Lathework for Beginners

For as long as I have been Editor of MEW, I have received regular requests for more content for absolute beginners. Thanks to a sponsorship deal with Arc Euro Trade, in this issue we are able to commence a regular feature aimed at helping those with no practical experience to safely and successfully get the most out of their workshop. In MEW 260 and alternate issues, I will be giving a detailed introduction to lathework. The issues in between will carry a parallel series by Jason Ballamy on using a milling machine. Jason is known for his big prize-winning models of stationary engines, which he produces at an exceptional rate!

There will be dedicated two threads for the two series on the forum at www.model-engineer.co.uk where you will be welcome to ask further questions or even suggest topics or techniques you would like us to explore as the two series develop.

This thread is for questions about the Lathework for Beginners series. Please keep it on topic, this thread is for general discussion of lathe techniques and using different accessories not issues like merits of one machine versus another. Off topic comments will be moved or deleted!

Jason and I both plan to include ‘tips and wrinkles’ that will be of interest to more experienced hobbyists as well, so we hope that this new initiative is something that all readers will enjoy.

Thanks,

Neil

I've created a separate thread for anyone who wants to suggest/discuss possible beginners articles on other topics and moved some comments there.

Neil

Just read the article in MEW260 and found it good. I'm not really a beginner yet still found a couple of tips I'd not thought of before.

There are a few questions that worried me about buying a lathe that might be usefully explored later in the series (if they're not already covered):

• How hard is it to learn to drive a lathe? (7 year apprenticeship, or dead easy.)
• Will it need a special electrical supply and be expensive to run?
• How dirty and noisy is it - will the neighbours or domestic authorities complain?
• How heavy is it and how will I move it? (Especially when there's no Wes in the family.)
• What happens when it's delivered; does the man just drop it on the pavement or what?
• What tools or other accessories do I need buy with the lathe to get started?
  • What's the 'correct' size of tool shank to fit the toolpost?
  • HSS or Carbide?
  • DTI, 4-jaw etc?
• What sort of thing will I be able to make?
• What materials can I expect to turn? Plastic, wood, copper, stainless, aluminium, old crowbars?
• What sort of lathe do I need given I'm into one or two of: clockmaking, airguns, general modelling, model engines, astronomy, motorbikes, traction engines or refurbishing railway axles?

Best bit for me was the cover photograph. All is revealed. You can tell that Neil's workshop is obviously set up in his bathroom and that he sat on the toilet for the photo. Doubtless Neil will deny it, but the camera never lies. The bog-roll is clearly visible behind his head.

Dave

Are you planning to write the series around a typical beginners model/project. ?

regards Martin

I knew I'd regret that...

.. but the sensible comments taken on board.

Edited By Neil Wyatt on 02/10/2017 21:18:35

No, I want to avoid making it specific, although I will be using the one lathe I will try and keep it as general as possible.

There may be some small exceptions, I bought in a truckload of steel to make some MT2 arbors

Any owners of either of the SC4 lathes please read this thread about correct operation of the lathes

I wanted to change the gears in the SC4 to cut 12 tpi threads. I knew which gears I needed to fit so uncovered the gearbox. Having taken a good look I decided to change the A gear first, only because it was at the top and closest, My first problem/worry was that the socket headed screw that holds the gear in is quite small and the fit of the hex wrench was not very good, in fact what I consider to be my 'quality' hex wrench was a sloppy fit. The screw was so tight It got to the point that I was afraid I was going to round off the socket. I gave the screw a few lite taps with a small soft hammer to try and persuade it to loosen up. It did eventually give but not before I saw a lot of twist in the shaft of the wrench.

The 'A' gear is mounted, keyed, to shaft permanently fitted to the 42 tooth gear behind it. Getting the gear off for the first time was a matter of putting two thin screwdrivers between the two gears and gently levering them apart. I suspect the fit will 'loosen up a bit' with repeated changes.

The B&C gears are keyed together on a stub that is fixed to the adjustable arm that rotates around the D gear on the lead screw centre. The adjustment arm is held by a socket screw 'pinch bolt' which is released to drop the B&C gears out of engagement with the A and the D gears. Be aware that B&C gear stub screws into a T piece that runs in the back of the adjustment arm and at the outer (gear) end there is a nut and spacer that goes onto a thread over a square end. Again the gears were a tight fit on the keyed stub but easier to deal with by placing them on a part open vise and tapping the stub out with a copper drift and a brass hammer. Again I suspect they will loosen up over time.

I would like to know about backlash in the cross slide feed please. It seems a bit excessive at 0.8 mm which is 40 divisions on the dial and I wonder if that has anything to do with the fact that it can be power fed. I will take a look at the exploded drawing and see if there is easy access to the nut and adjustment screws at the far end of the slide.

Another interesting feature, and disturbing the first time it happen, is that the saddle feed hand wheel will pull outward almost 1 cm which disengages its ability to move the saddle and exposes a gear which I presume engages on a rack to move the saddle. Is it supposed to do this and if so what is the use of such a feature ?

Many thanks, Nige

Good grief, the cross slide backlash seems excessive. Even my nearly 40 year old lathe is less than that. I can't see that it should be anything to do with the power crossfeed.

Disengaging the saddle feed handle is a safety feature usually found on industrial machine tools. If you're using power feed with the handle turning, and stand in the wrong place the handle may interfere with your nuts, which would be painful.

Andrew

Before you go trying to adjust the split nut is there any endfloat in the cross slide screw? May just need adjustment of the gap between handle and cross slide if that can be done on the SC4.

As Andrew says handle disengages for safety when it is being driven round fast, same reason the x axis handwheel on your mill has the dog teeth so it does not spin about when a table feed is fitted. Worth taking the spring out on the mill as it is not needed as you don't have power feed.

OK, been out to the lathe and:

Andrew: Thank you, I now understand the need to disengage the saddle feed handle

Jason: Thank you, Yes to the end float!! In my inexperience I was assuming the whole problem was backlash. The Nyloc nut that holds the cross slide handle on had only been tightened enough to locate the handle, when I took another turn or two on it with a 14 mm spanner the end float disappeared.

Today I have learned that getting a good 'feel' for the cross slide feed is about getting a balance between backlash and end float. Thank you guys

Nige

0.8 backlash, pah that's nothing. When my chester first arrived it was just about double that, yes really.

I used the old techniques of back winding and coming in again to eliminate or at least reduce errors and actually got very good results, but in the end I decided I was either being stupid, or lazy, even worse a combination of the two.

So I took the cross slide off, the leadscrew nut did indeed have a slot machined into it and two small grub screws so that the thread could be distorted enough to take the backlash out. I swear I got it so that I couldn't actually measure the small amount of play left in it, sadly it doesn't seem to last more tha about 4 or 5 months before it needs just the smallest of tweaks again, luckily it takes about ten minutes.

The SC4 lathe 'manual' has a chart giving the threads that can be cut with which gears. The imperial threads are given as 1"/n which I take to mean that the entry for 12 is 1/12 or 12 tpi, does that seem reasonable, if so the finest imperial thread it gives gear settings for is 24 tpi.

The metric threads are shown as just mm so I take it that 0.25 is the pitch which if my sums are correct gives a thread of about 102 tpi !!! While the coarsest metric thread is 3 mm or about 8.5 tpi. That seems a hell of a range in metric threads while imperial is given as 8 to 24 tpi! Am I missing something please?

Many lathes don't give the full list of possible threads as there can be hundreds of them, so they just focus on the most use ones. A 0.25mm pitch thread would demand a good deal of skill and a nice sharp tool, set dead right! I think 0.7mm pitch is the smallest I've done.

The cross slide and top slide on the SC4 both have split anti-backlash nuts adjusted by screwing in a small cap screw until backlash ALMOST disappears. It will stay in adjustment longer than if you do it up too tight.

Neil

Thanks Neil. Yes I took pictures of the cross slide backlash adjusters, two small cap screws, by putting a mirror at an angle behind the lathe so I could see what was going on. They are easier to get at if the cross slide is wound almost right across. I realised it wasn't wise to let it go right across as at some point the lead screw is no longer in the whole length of the split nut and no amount of tightening the adjustment screws will make a difference to the backlash UNTIL of course you try and wind the cross slide back again!!

If I wind the cross slide out until the lead screw comes out of the split nut should the cross slide just slide off the end ? and if it does is it just a question of reversing the process to put it back assuming you haven't dropped the gib strip 😊

A quick update on what I,ve found with my new mini lathe.

There is no evidence of any damage and all parts seem to be present except there is no manual. I,ve printed a copy off from the suppliers website but it looks years old and judging by the images in the manual the latest version lathe seems to have moved on a fair bit. Also you cant really call it a manual it contains the bare minimum and leaves a lot to be desired, so you have to work a lot out for yourself. I do have a copy of Neils book on the mini lathe which is excellent for the beginner, I would recommend it.

Everything on the lathe works as it should and I have found most of the parts to be well adjusted.

The cross slide and top slide have no play or side to side float in them and both are very smooth to operate. The cross slide has 3 thou of backlash and the top slide has 5 thou. The tailstock is very smooth but needs centre adjusting, I,ve only checked it by eye at the moment but the vertical looks spot on but the horizontal looks to be around 10-15 thou off centre.

I suspect the saddle is well adjusted but the the apron handwheel could be smoother. Its as if you can feel the rack through the handle which makes it feel lumpy, I,m hoping this can be adjusted.

The 3 jaw chuck is a bit stiffer than I would like and was wondering if I maintain the jaw 1-2-3 sequence but move them around 120 degrees to the other two positions if it would help...maybe not.

I am waiting for a dial gauge with magnetic stand so have not checked the run out on the chuck as yet.

So this is what I,ve found so far, but overall I am really pleased it seems to have been quite well setup at the factory.

Ron

Edited By Ron Laden on 21/06/2018 09:25:09

Ron, the tight or notchy feeling carriage handwheel may possibly be remedied by loosening off the screws that hold the rack in place then placing the carriage first at one end and tightening the end screw, then repeat at the other, then tighten up the middle screws. May need a slip of paper between the gear and rack teeth to get a couple thou clearance. The only other adjustment usually is to lower the apron by putting shims or gasket paper between the apron and carriage saddle. This then upsets the halfnut closure and needs further adjustment so you might be best to try the first method.

With the chuck, check for burrs on the jaws and the ways they slide in and remove with a small slip stone or flat file if found. You might try moving them around to the next slot, as long as the order of jaws remains sequential, but check runout when your DTI arrives as it can make a difference. And it might free up with use too.

Thanks Hopper, Thats really helpful I will give it a try.

Regards

Ron

Ron,

You should find that the tailstock can be adjusted in the horizontal. Not sure about your model, but normally one screw underneath and one on the back. A faff to adjust if you don't have quick release as it needs to be locked in place when checking it.

Neil