I’ve been testing curves for back slats recently. That’s meant a lot of time with my compass plane making bending forms. That plane is a chatterbox. It’s in its nature. There are so many light, movable parts only partially attached to each other that it’s a wonder the thing can stay quiet at all.
Most plane makers go to great lengths to make their tools out of heavy, solid lumps of stuff. It keeps the chatter to a minimum. Compass planes are not built the same way.
But there are things you can do. Starting with low expectations helps!
I used to think of my Record 020 as a jack plane. I expected it to do a lot of work quite quickly and give me a decent result. These days I see it more like a jointer plane. I use it for the last few shavings to get the final shape. The curve comes from a bandsaw, jigsaw or bowsaw followed by spokeshaves. They are my jack planes for curves.
As with all edge tools start with the sharpest iron you can hone. It won’t solve everything but at least you’ll know that’s not one of the issues. Grind and hone it like a jointer plane iron – with a small camber. Rather than trying to take a full width shaving I work the high spots and check for square frequently. I don’t expect to get beautiful long ribbons from end to end. Given that we’re making a curve the grain direction will change at some point and these things don’t go up hill!
If you’ve got a sharp, cambered iron, lightly set, you’re cutting downhill and you’re still getting chatter there are a couple of things worth investigating. The mouth of the plane is a magnet for resin. It builds up and needs to be scraped out. There’s little you can do about the step between the mouth and the frog. The frog has no fore and aft adjustment. I’ve tried shimming it with mylar and sheets of tin foil. Not worth the effort. Make sure that the cap iron fits well and the lever cap is tight.
With the mouth clean have a look at the peened pins that hold the frog to the sole. With the sole set for a concave curve these can stick out and catch. You won’t notice it when planing but it can’t help the chatter. You can sand the sole much as you might lap a smoothing plane. I didn’t notice a lot of difference but it can’t hurt.
And finally, with the plane perfectly set up a squiggle of wax on that rather rough sole makes the world of difference.