Broken Bits and a Shared Socket: Making 30 Bottle-Cap Keychains Safely
A workshop run by an NGO for Divyang trainees has eight students making 30 bottle-cap keychains for a school fair. The room is 4 m by 5 m with one window and one 6 A wall socket; two hand drills and one glue gun share that socket through an extension board. Ravi has a below-elbow amputation of the left arm and drills with his right hand. Meera uses a wheelchair; her seat height is 480 mm and the bench top is 780 mm, with a 700 mm deep top and a shelf above it, so she leans far forward to reach the work. Sana has low vision and works with a magnifier under a single tube light. In the first session two 2 mm bits snapped, one cap cracked, and Ravi's cap spun because he could not hold it and drill it at the same time. The epoxy adhesive smells strongly and the window stays shut because it is December. A drill cable lies across the walking path, and Meera has begun complaining of lower-back pain. The trainer wants the batch finished in six working days.
1. Rank the hazards in this workshop by how serious the likely injury is, and give one control for each, naming the level of the hierarchy of control you are using.
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Ranking by likely severity
- Unsecured workpiece plus single-handed drilling. This comes first because the foreseeable injury is a hole in the hand or a broken bit in the eye. Control (engineering): hold the work in a jig or machine vice fixed to the bench so no hand is under the bit, and use a drill guide or drill press. PPE (last line): goggles, never loose sleeves.
- One socket, two drills, an extension lead and a cable across the floor. Foreseeable injury is electric shock or a fall. Control (engineering/admin): one machine at a time, no daisy-chained extension boards, cable routed overhead or in a floor raceway, RCCB protection on the circuit.
- Epoxy fumes in a closed room. Foreseeable harm is headache, dizziness and sensitisation over weeks, not a single accident. Control (substitution): switch to a water-based adhesive or a low-odour one where strength allows; keep the window open, add an exhaust fan, nitrile gloves, eyewash within reach.
- Meera's forward reach and the back pain. Foreseeable harm accumulates. Control (engineering): clear the shelf above the bench, keep all work within a 300-400 mm reach zone, give 700 mm high by 800 mm wide knee clearance under the top, and rotate her between drilling, painting and packing.
The order is deliberate: controls that remove the hazard from the person's hand come before PPE, because a glove does not stop a spinning cap.
2. Design a holding jig, made from waste plywood offcuts already in the workshop, that lets Ravi drill a cap with one hand. Explain each design choice.
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Jig concept: a bench-fixed V-block cradle with a drill bushing
- Base: 12 mm ply offcut, 150 x 100 mm, screwed to the bench at the front edge so it cannot move. Ravi never has to hold the jig; his one hand is free for the drill.
- Cradle: a 30 mm wide, 4 mm deep groove routed or chiselled down the centre, sized to the cap skirt (32.5 mm measured, not the nominal 30 mm), so the cap seats and cannot rotate.
- End stop: a 10 mm ply lip at the far end so the cap always sits at the same depth; this also fixes the drill position, which is what stops wandering and snapped 2 mm bits.
- Bushing: a 6 mm ply top plate with a 4 mm hole as a guide, replaced when worn; the drill enters at 90 degrees without a centre punch.
- Clamp: a small G-clamp or a bicycle-cable toggle at the near end, operated with the same hand before picking up the drill, so the sequence is clamp, drill, unclamp.
- Colour: paint the jig edges yellow with a dark groove line so Sana can locate the groove by contrast as well.
Why this shape: the failure in session one was a workpiece moving, not a bad drill. Fixing the work and guiding the bit removes the two causes of snapped bits. Making the jig from offcuts keeps the cost at near zero and teaches the students that fixtures are a design output, not a purchase.
3. The trainer proposes adding two evening hours for six days to meet the deadline. Give your recommendation with reasons.
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Recommendation: do not add evening hours; reduce scope instead.
- Risk rises faster than output. Fatigue in single-handed drilling shows up as slipped bits, and these are 2 mm bits on curved plastic. The first session already lost work to two snapped bits and a cracked cap; tired hands lose more, so the extra two hours may not even add net output.
- Supervision and light. Sana's magnifier work depends on the single tube light; evening work means either poor light quality or extra fittings on the same overloaded socket, which undoes the electrical control.
- Legal and duty-of-care angle. Trainees are not production labour; unpaid or compulsory overtime for students with disabilities is both unsafe and bad practice for an NGO that must model good workshop norms.
What to do instead:
- Cut the batch to 20 keychains and tell the school the reason in writing, with a photo of the jig and the process; the reduced batch is still a complete demonstration.
- Batch by operation, not by person: one day cutting and cleaning caps, one day drilling on the jig, one day painting, one day assembly, one day packing. Changeover time is what is eating the six days.
- Ask for a two-week delivery date; a school fair date is usually negotiable, and a safe workshop is not.