cutting speeds for lathe

Does anyone know where I can get information of cutting speeds for cast, 316, gun metal etc. I`m new to metal turning and would like to have some idea of what speed to run my lathe at. Pete

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you mean rpm ... don't get these boys into feet per min....youd wish you never have asked in the end
depends what diameter it is ...
the larger the diameter the faster its circumference is travelling ..
so as the diameter goes up the speed of which the piece travels over the cutting tool increases.
anyway ......youre a beginner .....so go slowly and increase speed as your confidence goes up ...
start with 150 rpm ...if its two inches in diameter .
if its 1/4 inch you need over 300 rpm ....for now
3 inches in diameter ...80 rpm ...
these are beginners speeds
talking about beginners I'm one ....but thats how i would of approached it .
also, you probably need carbide to cut stainless.
defo need carbide to cut cast iron ..
gun metal ........not sure what gun metal is ..........hss ?
all the best.markj

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should of added
the larger the diameter the faster its circumference is travelling ..for given rpm
anyway ...larger diameters need slower rpm .
hope you understand
all the berst.markj

Have a look at this table its in rpm for different diameters which will be easiver than feet or meters per minute. If the tool starts chattering then you are generally going too fast.
http://www.aonx97.dsl.pipex.com/WS-page/table-page/tables.htm#Lathe
Although HSS will cut all the materials you list the skin of cast iron can be a bit abrasive and wear the tool quickly so either brazed or replacable carbide bits will keep an edge longer.
A cutting fluid will help a lot on steel and stainless, CI and GM can be cut dry.
Jason

On 5 Nov, 18:46, snipped-for-privacy@lineone.net wrote:
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Thanks all for the info. Pete

snipped-for-privacy@lineone.net wrote:
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The "trick" is to cut the skin in one pass (if there is a hard skin). Do not try to cut it in several passes. At least 1..2 mm feed for the first pass with HSS works good. Reduce rpm if the tool is suffering too much. No pointy tools but shapes that are for roughing.
Nick

On or around Mon, 05 Nov 2007 10:46:14 -0800, snipped-for-privacy@lineone.net enlightened us thusly:
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CI is dead iffy with lube in it - specially when drilling or threadcutting.

On or around Mon, 05 Nov 2007 10:28:16 -0800, mark
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fpm (or the metric equivalent) is the critical bit though. For any combination of tool and workpiece, there's an optimum speed and a maximum speed you shouldn't exceed, otherwise the tool gets buggered, most often.

wrote:
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Suggest you get a copy of Model Engineers Handbook, very useful to get started. Other books "Lathework A Complete Course" by Harold Hall and "The Amateurs Lathe" by LH Sparey. They are good value, though Spareys book is a bit dated.
Agree on the need for carbide to turn cast iron, but definitely need HSS to finish at very slow (say 50rpm) revs. Carbide I use carbide for roughing out, you can carve out girt big lumps with it, but it is fragile and the tips chip if care isn't taken. There is a view that carbide is unsuitable on small lathes because they aren't rigid enough for the big cuts carbide tools will deliver (I find carbide doesn't work well on light cuts). I get benefit from carbide on my 5x22 chinese lathe.
Material type makes a big difference - the harder the material the slower you go Diameter makes a big difference, the bigger the diameter, he slower you go.
So for say Aluminium (HE30 is nice) in the 1 - 2inch range, then you can be thinking about 2000 - 1000 rpm (but as in previous post, work up from speeds you are comfortable with) For Gun Metal, Cast Iron, 1 -2 inch range then 250 - 125 rpm are the sorts of places to start Silver Steel and Stainless 1-2 inc range than a bit slower 200 - 100
Notice how the speeds half as the diameter doubles.
These are a starter for 10 using HSS, you can typically go much faster with Carbide try doubling the rpm and see how it works for you.
Having said all of that, my old pal is old school time served "real" turner, and he turned up a 6 inch diameter cast iron pulley for me at 450rpm (his lathe is a big beast which won't go any faster) to a mirror finish using carbide. Absolutely beyond me how he does this, but he has been practising for 50 years longer than me!
To get a good finish, you need to make sure you are using super sharp HSS tooling and very fine cuts (I use the top slide set to 6degrees, which has the effect of dividing the calibration on the index by 10, eg if the calibration is 0.025mm per division, 6 deg offset makes this 0.0025mm).
You need to work out what shape of tool you need for what - In HSS I use an old style knife tool for steel and a round nosed tool for finishing.
Once you have it all nicely finished, then you need to PART OFF. You need to reduce speeds by much more than half I would suggest. Before you start parting off, make sure everything is locked down that doesn't need to move. You need maximum rigidity and a touch like a midwife. During this operation you might get the impression that some parts of your lathe were made from rubber.
Other tips - Cast Iron produces a very fine dust that leaves you black upto your armpits, and leaves the lathe looking like a piece of colliery equipment. It's worth covering the ways with rag (take care to ensure no snagging in the work) to keep the dust out, as mixed with the way oil it is abrasive. The lathe is also much easier to clean up afterwards. When turning Aluminium, I find that bits of aluminium can get welded to the tool and spoil the finish, so I use parafin to prevent this and touch up the nose of the tool with a small oil stone from time to time as the work progresses. Practice grinding your own HSS tooling to a good standard, I find that I quite often need to make a tool to complete a component so you end up having to do this anyway. Never modify an existing tool, always grind a new one so you end up with a useful collection of tooling. Always use freecutting materials when possible.

Steve wrote:
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Also with HSS and coolant. Lots of coolant that is. :-)
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Today I have been playing around with carbides I bought yesterday. I had some before but the ones I had were very un-systematic and partly Chinese desert sand. So I bought different tip-radii and geometries (SM and SF). And I can only tell: * First, they make you poor * The SF-geometry (steel fine) doesn't work with cuts less than 0.025mm (radial feed) * The SS (steel super-fine) needs even more minimum depth of cut. * Buy a tip-radius 4 times of your slowest feed to be able to play around. * SM make a really nice finish even with heavy cuts, but not less than 0.1mm depth of cut. * Forget them without coolant if you want finish and want them to last. * Carbides for Al (ALX-geometry) make the finest cuts and they also work great with steel (light cuts).
* And if you are working with small diameters, you won't get the necessary cutting speed. If you get too low, the finish will be **bad**.
I wasn't very astonished with the results, but I'm even more convinced that HSS is the best for fine work on a manual lathe.
Nick

Hi Nick,
I agree about HSS vs Carbide. I am a retired machinist and used HSS th majority of years, but every time I needed to make a very light finis cut I ended up with a rough finish. On another note, I have your Yadro DRO and just hooked it up to th scales for the first time. The scales power up with no problem, bu when I run the test on the laptop the readings fluctuate up and down They won't hold steady and I can't figure out what is wrong. Th readings on the scales themselves are rock steady. Please advise. Thank
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winanskeith wrote:
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My first guess is, that there are no caps in the battery compartments. As soon as the scales are powered from the interface, you have to solder a 1µF (up to 10µF) tantalum capacitor in in place of the battery. Lester should have provided them with the kit.
Nick

So that's what those extra unidentified capacitors were for. There wer
no instructions about them, nor having to solder them into the scales I saw the picture where they were there, but had no idea as to wha they were for nor how they got there. Can you please give me detaile instructions as to how to solder them in? I am not an electronic person and these things are not easy for me to understand. Thank
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winanskeith wrote:
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It isn't that complicated. First have a look here: <http://www.yadro.de/dro/setup.html> You'll see the battery-compartment with a capacitor (two in fact on this picture, but the one you got is perfect). The capacitor has a tiny "+" marking close to one of the legs (should be the longer one, but I always forget). Now if you look at a battery that once was in that scale, you know where plus is. Solder the "+" leg of the cap to the "+" contact for the battery and the remaining leg to the other contact in the compartment.
That's it! Hope that helped. Nick

Thanks Nick, sounds easy enough. I'll give it a try
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