Hello Ace,

Although I'm not qualified to offer specific advice regarding your questions, I can possibly save you some time, by suggesting you take and upload some photos.

You will certainly be asked this by the more knowledgeable folk here, and, as always, a picture tells a thousand words.

Good luck and HTH.

ATB,

Daniel

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The two most common causes of poor finish are the material and the tooling. So I'd make the following points:

Don't buy material from Ebay unless you know what you're doing and don't care about finish. The quality of material varies widely even for nominally the same specification. Proper EN1A is one of the more forgiving steels and should give a good finish.

HSS tooling should produce a good finish, but is dependent upon how it is ground. You do not need fancy guides and setups to grind HSS (I hand grind my tools) but the shape needs to be roughly correct with proper clearance.

Insert tooling can be fussier about cutting conditions. It's possible that a small lathe simply won't have the speed and power to get the best from inserts. The same caveat applies to inserts as to materials; cheap inserts may not perform as well as more expensive branded ones.

A stick out of 60/70mm without tailstock support is quite ambitious on a small lathe.

Recutting on the way back to the tailstock is normal, even on industrial lathes. It's due to work and tool deflection, and the cutting process itself. It will become second nature to simply withdraw the tool, wind back and reset the tool position.

For HSS tooling and 12mm diameter EN1A I'd be running at about 800rpm (100 feet per minute surface speed). For insert tooling you can easily be three or more times that.

Andrew

A photo of what you are getting is a bigger help. And what tooling you are using as well. Then more accurate advise can be offered. There are some carbide inserts that are very sharp these days. They work well on lower powered home hobby lathes. The very sharp inserts are made for cutting plastics and Aluminium. But do work very well on steels with light cuts. Sometimes you need a small nose radius to reduce deflection and tool cutting pressure.

Sometimes the poor surface finish comes from other factors, like vibration from the motor or belt drive system etc.

So no one answer to the problem. A photo can help to eliminate the various options.

Nothing wrong with hss steel and learning to grind and hone your own tools. Sometimes a shaped piece of hss is the best option , especially for forms or repeating short length tapers etc

Neil

Various comments, the first as |i climb aboard one of my hobby horses.

Is the tool sharp? AND is it on the centre line?

If it is not it will, not cut properly. Too low and you have excess clearances. Too high, and the tool does not cut, it rubs because the cutting edge is above centreline, and cannot contact the work..

Tool overhang from the toolpost should not be any more than is necessary. The longer it is, the more flexible it is. And rigidity is important. A tool that is waving about in the breeze is unlikely to produce accurate work.

This is why industrial machines are massive, heavy and rigid.

A quick check for tool height, if you do not have a Centre Height Gauge (Easy to make) is that when the tool faces the work, (Cuts across to machine the end of the bar )and reaches the centre, there should be no "pip" evident.

If you want to see a picture of a centre height gauge, and instructions on how to make one, PM me, with an E mail address..

For what my advice is worth, start off with High Speed Steel tools, and learn how to grind them.

You may think that is worth investing in some books.

"The Amateur's lathe" by L H Sparey is old but a good starting point, tending to centre around the Myford ML7. But the principles are good, neverthe less. There are other books on Lathework by folk like Harold Hall, Neil Wyatt, Dave Fenner and so on. They may not all feature your particular lathe, but the basic principles are the same.

Neil Wyatt recently wrote a series of article on basic lathework, in Model Engineers Workshop. It featured the Sieg SC4 lathe, which is a big sister to your S2 (Neil is one of the many users of the SC2 lathe, and his book will feature it )

Carbide tips are not sharp. They were intended for heavy duty industrial machines to remove lots of metal, fast!

A good all purpose tool for turning and facing is a Tangential Tool (On another hobby horse! )

You can make your own. There have been at least two designs published in M E W, (for 1/8" toolbits )or you can buy the Diamond Tool from Eccentric Engineering. I have made several, ( for 1/8 and for 5/16" toolbits ), for myself and for others, including The WaterWorks Museum in Hereford.

What feed rate are you using? A fine feed would be about 0.004" (0.1 mm ) per rev of the chuck.

Too coarse a feed rate will produce a rough finish. You are effectively cutting a screw thread, of sorts!

You will always have backlash in the machine movements, otherwise nothing could move.

The machine is new, so backlash should not be excessive. If it ain't broke; don't fix it!, You might make things worse!

Whereabouts are you located?

Hope all this rambling is of some help

Howard

Would have to agree with all of the above advice, Reason ? Have been there-done that-ruined the tee shirts !

Overhang from chuck is too much

Tool always cuts on the return stroke, that,s why you need to retract it

Forget about inserts at this stage, HSS is all you need to get perfect finish, easy to grind, cheap to buy.

Speed is easy to work out, most books give detailed info on it, Sparey mentions 80/1/4 of work dia= revs. all gone Metric now, but the idea is the same.

Tool needs to CUT, not rub, so centre height needs to be right

You think you have problems now ? Wait till you get to parting off !!!!!

One last thing ,keep in mind the size of your machine, it is not a factory monster tipping the scales at ten tons.

One of the first things that I was taught was how to provide a steady hand feed.

Practice makes perfect, so that one hand takes over the drive from the other without stopping.

A valuable skill, that will be needed quite often in the future.

If you are using power feed, use the finest that you can get, about 0.004" (0.1 mm ) per rev, or less.

A rigidly held, and correctly centred, sharp, (correctly ground ) tool is necessary starting point.

Don't practice on rebar; it is vile stuff to machine. Learn on some free cutting mild steel.

."Unknownium" can cause all sorts of problems, without admitting to being the cause!

Howard

M10 bolts are a swine to machine, particularly 8.8 grade. Even on an ex industrial machine, it is very hard to get a decent finish.

Bolts are made for strength, with tough steel, which does not turn well sometimes. The heads are hot or cold forged on, and in smaller sizes the threads are rolled on, not screwcut, again for strength. If you want easy cutting steel with a nice finish find some free machining grade steel, like 12L14 or 1144SP. You will not likely find this type of steel at the local hardware store. Don't be tempted to buy rebar for machining projects either, although it can be cheap – it again is made tough for a specific purpose, not for machining.