The following commentary does not necessarily reflect the views of AgWeb or Farm Journal Media. The opinions expressed below are the author's own.
As a farm machinery mechanic and writer, Dan brings a hands-on approach that only a pro can muster. Along with his In the Shop blog, Dan writes a column by the same name as well as the Shop Series for Farm Journal magazine. Always providing practical information, he is a master at tackling technical topics and making them easy for all of our readers to understand. He and his wife, Becky, live near Bouton, Iowa.
While researching a story about nuts and bolts I ran across some semi-useless trivia: Flat washers have a top and a bottom. If the edge of the center hole in a washer is subtly rounded, that's the top of the washer. If the edge of the center hole is "square," then you're looking at the bottom of the washer.
The reason for a difference between the "top" and "bottom" of a flat washer makes sense if you look closely at the underside of the head on a hex-head bolt. There is a slight curvature where the bottom of the head of the bolt meets the shank of the bolt. The curved edge of the center hole in a flat washer "matches" the curved junction between the bottom of the bolt's head and its shank.
Engineers tell me that sharp, 90-degree corners are more likely to crack than rounded corners, so quality bolts have rounded edges where the bolt's head meets its shank. The subtle curves in washers and bolts are easier to see on big bolts--like a 5/8 or 3/4-inch bolt and washer.
If the washers and bolts you check have square-edged holes and head-to-shank junctions--they might be economy-grade bolts made overseas that weren't designed to SAE standards.
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