The device shown by Ian P has a vertical lead screw for the Z movement. This is fitted (originally) with a mitre gear and the handle fits in place of the motor drive shown. So, it should be easy to extend the lead screw upwards (perhaps by a more complex nut) and fit a motor there, the motor having internal gearing to reduce its rpm. This would leave the original handle in place, and it would rotate in sympathy with the motor drive.

Of course, you also need a manual drive, without turning the motor. So, you need a dog clutch between the motor and the lead screw.

The motor you need will be geared down a lot to about 50 – 100 rpm, and the torque at the output wuill need to be rather more than the torque required to turn the lead screw nut in normal conditions. The motor is likely to be specified as output torque at the motor (not including reduction gears) and so many rpm. Knowing this the reduction ratio and output torque needed can be calculated fairly simply. Halve the RPM and you nearly double the torque. 10% of the rpm gives you about 80 times the torque. [It would be 100 times if the gearbox did not add a friction load.] And it does no harmn to have a bit of torque in reserve.

Remember that you must include switches to turn off the motor automatically just before the Z movement gets to the end of its travel. Best to do this first, or you might get carried away with your efforts and try switching on before it is finished … And another switch which cuts out the motor as you disconnect the clutch.

The voltage you need is not really a serious concern, but – a low voltage motor is much safer than anything on the mains supply. Just chose from what is on offer, bearing in mind it will need a power supply, so 12V seems favourite perhaps using a computer power box. But it must be a DC motor or you will have fun reversing it.

Hope this helps

Tim

Edited By Tim Stevens on 23/07/2019 15:00:29

You need a clutch because:

The motor drive includes a reduction gear which is likely to involve slowing the ouput down by a factor of several. In other words, the motor whizzes round like a fan and the drive rotates sedately and you can count the turns. If the drive is the other way round, you wind the handle slowly but the motor has to whizz round. This makes the drive seriously hard work, if it is possible at all. So, use a clutch to separate the drive and winding the handle will be no more difficult than standard.

The clutch does not need to be fancy – a peg which can slide into a notch will do nicely.

One other thing – it reduces the load on the motor if you can counter-balance the weight of the mill head. In principle – a rope going upwards over a pulley hanging from the roof, and a weight the same as your machine head hanging on the other end. In practice, something more fancy will help to put the dangling weight out of the way. Some users prefer a pair of sliding spring-rods, as used to hold up a hatchback – but finding the right strength is not easy.

If you don't do the counterbalancing, the motor will drive downwards much more quickly than upwards, and this can be disconcerting.

Cheers, Tim

This one would do nicely

**LINK**

and has a right angled drive saving you buying gears

The one i linked is 40rpm but also 7rpm???

i seem to remember mine is 50 rpm (i’m Not able to check until Friday)

suppose it depends how fast you want but i flick the switch and rarely have to wait long till the heads where i need

I'm thinking, why not a stepper motor? You can install it above the column (so its out of the way) and belt driven via timing belt (the timing gear I'd attach to the hand wheel itself. No need for a clutch as there are no reductions in the stepper motor. You can have variable speed as well.

Sorry Guys, I'm getting confused, I was thinking table feed.

But a wiper motor would still do the job of moving the head up and down.

I have done the same thing in a Chester 16V mill and fitted a stepper motor as well as changing the lead screw for a ball screw. There is a post on here look for Chester champion V16 Z axis mod. And on YouTube David George Chester Z axis mod 2 worth a look. If you want the drawings etc drop me a message.

David