As Electronic Lead Screw (ELS) systems seem to be getting coverage at the moment, I though I would share some thoughts I wrote for the Raglan forum.

I have the Rocketronics 2-axis system that I fitted to my Raglan 5” lathe a few months ago.

Basic turning is, as expected, straightforward. The system requires both axes to be zeroed at a specific position (usually the outer corner at the end of the bar). If I am starting with a piece of round bar in the chuck, I will usually position the tool tip just clear of the corner in both directions, zero the axes in the control, then face the end by a small amount (maybe 0.5mm) and zero the Z axis again at the cleaned-up face. Then, assuming the plan is to turn down the diameter for a specified distance, I will set the cut length on the control, set it to only remove a small amount off the diameter, then set it going. Once done, I will reset the X zero to where it finished, and measure the diameter (positioning the tool at the last cut and re-zeroing is very straightforward). I dial in the amount still to be removed (measured diameter minus final diameter) and set it off again. The system uses a strategy of taking cuts along the length to a position about 0.1mm from the intended shoulder, then, after the final cut, it moves that extra 0.1mm and reverses out to clean up the shoulder. It works very well. Once going you don’t have to do anything apart from maybe swarf management. If that is proving a problem, pressing the ‘pause’ button will stop the cutting when the tool is back at the start, and you can turn off the spindle, remove the bird’s nest, restart the spindle and press ‘pause’ again to restart the cycle.

Of course there is nothing here that can’t be done with the standard lathe – it’s just easier with this – and you can work to an accurate length, which is probably not so easy using the Raglan carriage trip bracket.

The same basic method works for boring as well.

Parting off is just the same as the standard lathe if you are using the power feed.

Screw cutting is probably the reason why most people are attracted to these systems. It is certainly very easy and effective. Just set the pitch, the length of thread, the total depth of cut, and the number of passes. You don’t need a run-out groove (though there is a routine for making a DIN standard one if required) as this will make it’s own – it stops at the same place every pass. You can thread close to a shoulder without a problem (though, when I first tried this, I was going to leave only 0.5mm clearance, then realised that I was using an infeed strategy that moved down the flank of the thread so would be moving closer to the shoulder for every cut! I decided a bigger clearance would be prudent). And it is all done without any rattling gears!

I have also discovered (maybe everyone else already knew it) that by starting with a turned diameter of the exact nominal size (eg 10.00mm for an M10 thread), and zeroing the (full profile) tip on that surface, you get a good fitting thread just by using the book depth of cut. I did an M10 thread on a stainless shaft this afternoon, and the fit was lovely after a couple of extra spring- passes.

Tapered threads are also possible but so far I have found no need for this.

Tapers – internal and external. These were of specific interest to me as I have removed the top-slide and replaced it with a solid tool post mounting block, so I am no-longer able to angle the top slide to get tapers. To me the machining strategy seems a little strange, but it certainly works. You can enter specific dimensions (length and diameter change) but I have found it better to use what they call the ‘cone ratio’. That way you can extend the tapered section just by changing 1 distance – useful if you are trial fitting a tapered plug into a body, for instance.

I should mention that this system will only offer to make tapers in a specific orientation – external tapers with the small end nearer the tailstock, and internal tapers with the big diameter nearer the tailstock. It is possible to do them the other way round by reversing the Z-axis direction in the set-up pages, but you do need to be careful doing that. The same is required for LH threads, if you are unable to machine with the spindle turning the other way (very unwise with a screw-on chuck!)

Cutting radii – internal and external. With the same proviso that it will only do them in certain orientations, these are also straightforward. The handbook explains the process. One thing that you can do is to make what are probably elliptical curves – basically by specifying a different distance for the 2 axes. I thought this was just a gimmick, but then I realised I could make bullet-ended dome nuts for a water pump impellor that I was making – very neat and easy.

Grooving – it offers grooving with radiused bottoms (useful for pipe-bending formers), plus standard vee belt grooves. I haven’t needed to use these properly yet – just a bit of playing.

So, do I like it? The simple answer is, yes, I think it is brilliant. But it does depend on your approach to this hobby. I like tools to be ready to go with minimal set-up (hence my Multifix quick change tool post with a drawer full of holders and a wide assortment of screw-on tip tools). I like to plan the work. I am not so keen on doing it! I tend to make things from solid blocks, rather than castings, hence I have the attitude that if I make a mistake it is no big deal to start again. Also, machining from the solid tends to require more material to be removed, so being able to stand and watch is far more attractive than endless handle winding. A few days ago I had some 4” round aluminium billets that I had to reduce to 50mm diameter for a distance of about 40mm. I was only taking about 0.5mm radial depth of cut, so there were over 50 passes. I probably wouldn’t have volunteered to do the job without the ELS!

I do like the lack of noise. I hated the rattling of the gears on the standard lathe – I always disengaged them if I wasn’t using the power feeds or threading.

What don’t I like about it? Thankfully not much yet. It slightly niggles me that the readouts rarely give a round figure – if you want say 24mm it might say 23.999mm. Clearly no problem in terms of accuracy, but you do have to be careful not to read that as 23mm. I guess this is something to do with stepper motor resolutions and imperial lead screw pitches – it may not be possible to have the exact figure.

It would be nice to have a wider range of radius options. You only get a full 90 degree arc. I would prefer to be able to specify start and end angles to blend in to a taper, for instance. I asked about that with the makers but apparently the computing limit of the controller has been reached so there will be no major changes.

I have on a couple of occasions mistakenly caught the cross slide handle when the machine has been running, which has presumably over-ridden the stepper motor and lost the position. It’s a nuisance because you have to start again. Having done it more than once I decided to replace the handle with a plain disc to allow me to move the slide when required but hopefully with less chance of me catching it by mistake.

And of course there is the fear factor! Have I set it correctly? That is probably why I don’t use my mill in CNC mode. You don’t always get chance to stop it before something crashes if you have got it wrong! Thankfully this ELS doesn’t seem to have too many vices. The main thing to check is that you have got the axes zeroed in the correct position before you start a new cycle.

I should point out that I am not trying to recommend this system over any other – I haven’t seen or used any other. But if anyone else is thinking about this conversion I am happy to share my experiences. This (Rocketronics) system is expensive – I think it was about £1000 with all the motors etc. – and there are plenty of cheaper options available (though most are only powering the Z-axis so can’t do some of the functions available with the Rocketronics one).

I had always expected to use the ELS in conjunction with the DRO. The idea of having the DRO giving the overall position, and the ELS having it’s own local datums, seemed sensible. However, for this to be really successful I would need to have all the tools set in the DRO tool table. So far I have found the tool table function to be extremely counter-intuitive. I need to get my head around how to use it properly before it will be much use.

Dave