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Advise: Knotty Cupped Top for Workbench

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Forum topic by Mauricio posted 1005 days ago 1684 views 0 times favorited 42 replies Add to Favorites Watch
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Mauricio

6747 posts in 1747 days


1005 days ago

Topic tags/keywords: question oak milling

Hello Lumberjocks,

I need advise on this top I acquired recently for FREE! I would like to use it for a future workbench project.

It is about 2 3/4” thick Red Oak. It is basically two slabs from the tree glued together side by side. It was made from green lumber against the cabinet shops advise to the client (a restaurant)

There are three problems:
-Since it was not dry it is very cupped.
-Also, it is very knotty which would make periodic flattening of the bench top hard to do with hand planes.
-Both slabs contain the pith of the tree which I think will make it very unstable and hard to keep flat

To overcome these issues I was going to let it dry, resaw it into maybe 4 pieces and re-glue and flatten. To overcome the periodic flattening issue I was thinking of gluing on a layer (maybe 3/4”) of straight grained wood that would be easier to plane.

So, my question to you all is: Is this worth using for a bench top or is it more trouble than its worth? Would it serve me better for the legs and stretchers?

Thanks in advance!

Mauricio

-- Mauricio - Woodstock, GA - "Confusion is the Womb of Learning, with utter conviction being it's Tomb" Prof. T.O. Nitsch


42 replies so far

View Don W's profile

Don W

14588 posts in 1163 days


#1 posted 1004 days ago

I think it would make a great bench top.

First, you didn’t say how cupped it is. Its possible to pull it back “maybe”. Early in the morning, on a sunny day, throw it on the wet grass cupped side down. I’ve never tried it with something this thick, but it may help.

The knots will make it harder to flatten, but also make it harder period, so you shouldn’t need to flatten that often. As for periodic flattening. How often to you think you’ll need to flatten it. Once every 25-30 years? That would be my guess for oak.

Resawing it and re-glueing would also work if you can’t get it flat. If its got less than an 1/2” cup though, I’d flatten it.

-- Master hand plane hoarder. - http://timetestedtools.com

View crank49's profile

crank49

3333 posts in 1566 days


#2 posted 1004 days ago

Theres a jig in FWW to level that size slab using a router.

Is the whole top cupped or does each half of the slab have a cup. Looks like the latter in the picture, but hard to tell. If its one big cup all the way across then you would probably have to rip it down and re-glue.

Might be worth it to rip out the pith and replace those parts with better wood if you have to rip it any way.

I wouldn’t worry about the knots if I could ever get it flat and re-glued and de-pithed. Would probably stay good a long time being oak.

-- Michael :-{| “If you tell a big enough lie and tell it frequently enough, it will be believed.” ― A H

View Mauricio's profile

Mauricio

6747 posts in 1747 days


#3 posted 1004 days ago

Thanks so much for the advice guys.

Don, I know you have a chain saw mill and probably have a lot of experience with this kind of thing. P.S. I have a decrepit wooden jack plane I am restoring that I will post soon. I’m going to use it as a scrub plane.

The cup is about 3/8” so it may be better just to flatten as is. I wouldn’t expect it to move much from there. I’ve heard of the wet grass trick before but have never tried it. Worth a shot, I wonder what will happen once it dries again.

Here is a pic of the pith, you can see it has already checked and had to be filled. This doesn’t bother me esthetically.

The other peculiarity with this situation is that it is finished on only one side (to let it dry the guys said). With that you would expect that it would dry/contract more on the unfinished side and cup in that direction but it didn’t. I think this is due to the pith being off center in the board and being more to the unfinished side so there are more arching rings on one side that want to straighten out. Hope that makes sense, if not the pic shows what I’m talking about.

Crank, I know I have read something about the pith being bad news but I can’t remember what specifically. If I can get this flat (with the router trick) do you think I can keep the pith? I’ve used the router jig on cutting boards it works great. The top is cupped about the same all the way down.

Don, I don’t know how often I will have to flatten since my bench now is OSB, Sounds like I’m making too much of that? I like how it looks now but I’m assuming it is not done drying and may need to be flattened a little more down the road. Sounds like neither of you are into the “skinning with straight grained wood” idea. I do like to keep things simple but I’m just dreading having to do the router flattening process twice. It’s a messy business. Planning it flat on the other had sounds enjoyable.

Don&Crank you guys both seem to suggest that Oak is a stable wood. I would have thought the opposite since it is so porous, I have about a 100bf of cupped oak boards in my garage. But once they’re done cupping and you flatten them they stay relatively stable.

Thanks again for the advise and any additional input.

-- Mauricio - Woodstock, GA - "Confusion is the Womb of Learning, with utter conviction being it's Tomb" Prof. T.O. Nitsch

View Don W's profile

Don W

14588 posts in 1163 days


#4 posted 1004 days ago

Its hard to see in the pictures, but it almost looks like it was glued cupped. Is it actually flat from center to each edge?

Having seen the better pictures, (assuming the back side is the same, other than finish) I’d rip it right down the center, flip one side, joint it so its as flat as you can get it, reglue it, flatten as needed, which should be minimal.

If its not dry, I’d rip it and let it dry before re-glueing. (coat the raw edges)

Once oak is dry, oil it. Oil replaces water cells and hardens the wood. BLO would be my choice, unless you want to darken it, then go Danish oil first, then BLO.

I know I’m in a bit of a minority lately, but I think oak is a great wood. That will make a great bench in my opinion. My bet is, unless you going to mis-use that bench (and yes, I mis-use mine a lot) you’ll probably never have to flatten it again, once its dry (assuming you keep it dry) and flat it’ll stay that way.

-- Master hand plane hoarder. - http://timetestedtools.com

View Lee Barker's profile

Lee Barker

2163 posts in 1446 days


#5 posted 1004 days ago

I’d tackle this in a slightly different way that would involve no compromises concerning the “will it recup/will it not” question.

I’d rip it into 2 3/4” pieces, square them, then select the good sides and glue it up. It will be a beautiful, multi-colored butcher-blocky looking thing, hard as a foreclosure officer’s heart, knotless on the top (luck being with you) and you can finish it any way you want.

If you had to make it wider because you lost some in the kerfs, a few strips of 4/4×2 3/4 (nominal) strategically placed walnut or mahogany will be stunning. You’ll smile out loud every time you walk into your shop and see this work of yours.

My oh my. You have a find there, Mauricio.

Kindly,

Lee

-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

View Don W's profile

Don W

14588 posts in 1163 days


#6 posted 1004 days ago

I can’t disagree with Lee. That’s another way to go about it. I like the look of knots though.

-- Master hand plane hoarder. - http://timetestedtools.com

View WDHLT15's profile

WDHLT15

1065 posts in 1071 days


#7 posted 1003 days ago

Wood cups toward the bark. Seems counter intuitive, that is exactly what happened in your benchtop.

-- Danny Located in Perry, GA. Forester. Wood-Mizer LT15 Sawmill. Nyle L53 Dehumidification Kiln

View Mauricio's profile

Mauricio

6747 posts in 1747 days


#8 posted 1002 days ago

Thanks again for the input guys. I’m inclined to do as little cutting and gluing as possible and I do like the current look. I would just go ahead and flatten it as is but I don’t want to lose 3/4” (3/8” on each side) of thickness.

Don I like the idea of flipping a side and regluing. It will keep the same look, I’ll just have to do some check filling. The underside of the top is checked all the way down the length of the pith. I’m also with you on the BLO, I’m not planning on treating my bench like a piece of furniture. It will get well used so BLO will let me touch it up easily.

I agree with you about oak. It’s a nice wood and hand plains well, I’ve done a few Oak projects and they look good if you choose the right grain and finish.

Lee, I don’t think there is any way to turn the pith and make it look differently. If I had to rip it down to a few pieces I would probably need to replace the pith.

Here is a pic of the underside.

Thanks again guys, I’ll post the project when I finish it eventually. Now I need to find some big wood for legs and stretchers. I have a bunch of 4/4 oak I could use but gluing all that up would not be fun.

-- Mauricio - Woodstock, GA - "Confusion is the Womb of Learning, with utter conviction being it's Tomb" Prof. T.O. Nitsch

View Bertha's profile

Bertha

12951 posts in 1288 days


#9 posted 1002 days ago

I would cover a 2×4 in chalk (the kind kidls like to write on sidewalks with). I’d scribe the surface, identifying the high spots. I’d hit those high spots aggressively with a scrub, and then get it close enough to put it through your planer or hit it with a Jack. I think I’d make a phenomenal benchtop, even with the additional work.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

View Mauricio's profile

Mauricio

6747 posts in 1747 days


#10 posted 1002 days ago

I like that chalk trick. I hadent heard of that one but have been trying to figure out how to do something like that. I happen to have a bunch of that chalk. Thanks!

-- Mauricio - Woodstock, GA - "Confusion is the Womb of Learning, with utter conviction being it's Tomb" Prof. T.O. Nitsch

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Mauricio

6747 posts in 1747 days


#11 posted 1002 days ago

And I just so happen to be finishing a restauration on an old wooden Jack that I’m gonna use as a scrub.

-- Mauricio - Woodstock, GA - "Confusion is the Womb of Learning, with utter conviction being it's Tomb" Prof. T.O. Nitsch

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Mauricio

6747 posts in 1747 days


#12 posted 931 days ago

Question on wood movement. What if after I flattened this thing as is with knots and everything which I think looks cool, and then if I want to get it to about 3” thick I laminated some more red oak on to the bottom? would that be like veneering only one side of a board? would it seal in the moisture on one side and make the other side contract more as it dries?

-- Mauricio - Woodstock, GA - "Confusion is the Womb of Learning, with utter conviction being it's Tomb" Prof. T.O. Nitsch

View Loren's profile

Loren

7222 posts in 2243 days


#13 posted 931 days ago

I think Lee has a good idea. My thought on the knots is that
the tissue in and around them will always be bucking up and
down on you if you have them on top – no matter how flat
you make it, those knots are likely to be proud when the
humidity is low and shy when it is high.

I don’t know what standard of precision you need from your
bench, but you’ll struggle to make flat frames on a chronically
distorted bench.

One strategy would be to just flatten it and observe it and
see if you can do accurate work on it. If not, the top could
be laminated with a “skin” perhaps 3/4” thick. The knotty
board may not make a good work surface, but as a heavy
substrate I think it would be acceptable and certainly give
your bench some real mass.

-- http://lawoodworking.com

View Smitty_Cabinetshop's profile

Smitty_Cabinetshop

9565 posts in 1214 days


#14 posted 931 days ago

Mauricio – Have you moved out on this yet? I would sure think about ripping this bad boy into four or five pieces then squaring those up prior to regluing. It’ll cost you four kerfs in total depth of your bench, but should likely save more than a half inch of thickness… And they don’t have to be equal pieces; I say that so you can avoid messing with the pithy parts of the boards. My .02. Good luck!

-- Don't anthropomorphize your handplanes. They hate it when you do that. -- OldTools Archive

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Mauricio

6747 posts in 1747 days


#15 posted 931 days ago

Thanks Loren and Smitty for the additional input.

Loren, do you think that “skinning” one side would cause uneven moisture exchange on either side of the top? I was thinking of doing it to the bottom but your making me think I should do it to the top.

Smitty, no I haven’t done anything yet but its moving to the top of my project list soon so I’m in the design faze right now. I read Landis’ book and now am reading Schwarz’s book on Benches. I don’t see any benches in Schwarz’ book that are less than 3” thick which is making me think mine would be look too skinny.
You raise a very interesting idea I hadn’t thought of, the chunks don’t have to be of equal size. I was trying to avoid as much lamination as possible but I think if I’m going to cut it up I might as well go with Lee’s idea but cut it into 3” strips and flip them on end, I would just need to laminate more wood in to get it to 24” wide.

The other idea I was kicking around is to just cut this up and use it for leg and stretcher parts and figure something else out for the top. I just found a good source for 4×6 and 6×6 Southern Yellow Pine, kiln dried and pretty cheap but I really prefer the look of a hard wood to Pine.

Thanks again guys!

-- Mauricio - Woodstock, GA - "Confusion is the Womb of Learning, with utter conviction being it's Tomb" Prof. T.O. Nitsch

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