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SIEG C0 Auto feeder S/N:10153

Information wanted !

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Paul Kennedy21/08/2021 21:34:36
49 forum posts
123 photos

Hey guys, Ive been looking for the SIEG C0 Auto feeder S/N:10153 for a while now and cant seem to locate on in the UK. LittleMachine.Com have them in the US but afaik they dont export. Anyone have ANY information on them ? I know the silicone drve belt/o ring is avaiabel from both arc euro trade and axminster but not the auto feeder unit itself. Id be greatly interested in any pdf or photo of its internals. pref with some dimmensions Any and all help is ofc appreciated.

John Haine21/08/2021 22:12:51
4170 forum posts
242 photos

It looks exactly like the Unimat 3 auto feeder though the dimensions may be different. Basically the shiny "knob" with a groove takes the drive O ring that couples to the headstock mandrel. Inside the red box there's a worm that drives a pinion that can engage the end of the leadscrew using a dog clutch operated by pushing/pulling the black knurled knob. I've got one from my Unimat, I'll try to take a photo of the innards.

John Haine21/08/2021 22:46:34
4170 forum posts
242 photos


this shows unit with cover plate off. The worm gear is pinned to a shaft with the knurled knob on the end under the plate. The shaft can slide axially and there's a sprung ball detent down the bearing hole in the cast housing. Fork on the end of the shaft engages with a tongue on the end of the leadscrew. So sliding the knob in and out engages/disengages both the dog clutch and the worm gear. The worm is driven by the pulley groove on its shaft projecting to the right.


Bit late in the day to measure it and anyway the design is different and I suspect a bit smaller than the C0 version. The belt drive from the mandrel is in my opinion highly unsatisfactory with a short belt with a 90 twist in the loop to accommodate the different axes. To be frank I wouldn't bother with making your own but just arrange a geared DC motor to drive the leadscrew.

Paul Kennedy21/08/2021 23:18:55
49 forum posts
123 photos

Hi John, Thanks for the photo, ATM i couldn't make the unit anyway as i have no access to dividing head for gear cutting etc and likely miss some other important tooling :/ After reading your comment i assume the silicone drive ring simply slips under load and is mostly ineffective ? I'm very interested in the idea of a geared motor though. Would you have any recommendations on this perhaps ? I hop to keep costs down if possiable but yea things add up i know. I was even considering totally replacing the leadscrew and feed nut as its basically just M5 threaded rod and maybe upgrade it to M8 or even acme but .. I tend to take on too much so .. i will leave well enough alone for now.

JasonB22/08/2021 06:53:16
21435 forum posts
2448 photos
1 articles

I used my Unimat one quite a lot and provided you don't get too greedy with the cut they work OK, neither lathe is designed for heavy cuts anyway.

The Autofeeds for the Sieg mills use gear head motors and a dog clutch arrangement, you would need to work out gear ratio by doing a few tests to see how fast you turn the feed screw both for cutting and rapidly returning the carriage and your variable speed drive to cover that range.

I thought the C0 had an M8 leadscrew not M5

Edited By JasonB on 22/08/2021 07:42:39

Clive Foster22/08/2021 08:53:17
2835 forum posts
103 photos

Given that these things are mouse power rather than horse power how practical would it be to rig up simple direct drive stepper motor system?

Generic motor and "twiddle a knob speed control" drive from the usual affordable sources. Simple fork drive on the end of the motor shaft. Motor mount arranged so it can slide sideways to engage and disengage the drive.

Obviously a belt drive speed reduction set up with sliding fork clutch would let a smaller motor be used and the speed reduction would probably give a more controllable drive but it needs more parts and more making. With a belt drive a DC motor would be fine too so probably a bit less costly.

That said were I to do the job I'd use a pair of nylon gears with the motor on a swinging pivot mount, like a car alternator, to engage and disengage the drive. Large gear living on the leadscrew shaft, small gear on the motor. Choose gear sizes to fit and give a sensible speed. Motor with speed control can be stepper or DC to choice, taste, price or lucky find.

I'm not in love with the standard direct drive from the spindle idea which doesn't allow the feed drive to be engaged or disengaged when the spindle is already running. But, as ever in the real world, its a question of how much performance and design elegance the customer can afford. Generally much to be said for "Cheap'n works ... but...!" so long as the ...but... isn't too obtrusive.


John Haine22/08/2021 10:58:55
4170 forum posts
242 photos

I just checked and the U3 leadscrew is 8mm but of course a LH thread.


This would probably be a suitable motor. It is this type available on eBay, though I bought a couple years ago and haven't used them. Size is 36mm dia x 60mm L. Shaft 5mm dia with flat, 8mm long. Speed at 16V supply 340 RPM so would need another reduction stage probably as well as a speed control such as the ubiquitous MFA one. There are lots of other similar motors around. The U3 drive is 0.02mm/rev, so at 500 rpm of the h/s that's 10mm/min. As the l/s pitch is 1mm (I assume) the leadscrew will be doing 10rpm. So driving it direct from the motor you would need 16x10/340 = ~0.5V average which would be right at the low end for the speed control. Hence the desirability of an addition reduction. Motors are available with significantly greater reduction. (Note to Mods: these links are given as examples to show what's available - if you delete them I will be disgusted.)

I think it would be easiest to position the motor at the handwheel end with a modified or new handwheel, possibly with a pin clutch of some sort or a slippable belt. Assuming the C0 uses the same fork and tongue arrangement as the U3 at the headstock end, making a stable connection to the motor could be a bit tricky.

A stepper would be equally good though bigger and more expensive but a modern size 23 one would have plenty of torque even for direct drive. I use a rather old fashioned stepper on my coil winder to drive an M6 leadscrew and there is quite a lot of friction but it works fine. If you used a stepper it's a short step (sorry!) to fitting a digital leadscrew system!

If you did want to use a worm reduction you could perhaps make the worm wheel by free hobbing using a suitably sized tap, with the worm itself being made from a bolt with the same thread. No need for dividing head or gear cutters.

Clive Foster22/08/2021 11:13:29
2835 forum posts
103 photos

Thinking out of the box would one of the heftier model control servos converted to continuous rotation have enough power and be sufficiently durable for this job?

There are various YouTube videos of folk converting the standard variety for model winch drive purposes. Either retaining the control board for the usual pulse control or stripping all the electronics and just using the motor and gear train. Judging by E-Bay the better ones seem remarkably well made.

The pukka winch drive ones, which are usually limited to only a few turns, have more than decent torque specifications. Bit spendy tho'.

Unlike John I'd go for headstock end mounting of whatever drive you use. From those I've seen the swing the motor to engage two gears system always seemed neatest. The big disadvantage is that the swing shaft and motor spindle have to be closely parallel to the leadscrew drive so the gears don't chew each other up. Belts are a bit more forgiving of alignment errors.


William Hulme23/08/2021 11:01:43
16 forum posts

LittleMachineShop have supplied me in New Zealand with spares and upgrade kits for my X2 mill.

Take a look at the Australian Sieg agents website, lots of spare parts pictured there.

William Hulme23/08/2021 11:19:05
16 forum posts

PS the Australian Sieg agents are

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