Hi all,
I’m looking to build a table top for a desk. I would like to avoid warping/cupping as much as possible. Is edge joining three 60” L x 9 1/4” 5/4 white oak boards with biscuits and glue good enough? Any wisdom that can help is greatly appreciated!
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You appear to have posted this question 3 times, you might want to delete a couple of them.
First question I have for you is do you mill your own boards from rough sawn lumber? If not you are alway going to be more vulnerable to wood movement.
If you do, the best way to prevent warping and cupping and other wood movement issues is to go slow. Buy the wood at least 2 weeks before beginning your milling sticker and stack it off the floor and forget about it for a few weeks.
Once the wood has had a chance to acclimate, do the first milling by jointing a face flat then one edge, before planing the board to within ⅛" of its final thickness remembering to alternate faces once most of the sawn marks are removed from each face. When this is done resticker and stack the wood again and forget about it for a week.
When the week is up finish planing the boards to final thickness, alternating faces as you go. Rip and joint all edge straight and square before assembly.
As for assembly, the biscuits are adequate as an alignment tool, but won't provide much protection against wood movement, this is where a Domino or full-length Spline would be stronger, but if you've taken your time with the milling they should be adequate. I'm old school and my grandfather taught me to glue up panels alternating the barkside up and down (you didn't say it was quartersawn so I am assuming facesawn wood) be sure to alternate clamps on both sides of the panel and don't over tighten the clamps. Use just enough pressure to close any gaps and produce a small bead of glue. Leave it clamped for at about 24 hours if possible, a minimum of 12. Then finish assembling as soon as possible remembering to allow for movement using slotted screw holes. If the desk can't be assembled quickly (I recommend having the rest of the desk completed before assembling the top) be sure to stack or stand the top in a manner that air can circulate around it evenly to insure moisture is evenly lost or gained from both faces.
If on the other hand you are not milling your own wood I would suggest you rip the boards into narrower strips and use a full length Spline(I assume you don't have a Domino since you plan on using biscuits and I don't know anyone who has a Domino who would do that) to provide more protection against warpage and cupping.
I would love to know where the logic and truth is in your statement following your first question.
What in the process of personally milling rough sawn lumber makes it inherently less vulnerable to wood movement vs. personally milling S2S or even big box lumber?
if i can be so bold as to attempt to answer for him, i believe what he's saying is milling the lumber yourself gives you an opportunity to eliminate wood warpage inherent in store milled lumber. by going slow (allowing the wood to acclimate to your shop) and doing multiple milling sessions (rough and final), alternating faces, gives you control over moisture loss. i use that technique every time, and have had excellent results.
i would just add one more detail. no mater how carefully i setup my jointer fence, i never get exactly 90 degree corners. by alternating your boards, one face against the fence, next away from the fence you will cancel out any error.
I get what he's saying about milling your own lumber but this applies equally to whatever lumber you use. Whichever lumber you use, let it acclimate before the first milling step and once it's close to finished sized let it acclimate again before the final milling steps are done and the thing is assembled.
Personally milling from rough sawn lumber saves you money and allows far more sizing options than S2S or big box lumber but provides no benefit on wood movement over S2S or big box if all are worked in the same manner.
Most S4S lumber is milled to 3/4" or whatever finished dimension you purchase, so there is no opportunity to mill it in stages or let it acclimate to your shop environment, so it is much more likely to cup and warp.
Why someone who has the ability to plane and mill lumber would buy S4S defies logic. You are paying way too much for your wood.
S4S is perfectly logical for a person who is learning the craft with no teacher directly available for guidance.
I'd much rather learn on S4S how to perform the various machining steps and various joinery methods than to learn on a piece that cost much more (I certainly won't lose sleep over rendering a big box 1x useless for the project at hand). An S4S 1x has enough material to be milled down to a smaller dimension in the step-wise acclimatizing fashion and it may be that a simple pine box fits the bill perfectly from time to time.
S2S is, in my estimation, a fantastic intermediate because it allows me to see, with more clarity, what the finished board will look like so I can make a better decision on whether to buy it or not, especially while I am just learning to "read" wood.
You are certainly entitled to your opinion, but I am pretty confident that it would be a minority opinion.
If I was wanting to "practice" milling wood I certainly wouldn't over pay for 1x material at a big box store when I can buy poplar for a fraction of the cost. Not to mention my reply to the OP was based on his using 5/4 white oak stock. When was the last time you bought 5/4 white oak stock at a HD?
I stand by my advise to the OP the best way to insure flat stock is to follow the process I outlined and yes you can technically do that with S4S or S2S, but I ask again why would you pay more for wood than you need to?
your argument makes absolutely no sense.
firstly, you do understand that per bf, big box lumber is significantly more expansive than at a hardwood dealer, right? to give you an idea, hd sells their lumber per linear foot, not bf. last time i did the calculation, their walnut is priced ~$15/bf. i pay $8.50 at my local hardwood dealer (almost half).
second, lumber bought sawn rough is the cheapest form of lumber you can buy. the moment you start reading things like s2s, s3s and s4s the price goes up.
third, if you invested money in to milling machines (jointer, planer and table saw) why in the hell would you pay for surfaced lumber?
and last 'practicing' (as you call it) on overpriced, warped hd lumber just so that i can't get the exact thickness i need is just counterintuitive to me.
Both of you seam to be assuming that rough sawn or even S2S lumber is easily gotten by me and all others.
I guess the gas money to go to a lumber yard approximately 35 miles or more away or the cost of shipping said lumber is being paid by someone else?
What of the cost of my time?
I can go down to the local big box (about 10 miles one way) and buy some big box lumber to practice on far cheaper than I can get my hands on some other similar BF priced rough sawn or S2S lumber.
The cost of the lumber itself isn't the only cost involved and it all has to be factored in so, yeah, my comment does make sense.
Ironically, especially in light of this conversation, I can purchase S2S lumber online and, with the cost of shipping, it is less than the closest place to me to get S2S lumber BUT it is still more expensive than me going to the local big box to buy some inexpensive, by comparison, S4S lumber.
As a side note, the investment of the machinery is basically a one time outlay. Paying for lumber, either to practice on or to build an item worth keeping, is an ongoing expense. Which makes more sense in the grand picture of learning? Approximately $3 per board foot or approximately $4-$6 per board foot for potential firewood? On the low end they're almost equivalent. On the high end it's almost double the cost.
With a top that 60" long, 27 3/4" wide and 5/4" thick, you can miss a few gym workouts moving that around.
Adding onto the question on the top, some I’ve seen will create a dado on the bottom side going side to side, then glue in a steel or alloy piece. The logic being if the table is getting some sunlight but not evenly it will help prevent warping. Anyone have experience with this?
A friend of mine tried to save a 9' bubinga conference table that way with epoxy and steel T-stock. The bubinga had the final say and the table had to be redone. Crazy expensive error.
I rout a dovetail into the underside of the tabletop and glue in either support strips or the leg assembly itself.
Example
https://www.finewoodworking.com/2010/06/03/better-way-to-attach-tabletops
Set two cletes into the underside using sliding dovetails. Driving the cletes into the dovetail slots can straighten a slight twist or cup.
If you position your boards such as the growth circles are in the same orientation, assuming this is not quartersawn oak, the apron, cleats or breadboards will all keep it from warping. This article pretty much covers it perfectly : https://www.finewoodworking.com/media/TabletopsFlat.pdf
Cupping will be minimal with QS material, that's the whole point of using it in the first place.
It all starts with 1) stable, acclimated wood, 2) properly jointed boards, 3), holding it flat once its glued up. I've had tops dry clamped together for a week be perfectly flat, then something happens after glue up to change that. Keep the top in cauls and covered when left alone.
Breadboards & cleats will not prevent cupping. Not even steel is a guarantee (see MJ's post).
The best you can do is start with stable, kiln dried lumber, joint it alternating faces against fence. Glue it up right after jointing - don't give the boards time to 'misbehave'. Use hefty cauls. Keep the top in cauls and shielded from airflow until you're ready to finish it.
"Start flat, stay flat"
1. Mill flat, square boards.
2. Glue them up with cauls to hold them flat and alternate clamps above and below so that you don't introduce a large cup across the width when you crank down on your clamps.
3. Use some method to keep the top flat (none of which can be glued cross gain):
Breadboard ends
Sliding dovetail cleat on underside
Dadoed square stock cleat screwed with elongated holes.
As Gulfstar noted above, the article by Christian Becksvoort outlines many good ways to go about starting and keeping flat tops. As also noted in that article -- pay no mind to orientation of the rings as it relates to trying to keep the top flat. Orient your boards for appearance (color, grain, pattern), there is nothing at all gained by alternating them.
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