Now that I’ve posted a work order, I can post about the difficulties encountered with the different aspects of the work order. Let’s start with material. Here is the material type from the work order I posted.
The vast majority of our heads are formed with steel. But there are all kinds of steel. The cheapest is carbon steel, also know as black iron. It is soft and malleable, relatively easy to form. It also machines easily. It has a high carbon content, hence its name. This makes it very dusty and dirty. Carbon steel dust covers everything in the shop. It can be filthy.
Much cleaner is stainless steel. There are different grades of this. 316 and 304 are the most common grades. It is a little more difficult to form, being harder than carbon steel. And it doesn’t machine as smoothly as carbon steel. Also, if the icr roll skids while the head is spinning, because you put too much pressure on it or there is grease in the head, it can mar the surface. Skid marks in the inside corner radius should be polished out; otherwise, these marks will rust over time. Rusty stainless steel looks terrible.
There are other grades of stainless steel. Some are springy, with high tension, and are difficult to bend into shape. These steels require a lot of pressure to form. Other grades have a high hastalloy content, which makes them not only very difficult to bend but also very hard to machine. You wear out insert after insert trying to machine these heads. The same goes for drilling a center hole in a hastalloy head. You can quickly burn up a drill bit if you don’t take it slowly. Monel is a grade of stainless that’s a little harder than 304 or 316, but not as hard as hastalloy.
Then there are the exotic metals. Aluminum is very soft, much softer than carbon steel. But it is not very malleable, it hardens and loses its elasticity quickly. So aluminum is flanged hot. Usually a hand torch is sufficient, a temperature of about 500-700 degrees is all that’s required. It machines easily. But there are different grades. Some grades are so soft it bends if you stare too long at it. Honestly. You have to be very careful with metal this soft, it will thin out in a second.
Copper is also very soft, like aluminum. It forms easily and machines easily, like aluminum. But it is more malleable, and does not need to be flanged hot. Heads of pure copper are rare. More common are cupernickle heads, an allow of copper and nickle. The nickle gives the copper more strength. This copper alloy is easy to form, but difficult to machine.
Then there is zirconium and titanium. These are very tricky metals to work with. They must be heated and maintained at a steady temperature between 500 to 700 degrees. They warp easily if you use too much pressure, or not enough pressure. They bend easily, when heated, and machine easily. Zirconium burns. It flames and the shavings catch fire while you machine it. Weird, metal burning. And titanium does not shrink. Aluminum shrinks a lot when it cools down from being heated; you have to provide for that, leave it a little big, when you flange it. Steel shrinks, too, especially when it is heated to 2000 degrees, the temperature the really thick heads – an inch, or an inch and a half – need to be flanged at. So they, too, are left big, so when they cool down they will shrink near to the correct size. But titanium doesn’t shrink. You can flange it right into size, and it will stay there. Or defy the laws of physics and actually get bigger upon cooling. I’ve seen that happen with some grades.
There are a lot of different metals we work with, and different grades of each metal. You learn how each acts merely by working with them over the years. By this point I know how every kind metal will behave when I put it into a flanging machine. But acquiring this knowledge has caused me many headaches.