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1400mm plywood table substrate - one piece or accept join?

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1400mm plywood table substrate - one piece or accept join?

Postby RogerM » 20 Sep 2018, 11:51

I'm about to make a start on a circular dining table which ideally needs to be 1400mm diameter and 25mm thick. It will be veneered both sides with home cut veneers which will be about 2mm thick. This is significantly larger than can be cut from the standard width sheet that is 2440 x 1220. You can get sheets that are 3050mm x 1525mm, but they are not readily available, and the PRICE! I guess that is partially because there is 50% more material in it apart from the lower demand.

So - how about joining a strip onto the standard width with dominoes? There could be a double staggered line of 6mm dominoes. The maximum width of the extra piece would be 180mm, but that would taper to nothing quite quickly when I cut it circular. My guess is that the join would be strong enough, but would the join line show through a 2mm veneer?

Alternatively I could get a large 3050 x 1525mm sheet of 12mm ply, which is about the same price as a 2440 x 1220 sheet of 25mm ply, cut it in half and glue them together to make a half sheet of 24mm ply. Probably use about £20 worth of Cascamite, but probably doable.

Any advice on offer please? Any option that I'm missing?
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Re: 1400mm plywood table substrate - one piece or accept joi

Postby Robert » 20 Sep 2018, 12:09

1 sheet of ply is enough for your circle with 1 join line where the end offcut goes on the side.

Why not stagger layered joins with a 1/4" ... 1/2"....1/4" sandwich? No edge joins needed. Glued and vacuumed together.
Last edited by Robert on 20 Sep 2018, 12:10, edited 1 time in total.
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Re: 1400mm plywood table substrate - one piece or accept joi

Postby RogerM » 20 Sep 2018, 12:30

Robert wrote:1 sheet of ply is enough for your circle with 1 join line where the end offcut goes on the side.

Why not stagger layered joins with a 1/4" ... 1/2"....1/4" sandwich? No edge joins needed. Glued and vacuumed together.


:eusa-think: Or maybe 2 layers of 12mm hardwood or birch ply, with the added offcuts on opposite sides? Would be very much cheaper than using large sheets. I'm going to need a bucket of Cascamite for the veneering anyway .........
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Re: 1400mm plywood table substrate - one piece or accept joi

Postby Robert » 20 Sep 2018, 14:29

I'd be interested in knowing more about 'home cut' veneering as it is something going through my head at the moment.

Thinking about surface finishes for glue side and face and how good each needs to be....and how you achieve it.
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Re: 1400mm plywood table substrate - one piece or accept joi

Postby RogerM » 20 Sep 2018, 16:39

Robert wrote:I'd be interested in knowing more about 'home cut' veneering as it is something going through my head at the moment.

Thinking about surface finishes for glue side and face and how good each needs to be....and how you achieve it.


Not sure I'm the best one to take you through this Robert. "Woodbloke" is the king of veneer cutting around here. However I have had modest success. I start by thicknessing my stock on the planer thicknesser to give me 2 parallel smooth sides.

Then I cut a 2.5 - 3mm veneer using a high fence on the bandsaw. I treated myself to a Jet 16-32 drum sander a little while ago, and I use that to smooth the cut face of the stock between each pass using 160 grit, although I think Rob uses 80 grit.

Once I have cut all the veneers I need, each piece has one smooth side and one sawn side, so I now take these through the drum sander in one batch without changing the thickness setting so that they all come out with the same thickness.

Before I had the drum sander I used a sled to take the veneers through the p/t, but it's a bit fierce, and no good if there is any curly grain.

In both cases I finish the veneered surfaces with a random orbital sander, going up through the grits as usual.
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Re: 1400mm plywood table substrate - one piece or accept joi

Postby Robert » 20 Sep 2018, 16:56

Thanks.

The drum sander was the missing step in my thinking.

I have tried before with a sled with some success but it will not work for the size I'm thinking of now. May try a few cuts and see what the sawn face looks like. Might get away with the ROS for finishing.
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Re: 1400mm plywood table substrate - one piece or accept joi

Postby Woodbloke » 21 Sep 2018, 13:23

RogerM wrote:
Not sure I'm the best one to take you through this Robert. "Woodbloke" is the king of veneer cutting around here. However I have had modest success. I start by thicknessing my stock on the planer thicknesser to give me 2 parallel smooth sides.

Then I cut a 2.5 - 3mm veneer using a high fence on the bandsaw. I treated myself to a Jet 16-32 drum sander a little while ago, and I use that to smooth the cut face of the stock between each pass using 160 grit, although I think Rob uses 80 grit.

Once I have cut all the veneers I need, each piece has one smooth side and one sawn side, so I now take these through the drum sander in one batch without changing the thickness setting so that they all come out with the same thickness.

Before I had the drum sander I used a sled to take the veneers through the p/t, but it's a bit fierce, and no good if there is any curly grain.

In both cases I finish the veneered surfaces with a random orbital sander, going up through the grits as usual.


Rog and I have nattered about this at length on the dog n'bone, and that's pretty much the plan, but I just use the standard fence on the big Ax bandsaw. There are a couple of obvious things to check, first and foremost that you use (especially for deep sawing) a brand new blade and that the bandsaw set-up is spot on, I use the Alex Snodgrass method; video on UToob. Second and foremost, take it very, very slowly! No need either to go for a wide blade; I use a 1/2" 3tpi Diamond Ground blade from Ax which is utterly fandabby but for really good results, you need to crank on the tension to max.

IMG_0452.jpg
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These are some 3mm thick Brown Oak veneers cut last year for my Wenger desk. They were glued to some 18mm ply, with backing veneers of 4mm Euro Oak so the total thickness of the top was 25mm. All of those veneers came out of a single board, which is one of the advantages of using thick, chunky veneers - Rob
I no longer work for Axminster Tools & Machinery.
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Re: 1400mm plywood table substrate - one piece or accept joi

Postby Robert » 21 Sep 2018, 16:14

Thanks for the extra tips.

I just bought a new M42 3tpi 1/2" blade from Tuff Saws and took my time setting it up. I'll try a slow cut with higher tension when I get to trying it out.
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Re: 1400mm plywood table substrate - one piece or accept joi

Postby Woodbloke » 21 Sep 2018, 18:02

Robert wrote:
I just bought a new M42 3tpi 1/2" blade from Tuff Saws and took my time setting it up. I'll try a slow cut with higher tension when I get to trying it out.


M42 is good stuff but very thick so you may not be able to crank it up to the required tension. I've got a 19mm wide M42 blade which I'm reserving for my stash of Bog Oak when the time comes to slice it up for veneers - Rob
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