Mini lathe leadscrew thoughts

[Nick Clarke 3Participant @nickclarke3]

I am thinking about the leadscrew on my mini lathe. It is one of the models with a leadscrew swarf guard and a single half nut.

My thoughts are around these points:-

• Would it be better to remove the swarf guard so I can fit a second half nut and maybe a dial thread indicator?
• Is leadscrew wear an issue in an amateur lathe – with or without cover over the leadscrew
• Is a second half nut worthwhile – this is not the only lathe to use a single nut and a pad?
• I don't intend to do that much thread cutting so is the thread indicator worthwhile in view of my inexperienced amateur status or not because I will use it so rarely.

All 'blue sky' thinking perhaps – in fact I wondered about posting this in the Tea Room, but any spare thoughts over the Festive Season welcomed.

[Nick Clarke 3Participant @nickclarke3]

Possibly over thinking??

[Andy StopfordParticipant @andystopford50521]

If your lathe has a metric leadscrew, I wouldn't bother with the thread dial indicator, the (many) graduations are so close together that its awfully easy to engage the clasp nut at the wrong point, usually (for maximum irritation) when you've almost finished the thread.
Better just to leave the clasp engaged and reverse back for the next cut.

I doubt that leadscrew wear is likely to be a problem with even the most enthusiastic amateur use.

[RobCoxParticipant @robcox]

I removed the swarf guard and fitted a replacement pair of half nuts (from arceurotrade if I remember correctly). I wasn't that happy with the off the shelf threading dial so I made my own complete with all of the gears needed for the various metric pitches. Having got use to the threading dial, I'd hate to be without it. It makes screwcutting quicker (and for me) more enjoyable.

Wear on the leadscrew hasn't been an issue… I upgraded to a bigger lathe and the mini lathe has been sat on a bench in the garage ever since, unused and unloved😥

[Brian WoodParticipant @brianwood45127]

Hello Nick,

For what it is worth, my thoughts are as follows:-

Leave the swarf guard in place, it is I think a tubular spring steel device that stretches and collapses as required to protect the leadscrew from swarf and dirt. Wear on an amateur lathe is hardly a serious matter even on an unprotected leadscrew.

Fitting a second 1/2 nut would be complicated anyway, making the mechanism and slides to open and close the pair in sequence would be tricky on any lathe not already built to do so. A pad would be simpler but would still need to be moved in sequence. Your last point on the thread dial indicator would also be an over complication of little value if only put to very limited use.

In summary, leave well alone and use it as the makers intended. It was built and priced to allow for the absence of these features and will still screwcut well enough for more that just occasional use

Regards Brian.

Edited By Brian Wood on 21/12/2021 13:02:41

[HOWARDTParticipant @howardt]

The only problem I find with the single half nut, and I have lived with it for five years, is that it needs regular adjustment to get it to stay in feed. The poor design means that the gib guiding the nut is awkward to set correctly. The cover is merely a right angled steel cover over the top of the screw but does its job of keeping the swarf off it. Fitting a pair of split nuts is on my maybe listl and it may well stay there.

[MikeKParticipant @mikek40713]

I've done plenty of threading on my 7×16 mini-lathe and have never used the threading dial. I find it easier to leave the half nuts engaged. I back out the cross slide, reverse the motor, put the cross slide back in (to zero), and advance the cut with the top slide. This is a necessity, anyway, for those of us with an imperial leadscrew when cutting metric threads. I simply have the same practice for all threads.

I've not noticed any wear on the leadscrew. Swarf is easily brushed off. And if, like you say, you don't plan on doing much threading then your worries should be low. Aluminum swarf is almost always long strings so that's not a problem for the leadscrew. And if I'm turning something that generates minute swarf, like brass, I'll use a vacuum to catch most of it.

Great benefit is had, though, by having two half nuts as it give the carriage rigidity. I engage the half nuts when parting off and even facing most times. Not locking the carriage in some way risks it moving.

[Niels AbildgaardParticipant @nielsabildgaard33719]

Some Schaublin models use a half leadscrew nut if my memory still works more or les OK.

[not done it yetParticipant @notdoneityet]

• Is leadscrew wear an issue in an amateur lathe – with or without cover over the leadscrew

I can only really respond to this part. My hobby lathe only uses the lead screw for threading – it has a separate feed shaft – so no issue for me.🙂

[Bill PudneyParticipant @billpudney37759]

My Sieg C3 7" x 16" mini lathe is probably 15 years old. It has a metric leadscrew and two half nuts. The threading dial was removed in the first week or close to it. The machine has cut a lot of threads, the half nuts do require adjusting fairly often….maybe annually. Cleaning the leadscrew is a simple matter, usually done at the end of the day as part of the clean down procedure. Most of the things I make are fairly small, so the leadscrew generally only gets used for screwcutting

I believe that the new machines have a sheet metal leadscrew cover not the telescoping spring one as suggested earlier, along with the single halfnut. If the machine was mine I would get a 2 halfnut conversion kit from Arc Euro, ditch the silly shield, and set up the halfnuts carefully and remember to clean the leadscrew occasionally.

cheers

Bill

p.s. I've just had a look at the Arc Euro site and the kits are available for metric or imperial machines their part number SC3-63B-MET or IMP, for under GBP30.  Sounds like a bargain to me.

Edited By Bill Pudney on 22/12/2021 05:01:54

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