Project 2 from Youngnstudly. Category: General Welding Repair
I bought an old 1950's lathe about a year ago and it was damaged pretty bad during shipping. The lag bolts that secured it to the bottom of the crate had broken off, allowing the lathe to "float" inside the crate during shipping. The lid on the headstock was busted in half along with all the (expensive) crank handles, the hand wheel, and the half nut lever. I took care of everything myself besides the cast iron lid.
When my TIG foot pedal started acting up the other day, I knew I was out of (unusable junk) scrap to run test beads on and figured "Why not weld the lid for my lathe?" So I did. The cast iron stick electrode's were used due to that being all that Airgas had in stock.
I started by stripping the paint off, mocking the part up on the lathe, and marking each half with a Sharpe for position. Next I ground a vee along both halves of the break, ground areas down that I thought would introduce impurities, removed a few cracks and a large chunk of cast iron that was ready to break off, and preheated everything. Two small tacks were placed on the backside to hold the assembly so I could flip it over and weld the front side. A drop of water was used to test the temperature of the cast iron before (and during) welding since I have no temp gun or temp sticks/crayons sitting around. If the water vaporized instantly, I let the cover cool until it would produce a light "sizzle." Certainly not accurate, but the propane torch flame (that was used to preheat) turned the part gold before it was it was too hot to touch, so I couldn't go off color alone.
I welded in a root pass using approx. 1" stitches and skipping around, letting the lid cool a few minutes between welds. The last 1/2" (going down the sides) had a large gap due to the hairline cracks I ground out before welding, so I saved those areas for last. The second pass was welded in 3/4" stitches and I tried to use the coldest weld puddle I could while building up the weld with filler. The part got hot a lot quicker than I expected, so I ended up taking numerous breaks between welds. I had to grind out one area of the root pass (where I removed that chunk of cast iron) due to small impurity that formed, but the other side welded really clean.
Upon flipping the part over, I noticed that my root pass didn't penetrate much towards the underside of the cover (which was almost 3/8" thick), so against my better judgement I welded a quick pass in to fill the bottom side cavity. I never like doing that after welding from the front side, but I just couldn't leave it like that.
Aside from a few minor low spots left by my 2nd pass (which I filled in easily), the rest of the cover sanded down smoothly. Past experience has told me that welding cast iron is never predictable, but at least this piece doesn't see the extreme temps of cast iron engine parts, or the pressures and flexing that vises and fixtures see. I will epoxy a small 10 ga plate on the underside to cover the weld and possibly keep it more rigid, and add some foam gasket around the opening to prevent the lid from slamming shut and breaking again. I ran out of sanding drums for the Dremel tool, so the backside needs to be smoothed out more.
I need to prime this and see if I shaped it as good as I think I did (LOL).Cost for the electrodes was $8.99 and it took just under an hour from start to finish, including quite a few cool down periods.
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Originally Posted by Rambozo
