Ground or silver?

[Brian Dickinson 2Participant @briandickinson2]

[Brian Dickinson 2Participant @briandickinson2]

Will silver steel do for loco axles or should it be ground
mild steel?

What’s the difference between the two?

Brian

Edited By Brian Dickinson on 29/11/2011 20:21:59

[Michael GilliganParticipant @michaelgilligan61133]

Brian,

Silver Steel is high carbon [like gauge plate] and can be heat treated; but is tough to work.
Mild Steel can, at best, be case-hardened.

Silver Steel is usually “centreless ground” and can sometimes come out tri-lobed instead of round … the diameter is constant, but the radius is not!

Precision Ground Mild Steel is typically just that.

MichaelG.

[David LittlewoodParticipant @davidlittlewood51847]

PGMS is also cheaper than silver steel. The latter has no advantages for this purpose, it is only necessary if you need to harden it. Also, bear in mind that if you do, it will increase in size very slightly, which might cause a perfect sliding fit to become too tight.

 

David

Edited By David Littlewood on 29/11/2011 22:19:25

[mgjParticipant @mgj]

Which is better- well case hardened mild. Much harder surface, which is what we are interested in, than silver steel in its normal state, a lot easier to machine and a great deal cheaper.

 

Why get PGMS. An ordinary bar of plain mild in a reamed bush is fine. You may have to be a bit more precise if you are using ball or small roller bearings. Bit of slack (as long as its not too much) won’t harm – how accurately have you made the frames/axle boxes, beause if you aren’t accurate to within a thou or so, there is a good chance it can bind. (less than the reaming tolerance).

 

Perhaps one needs to work it out. You have 2 or 3 axles. You have the axle boxes in their sliders, you have the axle in the axle boxes. You then have the wheels quartered, and connected by the conrods. Your reaming clearance is a thou per bush. So if you are to get your con rods to slide over the crankpins (both sides) the total error can only be 1/2 thou, or its going to bind.

 

If you can do it with a DRO and work to inside a thou, then one can be very precise. If you are on mandraulic dials, one might be more realistic.

 

My little Metre Maid fortunately (went the unadjusted machined route), and one can just just detect a very small tight spot – nowhere near enough to stop the wheels rotating, but with care you can feel it. That was PGMS, and that took real care to get that. But it will be fairly quick to run in. Which is a lot better than the alternative.

Edited By mgj on 29/11/2011 22:35:12

[Brian Dickinson 2Participant @briandickinson2]

Thanks for the replies – ground mild steel it is then.

 

Brian

[Clive HartlandParticipant @clivehartland94829]

I used ground mild steel on my Evening Star and its got five axles! It all runs very nicely with no high spots at all.

 

clive

[mgjParticipant @mgj]

Well that either means its spot on, or else it only fits where it touches!

 

I guess spot on, but it really takes something to hold the total error to within the reaming allowance of a standard H5 reamer, across 5 axles.

 

You have done very well.

 

 

Is that from brand new before running in, or after a little service. I’m hoping ot complete MM by Xmas.

[Brian Dickinson 2Participant @briandickinson2]

I was wondering if i should just turn them between centres?

[Clive HartlandParticipant @clivehartland94829]

Brian, certainly turn them between centers, this will help you to turn the flange radii on the wheels. You will be able to turn the wheel assembly as one unit.

 

MGJ, At the moment it is in the building stage and until I can afford a boiler I will just potter along on the smaller bits and the cab.

You can see from, ‘My photos’ the point I have reached, I have made the smoke box and some parts of the regulator (very fiddly) and will start on cutting out the cab.

 

Clive

 

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