Buying wood - thickness of board

[starlingwood]

When buying boards how much thicker do you go? With oak being so expensive I've considered this, for my next project I need several oak boards 2m long and 35mm thick, I have bought 52mm thick American white oak boards, the next size down was 38mm so it seemed a no brainer but is there a rule of thumb?

 

[Droogs]

Depends on if it is rough sawn or par and what conditions it is stored in at the yard. rough sawn 52 is what you want to as you should take an equal amount off each face and leave the board just over size by a couple of mm an then leave it to acclimatise aetc before final sizing and using. If it is PAR and has been kept inside then 38mm is fine if you are going to use it fairly soon other wise is may move/warp etc an no longer be usable at the required thickness but only much thinner.

just a very rough guide

hth

 

[starlingwood]

Depends on if it is rough sawn or par and what conditions it is stored in at the yard. rough sawn 52 is what you want to as you should take an equal amount off each face and leave the board just over size by a couple of mm an then leave it to acclimatise aetc before final sizing and using. If it is PAR and has been kept inside then 38mm is fine if you are going to use it fairly soon other wise is may move/warp etc an no longer be usable at the required thickness but only much thinner.

just a very rough guide

hth

Yes always sawn, if I was to spec PAR I would probably ask for the finished thickness or near as.

 

[Jacob]

Rule of thumb is 6mm over.
For short lengths this might be excessive, for longer bendy lengths it might not be enough by the time you've straightened it, so it also depends on your cutting list.
PAR is usually described as "ex" whatever it was planed from. e.g. 25mm sawn, ending up typically at about 18mm planed but called "ex 25mm"
If you plane your own sawn timber you can usually get a better thickness than bought PAR because you are cutting to length before you plane

 

[Doug71]

It's always best to try and design things around standard sizes/thicknesses. As said generally allow about 6mm to be planed off a rough board. If you could get away with 32/33mm finished thickness instead of 35mm for your project you could machine it out of 38mm saving quite a bit of money, time and bags of wood shavings.

 

[recipio]

Ouch .. you are wasting 17 mm thick wood with every board. I would only buy 52 mm because I have a Hammer bandsaw and would rip it down to about 40 mm + 12 mm, You will always find a use for a piece of 12 mm thick wood.!