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    Sharpening Plane Irons 101





    Sharpening is perhaps one of the most intimidating, misunderstood aspects of woodworking. Fact is, most folks who think they’re working with sharp plane irons or chisels, aren’t. I know, because for many years, I was one of those folks. Once you’ve mastered the basic steps and dedicate yourself to repeating them each and every time you sharpen however, you’ll find that it’s a lot quicker, and easier, than you ever thought.

    In Part I of this two-part series, we’ll cover the construction of a simple jig which, when combined with a $15 honing guide, will guarantee great results. Then we’ll cover how to properly flatten the back of a plane iron before continuing on to Part II: the final honing process.

    Honing Stop Board Makes Set-Up a Breeze
    Note: Click on any of the images for a larger view.


    The Problem: How do you accurately place your plane iron in the honing guide to achieve the bevel angle you’re after?

    The Solution: This simple stop board operates under the principle that the further the plane iron’s cutting edge extends from the honing guide, the shallower the angle you’ll be honing when the guide is set atop the sharpening stone. As the cutting edge gets closer to the honing guide, the angle gets steeper. In practice, this means that the cutting edge of your iron when honing the bevel to 25-degrees would be much further away from the guide then if you were honing at, say, 40-degrees.

    Note that this stop board’s design incorporates two longer hardwood strips which can be used to secure sharpening stones onto the plywood board. This is optional.

    A 10-in. x 12-in. piece of cabinet-grade 1/2-in. plywood serves as the base of the stop board. Attach a hardwood cleat to the underside of one of the shorter 10-in. ends. The cleat keeps the board from sliding around your benchtop when using the board.

    Now mill up some 3/8-in. thick hardwood strips—1-in. wide by 2-in. long. Pre-drill some countersunk pilot holes for attachment of these strips to the plywood base.

    To locate a stop at the correct distance from the edge of the plywood board for a given angle, place your plane iron in the honing guide and use a protractor to set the appropriate angle. Note that you’ll be doing this several times for the following angles: 25-degrees, 30-degrees, 35-degrees, 40-degrees, and 45-degrees.

     

    Now butt the guide against the board and place the stop against the iron’s edge. Use screws to secure the stop parallel to the edge. Bingo, your jig is done.

     

     

     

    A Flat Back is Key to Getting Sharp

    A brand new plane iron should have a flat back. If it doesn’t, or if you’re working with an older iron, the first step in the sharpening process will be to flatten that back.

    Sandpaper offers a quick, convenient, and inexpensive way to sharpen the backs of your plane irons. When glued to a piece of flat granite (which never goes out of flat), it’s easy to get the backs of your blades flat and polished.

    Start by using a spray adhesive like 3M 77 to glue the various grits (150, 320, 600, and 1,000) to the granite.

     

     

     

     

    Apply pressure with fingers from both hands and move the plane iron side to side along the length of the paper (not in and out). Stay at each grit until you’ve achieved a consistent scratch pattern. That pattern will become finer and finer as you move on up through the grits.

     

     

     

    After the back is smooth and flat, you can quite literally polish off those final, smallest of scratches, using either your 4,000/8,000 grit waterstone(s) or 1,500 and 2,000-grit sandpaper.

     

     

     

    Ruler Trick is a Real Time Saver

    As long as you don’t abuse your tools, you’ll only have to flatten the back of a plane iron once in its lifetime. Keep in mind however, that you’ll have to touch up the back from time-to-time during the honing process. To do this, use woodworker David Charlesworth’s “Ruler Trick.” Place a thin metal ruler on one side of your finest (usually about 8,000-grit) stone. Now place the back of the balde on the ruler and lower the blade’s tip onto the stone. Work the iron up and down until you can see an even mirro polish about 1/32-in. wide, from corner to corner, at the edge of the blade.

    Check back on Thursday, October 10, 2013 for Part II of this series on sharpening, where we’ll cover the actual honing process for your plane iron’s bevel.


     


    Ed_Pirnik