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Inspecting Sharpened Saw Blades

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Inspecting Sharpened Saw Blades

Everyone knows about the guy who shows up at your shop and promises you something “just as good” for “a lot less money”.  

With cheap equipment, sloppy work and a lack of knowledge a “saw butcher” can ruin a $100 blade, thousands of dollars worth of material and tens of thousands of dollars worth of customers. 

What follows are true stories of tools sent to Carbide Processors, Inc. in Tacoma, WA for analysis.  

Inspecting Saw Blades

Also refer to our Industrial Saw Blade Index for more Saw Blade Articles. 

1.  All the tips are the same height.   This is a picture of a saw sold to a Weyerhaeuser mill.  The supplier used two different sizes of tips.  

 

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2.  There are no cracks – not even microscopic cracks.  A cracked saw is dangerous and it is illegal to service. Repair or use it.     

 

 

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3.  All the tips are ground.   This tip was not side ground.   You can see it is too short since it does not clear the saw shoulder.

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4.  Solder is not burnt.  Here the solder (braze alloy) was overheated enough to bubble the zinc out of it. 

 

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5.  The carbide is ground but the steel is not.  Here there is a big cut into the shoulder.  (Exception some saws have the shoulder behind the tip roughed to give a rasp like, polishing effect.)   If you are running a gang of saws you may see the same thing if the saws move sideways enough to cut into each other.  In any case cuts in the shoulder are dangerous.

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6.  There are no chipped corners or edges

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7.  There are no dull edges

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8.  Grinding is done on solid, precision equipment.   Above is a big solid grinder in a saw shop.  (Notice how the floor shines.)

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9.  A good person can do a very good job on the one to the right but it takes some time and a very high skill level  which doesn’t go with lowball prices. 

 

 

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10.  This top of this tip was dubbed by a fast job on a cheap grinder.

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11.  Here are two teeth ground way too fast.  The excess heat of “hogging off” a lot of carbide in a single pass was more than enough to fracture the carbide.   It is cheaper to slap a blade on, grind off a lot of carbide and then ship it back without inspecting it.  Good shops don’t do it because teeth like these shatter ruining the work if nothing else.     

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12.  Good blades are brazed so that there are no gaps between the steel and the carbide.  See our articles on Brazing

 

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13.  Good blades have some braze alloy (not a whole lot) behind the tip and on the steel.  These are fillets and act like shock absorbers as well as guy wires to keep tips in place and absorb shock. A good fillet can improve impact resistance by up to 40%.   You  most often see this in hand built and custom blades as well as retips.  Factory blades will typically not show this and that is acceptable as well.   

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14.  A good sharpening has the grinds straight and square to each other (near right).  A bad sharpening has strange angles and (far right) a missed corner.

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15. A saw blade that is sharpened well cuts straight and square and clean (near right).  A sloppy, cheap job of sharpening gives crooked cuts with a lot of splintering (far right). 

 

 

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16.  Good blades are ground evenly and exactly to close tolerances.    Right is a chart showing the grind on a custom blade from a top end shop.  The blade is within one half of a thousandth inch. 

 This is currently as good as it gets. 

.001” is a very good job and .002” is pretty common. 

 

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