Serial Number: 12490300297

The Wen Variable Speed bench grinder is part of the workshop’s dedicated sharpening station.

• The left wheel is only for hollow grinding flat blades like chisels and planes.
• The right wheel is for sharpening other blades.
• The grinder should always be used at the lowest speed.

Here is a video covering the use of the sharpening station for a chisel:

Sharpening a Hollow Ground Chisel

A hollow grind means the blade is ground on the wheel to form a concave curve at the end of the chisel.  The advantage of a hollow grind is that you can sharpen the blade again and again simply by sharpening the leading edge.

The tip on the right is sometimes called the “toe” and the thick part on the left is sometimes called the “heel” because feet also have arches that are a convex curve like the hollow grind.  This is a useful metaphor because to sharpen a hollow ground chisel you make sure the heel and the toe are both touching the stone at the same time.  Then you make a few passes across the stone while holding the chisel with the heel and toe touching it.

The result is a newly sharpened edge.  It’s thin so you don’t need to take off very much metal at all.  You can sharpen it ten or twelve times before you need to grind it again, unless the edge has been damaged.

Setting Up for Hollow Grinding

To set up for hollow grinding you need to insert your chisel or plane blade into the sliding clamp.

It mustn’t be at an angle and the top and bottom of the sliding clamp must be parallel to each other.

 

 

 

 

 

 

 

 

 

 

 

 

You’ll need to adjust the platform on which the sliding clamp slides so that the blade is at the right angle.  And, the blade should not be touching the wheel until you rock it forward to make contact.

You can make several changes to set the correct position of the platform:

• You can raise and lower the platform: there is a locking knob on the right side of the platform.
• You can change the angle of the platform: there is a locking lever on the right side of the platform.
• You can move the platform closer to or farther from the wheel: there is a locking lever on the left side of the grinder.  Point it straight back and slide the whole platform forward and backward.  Then lock the lever again.
• You can slide the chisel closer to the wheel (or farther from) by loosening the sliding clamp.

Hollow Grinding

Once your chisel is mounted on the sliding clamp, and the platform is in the right position, turn on the grinder and set it to the lowest speed.

Rock the chisel forward so it contacts the wheel lightly and move the blade side-to-side.  Use a very light touch.  You are trying to minimize heat buildup.  If you are doing it right, the blade will be only slightly warm to the touch – not hot.  If you can’t touch it, you are definitely grinding way too hard or too long or at too high of a speed.

Do not let the blade move far enough so its side gets close to the edge of the wheel.  It is best to keep the edge of the blade no closer than 1/4″ from the edge of the wheel.  The risk is that if only a narrow slice of the blade is in contact with the wheel, the grind will be too aggressive and it can damage the tip in a fraction of a second.

You can coat the blade with ink from a sharpie or a whiteboard pen to see what is being ground away and what remains.

Continue hollow grinding until the entire leading edge is freshly ground and convex curve reaches the heel (the top of the chisel bevel).  It might only take a few light passes in total.

Honing The Back of a Hollow Ground Chisel

Whether you have just touched up the leading edge with a stone, or have just finished hollow grinding a chisel, there is always one more step to finish the job: honing the back.

Simply place the bottom of the chisel onto the stone and rub it back and forth across the edge few times (not parallel to the sharp edge).

The result is the bottom of the chisel is completely smooth and the burrs that form when the edge is sharpened are all removed.  This is a micro-sharpening step that leaves the finished edge ultra sharp.