Turning plywood. A couple of queries

[jonbee56]

I've been given about half a sheet of very good quality 1" beech faced ply, so I thought that I would try segmented turning. I cut it into 9" strips & then into octagons before gluing 4 of them together rotating each one a few degrees.
Stupidly I forgot to take photos at the beginning.

The initial cutting and gluing worked out excellently, but it was just that bit tricky mounting it to be true in each dimension (vertical/horizontal/plumb)

I am also finding it difficult to get any type of even finish. I realise that I am turning against grain in every different direction as well as layers of PVA all at the same time & its a right bugger. I gave up on HSS chisels once it was roughed out & purloined the carbide tipped ones that belong to the mrs. The plywood just trashed the edge of the HSS tools too quickly.
The timber appears pitted, but not evenly. I know why as when I am working with the grain the cutter cuts easier than the neighbouring "end grain".

I am also finding that even though the ply is good quality, there are still empty voids where the timber layers dont quite meet. I don't like the idea of twin pack filler , but I don't seem to have much choice.

Another mistake in my initial construction is that I found that with a depth of 4" (aiming at 3" deep inside), I am finding it difficult to hollow out as I do not own a bowl rest. Maybe I will cut 1" off the bottom to make it easier on the 1st attempt


So just a couple of questions here:
Am I missing a trick turning with/against the grain/PVA and how anyone else is overcoming this problem.
What technique is being used to create an overall flat finish as sanding the surface only seems to increase the peaks and pits.
How about filling the voids? Is there a product that gives a decent finish. How about a clear epoxy compound?

(I have glued another 3 ply layers together so will look at adding those photos and also current progress over the next few days) )

 

[Dalboy]

The only time I have turned ply I used the very top grade of ply which has not got any voids in it once you come down from this grade I personally find it is not worth it. There are so many grades of ply. How many layers has it got
Yes I found that you have to make extra trips to the grinder when cutting it.

This is the ply I turned and you can see how close the layers are. To give an idea of scale the ball is 4"

 

[duncanh]

Have you ever come across aviation plywood? Impressive stuff, with 2 plys per mm and no voids. I used to use it for making boomerangs but it's expensive and the best place I could find for it was a mail order company in Germany

 

[Mar_mite]

I'm not much if a turner, but if it was me, I'd get it close to the shape you want with your chisels. Then finish it off with very coarse sandpaper glued to a board.

 

[JandK]

In the latest issue, issue 281 of Good Woodworking magazine is an article by Les Thorne about turning a plywood bowl.

 

[jonbee56]

Thanks for the replies guys,
Theres 11 layers of ply so I thought it would be fine enough, but I will research aviation ply ( thanks duncanh) and see where I can obtain a wee bit as a sample. I dont usually pick up the monthly magazines but will check this one out (& thanks JandK).

The problem with sanding, either course or fine, is that sanding 'with' the grain abrades more of the surface of that layer, than sanding on 'end' grain so the peaks and troughs tend to be accentuated. Saying that, I think I will try gluing the sandpaper to a board (thanks mar_mite) to give a stiff backing. I've tried without the board and the sandpaper does tend to heat up really quickly, so I will be careful not to scorch either surface -or my fingers-.

Still, its such a shame to make a set of workshop shelves out of such a decent material.

I think I will investigate and persevere some more

 

[J-G]

Thanks for the replies guys,
Theres 11 layers of ply so I thought it would be fine enough, but I will research aviation ply

I think I will investigate and persevere some more

If you want to guarantee that there will be no 'voids' then you will have to make sure that you get Marine plywood to BS1088 which is made from Okoumé (Aucoumea klaineana).

Bear in mind that solid Mahogany/Sapele etc. is likely to be cheaper. ie. using plywood is not necessarily a cost saving option!