This is more of a "what did you do in the shop today" kinda post but I thought I'd make it its own thread so if someone googles this in the future they might find it and learn from my mistakes.
I got this starrett protractor head on ebay for fairly cheap but it ended up having a crack that was hidden by dirt and wasn't very visible in the pictures. I picked up some Nickel 55 welding rod at an estate sale a while ago so I thought I'd take a shot at fixing it. I packed the slot with .093" worth of shims which is the same thickness as the ruler. I should have also clamped it down from the outside so it would be totally constrained because as you can see in the pictures it expanded outward and the slot widened.
I used the general settings for nickel 55 welding rod that I found on the internet, preheat the cast iron, 40 amps 3/32 rod, and peen the weld a bit to expand it so it doesnt crack when it cools. I probably did that too much and that caused the slot to widen. At the start there wasn't good penetration and you can still see the crack, and then I blew through at the end. I used the little cheap diamond needle files with diamonds glued to a backer to clean up the inside of the slot. The weld was hard but not super hard and a regular file did cut, but all the thin files that would fit were super fine and getting nowhere.
If you do this in the future, preheat, constrain the protractor so it can't expand or contract and let it cool slowly, lightly and sparingly peen the weld so it doesn't crack while cooling, and maybe use something like nickel 99 filler so it isn't as hard and easier to clean up.
The inner part still fits and spins just fine, now I just need to repaint it and sand the bottom flat again.
I got this starrett protractor head on ebay for fairly cheap but it ended up having a crack that was hidden by dirt and wasn't very visible in the pictures. I picked up some Nickel 55 welding rod at an estate sale a while ago so I thought I'd take a shot at fixing it. I packed the slot with .093" worth of shims which is the same thickness as the ruler. I should have also clamped it down from the outside so it would be totally constrained because as you can see in the pictures it expanded outward and the slot widened.
I used the general settings for nickel 55 welding rod that I found on the internet, preheat the cast iron, 40 amps 3/32 rod, and peen the weld a bit to expand it so it doesnt crack when it cools. I probably did that too much and that caused the slot to widen. At the start there wasn't good penetration and you can still see the crack, and then I blew through at the end. I used the little cheap diamond needle files with diamonds glued to a backer to clean up the inside of the slot. The weld was hard but not super hard and a regular file did cut, but all the thin files that would fit were super fine and getting nowhere.
If you do this in the future, preheat, constrain the protractor so it can't expand or contract and let it cool slowly, lightly and sparingly peen the weld so it doesn't crack while cooling, and maybe use something like nickel 99 filler so it isn't as hard and easier to clean up.
The inner part still fits and spins just fine, now I just need to repaint it and sand the bottom flat again.
