Flush-cutting Without Frustration - Popular Woodworking Magazine

Flush-cutting Without Frustration

 In Chris Schwarz Blog, Woodworking Blogs

Cutting wedges, plugs or dowels flush with the surrounding surface is a source of great frustration for many woodworkers. Either you leave way too much of the plug behind, or you chew up the surrounding surface with the saw’s teeth.

Sometimes you can plane or sand away the damage (or the excess material). But sometimes you cannot. And wouldn’t you rather leave a perfect surface behind in the first place?

Like you, I struggled with this problem for many years and tried many solutions. When I build a chair, I might have to flush more than a dozen wedges and through-tenons. So I needed to crack this nut.

The Problem
It’s best to understand why this problem occurs because it will help you avoid bad technique. First problem: advertising. Many ads for flush-cutting saws show them being used in silly ways. In general, you don’t bend the blade as shown in the ads. Bending the blade can damage the saw and will steer the teeth off track. Keep the blade flat.

Second problem: The set of the teeth. Some flush-cut saws have no “set” to their teeth while other saws have teeth that are set to one side only. Both saws will work, but if your saw has set, you need to know it and you need to mark it on your saw. If you put the face of the blade that has set on your work, you will scratch it instantly.

Third problem: We clog the teeth. There are many ways that flush-cut saws can wander in the cut. The most common way is that the gullets get filled with sawdust and the saw starts to behave erratically. Keep the teeth clear of sawdust (and glue).

The Solution
The best fix is to use two saws: One for removing the bulk of the material and a second finer saw for cleaning up what’s left. While I’ve never found flush-cutting saws that I adore, the best combination I have tried is from Lee Valley. This saw for the rough work and the single-edge saw on this page for the fine work.

To remove the bulk of the material, apply some blue tape around the dowel or tenon to protect the surface. Use the coarse saw to remove as much material as you can. Do not bend the blade. Keep it flat against the tape.

Now remove the tape and get the small fine saw. The goal here is to nibble away what is left. This saw has no set, so it won’t scratch the surface if you keep the blade flat against your work. How do you do that? Don’t use the handle. Don’t even touch it. Instead, use your fingers to both press the blade flat against the work and to move the blade back and forth.

Take your time until you get a feel for it and keep the teeth clear of sawdust.

The result is a perfectly flush surface without a single errant scratch. And that is worth the extra effort.

— Christopher Schwarz

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Showing 9 comments
  • knothole

    I have a French flush cut saw that is set on only the upper side of the blade. Not sure if they are still available, but I got it from one of the major suppliers about 30 yrs ago.
    The blade lays flat on the work. One edge has coarse teeth, the other fine. The handle is mounted on the flat side of the blade, similar to a drywall finishing trowel.
    Maybe if you filed some teeth on a small trowel . . .

  • hankgillette

    I don’t do this all that often, but what I do is use a flush cut saw with a playing card underneath it (rather than using tape), then use a low-angle plane to get it flush with the surface. I think that leaves a smoother surface on the plug than a saw would.

    If you have a lot, and they are on a flat surface (and far enough apart) you can use a router with a straight bit. It probably goes without saying that the setup of the router bit depth is crucial in this method.

  • gcoyne

    Christopher, assuming that the plug is only proud 1/8″ to 1/4″, why would you do it twice? If anything, I can see where the very thin remaining plug might enhance the chance for the 2nd run to want to drift away from the base. I very much like your approach of avoiding the handle on such close work but wouldn’t that work just as well if the plug were taller?

    Otherwise thanks for another great tip.

  • ccarse

    Kerry Pierce once showed me how he removes set from a saw, just lay it flat on a sharpening stone and go to town. Works a treat especially with diamond stones but it’s possible to do even with water stones with a light touch.

    • Christopher Schwarz
      Christopher Schwarz

      You can also simply squeeze the teeth in a metal-jawed vise. The steel is quite ductile and easily bent.

      • ccarse

        I’ve found you can reduce the set with that method but not remove it. The ductility of the steel always springs back at least some in my experience.

  • JMAW Works

    Any tips for flushing up the legs in a saddled seat?

  • tucker tuck

    Thanks for the article. I have always just used a flush-cutting saw and then a chisel or block plane. My favorite is the Veritas block plane because it’s just so sweet for this purpose. I am not, however, as fast as this: https://youtu.be/RCtICNBU_I8?t=1m40s

    • Christopher Schwarz
      Christopher Schwarz

      For a seat, I cut the tenon as close as I can with a saw. If the saddle is shallow, I can use the fine saw to nibble away. If the saddle is deep, I use a shallow carving gouge to pare away the excess. Then a curved scraper and sandpaper.

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