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

John

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

+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.

Stainless steel? Correct grade of course.

John

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.

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.

Emgee

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.

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.

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&quot 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&quot diameter so not up to it even if you can reliably find it in R condition.

Clive

Chris

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?

Clive

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

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

Just an observation, the near equivalent of BS970 431S29 is actually EN57, usually supplied in the T condition (55 ton tensile), although the impact strength is only about 60% of the alloy steels. The EN58 series cannot be heat treated and are supplied in a soft condition (35 ton tensile). Could make a difference to your project.

Also be aware that you acquire material close to your finished size, remember that the core of a larger diameter bar will not have the same properties as the outside layers because of the "speed" of the quench through the material in the hardening process. In small diameters this is not a big issue.

As others have said, getting small quantities of the right material can be your biggest problem.

Neil

Interesting alternative but I'd stick with 605M36 T from a reputable supplier with a certificate. Inclusion modified for easier machining if I could get it but that would need to be pure luck with an offcut.

Compositions are near as damnit the same but USACUT has a slightly lower maximum permitted sulphur and, generally a touch more manganese and molybdenum. Mostly its going to overlap so you'd probably not notice any difference in practice. Brinell hardness is effectively the same.

What would worry me for spindle use is that USACUT55 elongation in T condition is given as 8% and Izod Impact 34 whilst the figures I have 605M36 T has an elongation of around 11% and Izod impact around 74. Izod tends to be rather variable, ± 5 or so for 605M36 T from the figures I have. The lower Elongation and Izod figures for USACUT55 suggest it may be more brittle and crack prone in T condition. Which would make it easier to machine. Its the tough, ductile, stringy stuff that brings out the curses. Yes Mr Pure Aluminium I'm talking about you.

Whether this actually matters in practice, strong enough is strong enough after all, I don't have the detail engineering knowledge to evaluate. But I have seen a cracked, fortunately not broken, front wheel spindle so its an area where I really am going to listen to a man who is proven expert. I have no knowledge of the history of the cracked spindle in question. Best guess is that it got bent in a crash and some penny pinching oik tried to hammer it (not quite) straight but I don't know if it happened in service. Auto-jumble purchase I was asked about repairing. Er Nope! Think it was £7 odd from the jumble when NOS factory could be found for £15! Some people.

Except.

Reliable friend tells me that local bike MOT place refused to let a customer take a Harley engine in Norton featherbed frame special away. Front wheel bearing bores were too large for the spindle so the wheel was jumping around. And the man rode it down there for its first MOT in his hands having paid £ "lots" for it.

USACUT55 is probably a fairly academic choice as it only seems to be available in full bars. 3.5 metres will make a lot of spindles.

Titanium is for the guys who know what they are about. Even harder to machine than stainless if you don't know the tricks, I don't really, and even easier to buy the wrong thing.

Clive