Convex Jointer

Re: Convex Jointer

woodburnbob

>This question is one you'll get many opinions about, I think, Joel. Here's my opinion.

Assuming you are talking about a Bailey type plane, a 24" cast iron plane is somewhat flexible. As well, how tight you clamp the iron alters to some extent the local "flatness" around the mouth. The measurement you report is probably dynamic even if it is accurate under the conditions you obtained it.

How did you measure the 0.004-0.006? Even an accurate straight-edge can give you error, depending on very local variablity. I wouldn't get too excited about measurements until I used a conventional granite surface plate and a three paper test, or ideally spotting...but even then there's a lot of room for confusing error, depending on where and how you are pressing downward during measurement and during operational use (planing). Measurements taken on a 24" piece of cast iron at rest wouldn't be expected to equal those taken when various forces are applied in use. Ideally, you'd have a 24" X ? surface plate and use the diagonal. Put a strip of paper under the far toe, the mouth area and the far heel. Does the mouth strip pull free?

This is all theoretical though. Functionally, what is the problem with a convex sole? It is that in order to cut a shaving, the iron must be advanced deeper because the sole at the mouth is high. Once the extended iron just grabs the wood, the slightly fexible sole and the hyper-extended (and poorly supported) iron dive into the wood. The symptom then is that you get nothing from the plane until the iron is gradually extended, and then the first thing you get is a very irregular, thick, broken shavings which typically choke a narrow mouth. Predictably, you also have massive chatter and tearout in the stock you are planing. What you won't get are precise, incrementally thin or thick, pretty shavings. Other things could produce this symptom, like a poorly fitting, wobbling frog, so you also have to work through various diagnostics if this is the symptom.

So, a good functional answer to your question, then, is: Does the plane work well despite the sub-par measurement?

What I don't think you want to start is the folly of "lapping" a #8 "flat" on sandpaper and plate glass.

There's a bit more to say about using a #8, but I'll stop with this. Good luck and how you report back. Bob

Ignore my post...it's about concave not convex

woodburnbob

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Re: Convex Jointer

ThomD

>Convex where? If it is imediately in front of the blade, that would be bad If it is somewhere on the forward part of the sole that probably doesn't mater much. You could always try it and see if it works or not.