Weird Nail Tales

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I wrote about the following trick to reduce splitting when nailing in “The Anarchist’s Design Book.” Since then, I’ve caught flack from people who say it’s not true. So much so that I’ve been doubting my own shop experience.

Here’s the problem: When you nail together a piece – especially using cut nails or Rivierre nails – it’s easy to blow out the end grain, reducing the holding power of the nail. Driving a tapered nail is a delicate balance. You need the nail to bite hard, so you don’t want to use a huge or too-long pilot hole. But if you use a pilot hole that is too small or short, the nail will split the work and ruin everything. Oh, you also have to account for the wood species and how thick it is.

It’s a balance of factors to get a good joint. (And that’s why I recommend you make a test joint before nailing together anything – especially if you’ve never worked with a particular brand of nail or species of wood.)

All this is a lot of set-up for…

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A common split. This joint was unclamped when I drove the nail.

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Here’s the joint (a few inches away from the failed joint) after the joint was clamped hard while I drove the nail.

Here’s the Trick
If you apply a bar clamp across the end grain of the joint, you can reduce the tendency of the wood to split out the end grain. The clamp has to apply significant pressure for this to work.

Today I tried a variety of strategies as I nailed together a mule chest using 40mm Rivierre nails. All the joints were in Eastern white pine. All the pilot holes were the same diameter (7/64”) and depth (7/8”). And all the holes were located the same distance (7/16”) from the end of the board.

Without a clamp, about half of the joints busted out the end grain (good thing I started at the rear of the chest). When I added a clamp and applied hard clamping pressure – what you would use to close a joint – the failure rate dropped to zero.

I wondered if I needed to have the clamp at full pressure. What if the clamp’s pad simply acted as a wall to prevent the end grain from fracturing? Nope. Clamp pressure – lots of it – was important to keep the joint intact while driving the nail.

I have all sorts of thoughts on why this hard clamp pressure works. But I am weary of theories. If you’ve read this far, give this trick a try yourself in the shop before pontificating in the comments.

Confession: I was greatly relieved that this trick still worked. The internet had made me doubt myself again.

— Christopher Schwarz

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About Lost Art Press

Publisher of woodworking books and videos specializing in hand tool techniques.
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37 Responses to Weird Nail Tales

  1. Hilton says:

    So you have to move the clamp for every nail or can you just use a caul?

    Like

  2. Blue tape. Collate a bunch of Rivierre nails. Feed them through your roofing nailer. The speed and impact of the pneumatic keeps the nail from splitting.

    Liked by 3 people

    • loxmyth says:

      I think I need to see video of this to convince myself it works safely. Plausible, but the thought makes me nervous.

      Liked by 1 person

      • Ben Brunick says:

        I would think adhering some sandpaper to the clamp faces may be beneficial also. Basically keeping the end grain together via friction so the path of least resistance is the crushing of the wood fibers instead of the splitting of the endgrain.

        Like

    • Pascal Teste says:

      I don’t think that Chris is interested in building pallet furniture.

      Like

    • Frank Hicks says:

      I had a old boss that made me work that same way. One morning he was on the other side of a breeze way we built and had his hand on it. I was shooting decorative nails into the inside top when i heard him yelp, he was stuck to the roof frame.a nail lost its head and travelled quite a distance to reach his hand and the nail had clinched to a boomerang shape. Be safe

      Like

  3. Joe says:

    Ditto screws, especially countersunk.

    Like

  4. jbjdivergmailcom says:

    Chris this maybe a crazy question but is the clamp vertical or horizontal. Are we squeezing the end of the board or clamping the board to the board we are nailing to? Jay

    Sent from my iPad

    >

    Like

    • Squeezing the ends of the board.

      Like

    • Oceaneer99 says:

      We are asking for the details on the clamping direction in part because the the first photo seems to show the clamping pressure arranged along the grain of the board, but your comments seem to indicate the opposite direction.

      Thank you so much for this article. This has been a frustration for me with some Japanese toolboxes I’ve built.

      Like

      • The clamp’s bar runs along the grain. The large red pad is always on the end grain, because that’s where the rectangle of wood gets split out if it isn’t supported. In the second picture, titled “A common split,” you can see the rectangle of end grain that the nail pushed out the end of the board because it wasn’t supported by the clamp pad.

        Like

  5. Steven Vlahos says:

    You definitely nailed that trick. You also hit the nail on the head by demonstrating the internet is sometimes full of crap.

    Liked by 2 people

  6. Dan Urban says:

    I think the clamp prevents the wood from moving, and, therefore splitting. So the wood surrounding the nail compresses. I suspect this trick may not work as well with a species that is less compressible, such as oak.

    Liked by 1 person

  7. loxmyth says:

    Question: Does the nail actually have to grip in the top board in this case, or is it sufficient (as with a straight sided screw) that it grip in the second board? The latter is what we generally ask of screws, and if that’s all we need we can make the upper part of the pree-drill larger and remove the risk of blowout that way.

    Clamping is a nice truck, but if we can avoid provoking the problem in the first place, so much the better!

    Like

    • I like to have a little bit beneath the head of the nail. I’m always pushing to squeeze a little more strength out of a nailed joint.

      But yeah, if you drill a large clearance hole, you avoid splits.

      Like

  8. ralmcc7yahoo.com says:

    Chris, Two things:

    What is the thickness of both pieces of wood?
    I fell with that pressure from the clamp the force of the nail take the least resistance so the clamp is giving more force to the end grain, the force of the nail is distributed in (equal) directions.
    Think of nailing a lath for plaster, they would split, sometimes across the lath to both sides.
    I could be wrong, Ralph

    Like

  9. denver80203 says:

    Since you’re gluing, these are decorative?

    Like

  10. “The internet had made me doubt myself again.”

    No!! Fuck the Internets! Don’t ever give it that power.

    I regularly doubt myself. I have a terrible case of Impostor Syndrome, as it relates to both my day job and my woodworking.

    In both cases, I’m able to overcome it with determination and focus and little lists of tasks I can use to check off accomplishments. It works for me.

    But I don’t ever let the Internets have that power over me. I know what it is and I’ve looked into its eyes. It is weak and easily defeated and hardly worth my time.

    Liked by 2 people

  11. Merddynn says:

    The results is your ultimate answer, ‘it works’. The nail acts essentially as a wedge. When clamped, the wedge can splay the needed space to fit and hold. When unclamped the splayed fiber will transfer that space as far from the point of ingress. Hold a bundle of drinking straws at one end, stab a pencil cross grain, watch the unheld end splay apart. Hold both ends of the straw bundle and the the difference. I hope this isn’t just repeating what others have posted. Happy woodworking.

    Like

  12. Clamping pre-compresses the material, and forces plastic deformation around the nail as it goes through the wood, so there’s no elastic springback that would split the wood. I is a engineering per-fesser!

    Like

    • Richard says:

      This I think is the correct explanation.

      Like

    • The clamp 8s running the length of the board, end grain to end grain. I think it’s impossible to apply enough hand pressure to a clamp to compress a board lengthwise, and if you could, the end of the board would show a dent where thge clamp pad was.

      Across the grain, a good clamp and smallish pad can compress and crush fibers. But not length wise.

      The clamp forces the wood to become compressed when the wedge shaped nail forces the fibers apart.

      Like

  13. JUSTIN REUTER says:

    I have used the clamping trick successfully on the DTC using the Reviere nails…it works! Deformation of wood fibers proximal to the nail while supporting the outside with a clamp makes sense. The thing I wonder is why then doesnt it blow out on the inside where there is no clamping pressure? This is fun!

    Like

    • JUSTIN REUTER says:

      Didn’t see the photos earlier. I was thinking of the potential for splitting action in the bottom board. How significant is the potential for splitting of the bottom board?

      Like

  14. occasionalww says:

    Have you tried blunting the nail? This is a trick taught to me by an old wooden boat builder. He would hold the nail against a hard surface and tap on the head to square off the point. His assertion was that the sharp corners created would cut the wood fibers rather than dividing (splitting) them. It was a technique that he used at the end of all his hull planking.

    Like

    • Chuck Pezeshki says:

      Probably works, but for a different reason. Smaller crack radii create greater stress concentrations.. larger ones less so. It’s why one drills out a hole at the end of a tenon one is going to wedge.

      Like

    • Chuck Pezeshki says:

      Probably works, but for a different reason. Smaller crack radii create greater stress concentrations.. larger ones less so. It’s why one drills out a hole at the end of a tenon one is going to wedge.

      Like

  15. oltexasboy says:

    I have been using cut nails from Tremont for quite awhile now, but I use a tapered pilot hole drill bit, and a hand powered reamer to “top dress” the hole. I very seldom ever have a problem with splitting. One observation if I may. I think that sometimes too much zeal in trying to “sink: the head causes the material to split. I have never used your method but I may give it a try.

    Like

  16. Mike Cundall says:

    Would cut nails work for plywood cases? I should think so, but there might be reasons not to that I can’t think of?

    Like

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