Warped Panel

[woodbloke]

I bookmatched some elm the other night, planed it flat and edged jointed it....this is for the back panel for my Elm Cabinet II. Taking it out of the cramps this morning I've found that both the bits are no longer flat but have warped so the shape now resembles a very shallow 'S'...trouble is I had to rebate all round to fit the frame. The long grain was not a problem, but how would be interested to hear how you would put the rebate, (which needs to follow the shape of the warped panel) across the end grain. The panel is only 9mm thick so there wasn't much to play with in the thickness. I have managed to put in the rebate, with a lot of fiddling about, but I'd like to see if anyone would do it the same as I did just now, no pics I'm afeard 'cos I have no picture imaging device at the mo' - Rob

 

[p111dom]

Personally I would have sandwiched the warped piece between two panels of 18mm ply held together with as many clamps as required to force the panel flat. Careful placement and measuring would mean I you could run the router against the ply as a guide.

 

[woodbloke]

...which is pretty much how I did it except that I used a curved caul to get even pressure right the way across the panel and I cramped it to the top of my bench, which is 75mm thick beech so it's not going anywhere. Even so it was quite difficult to set it all up so that the router cut the rebate accurately. I suppose the way to ensure that the panel didn't warp would have been to make it out of some quarter sawn stock, both of these bookmatched panel pieces were crown cut - Rob

 

[p111dom]

Personally to try and avoid this I tend to try and not leave panels in the cramps over night. In the workshop or garage there's a big change in temperature and sometimes humidity from day to night and this can sometimes guarentee a warp. With titebond I find I can remove the cramps within the hour and I've had no problems machining after 3. I try and make the frame and panel in one day, glue it up and then store it inside. If you keep the changes in temp and humidity within as close a range as possible it gives the wood a chance to settle in that position. I buy my stock from the same source which I know has a very low moisture contect already. I have never acclimatised the wood in the house for weeks on end before machining but by machining and assembling asap and getting the piece back in the house for the night I have never had a problem with warping.

 

[devonwoody]

My chevron box, I am bringing all timbers for its construction indoors after each operation in the shed. Just done 2 hours out there at 5C and can fell the damp.
BTW I have piched the wifes camera to take out to the workshop these days, £30 job, does 3M pixels and perfectly good enough for PC display use. And not to much lost if dust gets at the camera.

 

[woodbloke]

Personally to try and avoid this I tend to try and not leave panels in the cramps over night. In the workshop or garage there's a big change in temperature and sometimes humidity from day to night and this can sometimes guarentee a warp. With titebond I find I can remove the cramps within the hour and I've had no problems machining after 3. I try and make the frame and panel in one day, glue it up and then store it inside. If you keep the changes in temp and humidity within as close a range as possible it gives the wood a chance to settle in that position. I buy my stock from the same source which I know has a very low moisture contect already. I have never acclimatised the wood in the house for weeks on end before machining but by machining and assembling asap and getting the piece back in the house for the night I have never had a problem with warping.

My shop is heated, fully insulated and is constantly dehumidified so I would hope that any changes in the interior environment could be kept a minimum. That said, the conditions in the 'shop may well have changed overnight causing to panel to warp. I don't know how dry it actually is as it's airdried stock...I tend to avoid kilned timber like the plague if I can, so I don't really know how dry the timber is. Again, it's crown cut elm which will warp and twist and the drop of the proverbial, regardless of how dry it is. I guess I was a little bit too keen to get on with it and didn't leave enough time for it to fully condition. Anyway, the panel is pretty much done now, all I have to do is to tidy up the rebate with the big LN shoulder plane to make it fit the groove, then it's time for polishing and the glue up...will post some pics when I get the camera back from the menders - Rob