Grinding Jigs and Camber

[Jono M]

I have been building plane blade sharpening jigs.

Flat rest with magnets

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Fit magnets into holes - the small indentations, created with a hammer and punch, fix them in. I then glued on a mounting plate with tapped holes and fitted the rod blocks. A length of 12mm rod guides the assembly in front of the grinder wheel. The magnet clamping force is good and the blade will not move. Actually, it is more than enough and probably half the number of magnets would be fine.

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The 12mm rod is one meter long and I need to bend it to create a radius, that will in turn create a camber on the plane blade. A turnbuckle and wire pull/bend the rod.

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The cambered blade

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But the meter long 12mm rod and wire take up the whole length of the grinder and is not ideal.

Somewhere I saw this technique to make curves (cambers) using two points and hinged rulers. I plotted out the effects. You can change the curve by hinging the rulers more or moving the two guide pins.

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Then I tried to work out how to use this idea and turn it into a cambering jig - t slot aluminum- wood - rod - strut - angled blocks.....maybe I could but not today! ...then I just bent the 12mm rod to form the radius.

Bend the 12 mm rod with a clamp/s and check often you only need a very small radius. Make one for scrub planes and one for finer work. Of course, you need to keep one straight for flat blades.

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Showing the amount of bend for the large camber.

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Then....I "kinda" just stumbled on this idea.....

Place two fairly strong magnets on the bevel side of the plane blade. The second photo shows the magnets (hidden underneath) butted up against the board - push the blade up to the guide marks. This sets the bevel angle that I worked out earlier and aligns the magnets.

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Camber rod installed on grinder rest.

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Blade with magnets rests on rod and act as the guide for the blade. There is just enough magnet power to keep it stuck to the rod. Gently move the blade left and right as per normal to sharpen.

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You still have to check as you go and make small adjustments.

Square check.

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Camber check for both radiuses.

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Simple and cheap


I would also like to make a marking knife sharpening jig and maybe have the grinder motor movable back and forward to fine tune the bevel angle.

thanks

[D.W.]

Jono - these will help you reach your goal of getting sharp tools in the near term. i think in the longer term for both purposes you may wish do everything freehand for speed.

We typically maintain camber with honing and grind only to remove metal behind the honed edge (without removing the edge) to make it easier to maintain shape.

The confounding issue doing this is getting initial camber that's suitable for a given plane, of course.

But the thinking process is admirable, and thinking and experimenting in the shop is always good when results can be observed as in your case (not so much so when results are hypothetical and attainment of goals is also on a hypothetical basis!!).