I do love a good challenge. For this one-hour challenge, I'm going to attempt to build a set of rocker panels for my Jeep TJ in under an hour.
For those of you unfamiliar with the offroading world, a rocker panel is a thick steel plate designed to save your body panels from damage when going over rocks or other obstacles.
I started with a set of drawings that I slapped together during lunch and a half sheet of 3/16" stainless steel. I also have a few more tools available to me than your average DIYer would...
Center Punch, Hammer
Ultra Fine Tip Sharpie
Random Orbital Sander with 60 grit Zirconia Alumina
Scotchman Hydraulic Punch with 1" and 5/16" punches
Haco Hydraulic sheer capable of 3/16" stainless
Pacific Brake press, 250 ton with 60 degree die
Step 1: 5:25 Start Time; Minute 0-6
The first thing to do: cut the heavy sheet into two manageable pieces that will become the left and right sides.
Rough dimension of each rocker panel: 48" x 11.75".
Aesthetically, it would probably look a little better if it were 48.5" wide, but that would be a horrible use of material, so I compromised with 48". It also saves me a cut by using a 48" wide piece of material and not having to cut down a 60" sheet. The numeric-controlled backstop on the sheer saved me some time by not having to mark out those two cuts. Time to finish two cuts: 3 minutes.
Next, I've got to mark out the angled cuts that will follow the fender angles on the jeep. If I were laser cutting these like most major manufacturers would, these angles would only be 5-6" long and would end where I place my first bend. But that would take too long to send off to the laser cutter... no way I'm getting that back within an hour.
It took me an additional 3 minutes to mark and cut those four cuts.
Step 2: 5:32 Laying Out and Punching Holes; Minute 7-21
There are 8 holes to be punched in each piece: 7 @ 5/16" and 1 @ 1" diameter.
The top five holes are symmetrical - there is no left or right, so I don't have to worry about punching them in the wrong spot. But the bottom 3 holes are placed to line up with a body mount and bottom of the Jeep's tub, so it's important that they're placed as a mirrored image on the left and right rocker panels. If I mess this part up, I could just flip the flat 3/16" stainless over and bend it the opposite direction, but it would cost me valuable time. There is definitely a cleaner side to the material, and if I have to clean up two sides or spend extra time cleaning up the side that is more scratched up, I probably won't finish in my 1 hour deadline.
Each 5/16" hole gets marked with an X then center punched. The Scotchman punch has a little point on the bottom of each punch to line up with the dimple I made with my hammer and center punch. This makes it sooo much easier than trying to eyeball where a mark is, especially on larger diameter punches, where you just can't see your mark.
Note that I didn't mark out the 1" holes yet. It's too easy to lose track of which holes are what diameter and mis-punch something. So I only mark one diameter hole at a time.
That last photo is my mistake. Sometimes things move on a person. This little booboo is from the stainless sliding a bit while punching it, and the punch just-barely dimpling my material before I let up on the pedal. Luckily it's on the passenger side rocker, so I won't have to look at as often.
Step 3: 5:47 Die Change and Large Diameter Holes; Minute 22-30
I had to swap the punch set from 5/16" to 1". This isn't a quick process, but it's significantly faster than drilling two 1" holes in 3/16" stainless. Time to complete swap: 3 minutes.
Then I had to mark the holes and punch them. It's surprisingly difficult to line up a 33 lb sheet to an exact spot under a 1" punch. I had to center punch the same spot 3 times to get a dimple deep enough to catch the point on the hydraulic punch.
Step 4: 5:56 Initial Sanding; Minute 31-36
I've passed the 1/2 way point.
It seems odd to work on the finish before it's done, but it's significantly easier to sand a flat surface than one with two bends in it. There will definitely be marks left by the brake press in the next step, and I'll have to sand those out so it doesn't rust where the brake press die contacted the stainless.
Let me lay some science on those of you scratching your heads about rusty stainless: (or skip to the next step if you don't care)
For stainless to resist rust, it has to have about a 12% Chromium content on its surface. When the chromium contact oxygen, it reacts to become chromium oxide, which doesn't flake away from the base metal like rust does. This protects the surface from deterioration from oxidation. When steel scratches that surface, it disturbs the chromium layer, introducing iron (ferrum). When it rusts, it's because the iron has reacted with oxygen, creating ferric oxide, which likes to break away from the base material. When the ferric oxide breaks away, we see it as flaking or bubbling. It then allows the next layer of base material to oxidize. The easiest way to make sure this doesn't happen is to get rid of that iron that gets left behind when it scratches stainless. We do that by cleaning it with acetone and sanding it with zirconia alumina sanding disc. The sander material isn't critical to the process, but it lasts longer against hard metals than aluminum oxide (the standard for most wood sanders). If the stainless is going into an environment where chlorides are present (ie, sodium chloride - salt), the chlorides can react with the chromium layer. In this case, the stainless needs to be passivated to reduce its chemical reactivity.
Step 5: 6:02 Bending; Minute 37-48
Not sure if I can make it... This might be the slowest brake press ever.
There's a right way to bend parts accurately. You would take a piece of scrap material, bend it until it's perfect, then set a depth stop on the brake press. But I'm arrogant and don't have time for that. It could completely ruin my part if I overbend it, because there is no way to un-bend 3/16" plate that won't result in a weak and ugly corner.
Instead, I'm going to use my first piece as my test piece, then set my depth stop and bend the other side so it matches.I just hope I can do it without bending it too far.
This is not a quick process, as a 250 ton press tends to move slowly. And this one doesn't have any numeric or CNC controls, so it's guess and check: bend where it looks almost right; raise the die; pull out part and check it with a protractor; put the part back in the press; lower the die in small increments; repeat.
My first attempt was a bit shy of my target angle, which is a lot better than overshooting it. I only had to repeat the guess and check process a couple times before being close enough to set my depth stop.
Comparing the first two bends showed that one needed just a skosh more...
The final bend was simple enough - my piece should end up as a 90 degree angle with a corner chamfered out. I wasn't aiming for a specific angle for that bend: I needed a sum of both angles to add up to 90 degrees.
Step 6: 6:14 Final Cleanup; Minute 49-54
49 minutes into my 1 hour challenge. The fabrication part is complete with ten minutes for final cleanup. When it comes to long-term quality, the final cleanup is probably the most important part. But you know that, because you didn't skip ahead on my stainless lesson in the sanding step.
First, an Acetone wipe-down. This will get rid of my sharpie lines from punching/bending, and it will clean up some of those loose ferrous bits that can cause rust.
Second, more sanding. I've got to get ride of those bend lines as much as possible so there aren't any future rust spots. This is 304L stainless steel (basically the same as 18-8), so it's a bit more forgiving to imperfections in its surface. High Nickel alloys require a lot more cleanup and passivation to combat potential rusting.
6:18 Verify Fitment
6:19 Success! A complete pair of Jeep TJ Rocker panels with 6 minutes to spare. Almost enough time to clean up.
This is an entry in the
1 Hour Challenge