Thread: Rabbet plane throat opening question

From your pics & description, the gap is certainly minimal. When making a plane, I aim to get the mouth so the blade won't come through at first, so that I can file the front of the mouth 'til it's exactly where it needs to be. From trial & error, I've found that the gap needs to be more than the thickness of the shaving it has to pass, but by just how much is not something I can put a precise figure on, because it depends on the plane & its intended purpose and the sorts of woods you plane. A plane that will only be used for making very fine shavings can have a ridiculously small gap, but in your case, I suspect you are going to want to use your plane for a range of jobs, so you'll need a reasonably generous gap to cover all situations.

I find it can be hard to judge the actual gap by eye, the bevel of the blade & reflections off the shiny metal can fool you. To be precise, use a feeler gauge to determine exactly what the gap is. If your gap is really 0.3mm with the blade set to take a shaving of about 5 thou (0.127mm), which is a moderate shaving with the grain & 'light' shaving across the grain, it should be enough to let those shavings through comfortably, so if the mouth was jamming even with very light cuts, it's pretty certain there isn't enough room as it stands. Rather than aim for a specific gap size, I usually just sneak up on what I want by taking a bit off until there's a small, even gap, then assembe the plane & test. I take it very slowly & carefully, the thought of wrecking all those hours of work I've put into making the damn thing focuses my attention, so if it takes an hour to get it right, that's fine! You can always take a bit more off, but you can't put metal back, so it's better to be conservative. If you feel it needs more down the track, that's easy enough to mange.

If it were my plane, I think I'd be getting out the file pretty quickly. Fettling a bevel-up plane like your block plane is more difficult than a bevel-down, because unlike a BD., the size of the gap varies with blade extrusion on a BU, so you'll need to proceed carefully. Putting a good, clean bevel on the front helps prevent jamming, too - something I discovered on the first metal-bodied plane I made.

I don't use block planes for fine work, so I wouldn't be too precious about it, myself, but other mileages vary....

Cheers,