Carbide, in construction and industrially, is an EXTREMELY hard material often used on the tips (or as a solid piece) for router bits, saw blades, planer blades, masonry bits, and certain grinding pads.

Carbide is used very commonly for wood working and a lot of metal working. Accurately it is used in the form of Tungsten Carbide, which is put on the tips of sawblades and router bits for cutting into any kind of wood, soft metal (i.e. aluminum, brass, copper, tin), or some kinds of plastics.

The great thing about carbide is you can be abusive with it and it will out last pretty much anything. I've seen people cut aluminum plates with carbide tipped saw blades, which is somewhat slow and careful process, with woodworking ripping blades and it the end the aluminum plates were crappy looking but the sawblade didn't dent, snap, or shatter or anything. It is still cutting wood even today. Carbide on router bits is especially great since it has an incredible durability. Cutting wood with router bits can be very stressful on the bit and normal HSS (high speed steel) bits can easily break or lose their sharpness quickly. Solid carbide and carbide tipped bits never break (unless they happen to run over a metal screw too quickly putting too much stress on the bit and breaking it) or loose their sharpness.

Despite carbide's incredible durability it is very brittle like diamond. So using it in something other then cutting material wouldn't be wise. If your dropped your nice new Carbide Spoon (don't ask), it would shatter like a piece of glass.

Carbide within the caving or potholing community refers to Calcium Carbide which when mixed with water generates acetylene gas which is burnt to provide light.

CaC₂ + 2 H₂O ---> C₂H₂ + Ca(OH)₂

Calcium carbide is purchased as fist sized lumps of a grey rock like material which is then crushed into large pebble sized lumps to provide more reactive surface area. The carbide is then placed in a dual chambered mechanism in which one of the chambers holds a quantity of water. A dripping mechanism allows the water to flow into the chamber and mix with the carbide solid. The acetylene gas which is created flows out of the carbide chamber to a nozzle where it is burnt.

Because the burning reaction requires 1.5 the amount of oxygen than the amount of acetylene produced...

2 C₂ H₂ + 3O₂ ---> 4 CO₂ + 2 H₂O

a lot of free carbon hangs around for a bit being hot and giving off a nice white light until it forms the CO₂ or just free C if not enough O₂ is being provided at the burning point.

Carbide lamps have now started to fall out of favor with many caving communities due to the amount of smoke damage that stray flames can cause and also the mess that can be caused by dumping or spilling the Calcium Hydroxide waste. In many cave systems they are banned. Carbide lamps have been replaced by better batteries, halogen bulbs and LED systems which can last for the extended periods required in caving.

Carbide bombs made with PET bottles can be wicked fun but be careful as you will fuck yourself and your hearing up very rapidly by standing too close. The reaction does not reach an equilibrium and gas will continue to be produced until either the bottle bursts (small bang), spontaneous polymerisation followed by combustion occurs (BIG bang) or it runs out of water. The last case is bad as you now have to deal with a pressurized container of flammable gas.

Compressed Acetylene for welding use is packaged in cylinders meeting DOT specification 8 or 8AL. The cylinder contains a porous filler saturated with acetone. The acetylene stored in the cylinder is dissolved in the acetone to prevent the acetylene polymerising.

Needless to say making Carbide bombs with glass containers is way stupid and will definitely end up in tears and somebody will lose an eye (or worse). Strictly for those who want end up in hospital or jail.

When carrying spare Carbide underground make sure the container doesn't seal perfectly or the one of the above results will ensue

Some corrections provided by jasstrong
See also http://www.hoopersupply.com/msds/acetylene.htm

Carbide memories

   As lads we were keen speleologists, given the great number of abandoned metal mines in the area. Mines are not, in general, as beautiful as natural caves - no sparkling stalactites, calcites and pearls, but they have a strange attraction as places that men have built, and worked their often short lives away in. Mines are also considerably more dangerous, held up with wooden props that turn to chocolate cake over the years, and rotten iron staircases and ladders. Just the job, then, for young fellows...

   Nowadays we might use tough, economical LED flashlights, but they were yet to be invented. Conventional torches, or at least the ones we could afford, are fragile, fickle, and just eat batteries. We therefore used carbide lamps - crude, smelly, dangerous, and utterly reliable. These lamps (if there is anyone here young enough not to be familiar with them) consist of two chambers - the lower of which one fills with Calcium Carbide "rocks", and the upper with water. An adjustable needle-valve allows water to drip slowly onto the carbide, and their sizzling reaction produces acetylene gas. This gas, led by a tube to a flat ceramic nozzle on the user's "hard hat", burns with a noisy, luminous, almost white flame.

   Now, Acetylene is seriously energetic stuff, H-C=C-H with a triple bond between the two Carbon atoms, which makes it good for the welding and cutting of metals. Old garages, before Acetylene in cylinders became commonplace, often had a generator, a big version of the lamps and as often as not home-made from an old pressure cooker.

    So, one day we are proceeding along a low drift. We've been here before, and know that it leads to some interesting chambers, but today the lower half of the tunnel is occupied by a swift-running stream. Advancing doubled-over is hard work, but it's not too far. The roof is so low that we can no longer wear our back-packs, and so, as is usual, attach them to our belts with a lanyard and let them float on ahead. Food, cigarettes are in waterproof tins, and our spare carbide (we might spend the weekend underground) tied up in a length of motorcycle inner tube, to keep it dry. The chap in front of me, hearing a hissing noise coming from his pack, pulls it towards him to see what gives, and Whooomf!, the escaping gas catches fire, BIG ball of flame! In his panic he retreats past us up the tunnel, but, forgetting the lanyard, pursued by the flaming bag.

    No-one hurt, at the end of the day, apart from one lad who nearly drowns, so hard is he laughing...

Car"bide (?), n. [Carbon + -ide.] Chem.

A binary compound of carbon with some other element or radical, in which the carbon plays the part of a negative; -- formerly termed carburet.

 

© Webster 1913.