![]() I reckon it was mostly the tiny dimples reducing the bounce. Possibly the tiny dimples in the original battered surface reduced the CoR, or it could be the thin coating of iron oxide having an effect (the original surface was nearly black, while the freshly-milled surface was shiny metal-coloured). Machining a lovely flat surface certainly improved bouncability, but I couldn’t say for certain why. After machining, the coefficient of restitution was significantly greater, and much more consistent with respect to location. ![]() ![]() The bounce test before machining showed a lot of variability with respect to location.The milling cutter that does the facing is a tungsten carbide type that doesn’t noticeably heat the worked piece (most of the heat is transferred to the swarf chips), so the machining operation won’t harden the surface.The anvil is cast, and doesn’t have a hardened surface.I saw a random youtube video the other day that should provide some insight in it, a vintage Swedish anvil is re-surfaced, and a ball bearing bounce test is performed before and after to see what difference is makes. But maybe not enough to matter if you’ve got room to just use plain old inertia. Nowadays hardening an anvil can add a bit more of a spike to the force / time curve. By being highly resistant to being moved it increases the peak force delivered to the workpiece during the impact.īack in the day when hardening big hunks of metal was difficult, one way to get a better more efficient anvil was simply to make them heavier. A high inertia backstop (AKA an anvil) does exactly that. To actually reshape the material, you must hit it harder than its yield strength. If you hit metal less hard than its yield strength it doesn’t bend, it just springs back once the force is removed. Now consider a workpiece between the hammer and anvil. With the effect that the peak force applied to the surface will be much greater. How do you think the shape of the force over time curve will differ between the thick and thin anvil? The thick anvil will be much more resistant to being moved. So it weighs 36x as much in total, and also 36x as much per unit of top surface area. And sitting in the same spot on the same wooden bench. Same footprint as the 1" anvil, just lots taller. Now replace the anvil with one that’s 3 feet tall. Consider how little the inertia of the teeny anvil slows the progress of the impact forces from the hammer to the wood. Now place an anvil only 1" tall on top of the bench and give it a good whack. Imagine you’ve got a wooden workbench with some amount of give to it. It wouldn’t be correct to say that inertia has anything to do with orientation of the material, would it?Īs the material and inertia part of the snip above … It is also noted that orienting an anvil to increase the mass under the hammer blow will improve how the anvil performs. ![]()
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