Sheet metal work

This writeup is a guide to some common problems you encounter when welding and do steel work on cars. The focus is on the use of basic tools, expensive tools like English wheel is not covered.

Please read welding-sheet-metal for welding and Painting and rust protection

Steel work

When welding you need steel parts. Some times you can purchase new parts, but mostly you have to fabricate your self. I will cower how you can make simple parts without any expensive equipment. To make really professional parts you will need an English wheel, planishing hammer, bead roller etc which easily sums up to thousands of USD. But you can do a lot with simple equipment.

Tools

For cutting metal you need an angle grinder with a cutting wheel, I prefer a thin 1 mm wheel which is fast and precise. Actually I have several grinders to avoid changing discs all the time.

For more special tools see below on making patches and profiles.

Air tools

A compressor is really handy, and necessary if you shall paint or sand blast. And you have the possibility to use inexpensive air driven tools that can be handy because of their small size making it easier to work in awkward places.

Most important is a jigsaw for cutting, a small angle grinder, a turbine die grinder and a belt sander.

I don’t use these much as they are slow to work with, but when needed they are great. Except the die grinder which is fast and excellent when the grinder is to big to access the spot.

Making patches

I find it easier to cut out from the body first using a grinder with a 1 mm disc, but some make the patch first and then cut the body. To make the patch you can find the circumference of the hole by laying a paper sheet over the hole and fix that with magnets. Then use a dirty finger, which is no problem to find in the workshop, to mark the edges. Cut out the marked paper, making it 1-2 mm smaller than the actual hole and use that as a template for marking on the steel.

If the patch is single curved (curved in one direction) cut a square steel piece larger than the hole before cutting in the body and use your hands and a plastic hammer to form it after the body first.

Making straight profiles

To make angles of some length you need a brake. They do not have to be expensive. Shorter lengths can be done in a wise with a plastic hammer. If you don’t have a brake you can use the edge of a table and fix the sheet with a square tube and two clamps. In a brake you can normally only make two bends. If you need more bends you can weld several pieces together. To get a rounded corner weld from the back side and build it up a bit. Then grind down to get the rounding.

Also, when creating profiles cut out a piece larger than you need, bend it, and then cut it to the right dimension. It can be difficult to find the exact point where the bend comes.

A budget brake can only handle thickness up to say 1,5 mm. For thicker steel you can use steel profiles like square tubes which you cut longitudinally.

Making curved profiles

Double curves, that is a concave or convex shape is the main obstacle when you don’t have expensive equipment. But smaller parts can be made using a wooden stump or a sand bag. Take the stump and carve a concave hole in it, 10 – 20 cm in diameter and hammer the sheet down in the hole. Then try to find a part that fits your body the best way. The steel will be wrinkled, so after the shape is found flatten it out on a anvil using a curved or small hammer. If you have a spherical anvil or other heavy object that will give the best result. But you must use some filler also to get it nice.
An English wheel or planishing hammer would have made it perfect, but the cost is high.