flattening wood

[adrian]

I've been trying to flatten rough boards 4 ft long and 5-8 in wide. And I think think things could be going faster and better. My original technique for this was to deliberately make the board concave along its length by taking cross-grain shavings and then to try to fix it by taking shavings of increasing length along the grain at the ends. I was trying to refine my technique by using the stop shaving method presented in the Charlesworth DVD.

But I still seem to find some strange things going on. And I wonder if the stop shaving technique actually works on a board 4 ft long with a #7 plane. I have a board on the bench now with a recalcitrant bump in the center that I can't seem to remove. The straight edges say it's there but the planes don't want to touch it if I take shavings along the length of the board. I tried marking a plane length region around the bump and taking stop shavings and the plane basically won't cut even though there's a bump there.

And then there's the matter of twist. These boards seem to be twisted by about .05 inches along their length. What procedure is best for removing the twist. In the Charlesworth DVD he says to take stop shavings up to the low points. This didn't seem to work very well. And indeed, I notice that he says in his book that for "very long stuff" a different approach is required. I'm not sure what the threshold for very long is, but it doesn't appear that the different aproach is explained in the book. (I don't have time to search the DVD just at the moment, but I don't remember an approach for longer timber being given there either.) I've been planing diagonally from high spot to high spot, but this seems to upset flatness in all the other directions.

Is there any reference you would suggest that covers the task of flattening a board in great detail starting from rough? (I just read Christopher Schwarz book on Workbenches where he more or less says to just plane it this way and that way and it'll be flat. That's not what happens to me.)

 

[dunbarhamlin]

Hi Adrian
If the other face of the board is concave, try putting card shims under the center before planing away your bump. It could be the board is flexing under the plane. (A concave bench can have the same effect.)
Do the same thing for your wind. I find using my winding sticks to map out the area of wind and then using stopped shavings over that area does the trick.
Expect someone better experienced will be along after the birds stop twittering.
Cheers
Steve

 

[Wiley Horne]

Good idea by Steve. Also check to see whether the sole of the No. 7 is concave--specifically, is the mouth in the air. There are three things interacting--the board, the bench, and the plane's sole.

Wiley[/url]

 

[Philly]

Adrian
Steve has some good points, there. If the board flexes are you plane it it will never get flat so make sure you support any high points on the underside.
Rob Cosman has a good dvd on this subject, Rough to Ready. Worth a view!
Another thought - what kind of shavings are you taking? Really fine or thick? When first roughing out the board its is worth taking a heavy shaving to get the surface quickly into shape - then come back with the jointer set for a finer shaving.
Wiley's point about the condition of the sole is very important if you are trying to take stop shavings as per David Charlesworth instructions.
Hope this helps
Philly

 

[David C]

Adrian,

Well done.
You are discovering some of the difficulties of longer boards, and the importance of the whole under surface being well supported on the bench. If this cannot be arranged by planing then shims of paper card or whatever, will be very useful.

I often work on both surfaces alternately, reducing the gross errors until the underside sits firmly on the bench. Shims or wedges are vital for this work. Only then can the precision work on the top surface can begin.

Steve and Wiley are both spot on, the plane sole could well be an issue, depending on make.

The dvd is a demonstration of the easier problem of perfecting a board which is about plane length or 1 1/2 times plane length. Width of board up to about two times plane width.
On longer boards I do not plane hollow till the plane stops cutting, just till there is a hollow of a sheet of paper's thickness, about 0.1mm. (Clearly a No 5 plane is capable of producing a large hollow in an 8 foot edge!)

Unfortunately this is difficult to judge without a longer straight edge.

Wind can also be tricky, as it could all be in the last or first foot of length.

Here I would use the centre of the board as a datum and check wind every foot of length. It is then removed where necessary, Not with full length half stop shavings.

Another point worth noting is that long boards tend to remain somewhat flexible and don't often need the same degree of precision as a door stile.

Hope this helps,
Best wishes,
David

 

[David C]

Rob Cosman's Rough to Ready dvd is good for your problem and I think you will find Chris Schwarz's take somewhere on the popular woodwork site.

His dvd Coarse Medium and Fine would also be relevant.

David

http://blog.lostartpress.com/#
http://www.woodworking-magazine.com/blog/

 

[adrian]

I've been shimming the work so I don't think flexing of the work explains my difficulty in removing the bump.

The long planes I have are a Clifton #7 and a Veritas bevel up jointer. I think the Clifton has a couple thou depression around the mouth. The Veritas isn't perfect either, but I think it's closer. (I can measure these again...) But I don't think these flaws in the planes are enough to explain my difficulty. The bump I can't seem to cut is much higher than that (more like 50 thou or maybe more).

I've been taking 3-4 thou shavings, which probably isn't the best for being really fast. But to do much thicker I think I may need more camber. And if the shavings aren't too thick I have more opportunity to catch errors before they grow large. The boards seem to be fairly close to flat already, about 1/10 inch of deviation, so in principle 25 shavings in the right place would do the job. (The first board I ever flattened started an inch thick and was meant to have a final thickness of 1/2". But it was thinner than 1/2" in places when I finally declared it flat.)

Fortunately I have a straight edge as long as the wood I'm working, at the moment. I've been generally aiming for about a tolerance of about 0.1 mm along the 4 ft length.

Is there an adaptation to planing wide material (more than 2 times plane width)? I'm at more like 4-5 times plane width, and I have noticed the development of an excessive hollow (cup). This I can handle by planing across the grain. Right now I my board is crowned from side to side, and planing across the grain doesn't help this. (I suppose I could attempt cross grain stop shavings.)

After some contemplation, I don't think wind can be localized if the board appears flat in length and width as tested by the straight edge. (The entire shape of the board is determined by its four corners, in this case, and the wind is necessarily uniform over the whole board.) This would seem to get at the question of the proper sequence. I can't test for wind until I have a well defined surface (side to side) to lay the winding sticks on. And it's got to be at least somewhat flat in length or the winding sticks wobble. (At least mine do.) But your comment that the wind could be localized suggests to me that you don't wait to look for wind until after flattening in length, which I believe was the sequence described for smaller work.

 

[Paul Chapman]

Hi Adrian,

If your bench top is flat, Rob Cosman shows a neat dodge to find out where the high spots are. Turn the board over and rub it in a circular pattern on the bench top. You will find that the high spots show up as slightly shiney patches on the board's surface. I've used this dodge a few times myself and found that it can be helpful in the sort of situation you are experiencing. Once you've identified the high spots, plane these with a shorter plane before returning to the #7 jointer.

Cheers :wink:

Paul

 

[Karl]

Hi Adrian

My thoughts, for what they are worth.

I have been planing some 8' long planks of oak - some 8" wide.

I quickly realised that most of the work is done by eye - I don't think it is possible to take the methodical approach you outlined in your OP. By "eye" I mean regularly checking with a long straight edge and winding sticks. Taking out a bit here, and a bit there, until it looks reasonable. Then clean up with the Jointer.

For long pieces (certainly the ones I am working on), being accurate to within a few thou isn't necessary, and you must work out what you consider to be acceptable tolerances.

HTH

Cheers

Karl