Hinge Recesses in Ten Oak Doors
A workshop must hang 10 solid oak doors, each 2100 mm × 900 mm × 44 mm, using three 100 mm butt hinges per door. The only router is a 900 W plunge router fitted with a 12 mm two-flute straight bit and an adjustable fence. The bit is newly sharpened, but the collet has a small burr and the router cable has a taped repair. There is no router table and no hinge jig. Each door is carried in on two trestles. A student suggests clamping all ten doors together, aligning their edges, and routing every hinge recess in one pass to save time, using the door edge as a guide. The workshop has a 40-minute slot for the first door and needs a repeatable method for the rest. The door supplier specifies that hinge leaves must sit flush and that the oak is prone to tear-out.
1. Assess the student's proposal. State whether it is acceptable and describe a safe, accurate method for the first door.
Read the worked answer
The proposal is unsafe and inaccurate. Stacking ten doors and routing in one pass means one slip damages several doors, the clamp pressure can distort the edges, and the cutter is buried with no clear view. The doors also vary slightly, so a single setting cannot give flush hinges on all ten.
Safe method for one door:
- Unplug the router before changing the bit. Clean the collet and remove the burr, or replace the collet; a burred collet lets the bit run out or slip.
- Support the door flat on trestles with a sacrificial board under the edge. Clamp it so it cannot move.
- Mark hinge positions from the top and bottom using the same datum for every door. Mark the leaf length and width on the door edge.
- Use a straightedge or shop-made template and a guide bush. Score the outline with a knife to reduce tear-out.
- Take light cuts: 1 mm scoring pass, then 1.5-2 mm to final depth. Do not plunge 3 mm in one pass in oak.
- Feed against the cutter rotation; do not climb-cut. Square the corners with a chisel.
- Check the leaf sits flush; adjust depth, not force.
2. Describe how the hinge recess depth and width should be set and checked, including why a 12 mm bit cannot cut the full 100 mm × 25 mm recess in one plunge.
Read the worked answer
A 100 mm butt hinge has a leaf about 100 mm long, 25 mm wide and 3 mm thick (check the actual hinge). The recess depth must equal the leaf thickness so the leaf sits flush. With a 12 mm bit, one pass only cuts 12 mm width. For a 25 mm wide recess, make two overlapping passes across the width (for example at 0 mm and 13 mm) and then clean the edges; the round ends are squared with a chisel. Along the 100 mm length, use a template or straightedge to stop the router at the marked lines. Set depth with the turret stop: first pass 1 mm, second pass to 3 mm. Test with the actual hinge leaf; if it stands proud, take another 0.2-0.3 mm pass, not a heavy cut.
3. List the maintenance and safety checks before the router is used, and explain the collet burr risk.
Read the worked answer
Before use: unplug and inspect the cable; the taped repair is a defect, so replace the cable or use another machine. Check the plug and RCD. Clean the collet and bit, check the bit for cracks or chips, and fit the bit with the correct spanner. Check the fence locks and the plunge spring returns. Wear eye and hearing protection and use dust extraction. The collet burr is critical: it prevents the bit shank from seating squarely, causing vibration, poor finish and possible bit ejection. Do not use the router until the collet is cleaned or replaced.