Sieg C1 lathe autofeed and screw cutting

[Howard LewisParticipant @howardlewis46836]

As already said, if screwcutting (As opposed to using Taps or Dies) the leadscrew must not be disengaged from the gear train, so do not disengage the dog clutch, whether stationary or in motion.

If it is, the relationship between the cutting tool and workpiece will be lost. It will be very difficult, if not impossible to reestablish it

Although winding to and fro, with a mandrel handle, for working up to shoulder, or down a blind hole can be a pain, it is better than the risk of broken Taps, or stripped threads, for a scrap job!

For screw cutting, rather than using a Tap or a Die, the gear ratio used will determine the movement of the Saddle relative to the workpiece in the chuck.

The slower that the Leadscrew screw revolves, relative to the chuck, the finer will be the pitch of the thread, or conversely, faster equals coarser pitch thread.

With only 150 watts available, large diameter, coarse pitch threads might be beyond the capability of the motor. And running at low speeds, the motor will not be passing much air through to cool it, so could over heat, if used in this way for long periods.

And I would not rely on the overload facility, too much. If, eventually the motor or control  board (possibly both!) need replacement, you are looking at at least £100+ each.

The C1 does not seem to be imported into UK any more, so spares might be hard to find, and harder as time goes on.

A few minutes, rotating by hand will be cheaper and more convenient!

Howard

[Howard LewisParticipant @howardlewis46836]

For auto feed, presumably to get the best surface finish, set up the gear train so that the Leadscrew revolves as slowly as possible, relative to the chuck.

In the case of the C2 and C3 mini lathes,the gear set enables a train of 20:80/20:80 to be set, so that with a 16:1 reduction and a 1.5 mm pitch leadscrew, the feed rated is 0.09375 mm per rev. (0.0037″ in old money)

The 80/20 gears are compounded by means of a key connecting the two gears, on the stud.

It MIGHT be possible to use gears from the C2 and C3 on the C1 (They are Mod 1, and the bore and thickness might be the same)  to supplement those that you already have.

Spare gears are available, from importers, so measure one of your gears, and count the teeth.

The formula is          (Teeth+2) / OD in mm = Module

To see what is available take a look at the Arc Euro Trade website. (“C3 Change gears”) They list gears from 30 up to 80 teeth in 5T increments.  If you are unsure about dimensions of the C2 and C3 gears, ring or E mail. I am sure that they will be most helpful

Howard

[Howard LewisParticipant @howardlewis46836]

It looks as if the gears that you already have can be set up to provide a feed of 0.05 mm per rev, which is a fine enough feed to give a good surface finish with a sharp tool (preferably with a small nose radius) set on centre height.

So for auto feed, you may not need any extras. Just use a small depth of cut, and the fine feed.

For roughing cuts (Bear in mind the minimal motor power!) you can hand feed more rapidly.

But don’t over do the feed rate or depth of cut.

This is all part of becoming familiar with the machine, and how to use it.

Howard

[th1980Participant @th1980]

This lathe is a bit of an odd ball because the leadscrew is permanently engaged to the saddle. The clutch only connects the motor to the leadscrew. So position is impossible to loose while cutting threads. I’m not using the autofeed much (or at all really). Stopping the saddle takes as long as the chuck stops rotating after the power is swithed off (I don’t know if the clutch could be operated while under power). Moving the saddle long distance is a pain because you have to do it by hand cranking the leadscrew from the end of the machine.

If the control board breaks some day, I might be able to repair it myself.

I wont be buying the gears just now. I’ll need to research the topic further.

[th1980Participant @th1980]

And yes, there are gears already in the lathe that make two feed speeds possible. Stalling the motor has not broken anything in the lathe yet but the carbide inserts don’t like that very much….

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