Timber length through a PT

[StevieB]

I have been using the Axminster CT150 6" joiner and 330 thicknesser to convert rough stock this weekend. Taking some 1" oak and bandsawing in half, a 5ft plank showed considerable bowing when cut - fair enough with thin stock and released stresses etc. Last time this happened I just ran the stock over the jointer to flatten one face, but given it is so thin you have to push it flat to the table to get it to pass over the cutter head, and when you release it you have a planed face but with the bow still in place. Same with the thicknesser, the rollers push the timber to the table, plane the face and the bow remains when when it comes out the other side. To try and overcome this, this weekend I tried shortening the length of the stock first before doing the jointing and thicknessing. Cut the 5ft plank in 2, to give planks of 2'6". this reduces the bow, but with 12mm stock still gives the above problems - going down to 9mm finished size I still do not end up with perfectly flat thicknessed stock. Its 9mm all the way down, but with a small bow still.

So is there any way to get perfectly flat thin stock - am I doing anything fundamentally silly? Can you only get it right if the original stock has no stresses relieved when initially cutting on the bandsaw so the rough stock starts of flat? Seems daft that you spen a fortune on 1" planks, only to cut them down and find they are useless due to internal stresses. Also seems daft to have to plane down a 1" plank a bit at a time from both sides to get a final 9mm plank - when cutting in half first then thicknessing gives me two 9mm planks.

since this is for a jewellery box, which will have a final length of approx 30cm, the bow across 30cm is minimal to negligable, but if I wanted a longer length at 9mm thickness it would be a problem. Just curious as to whether this is a common occurence, whether people just ignore it and accept it or whether I am doing something daft/have incorrectly set up tools/bad technique?

Any advice appreciated!

Steve.

 

[9fingers]

1. Dont press down to take the bow out.
Flatten the concave side by taking a bit off each end
2. Rough cut to length first

Depending on how well your machine is set up, you might want to allow for cutting off any snipe when rough cutting.

hth

Bob

 

[StevieB]

1. Dont press down to take the bow out

I try not to, but I find with 12mm stock its extrememly difficult, if not impossible, to put enough pressure on the timber to run it over the jointer without taking the bow out - especially if you use a long hold down pad. Too loose and the cutter head 'chatters' the timber, too hard and you joint the bow. I think perhaps I just have bad technique!

Steve.

 

[9fingers]

If possible use two pads and as soon as you have some of the stock on the outfeed table, apply the pressure there and push lengthwise on the infeed side only. Wax the tables to reduce friction.
Take very fine cuts once you are nearly flat and take out any chatter.

Yes I'm sure it is technique but don't beat yourself up over it! Play with some scrap until you are comfortable with it.

Some of the problem can be the guard getting in the way but I'm not saying remove it naturally.

Bob

 

[stuartpaul]

I don't think you've got a problem at all.

If you didn't press down on the bow by the time you finished taking the bow out of 9mm timber you'd have 1mm thick timber!!

Using almost the same kit I never overcame similar issues. Can you still use the wood with clever jointing? Or having it 'braced' by other parts of the box?

Occasionally you will get a piece of timber you just can't rescue.

 

[9fingers]

I don't think you've got a problem at all.

If you didn't press down on the bow by the time you finished taking the bow out of 9mm timber you'd have 1mm thick timber!!

Using almost the same kit I never overcame similar issues. Can you still use the wood with clever jointing? Or having it 'braced' by other parts of the box?

Occasionally you will get a piece of timber you just can't rescue.

That is why it is normal to cut roughly to length before planing.

I can't think of any application (so far!) where a straight length of 5' long and 9mm thick would be needed and would not be braced by another component of the final product.

Bob

 

[StevieB]

Bob - you're a genius! You have just prompted one of those flashes of insight which I get all too rarely. Of course I don't need a 5ft length of 9mm timber - so why on earth am I trying to generate one?! I have been tending to follow the rule of keep it as long as you can as long as you can without thinking about downstream consequences. Your comments, although probably obvious to most people, I am ashamed to say I had not really considered before. Deciding on component length and cutting slightly longer before preparing is much better than trying to do a whole plank then cutting all the components from it. I made a small step down the right pathway by cutting it in half, just not the next step of deciding on component length

You may well have just stopped hours of frustration on my part! Thanks for taking the time to answer such a noddy question

Steve

 

[Ironballs]

Like Bob says, if you have a 15mm piece of timber with a 5mm bow in it then you've already lost that thickness to just sorting out the bow - on one side, never mind the hump on the other

 

[9fingers]

Bob - you're a genius! You have just prompted one of those flashes of insight which I get all too rarely. Of course I don't need a 5ft length of 9mm timber - so why on earth am I trying to generate one?! I have been tending to follow the rule of keep it as long as you can as long as you can without thinking about downstream consequences. Your comments, although probably obvious to most people, I am ashamed to say I had not really considered before. Deciding on component length and cutting slightly longer before preparing is much better than trying to do a whole plank then cutting all the components from it. I made a small step down the right pathway by cutting it in half, just not the next step of deciding on component length

You may well have just stopped hours of frustration on my part! Thanks for taking the time to answer such a noddy question

Steve

Steve, Questions are not daft or noddy when you don't know the answer.
Keen on asking.
Only too happy to help!

Bob