Tom Mallard’s Workbench L&B in 7mm scale and clockwork CR 828, 4mm Saints

[40057]

Cast iron as a material may not take too kindly to broaching, especially if the wheels are to be broached full depth of the axle hole. I'd be wary of splitting a casting or wheel boss. I assume Tom is replicating some vintage practice.

Expanding on Adrian's suggestion of using a taper reamer - the taper at the end of a regular hand reamer would suffice.

(Hand reamers are easily identified by having a square at the end of the shank. Machine reamers have parallel flutes full length and no square on the shank.)

It was ‘vintage practice’. Bond’s, Leeds Model Company and others all used a system where the wheel had a square central hole for quartering but the square hole was only about half the depth of the wheel. The end of the axle had a screw thread and the outer face of the wheel boss had a recess for a slotted nut that was used to secure the wheel. It meant the wheels could easily be removed and replaced (e.g. for replacing the mainspring in the motor) and the quartering preserved.