Sunday, June 27, 2010

Talking Bench Dogs

We get a lot of emails asking about bench dogs. They usually go something like this, "I'm building my bench using your hardware and am trying to decide between square or round dogs, can you help?" So here's my take on bench dogs.



I've built numerous benches using everything from particleboard (everybody's a beginner at some point!) to MDF and hard maple. And all of those benches had a different type of bench dog. But now all of my benches feature shop-made wooden square-section dogs with a wood spring, stepped shaft, and leather face. Here's why.
  • I can make a batch of dogs for every hole in my bench in about 2 hours, and I'll have enough dogs for the rest of the bench's life, even if I loose or ruin a few. And the total cost is just a few dollars, since most of the wood can be had from scrap.
  • The step in the shaft makes a flawless, effortless depth stop. I can push the dog down and be guaranteed every time that I won't push it through the bench to have it fall completely through. It requires no thought, no tedious adjustment to make sure the dog is below the surface of the bench.
  • The wooden spring holds evenly throughout the vertical travel of the dog, yet allows the dog to slide up and down easily due to the wide bearing surface against the inside of the hole.
  • The suede leather face provides a fantastic grip against the workpiece, allowing lower clamping forces and thus less chance for bowing or damaging the workpiece.
  • Square dogs can be raised high above the bench surface for more versatile workholding.
  • Wooden dogs have no exposed metal to bang into plane bodies or cutting edges.
  • Square dogs are always parallel to each other. 99% of my between-dog clamping has always been with parallel-ended workpieces.




And here's why I don't like all the other versions of dogs that I've tried.

  • Round dogs rotate in the hole. In my experience, 99% of furniture and cabinetwork is held between parallel-ended boards. I can't remember the last time I needed a dog to rotate a few degrees to hold something that was just a tad off parallel. Anything beyond a few degrees and the clamping pressure would pop the workpiece out anyway.
  • Round dogs require a less-than-ideal device to hold them in position. This device, whether its a wire spring or a bullet catch/spring plunger concentrates the force in one small area. I found that the wire spring can wear a groove in its hole (its mounted on the side, so it bears against edge grain), and the bullet catch shares the same problem. The bullet catch also requires a very smoothly drilled or milled hole to work nicely. If the hole is rough on the inside the bullet catch with cause the dog to move in jerky movements, and over time can cease to function entirely with wear. The threaded spring plungers do have some adjustability, but they are pricey. The commonly available bullet catches are cheap, but have zero adjustability. The bullet catch also has to be positioned precisely to get the most travel possible. It's also too easy to push the round dog past the bullet catch only to have the entire dog fall through the top and inevitably roll under some inaccessible place.
  • Square dogs with bullet catches solve a couple of these problems, but the issues with the bullet catch remain.
  • Commercial round dogs are made of metal, like brass or aluminum. When I built my first real bench after high school I outfitted it with round brass dogs. One day, while planing a thin board, I ran out of wood and my next stroke clipped the top of the dog. If I had been using a wood dog, I may have chipped out the end grain at the top of the dog instead of chipping both my plane body and iron. I have nicer tools nowadays, so there's no way I'll willingly place a metal barricade in the path of a finely tuned smoothing plane again.
  • Commercial square dogs made of metal. I never understood these. They have all the advantages of my favorite dogs, but are not only made of metal, they are steel. Why risk it? Nobody needs the shearing strength of a steel dog for woodworking. If you're breaking an ash dog you're doing something wrong.
  • Routing square dogs during a bench build allows you to cant the holes so they slant towards the end vise. This aids in holding workpieces to the bench top. This is difficult with round holes. Drilling a bunch of round holes in a thick bench takes longer than you might think. I can make a jig for routing square holes and have them routed in just a few minutes more than drilling round holes.
Having said all that, I can think of one situation where round dog holes shine: retrofitting an end vise to an existing bench without dogs. It's impossible to get square dogs into a bench top in this situation, unless you laminate a dog hole strip to the front of the bench.

Here's the drawing of the bench dog from our Split-Top Roubo Plans.

22 comments:

  1. why not put the spring on the side instead of the face?

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  2. Good post. I agree on all points. Since making a wooden dog per hole my bench time is more productive and enjoyable than ever.
    Here's how those Ulmia steel dogs messed me up. At first they worked smoothly but eventually got more and more difficult to raise. I figured it was due to humidity, so I would carefully chisel and file the opening a tiny bit bigger. Oddly, it kept happening throughout the year.I tried waxing the holes. Not wanting to continue widening the dog holes and make the bench look ratty I got used to giving them a rap from underneath with a hammer. Very unsatisfactory. Eventually it dawned on me where the problem lay: the sprung side piece, which is trapped at either end and bulging in the middle, couldn't lay flat anymore because sawdust and shavings had packed tightly underneath it. Not that it a was easy to see, or fix.
    Go with the wood, much sweeter.

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  3. Thanks Tico for the warning. All the more reason to use wood.

    To the first responder, you can put the spring on the side.

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  4. +1 on the square dogs! So glad you talked me into them on my build. Everytime I use them I'm still amazed at how silky smooth they work in the holes. And like you say it takes all but a couple of hours to make using scrap.

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  5. Good post Jameel,
    I made mine square as well with hollow chisel mortiser, I like the idea of the knotch as well so when it came time to make the dogs I cut them up on the bandsaw then a router plane to put the step in the dog hole. I had a bag of nice 3/8 bullet catches that work like a charm.

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  6. One reason I like round dog holes is that it provides me much more flexibility when using my beautiful handcrafted holdfasts (by Alaskan blacksmith Jake Pogrebinsky)

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  7. Great read.

    To the point with a page of details to print.

    Perfect

    Jamie

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  8. Cliff PolubinskyJuly 11, 2011 at 4:14 PM

    Would there be any problem to using both round and square dog holes? For example, making the dog block a bit longer and cutting a square and round hole and alternating square and round holes down the dog strip?

    Cliff

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  9. I've seen that done before Cliff. No reason not to in my opinion.

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  10. Is there a maximum size for square dogs? Are there disadvantages to using dogs of 1" or larger?

    Cliff

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  11. 1" wide is about as wide as I'd go. You're not gaining much past that in my opinion, other than huge holes in your top.

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  12. should the dog holes be tilted the 2 degrees or so towards the end vise? Or can the face of the dog be slanted like they do with round dogs?

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  13. I can understand how to cant the holes in the strip for the tail vise, but I wuold like two rows of dogs for my front vise too. How do you cant those?

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  14. great post,I decide to make square dog hole on my first bench after read your post.

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  15. Most of the pictures of the dog hole row I have seen position the dog holes very close to the front edge of the workbench (2" to 4"). Is there a practical reason for this or it driven by the wagon/tail vise design? The tail vise I plan on using would require me to place my dog holes 6 1/2" from the front edge of the workbench.

    I appreciate any feedback or comments.

    JDR

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    Replies
    1. You want them close in case you're working a narrow board, it places it closer to your body so you don't have to reach in so far. It's also important when using fenced planes (plow, etc.) so you can't let the edge of the board clear the front of the bench so the fence can engage the board (and not the bench.) Get your dogs as close to the front as you can without sacrificing strength or function.

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    2. edit: "....so you CAN let the edge of the board..."

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    3. Great reply.
      I am going to make it work so that the bench dog holes are 2 1/2-3 1/2 inches from the front edge.

      Now... round or square? This the question!

      JDR

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  16. The pictures on this post are broken, which is a bit unfortunate since they communicate the square/round differences. Can you fix them?

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    Replies
    1. Pretty sure those were just static shots of our benches, not anything especially relating to square dogs. The text explains it all. We're still trying to figure out the broken images issue though.

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