Here’s an assortment of various hammers. As you can see, each has a different shape and he
Thinking back over the past few years, something has occurred to me. I have written stories on chopping tops, frenching headlights, pancaking hoods, shaving door handles and so on. Really what it boils down to is I have covered stories from beginning sheetmetal work to about as advanced as it gets. Yet, somehow through all of that I skipped attaining an AA degree. What I’m getting at is, never once have I covered the fundamentals of metalwork. (As I think more about this, this issue is probably directly linked to my short-lived team sports go-around. I was ready to rock and skip all that fundamental practice. Coaches and I didn’t see eye to eye!)
Now before we get involved in our fundamentals of sheetmetal, one thing needs to be made clear: philosophies, techniques, practices, and methods don’t equal skill. If there’s one thing about sheetmetal, it’s the fact that “on the job training” can’t be substituted. In words and pictures, and even theory, it all looks so simple, but it’s quite the contrary. With that disclaimer out of the way, we’re about to delve into the basic fundamentals of metalworking.
Where there’s a hammer, there’s a dolly, and as you see they too come in various forms. Ag
Like opinions, each person has their own style of metalworking; therefore what you’re gonna get here is mine! The way I was taught to try and understand metalwork is that a piece of sheetmetal is nothing but thousands of little metal balls (let’s call them BB’s for the sake of the story) molecularly strung together as one big sheet.
Now imagine that you took a hammer and smashed the corner of your sheet. What just happened? Essentially you took a bunch of small BB’s and flattened them. True to most things, every action has a reaction. By smashing the BB’s they have been flattened and their circumferences have increased, which in turn pushed themselves farther apart from one another. One smashed BB won’t do much, but smash 25 BB’s and place them together, and your surface area has increased from the size of a quarter to a 50-cent piece.
In metalworking this action is called stretching. And any time sheetmetal is dented or dinged the molecular structure has been disturbed and the area has stretched. Luckily metal is highly malleable, meaning it can alter shape, which is why it stretches instead of breaks. However, there is a point where metal retains no more elasticity, and that is the point in which it will tear. Because of those properties, just about any piece of sheetmetal that hasn’t been altered past its point of elasticity can be worked to regain its original composition. Restoring a stretched piece of metal is carried out through its polar opposite—shrinking.
Here’s a look at a shrinking disc. This one is of the pie-cut variety. Like a grinding dis
What is shrinking? Let’s go back to that blow we hit in our panel mentioned previously. The low point of the dent is where the most stretching has occurred, which means those BB’s are at their flattest. Like before, every action has a reaction. Take an earthquake for instance. The fault moves at the epicenter, and then sends out a wave of reactions in a 360-degree motion—the same goes for our dent. As the metal stretched at its epicenter (its low point), it sent out a 360-degree wave. As the area stretched, it pushed more and more metal outward, and once it hit the ring around the dent, it collided with the rest of the metal and smashed up like an accordion. All of these BB’s have now crammed into one another at the point of impact to create a shrunken area.
Because the area has obtained so much more material, there is nowhere for it to go but up. Think about your old Hot Wheels days. Pretend you have just lined up 10 cars, placed a hand at each end of the train, and are pushing toward one another. If you remember correctly, eventually the cars in the middle would begin to lift off the ground. The more pressure you brought, the higher the cars lifted, and again eventually you went too far and the cars went crashing about.