Power at Work: So there is such a thing as a Grade 12 bolt
Thursday, June 4, 2009
An update on bolt grades, prompted by an observant reader
by RALPH WINFIELD
After my first article on bolt grading appeared in the December 2008 issue of Better Farming, the phone rang. An observant and knowledgeable reader assured me – very politely, I might add – that I had shortchanged you.
I had said that Grade 8 was the highest grade of bolt available in the imperial system. He assured me that, indeed, a Grade 12 is also available. When I inquired about the use and source, he told me that he regularly uses Grade 12 bolts to attach the bars to the feeder house chains in his combine.
The use of bolts allows him to change damaged bars without removing the feeder house chain.
Many of you will know that the bolts or rivets used to secure feeder house bars are small and short. Thus, there is a need for very high strength bolts capable of retaining high torque without vibrating loose. (I am assuming now that you read my earlier article on torquing bolts.)
This is not an application for lock washers. Lock washers should never be used under the heads or nuts of torqued bolts. They break and come out, leaving the bolt assembly loose – a recipe for disaster in many applications.
Grade 12 or L9 bolts are not available at your local hardware store. They are available from specialized fastener outlets and will cost about double the price of grade eight bolts.
There is no point in using high strength bolts together with low quality nuts. When torqued, the threads will distort or be completely destroyed before the desired torque value is obtained.
So, with Grade 8 bolts, make sure that you have Grade 8 nuts. They have two dash marks on one end of each nut. The Grade 12 nuts will have nine dashes on one end of the corresponding nut. The number nine goes along with the nine radial dashes on the L9 bolts.
At this time, I do not have torque values for Grade 12 or L9 bolts as they are not in common use, though available if you need them for specific applications.
Like the high strength bolts, specification grade (SPEC.) electrical receptacles are only available from electrical wholesalers. There was a time when they could be obtained in a separate bin at the local hardware store. They will cost three to four times the price of the competition grade (spell it cheap) electrical receptacles that are also CSA-approved.
It was another recent reader phone call about sourcing SPEC. grade receptacles that caused me to mention the source again. They should be used in all high-amperage use outlets, but especially in corrosive environments such as livestock and poultry buildings where items like pressure washers and heat lamps are powered. BF
Agricultural engineer Ralph Winfield farms at Belmont in Elgin County.