I make small quantities of one off set screws, pins etc for a specialist shop. As these items are usually made from 10mm diameter steel I usually use En1a. In the future I may want to case harden some of the items. Would EN3 be better. Does EN3 machine to give a good finish.

Dependant on any fine features you would probably better with EN8 or 16. They would be better in unhardened state than En1 or 3, but could be heat treated to suit requirements.

I use EN32B steel for base hardening. It is easily machined, welded with no problems and forms a tough core with a hard skin when case hardened.

David

Peter

En3b is much the better for parts that are to be case hardened as opposed to through hardening carbon steels,

In my experience it does not machine badly but no where as well as En1a.

Tug

My go to is silver steel for such jobs.

Jim

EN8 (080M40) machines nicely and can be hardened quite easily.

Silver steel machines reasonably well, and can also be hardened. Between the two, my choice would be EN8 because it machines to a better finish. I believe EN8 is stronger than silver steel, but could be wrong about that. If screwcutting, I would use EN8.

EN24T also machines easily to a good finish, and has a greater strength than EN8. The T indicates the material is supplied in a hardened and tempered state, but it still machines nicely.

I have bought both EN8 and EN24T from M-Machine Metals, with whom I have no connection other than being a satisfied customer. Other suppliers are available, etc...

Marcus

It depends...

If you are planning to case harden it, there is no need to use a higher carbon steel that could be through-hardened.

If you are doing small batch production runs, that is what EN1A is designed for, being free-machining and in some instances leaded for even better machineablility. It is often used to make commercial nuts and bolts etc. And it can be case hardened to give the desired hard surface. Trade-off is the strength of the free machining steel is a bit lower than higher grades. .

But if you are wanting higher strength as well as the case hardening, then one of the higher grades suggested might suit better.

Edited By Hopper on 26/12/2022 08:19:52

+1. The answer depends on the purpose the pins and set-screws are put to. Do the items need to be hard, or tough? Does it matter if they're brittle?

The reason different alloys exist is because their properties meet the need in hand. Last pin I made was Brass, not Steel, because it's a Shear Pin, designed to break first in the event of a head-crash.

Most of my pins are made of EN1A-Pb because it's easily machined, and strong enough for most purposes where safety doesn't depend on the pin. It's unsuitable for anything remotely safety critical.

Mild steel is rather soft, so not ideal for bearing surfaces, and, although tough it bends easily. Case hardening creates a thin hard surface on easily machined mild-steel parts, improving their wear resistance. Good for moving parts in clocks, guns, models and other mechanisms. But, because a thin hard layer may not last long in a hard working machine, it's often better to make the part out of a hardenable steel. The disadvantage being that these alloys are more difficult to machine and have to be quenched and tempered properly. The result is inclined to be brittle, especially if tempering is botched.

Although it's often machined, with the exception of the leaded variety, mild-steel is a cheap structural metal rather than an engineering material. Drills, saws, and welds without bother making it good for building ships, tower blocks and car bodies but it's not suitable for bolting wings on aircraft! EN3 is cheaper than EN1A, but it doesn't machine so well. Machines just about OK, but I find it tends to tear and smear making it hard to get a good finish. Leaded EN1A machines extremely well, but the finished part is about 20% weaker than EN3.

The important question is 'does it matter?' If Peter wants to case harden otherwise satisfactory pins just to resist scratching, then I'd stick with EN1A. Apart from availability and cheapness I see no advantage in EN3. And if the pins have important hardness, toughness, and strength requirements, then mild-steel of any type is probably unsuitable.

On the subject of specifications, no-one makes EN1 or EN3 steels. Although extreme resistance to change means many British customers and vendors still call steel by those designations, they've been obsolete since 1972. What you get when "EN3B" is ordered, will be one of several slightly different modern equivalents. Doesn't matter for most purposes, but steel bought for safety critical applications should be ordered more carefully. The correct steel depends on the requirement.

My home workshop requirements aren't demanding and I don't weld, so most of my steel is EN1A-Pb (probably 11SMnPb30 in real money). As only Peter knows what his pins and set-screws are for, he's in danger of getting some duff advice.

Dave

Edited By SillyOldDuffer on 26/12/2022 10:24:09

In many years of designing machines of various types the only time I called up high carbon tool steel (silver steel etc) was when I wanted a cutting edge. The OP is happy with the strength of his EN1 pins, and you can case harden EN1, so why would he swap to steels which are more difficult to machine? The surface of a case hardened pin is likely to be harder than a through hardened and tempered pin.

Just avoid the leaded variety. 

Edited By duncan webster on 26/12/2022 12:12:46

There is some really useful info in this thread though some might be just opinions or feelings and need verification.
It would be great to have a single sheet guide pinned on the workshop wall. I wonder if someone with the right additional knowledge could produce a guide/table in MEW that we could photocopy to hang up?

Using propane torch and firebricks and water quench I found en 8 does not fully harden and it shrinks, I thought that leaded mild steels should not be welded or case hardened.

En1a isn't leaded, that's EN1a-Pb, or whatever SOD quoted above in modern terminology

At the moment I will stick with EN1a as the finish rather than strength in the most important feature. of the items, I may purchase some EN3 just for a comparison between the two.

A slight thread drift. I have to make some special bolts to hold the balance weights on my 6" traction engine crankshaft. The drawing says to use "High Tensile Steel". Normally in this situation I machine down some tensile bolts. However, this time the shape of these bolts is outside the scope of modifying an existing bolt. I will have to start with some steel stock.

So my question is what is the spec for high tensile steel please?

Les

I think this question of what material to use to make special bolts to hold balance weights on with should really be on its own thread.

The simple answer as to what is "high tensile steel" depends on what you are after. General purpose high tensile steel bolts as used in industry are in "S" condition or 8.8 grade steel which is approximately 50 ton/ square inch UTS material.

At work we would only design around a figure of 64% UTS when calculating torque loadings for these fasteners. Special fasteners, particularly for balance weights, were given much more attention with regard to material, machining method, thread forming and finally torque loading.

The more difficult question as far as I am concerned is how have these fasteners have been designed, I would certainly want more detail of the design and the proposed machining before I committed myself to a specific material.

I am sure others will be able to give you more guidance on this specific application.

Neil

OK thanks, I'll start another thread and scan the drawing to give folks an idea.

Les

I'd want more detail of the proposed loading. Give us a drawing of the crankshaft and balance weights, and the rpm it has to withstand. The term 'high tensile' is fairly meaningless.

Kennions sell En1a and it’s a leaded steel. En24T is a reasonable machinery steel for pins bolts gears etc which has a good wear resistance and can be surface hardened.

For high tensile steel, if you were in Australia or the US, the go to would be 4140, a chrome moly alloy steel used widely for high tensile applications in general industry and machine shops. I think the UK equivalent code would be SCM440 or EN19 but you should do your own double checking on that.

If Kennions are selling steel with lead in it, it is EN1a pb. If you look at High Peak Steels website you will find En1a pb has 0.25% lead, EN1A hasn't got a column for lead, and it is quoted as suitable for case hardening. I haven't worked out how to do links on a phone

Edited By duncan webster on 27/12/2022 01:22:57