Thread: How to make sills.

Part 2.
Photo below shows the waste nearly removed.



5. For the curved part I use a cardboard template traced from the original panel; this can then be used to make a steel template, which will last longer. Add a line past the curve using the rule and scriber.

Photo below; using the inner hammer-form as a marking template and scratching the curve with a scriber.



• Label fold lines with an instruction e.g. "Fold up." This helps when you don't want to accidentally make two right-hand ones.

Cut off the waste material. There are several ways of doing this, all of them work; some are easier on the hands than others, some are easier on the wallet.
• For straight lines I prefer the bench shears, these are expensive to purchase but easy to use. They can also be used to cut curves. If you leave about 2mm of waste outside the curve and cut the waste off as in the photo below, then the remaining waste can be easily removed with the shears; the same technique applies to using snips.



• Use snips; which can be hard on the hands but are cheap to buy. In the photo above, most of the waste has been removed as straight cuts using the bench shears; the 2 to 3mm of waste left, can then be easily removed with snips.
• Fold the straight bends. This can be easier said than done; you may have noticed on my drawing that there are numbers within a circle pointing to individual fold lines; these represent the order of bending. There is also a view of the end of the panel, to help me work out which bends need to be done before the others. The reason being, that sometimes it is impossible to make a second bend because the work cannot be clamped, because the first bend gets in the way and this depends on what type of bender or facilities you have for folding. In the following photos I have shown different methods of bending that you might use; you need to decide what suits your budget and then work out the order of your bends to suit your equipment.

First photo below shows a piece of steel in the angle-clamps, clamped in the vice and with a G-clamp as well. The steel has been bent using a block of wood and a hammer as in the photo after it. It can be bent with a hammer alone but that will leave hammer marks on the surface; in addition, the hammer can only bend a short distance at a time, so the metal will be stretched unevenly producing a wavy or curved edge. This can be corrected afterwards with a planishing hammer, but it is all extra effort for little gain. Exactly the same process is used to bend aluminium.





More to follow.

Photo below; the completed bend is now clamped to the bench with a 12mm length of flat bar clamped on top of it. I am only using steel sheet, because I didn’t have any aluminium to demonstrate on. The two folds replicate what is on the top of the sill. For a long fold, rather than the short practice one I am doing, a heavy piece of bar, or angle can be clamped to the bench as in the photo and both bends folded with a hammer and block of wood. The only disadvantage with this method is some mild stretching. which will need to be fixed. The best method, is to use a sheet metal folder for guaranteed accuracy.



Photo below; how the steel folds turned out, they are not at 90 degrees due to elasticity in the metal and the second bend done on the bench, has more radius than the one done in the angle clamp. The bends can be dressed with a hammer and dolly but this is extra work.



Picture below shows my dummy panel in aluminium, after having the first fold bent in the magnetic-brake. I could have done the second and third folds in it as well, but I did the second one in the angle clamps for the sheer fun of it! In any case the metal was too small to fit the third fold on, so this piece is really for demonstrating turning-a-flange on a curve. I have a manual brake as well, which I made myself, it is good for folds but not as versatile as the magnetic one.



Whatever method you use, try to avoid making a straight fold on the curve, as this will make it harder to shape the curve later.


• Fold the curved flange – now the interesting part starts! Shape a piece of MDF, or similar, using the curved template and check that it fits inside the sill. When it is a good fit along the curved fold-line, use it as a template to make another one, this will sit on the outside of the panel sandwiching the metal in between and is called a hammer-form.

Photo below, shows left to right; panel sandwiched between two bits of MDF and clamped to the bench; wooden beater for outside curves; wooden beater for inside curves; plastic bossing mallet filled with lead shot. I used the mallet and the straight beater to turn the flange. The beater for inside curves was not used on this project, but it would be essential on for the wheel-arch lip on the wing, for example.



More to follow.

Clamp the hammer-form firmly in a vice, or clamped to a bench top and beat the aluminium with glancing blows using a wooden, or plastic mallet, or a wooden beater. You will quickly discover that the aluminium puckers and that after a while it becomes harder to work. This means two things; firstly the metal needs annealing and secondly the puckers need to be shrunk.
• Annealing has been explained previously, but in this context the metal must be removed from the hammer-form and heated separately. To prevent the flat part of the panel deforming in the heat, I lay an old towel, or rag soaked in water on the flat part. When the panel is cool, return it to the hammer-form.

Photo below; shows the wet rag and the blackened soap on the flange, which has been turned this far before annealing, using the mallet.



• To shrink the pucker after annealing, use a wooden mallet and beat the narrow end of the pucker and progressively work your way down to the high end. You will see and feel the soft metal move immediately as you force the pucker into itself. Search youtube for videos on tuck-shrinking. Repeat the process on all of the puckers. When I made mine, I had to anneal one place twice, to get the metal to shrink enough to fit the hammer-form. On this practice one, I had to anneal 3 times to get rid of the big pucker in the photo above.
• When the flange has been turned and shrunk, remove the panel from the hammer-form and file the curved face looking for high and low spots. Panel beat as required with flipper, hammer and dolly. In the photo below I am using a toe-dolly to help beat the low spots up with a planishing hammer. Later on I used a piece of 25mm round bar as a dolly, held in the vice and used the hammer to raise the stubborn lows.



• Mark the width of the flange; you may have noticed that after shrinking the puckers, the flange has grown too wide. Remove waste with small snips, or sand with a flap-wheel on the angle grinder. In the photo below; the increased width of the flange is noticeable where I have shrunk the pucker. Instead of using the above methods to reduce it, I experimented and used a dreadnought file, with the worked clamped to the bench, to remove the excess metal; it worked well.



• Mark-out and make the mounting brackets; the slots can be made by drilling the end holes and removing the waste with the angle clamps and a small cold chisel. The same method can be used on the sill upper-flange, as described previously.
• Locate the mounting brackets on the chassis and transfer the measurements to the sill. I used Sikaflex adhesive to glue the brackets in place, clean the panel with acetone first and rough the metal with coarse abrasive as well. Alternatives are spot-welding – as per the original – and pop-rivets.

Job done!

Photo below; curved flange filed and sanded. If I was making lots of these I would make a polished steel hammer-form to go inside the sill, which would double as a dolly.



Depending on how you want the finished product to look, remember that aluminium scratches easily, so protect it as much as possible when working it; use wooden, or aluminium protectors when clamping; make sure everything is clean before clamping.

Be creative! If the tool isn't working well, make something that will. If it works for you, then it is the right way!

Cheers Charlie