Bowed timber

[user 19915]

Hi any one know a good video on how to remove a bow in a piece of wood using a thickness er planer or a little bit of advice please
Mock

 

[marcros]

first, cut it roughly to your final dimension, in length. This should minimise the work that needs doing.
second, flatten one side on a planer.
third, run it through the thicknesser until flat.
forth, take material from both sides, down to final thickness, by flipping it over and passing through thicknesses, flipping it back etc.

 

[blackrodd]

Cut close to final length, check for grit etc or risk damaging you're cutters, check for knots especially dead or damaged ones as they can cause problems, going off like a bullet and wind the bed down as clogged shavings can throw the timber off and come out of control, as well as leave a nasty lumpy finish
With the ROUND side down, and going in the same direction as the grain, feed the workpiece in to the cutters.
NEVER pass you're hands over the cutters, and Never feed with the hand into the cutters,
This man shows exactly how not to face and edge timber, by not keeping pressure on the timber on the second, Outfeed table, and those silly pads are useless, But the gadget gang have seen the dodgy americans using them, so they go and buy them.
If they make you feel safer, then carry on, but the best idea is what I was taught above don't push into the cutters, feed with the other hand, either in front on the outfeed table, or behind you.
When flat, Assuming you have checked the fence for square, shoot the edge in much the same manner, ensure the cutter guard does cover the cutters, and pinkies are safer.
Clear out and set the thicknesser bed for the thickest part and plane down the same side, until that side is all planed.
You now need to plane the "face side" lightly, for finish, and taking into account the amount taken from the second side using the thicknesser, try and "equalise" the amount taken from each side to balance the timber left, this will help, but not prevent future movement of the timber,
You wont need any Ovaltine tonite after that lot!
Take you're time and be careful!
regards rodders

 

[Jacob]

Yep round side down.
I'd hold it down with pressure in the middle of the board from a push stick, and poke it along with another push stick at the near end but without pressing down and altering the trim - press down in middle only
If the board is very bent/twisted your first cuts will be from the middle and extend towards each end with each cut.
There's a very good reason for this procedure - the middle of a regularly bent or twisted board will be approx co-planer with the best finished flat surface you can get from the board, so if you keep to that plane you remove least waste.
NB hands never nearer to the cutters than the length of a push stick

 

[PAC1]

You can straighten a board on the planer either round side up or down. I was taught round side up such that on the first pass you plane the ends of the board. However it depends upon the length of your planer table and your technique. If the planers in feed table is short say half the length of your piece of wood then you are better going round side down as if you work round side up you are simply following the curve and not straightening the wood. It can be done round side up but you have to compensate for the tendency to follow the curve by planing one end until the cutters no longer cut, lift the board and pull it back to the start position again and cut again. Repeat this two or three times then turn the board around and do the same at the other end before running the entire length over the cutters.
If the piece of wood is shorter than the infeed table I still prefer round side up as you have better control and do not need to worry about not rocking the plank as can happen with round side down.
Once you have a flat face as others say to the thicknesser and once the board is parallel alternate faces to final thickness

 

[whiskywill]

I have some boards which are cupped across their width which I think can be sorted in my thicknesser. I assume putting the hollow side down would be the way to start flattening them. Am I right?

 

[blackrodd]

I have some boards which are cupped across their width which I think can be sorted in my thicknesser. I assume putting the hollow side down would be the way to start flattening them. Am I right?

You need to face and edge the timber first.
Most of the shape will be retained just using the thicknesser, the rollers will probably try and flatten it, if thin enough, only to return to the same shape when it comes out the end.
I have to say i'm surprised how some people haven't quite got the idea on facing and edging.
After you have cut to length, If it helps, draw a line down through the hollow side on the edge of the work piece, showing the 2 ends need taking down to meet the middle, making it flat, if this is outside, not the fence side, you can keep an eye on it, after each pass.
Facing the round side down needs some experience as to where exactly to start, and also stop the facing operation.
It is all to easy to end up with planing to the finish size and still have areas of "hit and miss" making the timber of no use in its present length.
Again, draw a straight line down the length, and use that as a guide, if needed.
On u tube I can never recall any demonstrators even looking at the grain, a very important factor, as when it "tears out" another pass is needed, the right way round, to give a decent finish, some don't even keep pressure to the outfeed table and a gap can be seen, which is not straightening at all.
Regards Rodders

 

[user 19915]

Thank,s for all your help i.m pleased to say iv,e done it thank,s again
Mock

 

[harvestbarn]

How do you decide how much oversize you need to resaw to allow for all this planning?
Do you ever use a flat Sledge with hot glued wedges?

 

[Benchwayze]

If you are going to start with the bowed side upwards, then fix the board to a stable piece of 25mm MDF and pass it through the thicknesser until flat. (You might need some packing under the board to stop it flexing. ) When the upper side is flat, remove it from the 'jig', and then thickness it, using the planed side as reference. I find it easier, (albeit long-winded) to flatten the cupped side first.
If it's a bad bow, then I would cut the board into shorter lengths to use for the shorter components; assuming it's for a project where grain orientation etc, isn't an issue. Obviously there needs to be enough meat to sink the retaining screws deep enough to avoid the cutters.

Hmmm! I missed harvestbarn's post. So I repeated what he said! Oh well never no mind!

HTH

 

[harvestbarn]

I have made a sledge with two 18mm sheets of MDF glued and screwed together and then glued a stop on the end. This avoids having to use screws, wedges are then hot glued to make the bowed timber firm. It is heavy as I made it the full width of my thicknesser so in and out table roller supports are needed. Have not actually used it much as only just made it.

Yesterday I went back to some of the methods above on the planner but you do seem to end up reducing the thickness rather a lot. This is why I enquired how much experienced operators allow at the resaw stage when bow is a little evident but seems to amplify once cut. Could be I should remove the slight bow before re_saw in?

 

[Jacob]

....
Yesterday I went back to some of the methods above on the planner but you do seem to end up reducing the thickness rather a lot. This is why I enquired how much experienced operators allow at the resaw stage when bow is a little evident but seems to amplify once cut. Could be I should remove the slight bow before re_saw in?

You don't know how much bow you are going to get until you start so it's guesswork. The rule of thumb is to expect to lose 6mm overall (3mm each side/edge) to get to finished size - more for longer finished lengths. So what you can do is set aside straight pieces for long lengths and save bent pieces for shorter lengths.
The sledge idea is not good and makes the job unnecessarily difficult.
Whatever you do DON'T plane anything until it is cut to size/length (plus 6mm etc). An exception to this would be if your design involves a lot of short/narrow components in which case you could combine them into a larger piece to be sawn down after planing to finished size.

 

[Benchwayze]

Well there's nowt to stop you striking a line along the lowest point, and then band-sawing the waste away, Not so much hairiness when you plane the face side, prior to thicknessing; which is a case of going on 'til the job's a good 'un.

You could even take a scrub plane to the ends first.

 

[Jacob]

Well there's nowt to stop you striking a line along the lowest point, and then band-sawing the waste away,.....

Except with already sawn boards it's a lot easier with a plane (hand or machine)

 

[Benchwayze]

Well there's nowt to stop you striking a line along the lowest point, and then band-sawing the waste away,.....

Except with already sawn boards it's a lot easier with a plane (hand or machine)

You could always make a bow and arrows! :mrgreen: