Wednesday, October 10, 2012

On Infill Planes (Part 1 of ?)

I like to promote the idea that good work can be done with humble and simple tools. So, talking about infill planes feels a little disingenuous. Recent experiences have taught me that while both humble and fancy tools can both be made to do good work, some tools make it a little easier to do.

My first infill plane was a Mathieson coffin smoother, with a dovetailed steel body. A couple of years later, I bought a cast iron Musgrave infill (possibly made by Norris?) and a Spiers coffin bodied smoother that is slightly smaller than the Mathieson. Both have required work to get them functional, and I’ve learned a lot about tuning up infill planes from them. (These are the two in the photo above)

I'm aware that infill planes have a certain aura. New infills can cost more than a decent used car, and the more notorious builders have impressive reputations for precision work. And to hear some folks talk about the older models from the British Isles, you’d think they were magical instruments, carried down from the days when gods and monsters walked the earth. What I’ve learned is that they’re not. They’re just as subject to wear and imperfection as any other tool that was made and used by the hands of man. Once they’re properly tuned, and once you’re used to setting one up, infill planes do make it possible to easily make very minute adjustments to shaving thickness, and allow for more accurate surfacing to be done. I'll talk about tune-ups in the next installment.

The Musgrave plane taught me the most about setting up an infill plane for use. I tried setting up with the blade short of the mouth, and using a hammer to adjust it to the desired setting. But eventually I realized that I could just loosen the lever cap, let the blade assembly sit on the bench, slide the plane slightly forward to bed the iron, tighten the lever cap, and work. It’s very fast, and requires no other tools to set up this way.

After using it for a while, I realized that the lever cap also doubles as a very fine depth adjuster, and it doesn’t need to be heavily cranked down. Whether this feature is by accident or design, I have no idea. But because the lever cap is built as a lever, and multiplies the force that’s applied by the screw, which is also a force multiplier, very light pressure on the screw will hold the blade pretty firmly in place. If the pressure is too light, it’s easy to knock the blade out of alignment, but it’s not hard to find the tension sweet spot with a little practice. Once the plane is set up, the lever cap has enough force to slightly affect the projection of the blade from the bottom of the plane, and make those delicate (sub-thou) adjustments I was talking about. With time and practice, setup and adjustment of an infill plane is much faster and easier than on a Bailey style plane.

In recent work, this adjustability has helped me to shape blanks more precisely than my power jointer or planer would allow. At the time I was putting together a complex compound miter joint with large surfaces, so accuracy was more important than normal. Because the adjustment on an infill is so precise, (using only the lever cap, I don’t have mechanical adjusters on my infill planes) I was able to take much finer shavings, and get the blanks accurately square and reference-flat. This in turn allowed me to make more precise cuts on a sliding table saw, thanks to the ability to reference more accurately against the table.

Infill planes do need to be very well tuned. It took me a while to understand what that meant. I’m used to Bailey style planes, and while Bailey style planes have many areas that need to be tweaked, tuned, and properly fitted, these areas have been described in detail in many publications, they’re more obvious, and more accessible. Infill planes are a lot more subtle. The entire assembly is one solid unit, and when there are no obvious assembly points to tweak, it’s hard to figure out what can be done... and what needs to be.I'll write about that in part 2

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