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Basic Working With Materials

By: Kristoph Minchau and Jim McGinn

Safety

  • Hind sight is better than no sight. WEAR SAFETY GLASSES whenever you are cutting, drilling, grinding, filing, punching, sanding, heating, SOLDERING, and anything else that might cause pieces or bits to fly.
  • When working with rotating machinery (for example, Dremel tools, lathes, etc.), make sure all clothing (like sleeves) and long hair is tucked in, and wear hearing protectors (it's much more enjoyable).
  • Be CAREFUL.

Plastics:

Attributes:

  • Easy to work with.
  • Soft, and light.
  • Strength (5-10 ksi)
  • Low softening point (143-171C).
  • Two main types Thermosets (two substances are mixed together to form plastic cannot be reheated and re-formed), Thermoplastics (has a relatively low melting point so for example can be heated and bent)
  • Some plastics include: ABS (large black pipes and white), Acrilic (PlexiGlass), Epoxies, Nylon, Delrin, Polyelthelene (mostly in sheets), Styrene, Polyurethane, PVC, and Lexan (used in the BattleBots Box to protect spectators, and to make 'bullitproof' 'glass').

Manipulating:

  • Cutting / Drilling:
    • Tin Snips (Nice clean cuts).
    • Hack saw (don't cut too fast, or the plastic will melt).
    • "Utility" (or Hobby) Knife and a metal edged ruler.
    • Do NOT use a scroll saw due to small blade (it typically 'melts' it's way through the plastic).
    • Can be drilled (best if drilled by hand).
    • Punched.
  • Shaping:
    • Heat.(Softens at about 290-340F or 143-171C)
    • Use a strip heater (or use a stove element with two heavy tiles to form a thin strip of heat, or your toaster).
  • Machining
    • Can be machined and manipulated a lot like wood, but you have to be careful that you don't go too fast and start to melt the plastic, because then you are no longer manipulating the same material that you started out with.
  • Recommendation:
    • Try to stick with Thermoplastics because they are bendable when you heat them.
    • Basically get 1/16" sheet of Styrene.
    • Or try a 1/16" ABS sheet.

Sources:

  • PM Hobbies (small pieces and expensive).
  • Model Land (also small pieces and expensive).
  • GE PolymerShapes (larger amounts (for example 8'x4' sheets (perfect for your 10cm x 10cm mini)) for much cheaper per square foot (ex. $50 for 8' x 4' for 1/8" ABS sheet (gaurunteed to last you a few years))) phn: 250-1670.

Metals:

Aluminium:

Attributes:

  • Light.
  • Soft 
  • Strength:10-70 ksi depending on type typical 10-30 ksi (depends on type (ex. Aircraft Aluminium is stronger)).
  • Good strength to weight ratio approximately 2-2/3 times better then steel.
  • Very hard to weld, solder to, glue to, and sometimes bolts can creep. But for small stuff nothing beats a few rivets and or bolts.
  • One of the most common metals used in robot building due to it's light weight (try to keep in mind the weight restrictions), good weight to strength ratio, and ability to be easily machined, formed, and cut.

Manipulating:

  • Cutting/Drilling:
    • Hack Saw (Remember Aluminium is softer then Steel so in some cases it can cut like butter)
    • Tin Snips (Can cut up to 1/8" thick if you really put the effort in according to Jim)
    • "Utility" Knife, and a metal edged ruler to score, and bend to break (use a knife with the snap-off blades, so you can cut a bunch of pieces and then snap-off the blade, and then you are left with a brand new knife edge).
    • Band saw, Jig saw, or scroll saw (only for thin sheet metal) with appropriate metal blade
    • Metal Shear
    • Dremel with cutting disc.
    • Use a file to file edges smooth.
    • Drilling: use normal HSS metal drill bits (cutting fluid can be used but is not mandatory).
    • Punch
  • Shaping:
    • Clamping in vice and pounding with a hammer.
    • 'Bending bars'.
    • 'Work hardened' can only bend once.
    • Brake.
  • Misc:
    • Do not try to bend Aluminium more than once (expecially the extruded stuff) and no more than 90 degrees because it gets weakened to the point it will easily break.

Sources:

  • Metal Supermarkets, lots of miscellaneous stuff with a LARGE selection of various metals, sheets, rods, etc. at a reasonable price and they cut to length.
  • Hardware stores(Revy, Home Depot, Canadian Tire), sells a few plates of Aluminium plate, but mostly extruded Aluminium tubing (box, 'U', and Circular), which is good for frames. But expensive
  • Calgary Metal, Various sizes of new and scrap metal (good if you want thicker plates then you can find in hardware stores) and dirt cheap (pay by the pound (Aluminum is light). New stuff, lots of stuff, and big stuff.

Steel:

Attributes:

  • Hard.
  • Strength 60-200 ksi. Typical 60-90 ksi.
  • Strong.
  • Need to use HSS tools for everything, and preferably things with Carbide, Titanium, or Cobalt in them or coated.
  • Heavy.
  • Hard.
  • Most is weldable and solderable.
  • Don't use High Carbon Steel or tool steel because it is approaching the hardness of the tools you are using (bad).
  • Hard.

Manipulating:

  • Cutting / Drilling:
    • Hack Saw.
    • Dremel with cut-off wheel.
    • For thin sheet metal use Tin Snips.
    • Bandsaw or Jig Saw (mostly only on sheet metal)
    • Shear.
    • Drilling: HSS drill bits with cutting oil and a lot of time and patience.
  • Shaping:
    • Clamping in Vice and big hammer (release a lot of stress).
    • Bending bars.
    • A good file to file razor sharp edges smooth.
    • Grinder.
    • Brake.
    • Sandpaper 220x grit for cleaning grease and rust.
  • Recommendation:
    • Music Wire should be avoided because of it's high hardness (DO NOT cut with side cutters use a Dremel cut-off wheel)
    • Cold rolled steel is good for most applications.

Sources:

  • Metal Supermarkets, lots of miscellaneous stuff with a LARGE selection of various metals, sheets, rods, etc. at a reasonable price and they cut to length.
  • Scrap yards, great deals at great prices, for oddly shaped pieces
  • Hardware stores (Revy, Home Depot, Canadian Tire), sell some plates, rods, box, and circular stock.
  • Calgary Metal, Various sizes of new and scrap metal (good if you want thicker plates then you can find in hardware stores), and some box, rods and circular stock, and dirt cheap new stuff, scrap stuff, and lots of stuff. Big and heavy you pay by the pound so try to

Tools You Should Have:

  • Hacksaw (try to get a HSS 'shatterproof' blade rather then a standard High Carbon Steel blade which (from experience) can shatter).
  • "Utility" Knife.
  • Files.
  • Big Steel Vice.
  • Bending Bars.
  • Dremel (has a good selection of metal tools).
  • Drill and good drill bits (try to get better then the standard HSS like Titanium coated (oooh Titanium.... Look a 3/8" ....oooh oversized), or if you really use your drill bits, and can spare the money, go with the Cobalt impregnated bits).
  • 1 to 60 (from Acklands Grainger), and 61 to 80 drill bits from Lee Valley
  • 1 Ton Hand Punch.
  • Hand drill (if you do a lot of work with plastic). Or
  • Digital Caliper.