Hello everyone. I have a question which is not strictly about knife making but something related. I want to make what's called a knife edge pivot, which is a fulcrum-based system used in electric guitars. The idea is that, at the center of the fulcrum you have the guitar's bridge. On one side of the fulcrum the strings are attached, and on the other side extension springs are attached. The tensions are balanced so that he bridge 'floats' in place, and then a lever is attached ('whammy bar') which you can push down or pull up, thus changing the tension and therefore the pitch of the strings. Here is a diagram.
The floating bridge pivots on knife edges machined into the bridge, either straight or circular. These edges are not sharp by any means; maybe about .4 mm. The bridge is placed so that these edges insert into grooves cut out of two pivot screws which are screwed into the guitar body, so the bridge can pivot up and down. My project is to make a piece of metal which has the knife edges filed into them, like so (except I'd have one circular and one straight) and also to make the pivot screws with precisely filed grooves and 1/4"-28 threads. And just to clarify, my system will work a bit differently than the last picture in that the edges will be held in place and the screws themselves will pivot, rather than the other way around.
The issue I am facing is which type of steel to use. Because the mechanism introduces lots of abrasion and wear, I want to use a hardened steel because as soon as the edge/groove starts to deform the guitar will no longer return to precise pitch after pivoting. However, in order to make the edges and create the threads and grooves in the screws I will need the steel to be in a softened state at first. Because the screw pivots back and forth, I don't think much ductility is required, but I'm not sure. I'm also not sure how much I should worry about rust, though sweat and dirt particles will certainly find their way onto the edges because they are exposed.
What I'm thinking of doing is getting some tool steel (D2? A2? O1?) in annealed state, make the edges and threads, and then take it to someone to heat treat it for hardening. But I don't know how difficult it will be to work with those steels because, even annealed, they are still quite hard. I also don't know if their brittleness will be an issue with this type of mechanism. Perhaps I should use a tougher steel that is still hardenable? Do I need stainless? 440C? My priority is zero deformation. I am coming to this forum in hope for some guidance. Any help would be greatly appreciated. Thank you!
The floating bridge pivots on knife edges machined into the bridge, either straight or circular. These edges are not sharp by any means; maybe about .4 mm. The bridge is placed so that these edges insert into grooves cut out of two pivot screws which are screwed into the guitar body, so the bridge can pivot up and down. My project is to make a piece of metal which has the knife edges filed into them, like so (except I'd have one circular and one straight) and also to make the pivot screws with precisely filed grooves and 1/4"-28 threads. And just to clarify, my system will work a bit differently than the last picture in that the edges will be held in place and the screws themselves will pivot, rather than the other way around.
The issue I am facing is which type of steel to use. Because the mechanism introduces lots of abrasion and wear, I want to use a hardened steel because as soon as the edge/groove starts to deform the guitar will no longer return to precise pitch after pivoting. However, in order to make the edges and create the threads and grooves in the screws I will need the steel to be in a softened state at first. Because the screw pivots back and forth, I don't think much ductility is required, but I'm not sure. I'm also not sure how much I should worry about rust, though sweat and dirt particles will certainly find their way onto the edges because they are exposed.
What I'm thinking of doing is getting some tool steel (D2? A2? O1?) in annealed state, make the edges and threads, and then take it to someone to heat treat it for hardening. But I don't know how difficult it will be to work with those steels because, even annealed, they are still quite hard. I also don't know if their brittleness will be an issue with this type of mechanism. Perhaps I should use a tougher steel that is still hardenable? Do I need stainless? 440C? My priority is zero deformation. I am coming to this forum in hope for some guidance. Any help would be greatly appreciated. Thank you!
