Why is my white oak warping as soon as I cut it?

[Billy Smith]

I bought some white oak lumber three weeks ago. I've just started milling it for a project. I began with a piece 4/4 thick about

6 in. wide and 50 in. long. It was farily straight and flat. I cut it into two pieces each 3 in wide. I jointed one face and one edge so they were perfectly straight and flat. I then resawed it with my bandsaw to reduce the thickness to a little more than 3/4 in. But a minute later I noticed that the smooth, jointed face was badly bowed (convex)! I repeated the operation with the other 3 in. wide piece and the same thing happened.

1) Why is this instant warping happening?

2) What can I do to avoid it? If this keeps happening I'll have to throw out all the wood I bought.

A little more info: The wood was dry when I bought it and has remained dry while in my garage (3 weeks). My garage is dry and varies between 40 and 65 degrees F. I don't know how long since the wood was cut for lumber. I don't notice anything unusual about the wood. The jointed surfaces look very good.

[Andrew Barss]

Billy Smith wrote: : I bought some white oak lumber three weeks ago. I've just started : milling it for a project. I began with a piece 4/4 thick about : 6 in. wide and 50 in. long. It was farily straight and flat. : I cut it into two pieces each 3 in wide. I jointed one face : and one edge so they were perfectly straight and flat. I : then resawed it with my bandsaw to reduce the thickness : to a little more than 3/4 in. But a minute later I noticed : that the smooth, jointed face was badly bowed (convex)! I : repeated the operation with the other 3 in. wide piece and : the same thing happened.

Sounds like case hardening, where the wood was dried too fast. This makes the outside hard and dry, leaving moisture inside. When you resawed, it exposed this moister inner part, which then caused the warping (did it warp toward the dry side)?

The other possibility is the wood had inherent internal stresses which got released when you cut it, but I don't think white oak has a problem with this.

Solution: buy your lumber from someone else, or at least find out if your supplier is aware of this sort of problem.

-- Andy Barss

[Andrew Barss]

You could also report the problem to whomever you got it from -- they might be willing to replace it to keep your business.

-- Andy Barss

[noonenparticular]

This sounds like case hardening. If wood is dried improperly, stresses remain in the plank and when sawn, these stresses are released, warping the wood.

I don't know of any way to know whether wood has case hardening other than to cut it, but you may want to take this experience into account the next time (if there is one) you buy from a particular lumberyard.

jc

[BobS]

Telltale signs of case hardening is usually a multi-checkered end which may be difficult to see on rough-sawn lumber when you're buying it. Take an apron plane with you next time, take a slice off the end grain to freshen it so you can see the fine cracks. Maybe run a pencil across the end-grain to see the crazing. Take a swipe across one face near the end and look for the same checking/crazing. Case hardening usually has many fine cracks so a piece with a rather obvious checked end does not necessarily mean it's case hardened - just dried quicker.

You should take the wood back to where you purchased it so he'll know he got a bad batch. Depending on how reputable he is, you should get a refund and a thank you for bringing it to his attention. If he's a butt-head and tells you it's not his problem.... let your wallet do the talking next time. I use a lumber supplier (Lakeshore Hardwoods near Pulaski, NY) that guarantee's his wood and no hassle if you return it. Never had to exercise that guarantee but nice to know it's there cause - stuff happens....

Bob S.

[marson]

I have ordered "white oak" from a hardwood supplier and what i have gotten is actually "burr oak" which is a much inferior wood. I remember that it really goes nuts with changes of humidity.

[marc rosen]

Bill, I can not offer any advice but I encountered a similar situation with several pieces of 6 inch T&G pine boards. Within a few seconds of ripping them, the boards curled right in front of my eyes. Three pieces out of about 80 was not too bad but they were useless, even for trim work. Marc

[Andy]

I've had this happen (instant warping/twisting) when ripping cheap pine

2x4s, but never with oak. I got a bunch of white oak from Lakeshore Hardwoods also, and it was great quality - nothing weird as I milled it. (BobS, where in CNY are you?) I'll agree that you should call up the place where you got it, and if they don't replace it, you should shop somewhere else. Good luck, Andy

[Mike Marlow]

Bob's not too far from you Andy. North Syracuse if I remember correctly. We need to put together a CNY dorkers meeting at Dunkin' Donuts one of these evenings. Looks like we've all spent some cash up at Lakeshore - great place to get lumber. Great people.

[Swingman]

As others have suggested, it is likely improperly dried, case hardened wood.

That said, it is not unusual to have one or two boards out a of batch that show signs of being "reaction wood", or that have internal stresses that are released when cut/milled.

When milling a batch of new lumber I can almost predict, after the first one or two exhibit the behavior, which boards are going to be a problem ... sometimes it is just the heft of the board, or a slight difference in color and grain. Although these indicators aren't always a consistent predictor, so you get fooled often, it is still worthwhile to pay attention and try to anticipate the problem boards, particularly when ripping.

It boils down to a cost of doing business ... and, IME, another reason why a prudent woodworker always adds a healthy 20% over his project needs to a wood purchase.

[Teamcasa]

As others have said, improperly dried wood or just internal stress is released but ripping. When I have to rip heavier pieces (6/4 or 8/4+) that show sighs of warping or twisting when ripping, I run them through the band saw first. This relieves the stress and I can for the most part, re-rip or plane to size and save most of the wood.

Dave

[John Martin]

It may be improperly dried. It may also be that your garage is too damp.

You shouldn't be resawing 4/4 stock to 3/4. Instead, take it down with the planer, and try to take an equal amount from each face.

John Martin