Gear Cutting with the Hobbymat MD65

Have just been cutting some gears (gears design) and thought it worth taking some photographs and writing up some comments on how to convert the Hobbymat MD65 so that you can cut straight spur gears.


The topslide is removed with four caphead bolts.

It is rather awkward that there is a pivot post protruding from the cross-slide as this stops you easily fitting just any angle plate. The angle plate that comes with the lathe has a hole to allow for this.md65-011

The angle plate is a large piece of cast iron and was primarily supplied with the lathe so that you can use the lathe as a mill.

I modified the angle plate with additional 6mm threaded holes that allow me to bolt the Unimat 3 mill column to the plate – I have created a small precision drill using the same Unimat 3 mill.

md65-012You do have to be a bit careful as there is quite a lot of extra mass on the cross-slide once the head and motor are attached as well.

It is worth tightening the cross-slide to reduce any possible chatter – as with any milling machine it is best to reduce movement in all axes other than the one you are moving.

md65-013The dividing plate fits to the shaft where the pulley collar currently sits.

I just undo the grub screw, remove the collar and in it′s place put the dividing plate and use the grub screw to fix it in place.

It is best to remove the drive belts as it is too easy to switch the lathe on instead of the milling machine….

md65-gear-003A bent arm with a pin plugs into a fixing on the bench and has enough spring for me to pull it out, move the dividing plate around and then release the arm to again fix the position.

The pin is tapered and this locates the plate very accurately and securely each time.

md65-gear-004Very easy with an indexing/dividing plate to lose count as to where you are and where to move next, one hole out when making multiple cuts would be horrific as you would need to start again, so I mark the holes I′m going to use with a permanent marker. I also mark the first start finish point (the “O” on the outer rim), just makes it easier to know exactly where you are – light at the end of the tunnel!!

md65-gear-006The indexing point is just a point that a tapered point that locates in a hole. The point is brazed to a 5mm diameter piece of silver steel and then locates in a hole in a wooden block that is fixed to the work bench.

The silver steel is springy enough that you can pull the point out of the index hole, rotate the indexing plate and then fix in the next hole.

Just remember that the rigidity of the lathe head is defined by how rigid this bar and fixing is as this is all that stops it rotating.

A small amount of force is applied to remove the point from the plate.

Just make sure the milling tool is clear of the part before you move the index on to the next point.

Here the setup is complete. Unimat 3 milling pillar onto the angle plate on the Hobbymat cross-slide, an indexing plate onto the back of the lathe spindle, a Unimat 3 milling head with gear cutter and I′m able to machine small gears.

md65-gear-001The top edge of the angle plate does limit the lowest position of milling head, but even so with the quill travel it can easily reach the centreline of the lathe.

md65-gear-007In this case you can see the part after the first cuts. I then move the tool in further using the cross-slide on the lathe and once again make each cut and then index the part round.

Take your time as the milling head is not as stiff as it could be when mounted to the saddle, as well as the motor for the Unimat 3 being rather underwhelming.

However, the results are worth waiting for. I’ve cut a lot of gears using this setup for a number of engines.

Brass GearsThese two brass gears were cut for the V-Twin Solenoid Motor – an unusual four-stroke solenoid design.

Gears for a small single cylinder 4 stroke with the small gear machined directly in the crankshaft. I cut these gears using the above method into mild steel in this case.

I must admit that I have now swapped to cutting gears with a rotary table, index plates and the milling machine – a much easier setup.

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Gear Cutting with the Warco HV4 Rotary Table

The Warco HV4 rotary table comes with a set of dividing plates. This with the Sieg SX2.7 make a great combination for cutting gears.

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Gear Noise

Gear whine is generated by meshing gears due to the vibration caused by failure of the rolling action between the mating teeth due to a number of factors.

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