Molded or turned plastic replaces scarce horn, bone, ivory and metal in buttons, handles, knobs, combs and other small hardware. Casein suits dry, light goods such as buttons and beads, Bakelite suits handles and knobs that need strength, heat resistance and insulation, and celluloid should be left to salvaged combs and decorative pieces because it burns.
Part of Plastics and Polymers
Plastic hardware is the small molded or turned goods, such as buttons, handles, knobs and combs, made from casein, Bakelite or celluloid.
Plastic Replaces What The Settlement Cannot Get Enough Of
Plastics from Scratch lists the targets: buttons, combs, handles, knobs, gears, bearings and containers, all of which replace materials that are scarce, expensive or hard to work. Metal is laborious to shape and too valuable for small items, and wood cannot be molded into complex shapes. Plastic can.
Match The Plastic To The Part
| Part | Plastic | Why |
|---|---|---|
| Buttons, beads, pen bodies | Casein | Polishes, dyes, machines like horn |
| Knitting needles | Casein | Smooth, light |
| Tool handles, knobs, switch bodies | Bakelite | Strong, insulating, heat-resistant |
| Combs, decorative sheet | Celluloid (salvaged) | Transparent, workable, but flammable |
| Handles for heavy tools | Wood or Bakelite with filler | Torque; see Tool Hafting |
For casein limits see Casein: Applications and Limits. For Bakelite, Bakelite.
Method: Make A Handle
Step 1: Make or choose the mould. A two-part steel mould with a draft angle and rounded corners, and a core to leave a hole for the tang.
Step 2: Weigh the charge of moulding powder: part volume × density × 1.05.
Step 3: Press and cure at the temperature, pressure and time for the material. See Compression Mold.
Step 4: Trim the flash and fit the tang with a hole or notch shaped so that the handle cannot turn on it. A snug fit with a pinned or glued tang holds better than friction.
Step 5: Finish. File, sand and polish. See Machining Plastics.
Method: Make A Button
Turn casein stock on a lathe or cut slices from a rod, drill the sewing holes and polish. Bakelite buttons can be pressed with holes in the mould, which avoids drilling a brittle part. Dye casein before hardening for a through-colour.
Worked Example: Material For A Button And For A Handle
Button. A flat round button 20 mm across and 3 mm thick has a volume of π × (10 mm)² × 3 mm = 942 mm³ = 0.94 cm³. For an assumed density of 1.35 g/cm³ (not a corpus figure) the mass is 0.94 × 1.35 = 1.27 g, and with the 1.05 overfill the charge is 1.33 g.
Handle. A cylinder 30 mm across and 120 mm long has a volume of π × (15 mm)² × 120 mm = 84,823 mm³ = 84.8 cm³. At the same density, 84.8 × 1.35 = 114.5 g, charge 120.2 g, less the volume of the tang hole.
Common Mistakes
- Using casein for a wet-use handle — it swells and splits.
- Unpinned tang — the handle spins.
- Thick, uneven walls on a handle — warp and shrinkage voids; keep walls uniform, as in Mold Design.
- Celluloid handles near a forge or stove.
Hot molds and formaldehyde
Pressing Bakelite uses a mould at 160-180 °C and a press, and curing releases phenol and formaldehyde. Hardening casein uses a formaldehyde bath. Wear gloves and eye protection, work outdoors or ventilated, and keep celluloid away from heat.
What’s Next
- Learn next: Lacquers and Coatings — finishing and sealing
- Combine with: Insulation and Tools — insulating handles