jig for grinding cambered #4/#5 irons?

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    tim rapp

    I’m a huge fan of cambered irons (#4, #5, #78, etc) for squaring stock. I follow the advice in Paul’s Making a Scrub Plane video to grind the edge to shape on a bench grinder (7-1/4″ radius for 2″ iron). Unlike Paul, I don’t have 50 years experience, and find it really hard to grind a smooth radius curve with consistent 25 degree bevel angle. For my #78 iron, I created a super simple jig that greatly sped up the process and gave me a perfect 2-1/8″ radius hollow-ground edge, requiring 3 min on bench stones to complete. Anyone know of a jig design for grinding 2″ plane blades? Somebody must have created one, since cambered 2″ irons are so common.

    PSA: if you have a cambered bench plane iron and love it, and don’t have a scrub plane (#40 or converted #78 ), I highly recommend.
    ps – yes, I know cambered blades don’t have to be perfect — but a jig made it much faster to radius my #78 iron, and I prefer to spend time working wood not sharpening.

    • This topic was modified 10 months ago by tim rapp. Reason: tweaked the title
    • This topic was modified 10 months ago by tim rapp. Reason: add ps

    Hi Tim. Could you include a picture of your jig? Many here might be curious. I certainly am. Sounds like it is a jig to create the camber on a grinder since you mention that it is a hollow ground edge. Besides your scrub plane, which do you like to put a crown on? Just curious.

    Lots of folk like camber for one purpose or another, as opposed to just taking the corners down a bit the way Paul does. They even talk about exactly how much camber to use for each type of plane. They can bet pretty precise. Obviously crowning a good bit is required for a scrub plane. Given what a scrub plane is for, that probably does not have to be very accurate. Some like it for planes used to joint the edges of boards. That has to be somewhat more accurate I suppose if you are going to take predictable amounts of wood off the higher parts of an edge. I did that for a while and it does help edge joint, but I seem to have stopped and just use uncrowned planes for that. Maybe that is a mistake on my part. And of course, a bit of camber is nice for a smoothing plane. That is the main place I like to use it. I have a number 4 I just use for smoothing and I put a bit of camber on it, but I do it by applying more pressure on various parts of the plane while basically sharpening as Paul does. It is not very accurate I suppose, but it seems to work okay. I seems to need only a tiny bit of camber for smoothing pretty well.

    I would be curious about how others use, or do not use, crowning on their planes.

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