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I'm building the Christopher Schwarz Knockdown Nicholson bench. This is my first foray into handtool building. I'm working on the aprons now and have cleaned up the boards and made them mostly flat on the faces. My question is, how flat is flat enough for the aprons? I understand that the top is the most critical and that generally flatter is better, but given that generally the aprons would be supporting boards while working edges and ends, is it important for it to be dead flat?

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    I would say no, but it's good practice for when you try to do the top...
    – bowlturner
    Commented Jun 20, 2023 at 19:17
  • Given it's a knockdown bench, I could always come back later to make the outside faces dead flat if I need them to be, and I'll have a workbench to work them on too!
    – ecline6
    Commented Jun 20, 2023 at 21:21
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    How clear is the wood you're working with BTW? If you're having to deal with any serious knots here's a top tip to make that go easier: dampen them. This almost instantly softens the wood and makes planing through knots tons easier. This tip also works well for end grain in some species, and to ease planing in some highly figured woods.
    – Graphus
    Commented Jun 20, 2023 at 21:23
  • The stock I'm using for the aprons and top is intentionally clear, very few knots, and I selected the truest to the eye boards for them as well. The knots that I've had to plane so far haven't put up too much fight, thankfully.
    – ecline6
    Commented Jun 20, 2023 at 22:24

2 Answers 2

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The simple answer is dead flat, with faces parallel, but that's too simplistic and it needs to be looked at a little closer if we're talking hand tools only.

There actually isn't a single standard for flatness or parallel-ness, despite how it might seem in the era of power tools with the enormous amount of time and labour they save in basic four-squaring operations. In some furniture work it's actually not vital for both faces of a board to be flat, or parallel, since e.g. only one face is visible, or interacts with other pieces.

You could think of this as an extension of that. So, how un-flat is acceptable given that:

  • the backs of the aprons interact with the halving joints/lap joints in the legs, so have to be flat enough for that to work;

  • the outer face of the front apron is a bearing surface when boards are held against it during edge planing (and for the occasional wide end that you can't shoot), so should be flat enough for that to work well.

This leaves the outside face of the rear apron as the only face where it can easily be argued that it doesn't need to be flat. You could even leave it rough from the scrub/jack plane if you really wanted. Especially if it'll rarely or never be seen.

But there's another way of looking at this given that you state they're mostly flat already — the bulk of the work has already been done and it's not much additional effort to get to flat, not if your longest plane's iron is good and sharp and you follow proper procedure. Assuming you're working on a decent surface for planing that isn't moving around on you a lot and robbing energy from each push!

Maybe it would help to see someone doing this for reals, so take a look at this video from Frank's Workbench, Stock Prep with Hand Plane vs Jointer/Planer.

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    Yea, I think the crux for me is doubting how little effort it will take me (a novice) to get to dead flat from mostly flat. For what it's worth, my current work surface isn't ideal for working on a 6ft board at all. Certainly any practice at this point would be good for me, but I also don't want to worry about things I shouldn't worry about!
    – ecline6
    Commented Jun 20, 2023 at 21:19
  • Your point about leaving it a little rough reminds me of a tip I picked up about aprons. Aprons want to be a little bit rough -- a la with a scrub plane. A smoother apron will have less grip to it whereas a rougher surface for an apron will offer some resistance to help hold work stable.
    – YoStephen
    Commented Jun 21, 2023 at 3:06
  • @YoStephen, I've heard the same rationale WRT workbench tops, but there's a difference between rough, like the sanding texture from 60 or 80 grit, and actually three-dimensional such as scalloped from a roughing plane. The only reason I was suggesting this was OK with the outward face of the rear apron is precisely because it serves little to no active function, esp. on a non-walkaround bench.
    – Graphus
    Commented Jun 21, 2023 at 7:11
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I would say this is down to the tolerances of your work and how out of tolerance your apron would be. The bench is after all an expression of your own process and preferences -- no more, no less.

Personally, I would want any workholding apparatus I'm on to be pretty reliably square, flat, and true. But that is because I would like to have the option to finely craft furniture and mill work with my bench. Any imprecisions in the tools in my process will be transferred into the work and will have to accounted for with addition checking and re-working as needed.

To illustrate this in the context of an apron, let's say I am edge jointing some stock for a table top and that my apron has some twist in it such that the right side protrudes out 1/4" or 6mm. I, as a right-handed person, will have it clamped to the left side of my apron with an end vice, supported at the bottom with pegs, and on the right side with a hold fast or two. As I am doing my jointing at my warped apron, the work will have stress on it to conform to the apron and the middle of the span will be somewhat less stable. I couldn't tell you how much error this will impart, but I would expect at least some mistakes from an unsupported stressed worm piece. This error, repeated on every work piece, will be something around which I will have to work. This means I'm going to have to add extra steps to make sure what I am producing on the bench is dimensionally true adding a lot of time over the many years of work I hipefully will be doing at my bench. I wouldn't want that personally, even though I will probably never do production work.

You may not share these aspirations though. For instance if you're making a bench for a plant nursery/conservatory and will be making shelves to water young plants and prepare seedlings, a bit of imprecision is totally fine.

My suspicion though -- since you're working off of a furniture makers' pattern -- is that you'd like to make some nice(-ish lol) pieces for inside your living spaces, your friends and family, and most importantly for your own satisfaction. I also suspect you're a hobbyist like me, meaning the bulk of your time is spent at your day job and chores. Free time is a precious thing. Setting yourself up at this early stage to have to work around as little as possible will have substantial compounding returns as you mature in the craft.

If that's the case I would strongly suggest flattening your apron. It's a considerably difficult task and I totally sympathize if you're feeling daunted.

It's also worth noting that, since your building a knock-down plan where the apron is a stand alone element, you could conceivably punt on flattening your apron to a later date when you're more experienced. There's probably trade-offs with having a warped structural element. But hey, you're not a machinist here and there's probably not reason to be counting thousandths of an inch in this. The most important thing is your enjoyment and that you're not stressing to the point you don't even want to swing a plane -- been there and it's no good.

You might also be able to outsource the work to a cabinet shop who have an industrial planer. When I was buying the maple for my own top I expressed such self-doubts to guy ringing me up at the lumber shop and he gave me his card saying he runs a shop and would be happy to square the top if it was too much for me and my garage sale #7 plane and hardware store bubble level.

Hope that helps and I wish you the best of luck and fun on your journey into handtool woodworking!

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    All your assumptions are correct. My intent is to build nice-ish furniture for my family and a few good friends. I do care about accuracy, but I'm not protecting a reputation on anything I build. I think I'll likely get as flat as is reasonable now and then return to flattening after the bench build is complete, if needed. I should be able to remove a single apron and use the new bench to true it up more easily than on my current work surface.
    – ecline6
    Commented Jun 20, 2023 at 22:27

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