Tool handling
The difference between a neat job and one that has to be redone almost never lies in knowledge: it lies in using the right tool, in good condition, in the right way. It is the easiest thing to learn and the most expensive to ignore.
01Hand tools
| Tool | What it is for and what it is not for |
|---|---|
| Combination pliers | Gripping, bending and cutting thick conductor. It is not a wrench: tightening nuts with it rounds off the flats. |
| Needle-nose pliers | Fine work, forming eyelets, reaching narrow spaces. It cannot take force: it spreads open and becomes useless. |
| Diagonal cutters | Cutting conductor flush. Never cut steel or hardened wire: it permanently nicks the edge. |
| Wire stripper | Removing the insulation without biting into the copper. Set to the correct cross-section, it leaves the conductor intact. |
| Screwdrivers | Slotted, Phillips, Pozidriv and Torx. The tip must fill the slot: a small tip ruins the screw and your hand. |
| Wrenches and sockets | For terminals and bolts. The open-end wrench only when the socket or box-end wrench does not fit. |
| Crimping tool | Pre-insulated terminals, ferrules and connectors. Each type has its own die: crimping with combination pliers makes a connection that will fail. |
| Voltage tester and detector | They indicate the presence of voltage. They do not replace the multimeter: they are never to be trusted to declare the absence of voltage. |
They carry the double-triangle mark and the test voltage. They are used in any job where voltage could be present, even if it is believed not to be. They are inspected before each use: if the insulation is cut, cracked, burned or peeling away from the metal, the tool is discarded. It is not repaired with tape.
And even with an insulated tool, the procedure remains the same: disconnect, lock out, tag and verify the absence of voltage with an instrument, checking before and after that the instrument works.
Each terminal has a tightening torque specified by the manufacturer, typically between 0.5 and 3.5 N·m in home distribution boards. Too loose, and the contact resistance heats the terminal; overtightened, the conductor is deformed or the thread strips. That is why professional boards use a torque screwdriver and the value is recorded. It is what makes later re-tightening meaningful.
02Power tools
| Machine | Use and criteria |
|---|---|
| Drill / driver | Drilling and driving screws. The adjustable clutch prevents overtightening and ruining the screw. |
| Rotary hammer | Masonry and concrete, with a carbide-tipped bit and hammering action. In metal or wood it is used without hammering. |
| Angle grinder | Cutting and grinding metal. The tool that causes the most serious accidents: it demands a face shield and the right disc. |
| Jigsaw | Cutouts in sheet metal and plastic for enclosures. Blade chosen by material and low speed in metal. |
| Hole punch | Clean round holes in metal enclosures, much better than the jigsaw for cable glands. |
| Conduit bender and threader | Metal conduit: bends without crushing the cross-section, and threads for the fittings. |
For ordinary steel with a high-speed steel bit, Vc ≈ 25 m/min.
n = 1000 × 25 / (π × 10) = 25,000 / 31.4 = 796 rpm. In practice, the nearest step on the drill: about 800 rpm, with coolant and firm, constant pressure.
With a 4 mm bit the same calculation gives 1990 rpm, and with a 20 mm one, 400 rpm. The rule of thumb: big bit, slow spin.
It burns out from turning too fast, from lack of pressure —the bit rubs instead of cutting— or from lack of coolant. A bluish edge is a sign of overheating: it lost its temper and will no longer cut again even if sharpened. Constant sparks and squealing are the two signs that the speed must be reduced.
03Safe use
- Check the power cord, plug and housing. A cord repaired with insulating tape is a reason to retire the tool, not to fix it.
- Verify that the guards and shields are in place. Removing the guard from a grinder “because it gets in the way” is what causes the most serious injuries in the workshop.
- Use the appropriate personal protective equipment: safety glasses always, face shield with the grinder, gloves when there are no rotating parts, safety footwear.
- Connect to a circuit with an RCD. It is the protection that saves you with a portable tool.
- The workpiece clamped, never held in the hand: the vise or clamp is not optional.
- No gloves or loose sleeves near a rotating tool: they catch.
- Wait for a complete stop before setting the machine down.
- Disconnect before changing a bit, disc or blade.
- Clean, inspect and put away in its place. A tool put away dirty is a tool that fails the next time.
The general framework of prevention, personal protective equipment and risk analysis is developed in health and safety.
04In the lab
Prepare three connections of the same conductor to a terminal: one with the bare wire twisted, another with a ferrule crimped with combination pliers and another with a ferrule crimped with the correct die. Measure the voltage drop across each one at 10 A and compare the temperature after ten minutes.
Tighten identical terminals with an ordinary screwdriver “by feel” and with a torque screwdriver set to the manufacturer’s value. Measure the torque actually applied in the first case: the spread among students is usually enormous, and that is exactly the problem.
Drill steel plate with 4, 8 and 12 mm bits, calculating the rpm for each. Repeat on purpose at the drill’s maximum speed and compare the finish of the hole and the condition of the cutting edge. Document with photos.
Mark, drill and mount a complete enclosure: hole punch for cable glands, DIN rail, wire ducts, and orderly routing of conductors. Verify at the end that the IP rating is maintained: every hole with its cable gland or its plug.
05Common mistakes
| Mistake | Consequence |
|---|---|
| Stripping the cable with pliers or a knife | Strands of the conductor are cut: the real cross-section drops and that point heats up. |
| Crimping with combination pliers | The compression is uneven: the terminal loosens over time or pulls out. |
| Screwdriver with a small tip | The screw slot is rounded off and the screw can no longer be tightened or loosened. |
| Hammering action in metal or wood | The bit is ruined and the hole comes out irregular. |
| Large bit at maximum speed | The edge burns, loses its temper and stops cutting. |
| Angle grinder without guard or face shield | It is the source of the most serious injuries in the workshop. |
| Holding the workpiece by hand | If the tool jams, the workpiece spins with it. |
| Trusting the voltage tester to declare “no voltage” | It can read wrong. The absence of voltage is verified with an instrument, checking it before and after. |
06Self-assessment
How do you identify a 1000 V insulated tool?
By the double-triangle mark and the indication of the test voltage. If the insulation is damaged, the tool is discarded: it is not repaired.
Is an insulated tool enough to work safely?
No. The procedure remains disconnect, lock out, tag and verify the absence of voltage with an instrument. The insulated tool is the last barrier, not the first.
Why does the tightening torque of a terminal matter?
Too loose, and the contact resistance heats the terminal and the problem worsens by itself; overtightened, the conductor is deformed or the thread strips. That is why a value is specified and a torque screwdriver is used.
Calculate the rpm for a 6 mm bit in steel, with Vc = 25 m/min.
n = 1000 × 25 / (π × 6) = 25,000 / 18.85 = 1326 rpm.
Why must a large drill bit turn more slowly?
Because the speed at the cutting edge is proportional to the diameter times the revolutions. To maintain the right cutting speed, as the diameter grows the revolutions must come down.
What does a bluish bit edge indicate?
That it overheated and lost its temper. It no longer cuts well even if sharpened: it must be discarded and the speed, pressure and coolant reviewed.
Why are gloves not worn near a rotating tool?
Because the glove catches and drags the hand in. Around rotating parts you work without gloves, with tight sleeves and nothing dangling.
When is hammering action used on a drill?
Only in masonry and concrete, with a carbide-tipped bit. In metal, wood or plastic you work without hammering action.
What electrical protection must the circuit of a portable tool have?
A residual-current device (RCD). It is the protection that acts on an insulation fault in the tool, which is the most likely risk on a job site.
What is done before changing a disc or a bit?
Disconnect the machine, not just switch it off. And wait for a complete stop before handling any part.