Hand tools and bench work
This domain covers the safe and effective use of bench hand tools: hammers, cold chisels, files, hacksaws, taps, dies, punches, scrapers and vice work. The exam tests technique, tool condition and the arithmetic of thread tapping.
Core rules
- Mount work securely in a vice at about elbow height. Use soft jaws or a cloth for finished surfaces.
- A file must have a tightly fitted handle. Cut on the forward stroke and release pressure on the return stroke. Cross filing removes metal quickly; draw filing produces a smooth finish. Use a file card to clean the teeth.
- Select a hacksaw blade to suit the section: coarse teeth for thick metal, fine teeth for thin tube or sheet, with at least three teeth in contact with the work.
- Cold chisels are hardened and tempered at the cutting end and softened at the struck end. Wear goggles and use a chipping shield.
- Taps cut internal threads; dies cut external threads. Use the correct tapping drill, keep the tap square, apply cutting lubricant and reverse a quarter turn periodically to break chips.
Worked example
A coarse metric thread M10 x 1.5 is required. Tapping drill size = major diameter - pitch = 10 - 1.5 = 8.5 mm. Reason: the tap needs a hole slightly larger than the minor diameter so the thread flanks can cut without the core of the tap jamming. Use an 8.5 mm drill, chamfer the hole, mount the work square, start the tap with light pressure, and use lubricant. For an M8 x 1.25 thread, the same rule gives 8 - 1.25 = 6.75 mm, usually rounded to 6.8 mm.
Traps that cost marks
- Using a file without a handle.
- Applying heavy pressure on the return stroke and dulling the file.
- Tapping without lubricant or without backing off to clear chips.
- Using a punch with a mushroomed head.
- Allowing a hacksaw blade to run without at least three teeth in contact.