Tweet
As a relative newcomer to the club and the forum, I'm always amazed at the wealth of knowledge contained and offered up here. I bought my first bike with I was 14 and have owned them off and on through the years. Initially dirt bikes, then dirt racing bikes - this was during the transition period from scrambles to motocross. Then mostly high performance street bikes. Due to rapidly declining reflexes, combined with a rapidly expanding wasteline, at 57 I find myself wanting to take the passion I've always had for modern motorcycles and for classic cars and transfer that to classic motorcycles. Time to stop and smell the roses.
Because I've never owned two wheeled iron I'm a babe in the woods here and thought I could only act like a sponge, soaking up all the information I can here, but contibuting nothing except an opinion now and then. But as I've read through most all of the threads/posts here, I did discover that there is something I can contribute here based on the fact that I've worked for fastener manufacturers/importers/distributors most of my adult life. Certainly long enough to know that most mechanics and hobbyists know only enough about fasteners to fill a thimble. Here is my attempt at making a contribution to this forum by giving you some good general rules of thumb regarding fasteners ... for what it's worth:
Bolt - used generically, but in fact most use the word "bolt" when they are dealing with "capscrews". What's the difference? A bolt is an inexpensive, antiquated, lower grade threaded fastener with a hex head, typically non-plated, and designed for use in non-critical applications. They are made only in Grades 1 and 2, with a plain head with just a manufacturer's logo/ trademark. They often had cut threads and were almost always USS/coarse thread.
A capscrew on the other hand has a thin washer face built into the underside of the hex head; comes in various Grades 1, 2, 5, and 8; has a chamfered point for easy thread starting; and usually is plated - (though not always); and has roll-formed threads. Available in both USS/coarse and SAE/fine thread.
Capscrew grades - how to identify. Rule of thumb is to count the number of radial lines on the head of the capscrew and add 2 to identify the grade. For example, a Grade 5 will have three radial lines on the head - three plus 2 = Grade 5
Which grade should use - Always replace a fastener with the same grade that was installed by the OEM. Some mechanics make the mistake of using the "if Grade 5 is good, Grade 8 must be better" mentality. Grade 8 is stronger, but stronger is not always better. In some applications the fastened joint is designed so that the 20 cent fastener fails first, before the $500. casting that it's holding together. Always error on the stronger side if you have no choice, but the best choice is to replace it with the same grade it came with from the factory.
Nuts - also come in various grades; both USS and SAE thread patterns; plated and non-plated. Always match the nut to the grade of the bolt.
Lock washers - come in both alloy and non-alloy; plated and non-plated. Always use alloy with Gr.8 capscrews. Installed against the nut, never against the bolt head.
Flat washers - come in both alloy and non-alloy; plated and non-plated. Always use alloy with Gr.8 fasteners. Both types are available in two distinct styles - USS which has oversized internal and external diameters. SAE - which offer smaller internal and external diameters. The SAE type fits snugly over the capscrew shank, whereas the USS type has a large enough internal diameter that it will usually actually fit over the shank of the next size larger capscrew than what it's made for. Either style can be used, most mechanics gravitate towrds the larger USS style, but anyone familiar with fasteners would advise you to use the SAE style in normal applications.
The flat washer is usually installed only against the head of the capscrew, not aginst a nut.
Here's a bit of trivia you can have fun with your buddies with - do you know that there's a right way and a wrong way to install a flatwasher on a capscrew or bolt? 99% of mechanics don't. If you run your finger around the internal (hole) edge, you'll find that there's a rough square cut side and a chamferred smooth side. The smooth side goes up against the head of the capscrew. Putting the rough, square cut side against the head can potentially cause little scratches in the fillet of the capscrew (fillet is the rounded surface that transitions the shank to the head) that could eventually lead to metal fatique and a stress fracture.
Lock nuts - Although improper for judging purposes on most old iron, under other circumstances you're always better off using a locknut rather than a lock washer and regular nut. When torqued to the proper torque setting, lock washers become nothing more than flat washers and do nothing to prevent the fastener assembly from loosening. Once loosened by vibration, the lock washer may keep the nut from falling off completely but you still have a loose fastener joint that will eventually fail.
Lock nuts come in several styles with the most common being the nylon locknut and the all-metal prevailing torque locknut. The nylon type should not be reused more than once as it looses much of it's locking ability after the first install. Also, not to be used in high heat applications. The all metal type can be reused several times with no appreciable loss in locking value.
Hope that helps someone, somewhere along the line. We can cover other fasteners: metrics / stainless /chrome at another time if anyone wants to know.
Ride it, don't hide it!
Kevin G
Because I've never owned two wheeled iron I'm a babe in the woods here and thought I could only act like a sponge, soaking up all the information I can here, but contibuting nothing except an opinion now and then. But as I've read through most all of the threads/posts here, I did discover that there is something I can contribute here based on the fact that I've worked for fastener manufacturers/importers/distributors most of my adult life. Certainly long enough to know that most mechanics and hobbyists know only enough about fasteners to fill a thimble. Here is my attempt at making a contribution to this forum by giving you some good general rules of thumb regarding fasteners ... for what it's worth:
Bolt - used generically, but in fact most use the word "bolt" when they are dealing with "capscrews". What's the difference? A bolt is an inexpensive, antiquated, lower grade threaded fastener with a hex head, typically non-plated, and designed for use in non-critical applications. They are made only in Grades 1 and 2, with a plain head with just a manufacturer's logo/ trademark. They often had cut threads and were almost always USS/coarse thread.
A capscrew on the other hand has a thin washer face built into the underside of the hex head; comes in various Grades 1, 2, 5, and 8; has a chamfered point for easy thread starting; and usually is plated - (though not always); and has roll-formed threads. Available in both USS/coarse and SAE/fine thread.
Capscrew grades - how to identify. Rule of thumb is to count the number of radial lines on the head of the capscrew and add 2 to identify the grade. For example, a Grade 5 will have three radial lines on the head - three plus 2 = Grade 5
Which grade should use - Always replace a fastener with the same grade that was installed by the OEM. Some mechanics make the mistake of using the "if Grade 5 is good, Grade 8 must be better" mentality. Grade 8 is stronger, but stronger is not always better. In some applications the fastened joint is designed so that the 20 cent fastener fails first, before the $500. casting that it's holding together. Always error on the stronger side if you have no choice, but the best choice is to replace it with the same grade it came with from the factory.
Nuts - also come in various grades; both USS and SAE thread patterns; plated and non-plated. Always match the nut to the grade of the bolt.
Lock washers - come in both alloy and non-alloy; plated and non-plated. Always use alloy with Gr.8 capscrews. Installed against the nut, never against the bolt head.
Flat washers - come in both alloy and non-alloy; plated and non-plated. Always use alloy with Gr.8 fasteners. Both types are available in two distinct styles - USS which has oversized internal and external diameters. SAE - which offer smaller internal and external diameters. The SAE type fits snugly over the capscrew shank, whereas the USS type has a large enough internal diameter that it will usually actually fit over the shank of the next size larger capscrew than what it's made for. Either style can be used, most mechanics gravitate towrds the larger USS style, but anyone familiar with fasteners would advise you to use the SAE style in normal applications.
The flat washer is usually installed only against the head of the capscrew, not aginst a nut.
Here's a bit of trivia you can have fun with your buddies with - do you know that there's a right way and a wrong way to install a flatwasher on a capscrew or bolt? 99% of mechanics don't. If you run your finger around the internal (hole) edge, you'll find that there's a rough square cut side and a chamferred smooth side. The smooth side goes up against the head of the capscrew. Putting the rough, square cut side against the head can potentially cause little scratches in the fillet of the capscrew (fillet is the rounded surface that transitions the shank to the head) that could eventually lead to metal fatique and a stress fracture.
Lock nuts - Although improper for judging purposes on most old iron, under other circumstances you're always better off using a locknut rather than a lock washer and regular nut. When torqued to the proper torque setting, lock washers become nothing more than flat washers and do nothing to prevent the fastener assembly from loosening. Once loosened by vibration, the lock washer may keep the nut from falling off completely but you still have a loose fastener joint that will eventually fail.
Lock nuts come in several styles with the most common being the nylon locknut and the all-metal prevailing torque locknut. The nylon type should not be reused more than once as it looses much of it's locking ability after the first install. Also, not to be used in high heat applications. The all metal type can be reused several times with no appreciable loss in locking value.
Hope that helps someone, somewhere along the line. We can cover other fasteners: metrics / stainless /chrome at another time if anyone wants to know.
Ride it, don't hide it!
Kevin G