Un workable steel

[Stephen FollowsParticipant @stephenfollows82099]

[Stephen FollowsParticipant @stephenfollows82099]

I have been given a 6" diameter x 2" thick piece of steel from which I was hoping to make a 6×1 inch flywheel. Problem is it won't machine. In the lathe I have used both HSS and carbide tools, it just takes the edge off them, after two hours not even through the rust layer.

Tried machining in the mill using fly cutter and 1/2" end mill. Blunted the fly cutter and ruined the end mill in the first pass, (about 2" in).

Any ideas about what I have got and how to machine it?

Almost giving up and buying a flywheel, if I could find one that the seller doesn't want stupid money for!

[Brian Sweeting 2Participant @briansweeting2]

Have you tried tempering it to reduce its hardness?

You know what they say, "No such thing as a free lunch."

[JohnFParticipant @johnf59703]

Hi Stephen, do you have any idea where it originated from ? has it been machined before — is it a machined finish on all surfaces or are the end diameters sawn ?

It would appear from what you say to be hardened, either through or case hardened, probably the latter ! however assuming it is steel it will be possible to soften it but with a large piece as this its beyond using a blowtorch unless its very large one. You would need a muffle furnace or do you have an open fire, woodburner or ?? If so you may be able to anneal it but it needs to be a red heat and cold slowly. Maybe you have local blacksmith or farrier who can help.
John

Edited By JohnF on 24/03/2018 23:17:24

[Clive FosterParticipant @clivefoster55965]

Stephen

You aren't the first person to spend more in tooling than the cost of a decent bit of material trying to make a free gift of "what-in-hell-is this" steel work.

Plenty of thickness to play with so maybe hitting one face hard with an angle grinder and working out from the middle might be productive. Worked for me once with a piece of hardened steel. Grinder got under the hard face and the periphery cracked away. But I was only trying to make it thinner.

Realistically probably best chalked up to experience and binned.

Clive.

[VicParticipant @vic]

If carbide won’t touch it I’d bin it.

[Mike PooleParticipant @mikepoole82104]

It would be interesting to know what you have, a spark test may give some clue. It would seem some heat treatment may be required to bring the mystery material into the machinable range. A flywheel does not need to be made of anything other than a basic mild steel or cast iron and neither of these should have any more than a hard skin to deal with.

Mike

[Martin DowingParticipant @martindowing58466]

Buy CBN insert (Chinese ones are cheap enough and if you are not tight on money look on Sumitomo Electric range) and no imaginable steel will be too hard to work with. Toolholders are the same like those for standard carbide inserts.

Claims that these need extremely rigid machine to work with are rather mythology – my ML7 copes well.

Try to keep surface speed above 1.5 m/s or so. Avoid turning *soft* steel with these inserts – they hate it and will get damaged easily.

You will also get a beautiful surface finish as a bonus.

Martin

[JasonBModerator @jasonb]

I'd use it as a door stop. Even if you could turn it with fancy inserts you will still have problems putting a hole in the middle and cutting out some spoke shapes.

1" of 6" dia EN3 will set you back about £10-11 from our suppliers and maybe less if you search around e-bay

As well as the flywheel suppliers I listed in your other thread this e-bay seller has quite a few, I have had a couple from him and they are well made, he used to cast for College Engineering.

[I.M. OUTAHEREParticipant @i-m-outahere]

Just out of curiosity does a magnet stick to it ? If you have an indoor fireplace in use at the moment chuck it in there before you go to bed and fish it out the next morning when the fire has died down , if that doesnt anneal it peg it in the bin as it will only give you grief ! If you can't machine it with carbide you have no hope of tapping holes for grub screws !

[Wout MoermanParticipant @woutmoerman25063]

Don't bin it but use it as an anvil.

[I.M. OUTAHEREParticipant @i-m-outahere]

Posted by Wout Moerman on 25/03/2018 08:18:31:

Don't bin it but use it as an anvil.

I don't recommend that ! If it is so hard that carbide won't touch it then it could either shatter or send a chip flying off that can imbed itself in the person weilding the hammer . It could be cleaned up and surface ground then used as a lapping plate for small items though .

[Ady1Participant @ady1]

Use the backgear with carbide or cobalt tooling, I prefer cobalt but each job is different

High speed for some materials simply cant be done, you need torque not power

Finish off with a high speed skim if possible

A shaper would also deal with it

Edited By Ady1 on 25/03/2018 10:03:17

[SillyOldDufferModerator @sillyoldduffer]

My advice to beginners: avoid unknown metals! Or at least be prepared to move on gracefully if you can't turn it.

When I first owned a mini-lathe, it struggled with all the odd bits of scrap I tried. Very disappointing. Buying a known mild-steel made a huge difference, and the free-cutting variety was pure joy. I went from thinking the lathe was rubbish to finding that it works well.

Steel is an alloy and there are thousands of them with a huge range of characteristics. Many have properties chosen for a particular purpose that – like as not – does not include machinability. Railway line, many types of Stainless, armour plate, tool-steels, Boron steels – all horrible. On top of that many steels can be hardened by heat treatment, or on the surface by carburisation or nitriding. Suitably treated carbon steel is very hard ; nitrided steel comes close to being diamond hard. Those processes have to be undone before machining.

Many common steels are reasonable; if your source is scrap from an engineering works it's likely to be good. Metal recovered from manufactured items is much more variable, and steel made for a particular purpose really has to be understood.

Gas-pipe is an example. Although it's a species of mild steel, the metal is relatively soft. It bends, saws and threads well and it's cheap. Seems a promising candidate for a lathe but it doesn't turn well. The metal is gritty and slightly sticky. The pipe was made by rolling a strip and then welding the joint. The weld is much harder than the rest, clunk, clunk. I use it only for crude work. Avoid it when finish matters.

Likewise I've made good use of scrap steel rods removed from old printers and scanners. Usually they machine well but I have one example that carbide won't touch. Visually identical to the others, it's a cuckoo in the nest.

Life's much easier when you know what the alloy is. Then you can look it up and see if it can be fixed by heat-treating or whatever. Just guessing is likely to waste a lot of time.

Dave

[Ady1Participant @ady1]

If you're a newbie stick it to one side and come back to it when you have more experience

[Anonymous]

Posted by Ady1 on 25/03/2018 10:18:23:

If you're a newbie stick it to one side and come back to it when you have more experience

When you have more experience you'll realise that it is pointless using unknown materials and you'll bin it. So save time and bin it now!

Having said that it's a bit odd that carbide tooling won't touch it. As an experiment a while back I machined hardened silver steel (~65Rc) with carbide tooling. The inserts showed signs of wear, but did cut. I also tried a CBN insert, which sailed through with no problems. However, you need to use high sfm, lowish DOC and highish feedrates. The idea is to get the material at the shear zone red hot so it is relatively soft. Toodling along at slow speeds and feeds simply doesn't work.

Andrew

[Chris Evans 6Participant @chrisevans6]

It is common practice for steel suppliers and engineering works to cut the first inch or more off the end of a bar and bin it. This eliminates all the impurities and slag from steel manufacturing. I use a steel stockholder about 12 miles from me and buy mostly from their offcuts rack. £5/10 buys a fair bit of steel when paying cash. Recently had about 2ft of 60mm EN1A for less than £10.

[Neil WyattModerator @neilwyatt]

What's the lowest speed you can get?

Do you have any nasty brazed carbide tools?

Neil

[norman valentineParticipant @normanvalentine78682]

Yesterday, at a car boot sale I bought 3 flat irons as a potential source of cast iron. I tried machining one and found it rather hard, so I put them in my furnace and heated them up to red heat for about 20 minutes and then left them to cool down overnight. I have just tried to machine one again, it is hard but machinable. I am pleased to have found some cast iron that I can use for future projects.

[Jim NicParticipant @jimnic]

I came on a piece of 3" dia steel bar of unknown composition a while back and kept it as a "come in handy". When I found a use for it and tried to machine it I could cut it only with carbide tip tool and then only if I ran it at a very low speed and with a small cut. Even then my lathe was working hard but I kept going because the steel was "too good to chuck away".

The result was that after an hour or so continuous working I had overheated and burnt out my lathe motor.

An expensive lesson! I now only have material that I have bought and know it's composition.

Jim

[Clive FosterParticipant @clivefoster55965]

Posted by Andrew Johnston on 25/03/2018 10:49:34:

The idea is to get the material at the shear zone red hot so it is relatively soft. Toodling along at slow speeds and feeds simply doesn't work.

Andrew

Indeed so. Which needs fairly serious machines.

Realistically anything much over HRC 30 – HRC 35 nominal, bearing in mind that actual values can be ± 2 or 3, is likely to be too much for typical home shop equipment to sensibly cope with.

Hobby time is limited and spending it trying to push the limits of your kit doesn't seem awfully productive. Anyone spending time on American forums will soon see that 4140 Pre-Hard is a very well thought of general purpose material for when something a bit better than a basic steel is needed. Justly so. Nominal hardness is HRC35 so its just about home shop machine friendly.

Pity there is no easy way for ordinary guy to roughly assess the hardness of mystery steel before wasting tooling. I wonder if something like an automatic centre push could be figured out with a simple indenter on the end. Measure the indentation width. Calibration basically Cheese, Easy, OK, Hmmn, Fergeditt. In the home shop practicality beats theoretical accuracy every time.

Clive.

[Dave HalfordParticipant @davehalford22513]

Posted by Jim Nic on 25/03/2018 12:10:52:

I came on a piece of 3" dia steel bar of unknown composition a while back and kept it as a "come in handy". When I found a use for it and tried to machine it I could cut it only with carbide tip tool and then only if I ran it at a very low speed and with a small cut. Even then my lathe was working hard but I kept going because the steel was "too good to chuck away".

The result was that after an hour or so continuous working I had overheated and burnt out my lathe motor.

An expensive lesson! I now only have material that I have bought and know it's composition.

Jim

This raises a somewhat off topic issue of motor ratings.

The motor plate will have the hp or Kw output on it and right next door it should have the rating as CONT or INT.

CONT gives you continuous output at that power output all day. INT gives you intermittent power output for something like an hour or less. Then it needs a cool down period like a welder does and so must be run lightly loaded for a while.

Some machines with electric speed controllers will blow the electronics instead when you stray outside the duty cycle. Trouble is it's difficult to tell how hard we are driving our motors.

Same result though. Ouch, my wallet hurts.

Dave.

[Neil WyattModerator @neilwyatt]

Posted by Clive Foster on 25/03/2018 13:36:52:

American forums will soon see that 4140 Pre-Hard is a very well thought of general purpose material for when something a bit better than a basic steel is needed. Justly so. Nominal hardness is HRC35 so its just about home shop machine friendly.

Equivalent to EN8?

Neil

[Neil AParticipant @neila]

Just out of interest, AISI 4140 is closer to EN19 (or 709m40) in composition. It has a Chromium and Molybdenum composition which EN8 does not have.

Looking at the hardness, HRC35 roughly equates to a V condition, 65 ton. It's a bit in the "Hmmn" region for me, but still machinable with a good machine and tooling.

Neil

[Trevor Crossman 1Participant @trevorcrossman1]

Some time ago I sawed a piece of 4140 from 4" x 1/2" flat bar stock then bored, faced and turned it to make the camshaft for my 9 cylinder radial. On my Boxford LOO I had no trouble with this steel and obtained a very good finish using quality carbide tips in 16mm tools and using Lubysil flood, so this relatively small machine can handle it okay.

Once my mill has been rebuilt and tested for accuracy, this cam blank will be set up on a rotary table to cut the lobes. As this machine is only a tiddly Emco FB2, a bit more thought and care might be needed.

Trevor.

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