Intro: Building With Brass
Working with brass is fun and easy. It is a favorite of machinists, metal artists, and the Steampunk crowd. Using a few simple tools you can form and solder brass sheets and shapes.
For this particular project, I had a motor gearbox and servo to mount in a box (separate Instructable TBD).
Step 1: Brass Types and Tools
There are many types of brass, but for my projects I mostly use:
C260 half-hard sheets and tubes - It is low lead and easily formable (bendable). If you want high polish, try to get sheets with protective film that you leave on till the last possible moment. You can put tape on the sheets to minimize scratches. It is also known as yellow brass or cartridge brass.
C360 rods, hex, square bar - It machines very nicely. It has 3% lead so I wash my hands after working with it and clean up all the residue.
Brass anneals (becomes less stiff) with heat but cannot be heat hardened. It hardens by bending or stretching it. In the home shop you cannot really harden brass. When you bend it too tightly or too many times it will crack from hardening stress. Half hard brass is a nice balance between stiffness and workability.
For this project, used .032 inch thick (20 gauge) sheets and strips from K&S bought from the local hobby store, or eBay
For larger projects and to stock up, I use OnlineMetals.com, they have a nice sample pack here.
Compound Aviation Snips - There are straight, right and left cutting. A nice pair is $16
Rulers and calipers - I love my $2 plastic calipers
Step drills - good for clean hole drilled in thin sheets
Twist drills - not as good a step drills on thin metal, but can get more exact hole sizes
Center punch - lightly punch centers before drilling so the drill doesn't wander
Files - rounding corners, removing small amounts of material
Deburring tool - clean way of making softly rounded edges
Fine-point magic marker
Tinsmith or ball peen hammer - not a woodworking hammer please
Cereal box cardboard - for templates and mockups.
Drill press or electric drill
Vise with soft jaws - I made soft jaws from HDPE plastic scrap, (like plastic cutting board material)
Propane torch with cylinder
Stay-Brite silver solder with flux - 1/2oz package will last a long time. No cadmium or lead or other undesirables
C-Clamps or vise to hold parts in place
Cleaning and polishing
Ultra fine sandpaper
Bar Keepers Friend cleaner and polish
Step 2: Layout and Cutting
To match other component mounting holes, measure and cut templates out of cereal box cardboard. I made pinholes through at the hole centers. You can model your design in a CAD/CAM program but I needed to try several options and this was quick and direct.
Tape or firmly hold the template on the brass sheet stock then outline it with fine-tipped sharpie and mark the centers by punching through with your center punch. Be sure to take into account that the sharpie line is a little larger than your template.
Cutting with aviation snips is the easiest, but you can also cut brass with a hacksaw, saber saw, jigsaw, bandsaw, or even Sawzall. The third and fourth picture show using a power jigsaw with holes drilled to turn corners. This wastes less stock that cutting large chucks off with aviation snips then cutting out the notches.
Deburr and file all the edges and corners.
Step 3: Drilling
The step drill makes the nicest holes but regular drills work too. For very large holes you can chain drill and file it with a round file.
You can deburr holes with the deburring tool too.
Step 4: Bending
Traditional tools for bending sheetmetal are a benchtop or floor sheetmetal brake, sheetmetal pliers, or press. We will just use a vise with soft jaws for small work and a ball peen hammer.
If you are building something with multiple bends, you need to plan out what order to do the bends so you can complete all of them without a previous bend getting in the way of your vise or brake.
Clamp squarely in the vise, gently press and hammer the bend until it is at the angle you need. If the straight parts get bent a bit you can straighten them by hand or on a flat surface with your hammer.
The minimum bend radius tends to be the thickness of the stock so take that into consideration if your parts have tight tolerances.
Bending a larger radius can be done by clamping a solid rod of wood or metal next to the sheet and forming it around the bend.
Bends longer than the width of my vise jaws can be done by clamping two pieces of angle iron around the piece for bending and gently working the bend over with a hammer.
Step 5: Soldering
Silver soldering makes very strong, almost invisible joints if done carefully.
I needed to mount a servo to the baseplate so rather than make a series of complex bends for it, I just bent up a brass bracket and soldered it.
1. The fit should be snug, no ragged edges or gaps.
2. Clamp with flame proof clamps, I put a wood block underneath though so the clamp would not soak the heat out of the sheetmetal. Brass transfers heat quickly. You can use wire to tie pieces together as an alternative.
3. Flux. A good joint needs a clean surface free of oxides. The flux included with the stay-brite package is an acid flux so do not touch it or breathe the vapors when it boils off during soldering. I used a q-tip to apply it just where I needed it. It should wick into the joint.
4. Heat. The solder melts at 430F (220C) . Brass melts at 1660F (904C) so you won't melt the brass with a propane torch, but heating it too hot or for too long can leach the zinc out and leave only copper. This will weaken the metal and look bad. So use just enough heat and no more. The technique is to move the torch back and forth along the joint to drive off the flux and heat evenly. Every so often, remove the torch for a second and touch the solder wire to the joint. If it is close, it will stick but not flow in. Keep heating until when you touch the solder it pulls into the joint by capillary action. That will use the least solder and get a great connection. Heating the solder will just melt it and make it blob onto the surface, staining it permanently sliver and wasting it. Do a few more passes with the torch to make sure it wicks into all the nooks and crannies. DO NOT BREATHE THE FUMES use a face mask or well ventilated area, acid vapors are not good to breathe.
5. Let it cool. You can cool it in water if you like, brass doesn't quench harden like steel.
6. Clean with soap and water. To remove any acid residue I just use Dawn dishwashing liquid and my fingers or a soft toothbrush.
7. Slight discoloration to copper color is unavoidable. I just polish with a little Bar Keepers Friend powder and it brings the brass color right back. If you want a mirror finish you will have to do polishing which is outside the scope of my instructable.
Step 6: Prototype Complete
Brass has such a warm metal look that I hate to hide it inside my projects but it allows me to change things easily by redrilling, chopping off or adding pieces with soldered splices, also unsolder and move things.
You can go very far with these few hand tools but if you are doing alot of brass sheet work, you may want to build, buy, or join a shop with a sheetmetal brake, shear, roller, punch, and other serious tooling.