Lesson: Working with Castings

Lesson 4: Working with Castings
The Tools
When working on the flexshaft: Always wear eye protection!! Don’t over tighten bits in the flexshaft. Make sure to return chuck key to drawer! Leave flexshaft handpiece hanging, not on the desk or in the drawer.
Types of flexshaft bits:
Heatless Grinding (mizzy) wheels: White
Highly aggressive removal of material. Used for grinding down a lot of excess metal, or sprues from castings. Use mask and grinding box.
Hard Abrasive points: Usually green or brown.
These are shaped bits used to aggressively remove material. Can get places a file can’t. They usually leave a rough texture.
Rubberized Abrasive wheels: Various colors for different grits.
For the ones we use… White= coarse Black= medium Blue= fine (pre-polish)
Knife-edge wheels are good for joints, textures, crevices. Regular wheels are better for flat surfaces. Start with white, and then move to black, then blue. For the best results, keep wheels moving and use light pressure. Use mask and grinding box.
Steel burs-
We have a variety of different sizes and shapes. Use all of these with bur-life. All aggressively remove metal.
Ball Bur: all purpose for concave areas. Cup Bur: good for rounding ends of prongs,
ear wires or shaping balled ends of wires

Bud Bur: good for crevices and tight spaces Hart Bur: good for setting, cutting grooves

Setting Bur: good for settings
Sandpaper rolls: Great for inside ring bands and bracelets, concave curves. Use mask.

Sandpaper discs: Great for flat or convex surfaces. Can sand in areas files don’t reach. Removes metal much quicker than regular sandpapering because of the rotation. Go from coarse to fine. Use mask.

3M Bristle Discs: yellow= 80grit red=220grit blue=400grit
Good for finishing tight areas and Matte finishing. Gets into everywhere. They do wear out quickly. You must use 2+ discs at a time. Use mask.


Polishing wheels: We have hard felt in both point and wheel shape as well as soft muslin in wheel
shape. Felt is good for flat surfaces or if you want to polish high points of texture. Points are good for inside rings, or concave shapes. Muslin is better for getting a bumpy or uneven surface. You must use polishing compound with these. Use mask and grinding box.

Bristle wheels: We have natural bristle wheels that can be used with polishing compound to polish in small hard to reach areas. Gets into filigree and fine details better than muslin buffs do.
Also have brass and steel bristle wheels that burnish the surface of the metal. Not as even as a polished surface, but a high shine.



Bits: general term for flexshaft thingies.
Buffs: specific to polishing bits, especially wheels (they buff a piece)
Burs: any steel bits

Soldering, Cleaning, Finishing
Working with castings is much the same as working with any other metal piece. There are some important differences to remember.
• Castings are solid, and tend to be heavier than fabrications. Make sure that when soldering you concentrate your flame on heating the casting. Most findings are small and light to begin with. Use a third hand to hold the findings and act as a heat sink when possible.
• Castings have a tendency to be a bit “soft” when you get them back. When sheet and wire are made, they are put under pressure to form them into sheet or wire. Castings are poured metal, and haven’t been under any pressure. Before soldering, it helps to either burnish or file the areas you are gong to be soldering to remove some of that “softness”. You can also tumble the pieces prior to soldering. This makes the soldering go much more smoothly.
To clean your castings (this is where that flexshaft comes in…):
• Saw off the sprue with a large size saw blade (1– not 1/0, 3, or 4)
• Cut as close to the piece as you can with out cutting the piece!
• Use the bur life on your saw blade and be patient
• Use the mizzy wheels to grind down the remainder of the sprue stump to the surface of the piece. Grind down any big lumps or bumps in the piece.
• If possible, use your files now to even out the ground areas.
• GO to the sandpaper discs or the rubber abrasive wheels and begin to finish any areas.
• You can use the tumbler to achieve either a matte, satin or polished look for your pieces.
o Green ceramic media: matte finish
o White ceramic media: satin finish
o Steel shot: polished finish
• Remember that the shot doesn’t remove metal so it will not take away any scratches in your piece, it will just polish the scratches.
• For the green and white media, you can stop finishing with the flexshaft about halfway- black wheels or red bristle discs, or 400 grit sandpaper
• For the shot, you need to go up to pre-polish- blue wheels, pink bristle discs, or 1000 grit sandpaper.
To tumble:
• Put appropriate shot into tumbler, enough to cover your piece(s).
• Put your piece in.
• Fill with water to cover both media and piece.
• Add about ½ capful of soap solution.
• Screw on top.
• Put tumbler on base with top facing out.
• Turn on.
• Check for any leakage.
• Let tumble: 45min-1hr for matter or satin finish; 2-4 hours for hardening.
• After done, take sieve and place in sink.
• Open tumbler and pour contents into sieve. This will retain your pieces and the media while getting rid of the dirty water.
• Pluck your pieces out and dry.
• Rinse the shot and air dry.
• For a gunmetal finish, you can tumble with steel shot after using liver of sulfur. If you do this, make sure that you wash out the inside of the tumbler with soap and water, and wash the shot thoroughly before air drying.