when not to use mild steel ?

Hello ........ Am wondering what books / websites / threads / back issues of magazines I should be reading to get a better understanding of what I can and cannot use mild steel for and when I should start considering other materials ...........

For example - I've made a copy of my lathe nose - 1.5" diameter x 8tpi out of mild steel, what should I be reading to find out whether or not I could use that in a diy wood lathe - am guessing that things like that should be hardened high carbon steel ? Similarly have made a couple of morse tapers in mild steel - they seem to work okay but I think the bought ones I've got are all hardened steel.

Would a "light use" hobbyist, like me, be able to get away with using mild steel for some things whereas in an industrial situation things like these would always be made of stronger harder materials ?

What logic do others apply when deciding what materials to use to make a part ?

Bill

Mild steel for light hobby use should be fine. For things requiring a tougher steel I use EN24T which is tough enough without further heat treatment, ideal for the lathe nose.

Hi Bill,

Years ago I made a wood turning lathe and used mild steel for the spindle. It hasn't been used much so the spindle is still Ok. I have also made MT shanks in mild steel, works well. A part made using a tougher/harder steel may last longer, but for my hobby use mild steel is Ok for most of what I make. I have made a few tapered mandrels using a Cr Mo alloyed steel, they are used to finish turn pulleys or gear blanks made from free cutting steel.

Thor

Edited By Thor on 01/10/2016 15:42:23

Personal opinion only, if buying in from a supplier i usually go for EN 8, reasons being it can be harden`d by heating to bright cheery red & quenching, difference in price is minimal, quality seems to be more consistent than EN1 or EN3, can be welded if need be,

As for anything else am in agreement with Chris E spindles and the like, where something tougher is needed EN24T

Apart from that do a bit more looking, searching on the web ..............b

Mild steel is good stuff unless you need to:

• harden it to resist wear
• carry an edge
• resist corrosion
• carry more than a lightly stressed load.

Consequently, it's not ideal for axles, shafts, gears or connecting rods but could be used unless the application was safety critical. Rather soft for tools like screwdrivers. Far too soft for drills, dies and taps. Hopeless for knives, files and saws.

Within my limited experience making small model engines and the like I've got away with mild steel and silver steel aka drill rod. (The latter can be heat treated to improve hardness & toughness when required.)

I'd be much more careful about choosing an appropriate steel if I was making anything more demanding, such as brakes for a motor-bike.

Dave

Edited By SillyOldDuffer on 01/10/2016 18:42:25

HI all,

where's a good reliable place to buy en8-16-24......upto 30mm dia......they need to post my stuff unless it's in Cornwall or on the way to Manchester......

mainly I want to be sure what I ask for is what I get.........

ta Clogs

Clogs

Try Live Steam Models incorporating Model Engineers Supplies www. livesteammodels.co.uk they do on line catalog you can down load, also College Engineering Supplies, www.collegeengineering.co.uk there is also Metal Supermarkets they may have a branch near you so you could call in and get what you want............b

edit for typo error 

Edited By bodge on 01/10/2016 20:42:30

M-machine are quite good too

You will not want to make a spindle out of EN8 and heat treat treat it because it will distort and will then need grinding.

I too think mild steel would be fine. If your worried about strength don't put too big a hole down the centre. I'd say that 1 1/2 dia is rather on the large size for anything other than a very hefty wood lathe.

Wear resistance needs heat treatment really but that is out of the question for most of use as we don't have cylindrical grinders.

John

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Lots of steel suppliers within a short drive of M6 Junction 10. I sometimes use one in Darlaston who will cut on a while you wait basis and reasonable prices, They seem to stock most EN grades, not enquired about stainless though.

EN1A probably rusts the easiest of the lot, so any work you make, don't run it under the tap, just wipe it clean, as you're not going to get it 100% moisture free and we all know what that leads to.

Some companies use varnish over steel to keep it's finish. Mild steel is a good ductile steel, so it'll bend before it breaks, useful for some things i'm sure.

Michael W

Edited By Michael Walters on 01/10/2016 23:43:15

I look at it differently. If the part needs tensile strength, use a high tensile steel. If it needs to be rust resistant, stainless tool steels like Stavax is really good and very stable after heat treatment and ok to turn etc. Another good steel is P20 or 718 and other numbers. It is pre hardened to about 30 Rc and gives a very nice finish as well. I don't make much where MS is a good choice so I don't buy it. I can't see the point in making something and then making it again because that material choice was not the best. There are many things that MS is an ok or in some cases a good material choice. Learning what you need in a material is always a big help in what you are making, so is researching what the part has to do and the appropriate material for that situation. Neil

My wood lathe, a New Zealand made B Line lathe has a mild steel spindle, it shows no sign of wear. We use is on the lower stressed shafts on the agricultural machinery that we build, the stress bits we use 4140, but compromise that by welding it without stress relief (we havn't actually had any problems).

Ian S C

When i was at college we made absolutely everything out of EN3B, humdrum mild basically, it can't be that bad, it's good for general use.

Good for welding also, go to any agricultural yard and they have plenty of mild plate lying about. I knew a guy who made an entire trailer (he bought/found the chassis and welded the cab, for transporting chemicals) out of some and painted it dark green to match the sprayer, no doubt. Still going strong... 

Michael W

Any thing you want to keep nice just put a little WD40 on occasionally. 

Edited By Michael Walters on 02/10/2016 12:18:50

There is a booklet here on various general properties of steels in general.

**LINK**

John

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John,

That's a really useful handbook. PDF saved, I might even print it!

Thanks for the link,

Rod

My advice to you Bill would be to never use mild steel as I never do. I am sure that those reading this and know the type of things I make will wonder just how do I manage. Let me tell of a situation I had early in my metal working activity, that being when I became editor of MEW.

I was making a device that needed two quite complex spindles that ran in cast iron bearings. I made the first and was very pleased with the result. However, when making the second I could get nowhere near the finish I wanted for the bearing part of the spindle. Why was this.

Well, the first was the last piece from a bar whilst the second was off a new bar, obviously two different grades of steel. To make the situation worse I did not know what either of the two bars were. From then on I would not purchase from a supplier who just stated "Mild steel" or even "Free cutting mild steel" I would go elsewhere.

As to your question regarding grades of steel to be used in the home workshop, this is difficult to answer precisely. Typically, your tapers are unlikely to get anywhere near the amount of use as would be in industry so just a common workshop steel will be OK. If though you were making a centre then a steel that could be hardened should be used. Having said that, unless you have the necessary equipment for making such an item, purchasing the finished item is all that can be done.

Having said I never use mild steel I will come clean and say that after my experience I never purchased steel without being told its type. Any that I had in stock I would mark the ends G good. P poor and VP very poor as I used them. I do of course mark the end of any steel I now purchase.

With regard to material types these are the common general purpose types. That is, not for hardening or for strength

230M07 (EN1A) Free cutting mild steel, available in round and square bar , also in flats if you search around

230M07pb (EN1Apb) Leaded, very free cutting steel, available in round and square bar.

070M20 (EN3B) Turns and mills but not as easily as the two above.

Those in brackets are the earlier numbers

I am sure someone will expand on these material types.

Harold

As someone with "the shed of a mere mortal" I think this is as much about what tooling you have to attack with, as it is about the design of the thing one is making.

I doubt I would ever go anywhere near complex alloy steels, except maybe for springs.

I'd use silver steel for holding an edge. If I'm going to weld it then I will buy EN3 for the job, but otherwise it's EN1. If I already have EN1 then I'll weld it, but I shouldn't. If I know it's leaded then I'll avoid welding it, unless I have no choice, and then that its only a small job.

If you have mainly small machines and HSS tooling, using tougher grades of steel gets pretty tiresome.

There's really nothing wrong with other materials like plastics and ally, grey iron. I love a nice bit of leaded bronze.

For a woodworking machine I would have thought a mild steel nose is going to last a good while.

With steel, I think the need for high grade steel comes from light weight, low density, applications. All the time you don't mind how massive the thing is, mild steel is all you need.

Mild steel is incredibly strong. Just get an old bit of 2" 1/8" thick box and see how difficult it is to bend. How strong does it need to be?

I think Harold summed it up really. A lot of model engineering has been done with little else. 2 other materials also figure in it heavily, once cast iron and the simple to heat treat tool steel - silver steel. Probably the nearest grades to that which are probably cheaper are the Wx's. They should be available some where but I don't know of any.

Where not to use mild steel is a better question really. I have a Eureka made out of it. Sliding and moving parts with a fairly close fit. Not a good idea but can work if well greased. Another was a design I saw in MEW some time ago. A boring head with an auto facing feature. From memory more or less entirely mild steel with the same problems - close fit and sliding parts. Even .back plates for chucks on lathes with a register and thread can pick up which is why cast iron is usually used.

Cast iron is probably the easiest hard wearing material available to model engineers and some of the sg / malleable irons are pretty strong. I'm not so sure I would fancy machining the strongest but I notice that the company Jason linked to supply a 400 grade, the weakest. Some grades of the ordinary continuous cast bar aren't far behind.

If people want a high finish what ever material it is black bar is the best option. It hasn't got the increased stress forced into it like bright drawn and that can make a significant difference.

I don't know of any black sliver steel equivalent which I feel is a pity because as supplied I don't think it's very well annealed.

I can't really see any problem using it for a spindle really providing it's big enough. Bearings though could be a problem - easily fixed - run in some sort of hardened bearing or plumber blocks etc.

John

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This is getting really confusing. Harold advises us never to use mild steel, then goes on to quote specs for EN1 and EN3 which are both mild steel, then AjohnW recomends black bar, but you can get black bar in many specifications. What would be nice is for suppliers to tell us what they are selling. I've moaned about this before, but GCQ is meaningless. It is meant to mean Good Commercial Quality, but a reputable stockholder will insist that you have a cert telling you what it is. If he doesn't he has probably lost track. I don't expect the man selling you the odd couple of feet to maintain traceability, but he could at least tell us is it EN1, EN1A, EN3 etc. It's probably EN3 but it would be nice to be told. This costs nothing

To answer the original question, use a know mild steel unless there is a good reason to use a higher grade, and note that welding EN8 is not a good idea (opposite to advice from a previous answer) as the heat affected zone can be brittle unless special precautions are taken. Leaded EN1 is a revelation when it comes to getting a surface finish, but is a tad less strong (and should not be welded as Andy says) . Unless you can use the drawn diameter without machining, black bar is just as good as bright, not quite as strong because it hasn't been work hardened, but more ductile. A lot of engineering equipment is designed on the basis of deflection rather than stress, using a higher grade material will have no effect on deflection, will increase the cost and reduce the ductility.

Just to bring it all up to date, leaded EN1a is now known as 230M07 PB, EN3 is 070M20, and EN8 is 080M40.

Edited By duncan webster on 03/10/2016 01:06:33