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Silver steel axles

Silver steel axles

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Trevor Crossman 117/08/2020 11:40:36
152 forum posts
18 photos

I'd like to tap the wisdom of experienced locomotive builders . I'm building the Adams 4-4-0 to the Salisbury design from Kennions where the drawings call for silver steel axles running in needle roller bearings. I've read that this is not advisable unless the axle is hardened because of the likelihood of brinelling , and quenching in water, even vertically would likely cause distortion, or maybe not, what are the chances? Can those with experience comment on the other options?

1/ Unhardened silver steel axles running in bronze/oilite bushes

2/ Try quenching silver steel in proper quench oil followed by appropriate tempering.

3/ Use a different steel altogether such as EN 19 with no further hardening and with what bearing style/ material.

Although it's quite unlikely that I would ever run this loco enough to cause such wear ( assuming that I finish it! ) I see little point in building-in a potential problem.

What do those who know think?


Clive Foster17/08/2020 12:51:54
3104 forum posts
107 photos

Might be worth investigating the round linear bearing rails now available at reasonable price to see if a suitable size exists. Case hardened to HRC 60 which should be adequate and H6 tolerance so certainly up to the job when used with plain bushes.

Presumably ordinary needle roller bearings can be found of appropriate size and tolerance to use such rails as plain rotating axles. Metric only so you'd have to do some size revision and getting under the skin needs a good carbide or ceramic tool but the core is soft enough to machine.


Dave Wootton17/08/2020 13:01:14
290 forum posts
65 photos

Hi Trevor

Have a look at John Baguleys website under the Helen Longish section, he experimented with needle roller axles and there is a full write up there, he incorporated them in his Curly bowl winning loco with sucess. I do remember a loco built to the Martin Evans Springbok design that had canon axleboxes with silver steel axles running straight in needle rollers, ran hard for years without any problems, sadly the builder died a few yearsago and the loco was sold, no idea where it is now.


Edited By Dave Wootton on 17/08/2020 13:02:04

Phil H117/08/2020 13:37:06
458 forum posts
60 photos


I am in your position i.e., not finished a build yet (I'm building Rob Roy at 31/2" gauge). I am beginning to ignore calls for gauge plate for this and silver steel for that. Maybe you and others will take a different view but I will honestly take great pleasure in renewing axleboxes and various pins because it will mean that I actually finished the bloody thing and had it running.

Loads of engines before yours have run for a long time with BMS axles and plain gunmetal axleboxes or even BMS and cast iron.

I bought some EN8 (Im sure it was) from Kennions for my Rob Roy axles and it appears to be nice round material and tougher than my ordinary BMS to machine.

Designers get carried away sometimes.

Phil H

Martin Kyte17/08/2020 14:13:14
2725 forum posts
48 photos

You are making the assumption that the specification of silver steel is about the material. Often silver steel is specified because it is held to tighter dimensions. 1/4" silver steel will be 0.250" rather than a couple of thou under for bright mild for example. It is 'generally' straighter too. So maybe precision ground mild could have been specified but silver steel possibly easier to get hold of.

How many times do we come accross designs calling for some really odd size of material when the reason for it was the designer had some in the scrap box and just used that without rationalising the design.

Don't always assume the reasons for a specification.

As a diversion one of my favourite stories relates to a newly wed couple. The first time she cooked a roast she cut the sides off the joint, stuck them on top before shoving the whole lot in the oven to cook.

A few weeks went by and after watching his wife do the same trick the husband asked why she did that. Her response was 'Thats how you do it' 'my mum always did that so I do too'.

Later that week her mum came round and he asked her about the roasting technique and why she did what she did.

"My mum always did that so I do too' came the response. As the grandmother was still in the land of the living and was due for a visit in a couple of weeks they resolved to solve the riddle once and for all.

Finally the day came and the old lady was asked the pertinant question. "Oh" she said "when I first got married we only had a little oven and thats the only way it would fit and to be quite honest I never got out of the habit.

See what I mean?


regards Martin

Edited By Martin Kyte on 17/08/2020 14:13:57

not done it yet17/08/2020 14:49:35
6736 forum posts
20 photos

A bit like newly wed who put the frozen chicken in the sink, and covered it with a colander, while it thawed.

When her hubby asked why she did that she replied that it was the way her mum always did it.

When mother-in-law visited, hubby asked her why she always thawed the chicken in the sink while covered with a colander.

She looked at her daughter and said ‘You don’t still do that, do you? Daughter replied ‘Well, that’s the way YOU always did it!




To which MiL replied ‘But you don’t have a cat!’

Dave Halford17/08/2020 15:34:20
2007 forum posts
23 photos
Posted by Clive Foster on 17/08/2020 12:51:54:

Might be worth investigating the round linear bearing rails now available at reasonable price to see if a suitable size exists. Case hardened to HRC 60 which should be adequate and H6 tolerance so certainly up to the job when used with plain bushes.


Be careful with these, my lad bought some from Spain for his 3d printer they weren't round nor straight.

Dave Wootton17/08/2020 16:59:52
290 forum posts
65 photos

Hi Trevor

Just had a look at john B's website mentioned above, the section on testing needle rollers with silver steel is on page 11 of the helen Longish write up. Worth spending some time on john's site he has some good practical ideas for loco building, I must admit I've pinched loads of them!

If your engine is to the late Kelvin Moodie's design it should be ok, I remember him running his radial tank and 0-4-2 at rallies some years ago and they always performed very well, I did get to drive the radial at one time, a very good engine.

One thing I can say with complete confidence is don't use oilite bushes in axleboxes unless you can be 100% sure to keep ash out, the rear axleboxes of my simplex have picked up the ash and used it to lap the rear axle (EN8) the wear is horrendous, although it has done a lot of running. The others are ok but they are not next to the ashpan, I would never use oilites again on a loco. The engine still goes ok though!






Edited By Dave Wootton on 17/08/2020 17:08:00

Trevor Crossman 118/08/2020 11:01:52
152 forum posts
18 photos

Thanks to you all for your replies, even the allegorical culinary tales!

Phil H......I tend to follow the specs and dimensions that are called for on the drawings because it's a habit of a lifetime of aircraft engineering. Although in this instance I have already departed from that by fabricating the axleboxes from steel seeing little rationale in using expensive gunmetal castings and then fitting a bearing, these steel items have cost 1/10 of the castings.

Dave Wooton....... The locomotive is indeed the KS Moodie design and I've had a good read of the Helen Longish build, and particularly note the testing recorded on page 11. Judging by those results, I'll certainly not bother myself with the hastle of trying to heat treat and produce a distortion free set of axles, I very much doubt that I'll get it to run 1000 miles let alone 3000+!!! In fact there'll be a good celebration after the first mile.

As this is the first and will almost certainly be the only locomotive that I shall ever build my inclination is to follow 'expert' advice and so when I read in the well known Martin Evans loco building book where he stated that ' there's no advantage to be gained by using Silver Steel', I thought that I'd ask what others think. Assuming equally accurately ground samples of mild steel and silver steel I am of the opinion that the latter has the harder surface in the normal, untreated condition.

Regarding oilite bushes why would these be more prone to ash damage than the common solid gunmetal casting, indeed, a needle roller will require a dust shield to prevent grit getting in. As an example, the BMW K75 bike has a common seizure of the clutch operating shaft which is mounted on needle rollers and gets exposure to water grit and crud thrown out from the resr tyre. I've owned 3 and they all needed replacing, a simple but time consuming job.

Once again thanks to all.


John Baguley18/08/2020 11:08:22
503 forum posts
54 photos

The biggest problem I find with using needle roller bearings is that the chassis is so free running that it will roll off the bench as soon as you turn your back! It nearly happened to me a couple of times. I only just caught it the second time it happened and it nearly landed on the floor! This was before I had fitted the coupling rods etc.

If you can, use the bearings with the built in seals at each end. For lubrication I drill down the centre of the axle from each end and then drill a cross hole into the bearing surface. You can seal the end of the axle with a grubscrew. You don't need to oil them very often.


Edited By John Baguley on 18/08/2020 11:11:15

Trevor Crossman 118/08/2020 13:11:15
152 forum posts
18 photos

Free running eh? Probably not on any of my benches, they tend to magically accrue 'stuff' !!. However, to make sure that such a disaster as a part built locomotive rolling off the edge and onto the concrete, I'll now fix a bead edge on the 3 open sides of my supposedly clear and clean assembly bench!!

Thank you John for the lubrication system tip, so far I've only obtained the bogie bearings, these are without seals but I'll look for sealed ones for the main axles. Failing that I could try fitting a teflon ring into both ends of the axleboxes.


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