glue is completely set, I don’t want any pieces coming apart on the lathes. They look awfully chunky, but that is because they are all larger than required to allow me to turn them down to size. For my clamps to squeeze the pieces all together I have also glued in extra “filler” blocks that will get turned away.

table1.jpg table2.jpg table3.jpg

Good work Neil!!

Originally Posted by dai sensei

I placed the glue-ups on top of each other for the photos.
They look awfully chunky,

table1.jpg

for an "industrial look" you could just clean up the squeeze out and call it done.

Finally finished them
final tables 1.jpg final tables 2.jpg final tables 3.jpg

More details in a WIP here Laminated Pine Bedside Tables WIP