I am working on a kitchen table 39” to 41” square. I purchased some walnut from a local sawmill. I paid to have the boards planed on both sides to 1 ½” thick. The boards were approx 7” to 9” wide. I don’t think the sawmill used a sled to flatten the boards so they have a slight twist. Maybe an 1/8″ gap. I ripped the 9” in half to lessen the twist a little. I would like to keep the thickness at 1 ½” if possible. I am wondering what my best option is to correct the twist? I don’t have a thickness planer so I would need to build a router jig if I attempt to flatten. Thanks in advance
- I plan to use biscuits when I join the boards. If I clamp the boards straight when I cut the biscuit slot, will that be enough to correct the twists? Any issues with stress down the road?
- Take the boards back to sawmill and ask them to re-plane? I realize that would make them thinner. I have enough extra on the sides to make some ½” x 1 ½” wide framing pieces to wrap around the edges to keep the look. The boards were 8’ to 9’ long when originally planed and are now cut down to half so easier to sled.
- Build a slab flattening jig to either flatten boards individually or after the pieces are joined?
Replies
Re-planing the boards will only give you thinner boards with the same twist. They need to be jointed on one face to get them flat and then planed on the other to make the faces parallel.
Don't try to assemble the boards by forcing out the twist, it won't end well.
Before we can adequately answer, we need to know if the lumber has been dried. Frequently, rough sawn lumber straight from a saw mill is not kiln dried. If that is the case, you are wasting your time and lumber trying to build your table. The table will destroy itself as the lumber dries and shrinks. Even if the lumber is air dried, it may not be dry enough and needs to be checked with a moisture meter.
If the lumber is dry, but has warps and bows, etc, you will need to find some way to have it flattened, straightened, and planed to a consistent thickness. The advantage to having a jointer and planer when working with rough wood is that you can break down the larger boards into the smaller components you need before jointing and planing. You waste less wood this way. But MJ is correct. Running a twisted board through a planer will only result in a thinner twisted board. It needs to be flattened on one side first.
I was told they were kiln dried. When I picked them out they were stored together without stickers. I was thinking if they get re-planed to shim on a sled to get a good flat side. Then re-plane the other side
Lumber yards don't typically do this type of planing that is left up to the end user. This is why I mill all my own wood. I buy it typically a month in advance to allow it to acclimate to my shop conditions then do a two stage milling process to insure my boards are as flat as possible when I'm ready to use them.
This was a "boutique sawmill" near me. Thinking of reaching out to see if they would re-plane with a sled. Prob still cheaper then buying a planer at this point
The only thing I will add to relying on the mill to do your planing is, that is entirely possible that the wood was perfectly flat when they finished planing it and once you got it home to your shop difference in humidity caused the movement. I'm a big believer in acclimating lumber for weeks before milling. The only time I've had significant problems with movement have been times I deviated from my standard practice.
If I understand your finished table is going to 39" x 41" and you say there there is ⅛" gap is this gap when you butt the boards together? Or is it measured with the boards sitting on a flat surface and represents the high corner above the work surface?
Biscuits have no inherent strength and are good for alignment purposes only. A full length Spline would probably be a better guard against further movement.
If it is the latter, the only solution is to flatten the boards, either by planing, hand planes will work, or the router jig as you mentioned. I would recommend a 3+ hp router and a bit design for this but a 2½ will work if you aren't to aggressive.
The first step would be to identify the worst offender because this board will determine how much you need to remove. Once you have identified this board place it in your jig with a shim supporting the raised corner. Use the router to flatten the first side then remove the shim turn the board over and remove the same amount from the second side. If the difference is truly ⅛" expect to lose ¼" of overall thickness. This is definitely a case where you will want to set your routers preset stops for your final depth to in sure you mill the boards equally. Set two depths one for the final cut on the first side and then one twice that deep for the final cut on the second side. You will need to cut all the remaining boards the same way to reduce the chance of further cupping. Half from one face flip it over and half from the other.
Dust collection on routers is very iffy, unless you have a Festool, so expect this to be a very messy job and take precautions. Walnut dust can be an irritant to some people so a good dust mask is highly recommended.
Table will be square either 39" or 41" (replacing a 41" round table) and it is an 1/8" gap on the face side when the boards are laying on a flat surface. I was going to use the biscuits for alignment by going off of the top face for reference for all of my cuts
Given your tools you've listed elsewhere I will stand by the method I outlined, unless you have well tuned and sharp handplanes and prefer less mess and noise. Either way your boards need flattened before glue up.
Or plan B use this as a reason to convince the better half (if you have one) that you need a planer 😉
Planer is on my list. Unfortunately I would get killed right now by my better half and that is too big of an item to sneak in :-)
Unless you have VERY big trousers....
I will add one more agreement to the fact that planers do not flatten, only thickness.
If you are cutting the boards to a 41" length, don't try to flatten a full length board of 8 or 12 feet. The twist of a 41" piece will be less than a third of the 12 footer and you will lose 1/3 of the material flattening it, assuming the twist is even.
It you have 1/8" of a rock on a 41" piece, that's not too bad. 1/8 on a long board is actually pretty good or at least normal. With twist you have two high corners and two low. Even out the material removal on the highs to minimize the loss in thickness.
Boards are about 50" right now and I was going to cut to final size after glue up
What tools do you have to flatten this yourself? Belt sander? Planes?
Random orbital sander, some hand planes, and router
Handplanes are your best bet.
I've never seen any planer sleds in a lumberyard and loose shims in a planer would probably be a safety hazard.
I have an 8" jointer that I no longer use. It's an expensive piece and a 9" board is too much. Same goes for planers - a 13" board won't go through a 12" planer.
Hand planes are very versatile and will work on very large pieces. You'll need them to clean up a power planed surface anyway. They are more of a commitment than sanders, etc.
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