OTHER: Mechanics - General - Hardware

• For additional information see Machinery Handbook; [MH p.1641], [MH p.1407], [MH p.1416] , and other pages in [Fasteners] section.
• My approximation; Stepping down one size from the Gyrobee for the twin rotor Electrotor on the attachment stock for the rotorhub etc will result in a weight reduction of about 33%. Is it worth it, particularly when the risk of over-tightening is greater?

• Stainless bolts with 316 on the head are US Grade 5 which is Metric Grade 8.8. The metric grading system confuses a lot of people.. US Grade 8 is Metric Grade 10.5.
• M8 refers to an 8mm metric bolt. That is the bolt size on my 503. I don't know the length, but it depends on the prop's hub thickness. The bolt grade would be B8.
• Here is some info I found on a site by Garrett D. Euler. The link is http://euler9.tripod.com/bolt-database/22.html

• Metric fastener size designation nomenclature.
• Metric fastener size designations always begin with capital M or MJ followed by fastener nominal diameter and thread pitch, both in units of millimeters (mm), separated by the symbol "x", as follows. M10 x 1.5-6g-S means metric fastener thread profile M, fastener nominal size (nominal major diameter) 10 mm, thread pitch 1.5 mm, external thread tolerance class 6g, and thread engagement length group S ("short"). If referring to internal thread tolerance, "g" would be capitalized. A fit between threaded parts is indicated by internal thread tolerance class followed by external thread tolerance class separated by a slash; e.g., M10 x 1.5-6H/6g.
• ISO metric fastener material strength property classes (grades).
• ISO metric fastener material property classes (grades) should be used. For example, fastener material ISO property class 5.8 means nominal (minimum) tensile ultimate strength 500 MPa and nominal (minimum) tensile yield strength 0.8 times tensile ultimate strength or 0.8(500) = 400 MPa. (In a few cases, the actual tensile ultimate strength may be approximately 20 MPa higher than nominal tensile ultimate strength indicated via the nominal property class code. Consult Table 10, below, for exact values.) Many anchor bolts (L, J, and U bolts, and threaded rod) are made from low carbon steel grades, such as ISO classes 4.6, 4.8, and 5.8.
• Hope this helps, Alan

• A metric Grade 8.8 bolt is closer to a Grade 5 SAE bolt than a Grade 8.
  You can get Metric Grade 10.9, which is comparable to Grade 8.
  A metric 12.9 is even stronger.
• An excerpt from www.motorcycle.com's tech tips :
• "Metric strength designations run along the same lines as the SAE designations. Standard duty bolts have no marking, while medium strength bolts will have the number 8.8 cast into the top of the head (comparable to SAE grade five) and high strength bolts will have the number 10.9 cast into the head (comparable to SAE grade eight). In metric fasteners, you’ll also find a stronger high strength bolt, indicated by the number 12.9, which is said to exceed the strength of SAE grade eight and have minimum material tensile strength greater than 175,000 psi. Socket head cap screws, like the ones typically used on European sleds, are often these highest strength fasteners."

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