Monday, April 24, 2017

Spring Sharpening

With the arrival of warm weather my grass has redoubled its effort to make my yard an uneven carpet of green.  Before getting the lawn mower out I needed to resharpen the blade.

I’ve stopped taking it to a lawn or garden center and getting the blade resharpened.  I bought a little attachment for my Dremel tool.  The attachment screws on to the front of the tool and come with a special diameter grinding stone.  A guide helps me hold the blade angle and lets me grind out the really dull and damaged
areas. 


sharpening the edge
Start your sharpening!


 On my electric lawn mower the blade rotates at 3600 times a minute.  A rounded edge will cut the grass by tearing it, but cleanly cut blades make for a better lawn.  Better looking grass without significantly increasing my work load is my goal, so sharpening the blade makes sense.

I clamp the blade down on a sheet of plywood and run the Dremel grinding stone over the old edge several times until the old discoloration is gone and so are the majority of nicks and gouges in the edge.  I use the plastic guide to hold the angle, but perfection isn’t required.  A fine dry stone pulls the wire edge off the other side.  I should mention my mower blade is a classic chisel grind.  I test the sharpness by shaving the edge of the plywood board I use as a work station.

sharpened grass cutter blade



The last step before reinstalling the blade is to check the balance.   If one side of the blade was significantly heavier, the mower would vibrate and damage itself, perhaps even break a blade.  The heavy side just gets another pass and a second balance check.  Repeat as required.


Since I was in sharpening mode I got out my Ken Onion Work Sharp blade grinder and sharpened my hatchet. 

As you know I recently discovered my SOG camp hatchet was extremely dull but luckily my friend Derrick brought his Gerber hatchet.  Having a fire in the fireplace as part of the evening’s entertainment and as a back-up to winter storm power failures is a nice luxury.  The price you pay for this is splitting wood into suitable burning size.  A sharp hatchet is required and mine needed a good sharpening. 

Every fire deserves a sharp hatchet

 I selected the course belt and an angle of 25 degrees as a starting place and ran a black marker pen over the edge.  The marker helps me see what I’m doing and where I’m taking metal off.   A couple of passes and I had removed the entire marker pen.  I flipped it over and did that side. 

dull SOG camp hatchet
Before sharpening, note nicks in blade


The blade looked good so I changed to a medium grit.  That took a little more off and I was satisfied.  But how you really tell if your axe is sharp?

I decided performance was the only way.  I grabbed a section of a landscaping tie and a length of pine 2X4 and tried it out.  I was less than impressed.

The hatchet didn’t cut the wood fibers, but crushed them.  Definitely not sharp.  I changed the angle to 10 degrees and repeated the process.  This angle worked better. 


bye-bye nicks!


While I was touching up the edge I noticed the cutting edge wasn’t centered in the blade’s secondary bevel.  This typically happens when one side of a blade is sharpened more than the other.  I played with it for a while and discovered one side the bevel is flat ground while the other is slightly convex.  This bevel asymmetry is the cause for the non-centered edge.


I worked on the edge a bit more and called it finished.  It’s not perfect, but it’s sharper than it was.  Chopping pine boards may not be the best material to judge hatchet performance.  I’ll look around for actual logs to try it out.

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