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Harbor Freight Circular Saw Blade Sharpener


  • Harbor Freight Circular Saw Blade Sharpener

    The Chicago Electric Power Tools Professional circular saw blade sharpener (Item#96687 at Harbor Freight) was on sale after coupon for $36 this month. My BT3 was bogging down ripping a stud earlier this week so I figured that after 8 years of intermittent use maybe the blade was due for its first sharpening. I was up for a new learning experience, and I like a bargain, so I picked up the sharpener on Monday.

    The included instructions are fine for assembling the machine. The machine is lightweight and sits on a small, 1 sqft footprint. It is highly adjustable, but all adjustments are secured by tightening nuts so it takes patience to get angles just right when setting up the diamond grinding wheel to make square contact with the saw blade's carbide tip face and top. It reminds me a little bit of the patience needed to square the BT3 SMT.

    The included instructions are not sufficient for actually doing the sharpening. That's not unexpected since tool sharpening is a trade that takes time to learn and the geometry of saw blades is more complex that one might think at first glance. Luckily, there are many online resources for learning about blades that will help quite a bit when using this sharpener.

    I particularly recommend these resources:
    • Youtube video series "Saw Blade Technical Information" by Dynamic Saw's Daniel Callari especially #6 on terminology and #7 on top grinds, but all are worth watching.
    • CMT Utensili PDFs on saw blade definitions. Their blade descriptions include good images of tip angles.

    Based on this information I identified my blade as a flat top grind (FTG) that is great for ripping, but perhaps not the best for cross cuts.

    I found online videos and descriptions of how to use this tool that focused on sharpening the face of the carbide tip. The first step in setup, and one that is under-emphasized in these posts, is to square the face of the carbide tip with the grinding wheel. It is this step that takes the most time and patience in the whole sharpening process, and I would argue that it is the key to a good result. In this $36 tool you don't have fine adjustment worm gears that help you set a 20% hook or insure that your blade is perpendicular to the grind wheel, so you have to do it by eye with an engineer's square and a wrench plus a bit of black sharpie on the the carbide face to see if you are getting a even grind from your set. While the result may not be computer-perfect, with patient, iterative adjustment you can do a pretty good job.

    When sharpening the carbide tip face I prefer to pull the grind wheel forward into the gullet without contacting the carbide or steel, and then gently rotate the blade back to the grind wheel so that the carbide face lightly "kisses" the wheel for 3-4 seconds. Here's where a sharpie is your friend. Blacken the carbide face, briefly and lightly kiss the wheel, check for any spots where the black sharpie remains and make the needed adjustments so that the face and wheel are absolutely square. Once you've got this set, the rest of the face grinding is just careful repetition.

    I found no instructions on how to grind the top of the carbide tip using the diamond wheel (the instructions said to use the included emery wheel). In fact, many instructions for home sharpening skipped the top of the carbide all together. If you watch Daniel's Youtube videos that I referenced above he shows a good diagram of why doing only face grinding or doing only top grinding results in a poor sharpening job or removes too much carbide, and why doing both face and top grinding is recommended. I've attached two pictures showing my setup for doing the top grind since I haven't seen that explained elsewhere. I needed to remove the grind wheel cover to get the clearance I needed, and I also needed to change the position the motor and blade support from the face-grind settings to get the correct top grind angle. I had a flat top blade, which simplified the settings, but if I had an ATB blade I could have adjusted the motor to grind the required bevels.

    Setup and sharpening took about an hour. I took my time and enjoyed the process. I examined every one of the 36 carbide tips several times using a magnifying glass during the process and it was obvious that the grinder left striations across the top and face. My sense is that the coarse grind is real, but minor in impact compared to the positives of having a much sharper blade.

    I'm pleased with the purchase and the result, but if you don't like fiddling around with a tool and/or are under time pressure and/or use premium blades and create professional-grade projects you may have a different opinion.
    Attached Files

    • cabinetman
      cabinetman commented
      Editing a comment
      Very good write up. Makes for understanding a maintenance tool easier. Thanks for the review.I didn't get to enter any ratings.

      Last edited by cabinetman; 06-26-2013, 05:01 AM.
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