Blog: Designing New (Wooden) Tools By: John Heisz
When it comes to new projects and the videos / articles I make for them, there’s usually a lot more work that goes in before the finished product appears. Very much like that iceberg that only shows 10% of its mass above water, there can be weeks or even months of work that goes into what I would consider a successful build. And this is especially true for a project where I make a plans available – I go to great lengths to not only make sure that it works properly, but also to refine the design to make it easier to understand and build.
A great example of that is my recent power wedge bar clamps, these went through a number of revisions before I was satisfied enough (never fully satisfied…) to call the design final. And with the success of that one, I used those methods to start work on the design of another clamp – a long parallel jaw version, similar to my wooden bar clamps. These use the wedge to lock the moving jaw on the bar, but also have the lead screw angled down to force the pad tight to the bar as well:
What this does is it keeps the pad parallel to to the fixed jaw with stock clamped at the bottom. That’s the benefit of a clamp that acts this way – you can lay the parts to be clamped down tight to the bar and the bar will help to keep them lined up.
I made another change for this one in that I used rubber on the wedge instead of sandpaper. The rubber has two advantages: first, the grip is immediate without the need for holding the wedge in place. Depending on the orientation, the sandpapered wedge can slip before enough pressure is applied to lock it, and to solve that you hold the wedge and keep it from moving. This is not really much of an issue, and something that you very quickly get used to after using the clamps, but the rubber does improve upon it. Of course, the rubber I used is less commonly available than sanding belt, so that goes against it.
The other advantage is that it won’t abrade the surface of the bar like sandpaper can. Not that it’s a significant problem – it would take several hundred uses to see the impact on the bar – but again it is an improvement.
The value of building a prototype to test these ideas is incalculable, since while something may look good on paper, it may not work as expected in when built. Perfect machines exist on paper, but never in reality. There are always a number of seemingly insignificant or hard to foresee problems that don’t appear until you make and test a design.
One potential problem with a down-angled lead screw is the range of motion for the pad. Obviously when the pad is being continually forced downwards it will eventually get harder to move as friction increases. But given the infinite adjustability of the wedge system, it doesn’t have to move very far to apply adequate pressure to the stock. I tested the range on the prototype and found it to be more than enough, in my opinion:
I talked about this clamp design in this video (it’s longer, but feel free to skip ahead to 4:50 where I talk about the clamp):
While I’m not finished with that new bar clamp design, I started on another (I’ll often do that – I find it can make it easier to break up a longer project to get a clearer perspective and not get burned out on it too quickly) one, this is based on the vise grip style c-clamp that’s fairly popular:
This is a very rough mock-up (not worthy of the “prototype” label) mainly built to determine how finicky the locking mechanism would be, and how accurately it has to be made. Not that wooden things can’t be made with high precision, but the chance of success goes way up when less is required.
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From that mock-up, I took the time to draw a more refined model in SketchUp and used that to produce the first prototype:
I consider a prototype to be close to the final design and built to test how well it will work and look for problems. I’ll often make it from inferior material (like the lower quality plywood I used here), since it’s not meant to be a fully functional unit. Along with that, I generally don’t take the time to complete it – this is missing the adjustment screw from the end that the locking strut pushes against:
I used one of my new clamps to just hold a strip of plywood inserted into the end to the right depth to act as that screw. The grip is reasonable – it’s holding itself and the the weight of the other clamp, and better materials will improve that and make it quite usable.
Along with looking for problems and checking the action, I can also start giving the parts names, like that “locking strut” mentioned above. When I started making plans, I used letters to name the parts, but gradually shifted to assigning names instead. I think that it makes it easier to understand how it works while building it if the parts involved have a specific, descriptive name.
Another question the prototype answers is whether the project is worth making a plan set for. I’ve said before (many times) that making plans consumes a huge block of time, and can be quite stressful. Along with the fully debugged and optimized design from initial idea through to the final build, I also need to produce the step by step plans and make sure there are no (major) mistakes. The build article usually has to be more comprehensive to provide details that the plan doesn’t include, and then there’s setting up and creatively writing a sales page for the plan set. The whole process can take a toll and that’s why so few (relatively) new plans come out each year.