Gear Cutting Machine (preliminary notes)


(Jonathan) #1

Hi All

Frank and I (Jonathan) made the gear cutter work for an initial test. Until formalised, I suppose he and I are the keepers of this piece of equipment.

IT IS HAZARDOUS: DO NOT USE WITHOUT INDUCTION

Once Frank and I do a proper risk assessment we’ll cosnider what inductions are required.

What is it?

Also known as a “hob cutter”.

It’s for cutting toothed wheels: one notch at a time. Best suited to gears for clocks and similar; also toothed belt wheels, servo motors and so on. Will suit brass, aluminium.

The motor is connected to a spinning piece containing a fly-cutter (pointy lathe-tool bit) or a cutting wheel. This moves up and down on the handle in the centre, and can move left to right by a screw. The work is held horizontally on the central spindle. The central spindle can turn but is held in position by a pin which goes into the holes in the indexing plate. You cut one notch, turn the work by a precise amount such as two holes of a particular ring of holes. Then cut and repeat until all the way round.

Electrics

The cable was perished and was replaced and checked with multimeter. Motor appears sound, R=100ohm.

Mechanical

The drive belt is quite loose and sloppy. Surely it needs a tensioner of some kind? We couldn’t work out immediately how to fit the cutting wheels (positioning of the arbor is tricky, need to adjust the slide). Some of the allen key holes are imperial.

The indexing plate has 10 sets of holes, suitable for these fractions (if I counted the holes properly):
62: 31, 2, 1.
64: 32, 16, 8, 4, 2, 1.
72: 36, 24, 18, 12, 9, 8, 6, 4, 3, 2, 1.
78: 39, 26, 13, 6, 3, 2, 1.
80: 40, 20, 16, 10, 8, 5, 4, 2, 1.
84: 42, 28, 21, 14, 12, 7, 6, 4, 3, 2, 1.
90: 45, 30, 18, 15, 10, 9, 6, 5, 3, 2, 1.
96: 48, 32, 24, 16, 12, 8, 6, 4, 3, 2, 1.
106: 53, 2, 1.
120: 60, 40, 30, 24, 20, 15, 12, 10, 8, 6, 5, 4, 3, 2, 1.

Test run

Frank and I cut a few notches in a 50mm disc of 3mm perspex. Central hole apparently 6.5mm, would guess it’s actually 0.25-in.


Is the gear cutting machine working?