thicknessing by machine

[marcros]

This is a basic question, but I am going to ask it all the same.

I know the practice- you plane a face flat, square a side, and that flat face is the reference that sits on the thicknesser table. The timber then sits square, and the thicknesser removes from the top, leaving a section that is parallel to the reference.

If, hypothetically, for example, I had planed a couple of 5" pieces, but not quite squared them. Hypothetically :wink: they may not have glued up great, giving a larger board that is not quite flat, but has a slight pitch to it. Now, I will probably just flatten the high spot by hand (too wide for the planer).

What would happen if I was to put this into the thicknesser planed (but not quite flat) side down... take a couple of swipes of the rough, non planed top surface, turn it over and take a couple off the pitched surface, and turn it back. I have plenty of thickness on this to work with, and enough width that I could square both sides afterwards.

Any thoughts?

 

[Teckel]

I'm sure it would be fine if you had plenty to play with

 

[No skills]

With the tiny amount of playing around I've done with a thicknesser I found that if a cupped board would sit flat on a bench/worktop (convex side up) with no rocking then I could run it through with the convex side up and take some off (few passes) make a flat area then turn it over and start taking off material from the other face. One bit I tried that rocked from one corner to the other would plane unevenly.

Now I have literally only spent a day messing round with a thicknesser and what I did might of been luck, hope an experienced forumite will be along soon.

 

[RogerS]

I would rip down the joint, square the boards up and reglue them.

 

[marcros]

that was my alternative option. I will have a look at what it is like later on and decide.

 

[Mark A]

I would rip down the joint, square the boards up and reglue them.

I had to do this with some reclaimed pine floorboards I had bought for a blanket chest last year. Sanding or planing them flat would have taken too long so I ripped them into narrower strips and reglued, arranging them so that the grain alternated as I went along. They haven't warped yet so it must have worked! [-o<

 

[custard]

What would happen if I was to put this into the thicknesser planed (but not quite flat) side down... take a couple of swipes of the rough, non planed top surface, turn it over and take a couple off the pitched surface, and turn it back. I have plenty of thickness on this to work with, and enough width that I could square both sides afterwards.

Any thoughts?

Is your question, is it possible to accurately thickness a board when you don't have a completely true reference face?

The answer is a qualified yes. If the board's too thin the feed rollers will flatten it out and then it'll spring back when it emerges with the same convex/concave problem. And besides, if the degree of convexity/concavity is too great you won't have a sufficiently thick board when it's been eventually flattened. But providing you don't fall into either of these traps then you're good to go. You might want to take the highest spots off with a hand plane first, and in any event take light cuts in the thicknesser until you've established a true face. Probably also worth putting pencil lines across the board so you're really clear about where the thicknesser is removing material, if it's cutting across the full width of the convex face on the first pass then you know the rollers are squashing it flat and it won't work.

If however you do decide to rip it back down and start again then be aware that ripping a cupped board brings it's own problem. I don't want to teach granny to suck eggs, just to say there's a significantly increased kick back risk with a cupped board.

 

[RogerS]

He hasn't got a cupped board by the sound of it.

 

[custard]

He hasn't got a cupped board by the sound of it.

Isn't it effectively cupped due to innacurate jointing?

 

[RogerS]

Not in the same sense that you and I know as a cupped board.

He has got two flat boards but with edges that are not square to the face. So there are no stresses down that joint line at all. He can rip away to his hearts content.

 

[marcros]

Not in the same sense that you and I know as a cupped board.

He has got two flat boards but with edges that are not square to the face. So there are no stresses down that joint line at all. He can rip away to his hearts content.

Roger has described the situation as I had it.

I had a look in the llght of day and they were not as bad as I had them in my mind. I managed to take a couple of swipes with a hand plane and then thickness them down Whilst not of exhibition quality they will do for the workbench.