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Equipment Hub: Sharp as you want to be

Andy Overbay for Progressive Dairy Published on 30 October 2020

There are a good many lessons I learned hoeing tobacco. One thing I learned early on was: If you picked out the lightest hoe, so it would be easier to carry, you soon found out the lack of weight meant you had to work harder to cultivate the soil.

You also learned quickly that a sharp hoe or tobacco cutter made life easier as well.

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After a few scoldings from Dad, I soon also learned there was a proper way to put an edge on a piece of metal – and from observations of others trying to sharpen a tool or knife, it is probably a lesson that needs telling.

First off, let us agree that there are many degrees of sharpness. What is perfectly fine to me may not suit you at all, but there are some common mistakes that, if avoided, are sure to yield better results.

The first thing I learned is to not make matters worse. Filing metal toward the cutting edge will only dump material on or near the edge, in effect dulling it. You always want to file from the cutting edge to toward the centre or backbone of the tool.

Once you get started, there are still common errors that need to be monitored. For example, do not begin to sharpen a tool that is completely dull. Sharpening takes time and practice to learn, so don’t go from little league to the major leagues on your first attempt.

Another common mistake is to use too steep an angle on the blade as you apply it to a stone, grinder or whatever you are using. The optimal angle for a knife, for instance, is 22.5 degrees. A simple trick to teach your hand to hold a near-perfect 22 degrees is to place two pennies under the blade’s back and use them to set the muscle memory in your hands to 22 degrees. You can also fold up a Post-it note and set a 22.5-degree angle. Since the note is square, a diagonal fold will produce a 45-degree angle. Fold it once more and the angle is again cut in half – 22.5 degrees. You can then use the folded Post-it to “train” your hand on the proper way hold the knife.

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Mower blades are probably one of the most “in need” cutting edges on the farm or in the garage. The fact that mower blades can and will be subjected to dirt, grit and rock means they are bombarded with edge-dulling materials during each use.

Mower blades should be aggressively sharp – but not as sharp as a razor’s edge. You should be able to touch the blade with your hand without getting cut. Contrary to popular belief, a lawnmower blade can be over-sharpened. In fact, an edge that is too sharp has the tendency to roll over, which can cause blades to get nicked and chipped. Additionally, lawnmower blades that are too sharp get duller faster, resulting in the need to sharpen more frequently and a shorter blade life.

I might also add that while a mower blade needs a properly maintained edge, it is easy to overlook that the turned-up edge opposite the bevel that creates lift can also wear down over time. If the blade is too worn, replacing it is the best option.

Replacing sections on a sickle may also be advisable, but if you feel like you want to try to sharpen the blades, it can be done. It is best to disconnect the sickle and remove it from the mower completely. A 4-inch handheld grinder will do a good job restoring the edge on each section, but be careful. Just like any other sharpening session we have already talked about, you need to exercise care not to get in too big of a hurry and overheat the blade. Heating can cause the blade to lose temper and greatly reduce the strength of the section.

You also need to be careful to adhere to the established bevel angle of the section. Keeping the blades even will help the bar work more smoothly and keep the sections working in concert with each other.

Chainsaw blades can be sharpened easily using several methods and tools. If you use a chainsaw much around the farm, you will invariably find the odd nail, barbed wire or any number of ferrous objects in trees. I was sawing down an old tree that threatened to fall on a fence that kept our dry cows out of the corn, but I hit something hard exactly halfway through the trunk. Luckily, I had more than one saw with me and, when I felled the tree, the mystery was revealed. Apparently as this tree grew, it pulled a large limestone rock up into the base of the trunk and grew around it. (I mean really, who would think to look for a rock 10 inches up into a tree trunk?) Once my saw found the rock, the chain was done for the day.

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Again, I was lucky to be carrying two saws so I could complete the job that day. Continuing to use a dull chainsaw will soon spell the end of the bar as well. Dull chainsaws generate heat and, as we said earlier, heat is the enemy of steel – especially blades made of steel.

Finally, no matter what you are sharpening or how you are going about putting an edge on the blade, you should always wear proper eye protection. A tiny sliver of metal can cause a good bit of damage and a great deal of pain. Over time, grinder wheels can fail, and if you ever have had a bench grinder wheel blow out on you, the results can be very dramatic. Safety is a habit you can always live with.  end mark

Andy Overbay holds a Ph.D. in ag education and has more than 40 years of hands-on dairy and farming experience.

Andy Overbay
  • Andy Overbay

  • Extension Agent
  • Virginia Cooperative Extension
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