Should EN8 be difficult to machine?

Having become confident that I can now turn EN1 to size and finish, I've just spent a weekend making a real bugger of a piece of 1/2inch EN8. All
I've been trying to do is turn it to 12mm with a good finish and finally almost got to a decent finish. Even fine cuts with a small round nose HSS tool sharp enough to cut fingers and a going slow rpm didn't do the trick.
What I can't understand is the last piece of EN8 turned up really nicely with care. EN8 shouldn't pose any difficulty should it?
In the mill the finish is poor too - just cutting a flat with a 10mm slot drill produced a horrible finish. The bar was colour coded, just marked with an "8" on the end, so could be any old crap really I suppose.
I've no coolant system yet, perhaps a tall stool and a bodily secretion is the answer?
Steve
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I can't specifically remember how EN8 cuts although some grades of steel are a bit prone to tear. Leaded mild is a doddle and EN36 cuts very nicely. If you're struggling for finish you probably want a high speed and a pointed tool not a slow speed and a round nosed one. Other usual precautions apply - minimum tool overhang, grub screws nipped up to take as much slop out of everything as possible, in other words get the setup as rigid as you can.
--
Dave Baker - Puma Race Engines



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wrote:

EN8 isn't the worst steel to turn by a long way, but it certainly isn't EN1 or EN1A.
for example:- the machinability index of EN1A is taken to be 100, EN8 is45, EN24 is 30.
It can produce a very nice finish with a radiused tool, a _heavy_ cut, fairly high speed and lots of coolant. Trouble is that if the lathe won't pull a heavy cut at high speed it tends to tear, the tool rides up on the steel and digs in and you can get a finish that looks like you were turning threads with a spade.
I have achieved a good finish with a HSS tool with a very fine cut and running it backwards. This presents such a large width to the cut that the tool won't dig in.. An other way is to use a tool with no radius at all. This allows a fairly light lathe co take small cuts without the tool digging in.
Mark Rand RTFM
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I find one or other of the four coolant systems I have is usually sufficient:
1) A Fairy Liquid bottle with a bit of copper tube and a little brass nozzle sticking out of it, filled with 'Cutmax' obtained years ago from Reeves because you could dilute it with paraffin instead of water, but which they do not do any more and which I cannot find anywhere else and am rapidly running out of. For mild steel.
2) A tuna tin and 1/4" paint brush with Shell Garia H as recommended by George Thomas, but which is also running out and no-longer available, and I don't know what grade to get instead but something that has EP properties but does not stain brass as much would be nice. For more difficult steels. (The oil gets replaced with plain paraffin for machining light alloy and with real turpentine from trees for copper)
3) A tube of pasty Rocol RTD, nearly finished. For Reaming, Tapping & Drilling, oddly enough.
4) A bottle of runny Rocol RTD, nearly new, but not yet sure how well it compares with the paste. Ditto.
--
Charles Lamont

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Sad to hear Garia H is nla - good thing I bought a 5 gallon drum a few years ago, at the rate I use it, it may well last my lifetime. There was an equivalent he recommended, can't offhand remember the name though.
My wife cordially dislikes the smell of overheated Garia; anyone know a better-smelling alternative straight cutting fluid?
David
--
David Littlewood

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Charles Lamont wrote:

> "Shell Garia H Shell Garia Oil H is a premium quality, low viscosity cutting oil manufactured from a blend of selected solvent refined mineral oils and a high proportion of additives and sulphurised fatty oils, specially chosen for hard material and high speed-metal cutting operations. Shell Garia Oil H should not be used for machining yellow metals because of the risk of staining. :-) >

>
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There appear to be many flavours of "Cutmax" (See http://www.houghton.ca/products.asp?Cat=1&SubCat ( ) Which do you use?
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Dunno. It was in Reeves own litre can, if I remember rightly the label also said 'Evcut S' or something like that.
--
Charles Lamont

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EN8 is a high carbon steel, so is stronger in its annealed state than low carbon steel, and can be extremely hard if hardened by heat treatment (unlike EN1 which is fairly insensitive to heat treatment).
Its a long time ago for me, but EN steels used to have letter after the numbers. I think the free machining version had an M afterwards, and had some sort of addition to make it short chipping. Other letters would indicate the degree of heat treatment, and maybe some other minor variations in quality that could affect things like fatigue resistance, or cold temperature brittle fracture.
Not much help if you can't go back to the source though. Annealing will help if it is in a tough state, but the free machining came through additives to the composition.
Steve
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Cheshire Steve wrote:

But it's a really nicely made piece of kit, & does the job well. Comes with heaps of accessories too. I can recommend it from personal experience with it.
--
Karen

If you can't be a good example, then you'll just have to be a horrible warning.'
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Duracell Bunny wrote:

Sorry, posted that on the wrong thread. it's late in the day ...
--
Karen

If you can't be a good example, then you'll just have to be a horrible warning.'
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Duracell Bunny wrote:

Time to change the battery?
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En8M is the only grade that is easy to get a finish on, all other grades
work best with high speed and carbide tooling and even then finish can be iffy.
We used to have one job that used En 9. Nobody could get any sort of finish on it. Just tore. En 8, 16, 24, are all heat treatable but annealing does little to improve the chance of getting a good finish.
Regards Colin Docherty.
Steve W wrote:

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On Mon, 06 Aug 2007 17:13:23 GMT, Colin Docherty

En8 or its close relatives used to be the standard material for boat propellor shafts, now largely replaced by stainless but some people still use it. I reckon it's better than stainless for a *working* boat, which will wear out the shaft before it's killed by corrosion. As a result, I've often had scrap shafts of EN8 or similar to use as material. One thing I've found is that finish can vary tremendously over the length of a cut, probably because of small variations in deflection etc. Sometimes, though, it really does seem to be a variation within the material. Of cource, this is stuff of unknown provenance which might have been spinning around underwater for 30 years.
Tim
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