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Turning EN8

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c wastell06/08/2020 21:27:17
37 forum posts

I'm about to attempt to turn motorbike wheel spindle out of EN8. Is there any advice that I should be following please? Thanks in advance

JohnF06/08/2020 22:03:01
1175 forum posts
193 photos

I would use a different material ! EN19T would be better, easy to obtain and machines well.


Edit! Standard practise really but forgot to say turn all diameters in one operation, support it with a centre in the tailstock and don't forget to leave a service end to remove the centre. If there are threads [most likely] I would screw cut them.

Edited By JohnF on 06/08/2020 22:06:38

Bill Pudney06/08/2020 22:06:49
617 forum posts
24 photos

For what it's worth Norton Commando front wheel spindles were EN16

best of luck



Oily Rag06/08/2020 23:03:56
540 forum posts
184 photos

+1 for either EN16T or EN 19T alternatively Ti614 also makes a good lightweight spindle!

...And no sharp corners at transitions of diameters! Nice radii.

colin brannigan07/08/2020 07:41:52
110 forum posts
18 photos

I use EN16T, but 19t will also do quite nicely, EN8 can be troublesome to cut on a small lathe.


John MC07/08/2020 08:05:09
386 forum posts
45 photos

Stainless steel? Correct grade of course.


c wastell07/08/2020 08:28:06
37 forum posts

Great answers, thank you very much. I have an old Myford Super Seven and O level metalwork, so not much idea on best materials.

Chris Evans 607/08/2020 08:30:31
2068 forum posts

I only ever use EN16T for spindles and would never consider EN8 for such a critical part. If folk insist on stainless maybe 316 would do but I would refuse the job.

c wastell07/08/2020 09:33:43
37 forum posts

My local stockist has EN24T as the nearest thing to 19T. Is this any good as a replacement please?

Emgee07/08/2020 11:27:39
2446 forum posts
291 photos

I would say OK for the job but may be more difficult to machine, plenty of EN16T on ebay at low cost from reputable sources.


Swarf Maker07/08/2020 11:33:53
118 forum posts
5 photos

I find it worrying when people with little metallurgical or manufacturing knowledge choose to make safety critical items for their vehicles. In this case 'c wastell' has chosen to ask for much needed advice and for this he is to be applauded.

There is a slight problem in that we have no knowledge of the duty that this wheel spindle will be required to fulfil, and no knowledge of its design parameters.

We all should exercise our 'duty of care' when offering advice, particularly when we know so little about the actual requirement. So whilst EN16T, now better identified as 605M36, is likely to be the preferred specification if this is for a simple spindle supporting individual bearings, there may be other limitations that need to be considered first.

So please 'c wastell', let us know exactly what it is that advice is sought for. And furthermore, when that advice is given, please ensure that you have adequate assurance from the supplier that the material is truly what has been specified. You may well not find the material locally so don't limit yourself to whatever the nearest stockist may have.

Edited By Swarf Maker on 07/08/2020 11:34:58

Oily Rag07/08/2020 11:40:42
540 forum posts
184 photos

Stay clear of stainless steel, too 'notch sensitive' for a critical part such as a wheel spindle. I remember well a scrutineer at a classic bike meeting checking wheel spindles with a magnet to see if they were stainless and rejecting any that were. I had a problem with my bike as it had Ti614 spindles and had to argue that they were not stainless but titanium, along with the spokes and spoke nipples and most of the bolts and nuts holding it all together!.

Fortunately he let the bike pass scrutineering on this evidence when I showed him a Titanium bolt from my spares box.

John MC07/08/2020 14:34:32
386 forum posts
45 photos

I think the OP has done exactly the right thing in asking advice on the grade of steel that would do the job. Knowing its a wheel spindle for a motorcycle is enough advice to determine a suitable grade of steel.

I'm surprised at the hostility towards stainless steel for the job. As with non-stainless steels the correct grade is essential, for stainless EN58(T), 431 is entirely satisfactory as is either EN16(T) or EN24(T).

Modern motorcycles use stainless in abundance, wheel rims, spokes, fasteners, spindles, Inlet and exhaust valves. The latter being the most arduous of duties, constantly being hammered at one end by the seat, the valve gear at the other end. The bit in between being rubbed against its guide with marginal lubrication All this happening at elevated temperature. Stainless steel is entirely satisfactory for wheel spindles when a suitable grade is chosen, as is true for the choice of the correct material for any job.


Henry Brown07/08/2020 15:46:28
559 forum posts
119 photos

If you do go for EN8 its not particularly nice to machine, I turned some a while back and finished with a very sharp HSS ground tool, more recently I've used a **GT tip for aluminium that also gave an acceptable finish.

old mart07/08/2020 15:57:15
3912 forum posts
268 photos

I would go for en19t, or en24t, they are stronger than en8 and machine well,

Clive Foster07/08/2020 16:55:20
3173 forum posts
113 photos

John Bradleys' 3 books "The Racing Motorcycle, A technical Guide for Constructors." are the bible for advice on this sort of thing. Volume 2 covering chassis materials & construction techniques is superb guide to materials and their appropriate use even if you have no intention of building a bike. Hopefully it will be back in print sometime. He is a professional engineer who has built his own racing bikes from scratch (all bar the engine) in a home workshop and remains a well respected consultant to race teams on suspension and set-up matters.

An all round nice man too.

John says :-

"I really like 605M36 T (EN16T) and use it in the T condition for virtually all spindles that do not involve individual heat treatment. It is widely available in this condition and may also be inclusion modified for easy machining.

This is a manganese-molybdenum steel with excellent toughness and shock resistance at normal temepratures. 605M36 is much less suceptible to temper brittleness than the chromium based alloys. 605M36 can easily reach T condition in our sort of sizes and only much larger sizes (eg 60 mm diameter and above) will be offered in the lower ranges such as R or S. I have used 605M36 T for 35 years and it has alaways been a trouble free option."

"709M40 T (EN19T) is a very popular chrome-moly steel which is again available off the shelf in T condition. It is more highly alloyed than 4130 chome-moly and actually corresponds to SAE 4140.

There have been several variants, each with slightly lower chromium and molybdenum than the original due to the Euro Norms rationalisation. Talk to your supplier.

I use709M40 if 605M36 cannot meet my ruling section requirments. 709M40 can go higher up the tensile range, it also nitrides well."

"817M40 (EN24T) is a long established nickel-chrome-moly steel, extensively used for larger components, or those where high tensile strengths are required.

It can cover tensile ranges W, X and Z up to 29 mm (1 1/4" diameter. It is, in effect, overkill when limited to T range in small sections. Many people use 817M40 on the grounds that is is more expensive.

I don't completely agree ..... Table 2.7 shows the actual mechanical properties of 605M36 T, 709M40 T, and 817M40 samples. You will note there is little to choose except that 817M40 tends to come out towards the top of the range, 709M40 T towards the middle and 605 M36 fractionally lower. Over the years I have talked to many manufacturers and no has been able to give any significant advantages for any one of these three when used in T condition except for 605M36 becomes brittle sooner at very low temperatures (-20°C) than the others.

However one thing is certain 817M40 demands much more careful control of heat treatment than the other two. Faulty heat treatment leads to brittle failure, even in T condition."

For folk like us the big difficulty is getting a foot or so of steel to known composition and heat treatment. 605M36 T with a proper certificate is the only safe choice. Wheel spindles are no place for a steel which may not have the expected impact and shock resistance (709M40 T) or is likely to be vulnerable to brittle failure (817M40 T) if you happen to get the bad bit out of the bar.

Our suppliers aren't equipped to verify properties. They have to take it on trust. I've had some right weird stuff appear that really wasn't what it said on the tin. Generally materials are good but sometimes..... That said the only time I'd make a wheel spindle was if I didn't trust what I could buy. And if it costs silly money for tested material its a darn sight cheaper than my neck.

John MC is quite right in saying that properly selected stainless steel is up to the job but can you actually buy a short length of the right stuff in the right condition.

80M40 (EN8) can only manage tensile range R up to 19 mm (3/4" diameter so not up to it even if you can reliably find it in R condition.


Chris Evans 607/08/2020 17:20:32
2068 forum posts

Nice and knowledgeable article Clive. My reservations against stainless are my own in not wishing to have the responsibility of a defective component.

Clive Foster07/08/2020 18:25:38
3173 forum posts
113 photos


Glad you liked it.

As I said the major issue is that folk like us are supply constrained. Not so much a matter of getting the absolute best material more a case of being sure that we have got a suitable piece of material in the right condition and properly heat treated for a safety critical job.

For something like a spindle I'd never order against an EN number.

Had a couple of 1 foot lengths of EN something a fair few years back from one of our suppliers with well deserved reputation for being both good and reliable that were actually last 14 inches of one bar and first 14 inches of another, or thereabouts. So I got a bit of a bonus. They machined rather differently so obviously not the same. Quick check back with the supplier showed that they were from different stockholders. As it was a very uncritical application, "needs a bit of steel this size" sort of thing, I'd not have bothered except that some parts needed to be welded so I wanted to be sure an error hadn't been made with one length being unsuitable for welding. Apparently I wasn't the first person to notice such variations.

Another time I needed 4 lengths of modern "number-letter-number" designated steel almost immediately. Local guy I liked to use for pick-ups only had one length of what I wanted but as the designation overlapped an EN number he offered to make up with the last 3 bars in the rack of what he was supplying for that EN. On a 4 for 3 pick up this afternoon deal so I bit. All machined differently, all up for the job (could easily have ordered EN but had got into the habit of going all modern with that guy and doing it right) so I worried not except that one end of one bar was harder than a woodpeckers beak. Ripped the tip straight off a tool. Angle grinder took the first 4" off as a sacrifice and the rest machined fine but clearly harder tha the others. I'm darn sure I got something a lot better than I paid for!

Most of the time there are no issues but do you want to risk being Mr Unlucky?


Edited By Clive Foster on 07/08/2020 18:39:50

bernard towers07/08/2020 20:50:18
691 forum posts
141 photos

Instead of using en16 use USACUT55 from acenta steels this is a modern easy machine en16t.

Kettrinboy07/08/2020 21:31:50
94 forum posts
49 photos

I made front/rear and swing arm spindles for my 96 Kawasaki ZX6R 15 yrs ago now out of Ti6 al4v Titanium plus every other external nut and bolt and they have been excellent, no corrosion and saved several kilos in weight, I would nt use EN8 as it's a relatively low tensile strength whereas EN16T/24T are 55 tons and for stainless i would use EN57T also 55 tons/square inch, it does rust slightly but is a tougher steel and easier to machine than 316 .

Edited By Kettrinboy on 07/08/2020 21:34:32

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