Ergonomics

When you push a plane, you are exerting a force down, against the bench and forward against the stop. We build our workbenches to react these forces. But those forces don’t come from thin air. The force you apply toward the stop is reacted in friction between the soles of your shoes and the floor. The force you press down with is counterbalanced by your lower back and “core” (more about that tomorrow). If you followed my physics, you now know what we should have in our shops. But how many of us do?

Bench height:
Conventional wisdom suggests a high bench is easier on your back. It saves you from leaning over. If your bench is used primarily for coffee drinking and client impressing, then by all means make it bar height and don’t forget the curly maple and purple heart. But if you do a lot of planing, it really makes sense to make your bench low enough to allow you to use your upper body weight. The exact height depends on the thickness of your most oft planed stock and the sort of planes you use (wooden or metal). My bench is 2″ under palm height. And I’ve worked comfortably on benches 4″ under palm height. I really recommend guys think again about the palm-height rule of thumb for work bench height.

Traction:
Guys in powered up shops stand in front of their machines for prolonged periods. Many wear shoes and have mats to make their work more comfortable. But hand tool users have different needs. Planing gnarly wood requires a good connection to the floor. My concrete shop floor gets very slippery with even a fine layer of oily wood saw dust (I was working Lignum Vitae recently and my shop floor was like a skating rink). I’ve since added an anti-fatigue mat that has really helped.

Shoes like these can help you stay safe in your woodshop. But they can also get you shot in some inner cities!

Even the skimpy 3/8″ thickness makes a huge difference for prolonged periods standing at the bench, not that I do that often. It’s also less height to trip over. Its sweepable surface is key to maintaining good traction. I chose a mat as long as my bench and 2′ wide (which is plenty). If I had it to do all over again, I would have chosen a 10′ mat for my 8′ bench with the extra 2′ at the right end. I know there are other, possibly cheaper mats available and I don’t know anything about them (so please add your comments). But I like this mat.

I think it makes sense to wear athletic shoes designed for side to side motions in the shop. Shoes for tennis or basketball, featuring low flat soles, really make sense for planing. When working long stock I find I do a fair bit of footwork, walking along sideways with my plane. The traction that athletic shoes offer also helps when securing work at the horse. Neither boat shoes nor work boots make sense for this. And in case you are curious, 18th c leather shoes with heels are absolutely scary to work in.

Shop Layout:
Moving lumber into and projects out of your shop should be easy, with a minimum of maneuvers and turns. In my ultimate shop, my wood rack would be on the same wall as my workbench and the entrance would be at the end of the shop. As my shop is now, the wood rack is in the center of the shop opposite the workbench. Lumber removed from the rack must either be swung 180 degrees or I have to do the limbo, ducking under long boards. This is an ergo no-no.

In terms of this blog entry, your sharpening station can be anywhere. Focus instead on ensuring you can move lumber or other heavy items in your shop easily. I pulled a muscle in my back carrying a heavy flake board kitchen base cabinet from one side of my shop to the other. I had to duck under the heating ducts while stepping over something. I could have used a moving dolly, but my floor was too messy and the aisle too crowded., which brings me to my next point:

Trip Hazards:
The splayed legs of my saw horses present trip hazards. I’ve tripped or hit my shins on my saw horses’ legs countless times. Scrap wood, tools, dollies and other workshop items all create opportunities for you to fall. Keep your floor clear around your bench. Clean shops are always nice to work in. In my experience, clean up time is the first thing I skip when time is short. But that’s probably not smart. Use Woodworking Safety Week to perform a spring cleaning (I have). Get the scrap wood out from under your bench and find a spot out of the high traffic areas for your horses.

Some folks think of ergonomics in terms of comfy office chairs. We need to think about ergonomics in terms of safety. Think of your body as a machine and give it every possible mechanical advantage possible.

Adam

5 thoughts on “Ergonomics

  1. Auguste Gusteau

    10 cm under the crease on the inside of your wrist is your comfortable working height???
    Well, at this point why don’t you work directly on the floor?
    Seriously, if I had to work to that height I would have back pain after only 10 minutes.
    My working ideal height for planing, filing and sawing is the one in which I have my elbow bent to 90 degrees.
    Only when chiseling and sawing i need the working piece a little lower, so i put something under my feet.

  2. Mike Siemsen

    Adam,
    As to bench Height I went with the first knuckle on the pinkie which is about 3 inches below the palm, which I believe I got from Chris S. I blogged a bit for saftey week on cleaning the shop too. I believe the broom is one of the most important and underrated tools in the wood shop! A quick temporary fix for slipping around on your floor is spray glue. Just spray some where you need traction, it wears off after a while. Good if you are in a temporary demonstration set up and they don’t mind.
    Mike

  3. Adam Cherubini

    I think Schwarz’ benches are lower than that. I talked to Mack Headley in Colonial Williamsburg about this very issue a few years ago. He said he recently sawed the legs off his bench to bring it down an inch or so.

    None of us can tell you what to do. All any of us can do is highlight the issue, ramifications, and provide some analysis, which I think we’ve done. What’s needed now is for thoughtful earnest workers like you to try stuff and see what you think and report back.

    200 years ago, your master’s instructions represented the collective wisdom of hundreds of dedicated professional craftsmen. Today, we have the internet to collect these views. While on this subject many different view points and recommendations pervade, I’ve seen concensus form in several other key areas.

    So try it, don’t be afraid to change it, and share what you learn.

    Adam

  4. Jon

    About a year ago, I bought 2 anti-fatigue mats at Woodcraft. They’re 2′ x 5′ and cost about $15. I have never tripped over them, which was a concern. However, I can now work on my concrete floor for hours without killing my back.

    My wife started turning recently and agrees with me about how they help your back. They are on sale this month, so I went back and bought 3 more so I won’t have to move them.

    As far a bench height is concerned, you and Chris need to get together and figure this out. I just finished my Roubo and it is just under palm height. (Is a workbench ever finished?)

    Thank you for your fine articles and blog.

    Jon

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