silver steel

Hi I have a 1920, 35HP car with a poorley gearbox....need to replace the case hardened layshaft......

first the repair must be able to be good for 5,000 miles per year for at least five years......this is no museum piece......

the gears run submerged in oil and the gear set has heavy bronze bushings..

can I use silver steel as is..??........have read the threads on hardening and seems to be a very complicated subjuct......if it needs to be hardened and tempered I woud do the machineing of oilways and location flats first the after the heat treatment have it centerless ground.....how much over size for the grinding....the original shaft is 19mm dia....and is there anyne able to do it or recomend anywhere..??.....

many thanks Frank

Hi Frank,

I wouldn't use silver steel for that. Hardened and tempered silver steel has the same hardness all the way through so if the surface is hard enough it will be brittle. Case hardening a lower carbon steel gives a hard surface and a soft, more resilient core but gives a poor finish and has to be finish ground.

Perhaps a better alternative might be to use a special nitriding steel and get it nitrided after machining. The surface finish is better than case hardening and can be used as is or given a slight final polish with fine emery.

Russell.

en16 maybe ? I know from working on the gearbox of my old bsa 650 that they made the gears out of en36 and case hardened them, maybe a steel to consider too. alternatively you could use a nitriding steel as distortion is low (or lower) with that process.

**LINK**

Is it definitely case hardened? If a file touches it then EN24T would save heat treatment and any finish grinding

I would use EN 36 and get it case hardened for this. Silver steel will be likely to let you down and cause enormous damage to everything else in the gearbox. Colin

I have now decided to go down the en16 / 36 route...but can any body recomend a place to go for Nitride coating....

I've have tried a few but they will only batch work.....

many thanks Frank

Frank,

How badly worn is the original shaft?

Some years ago I had a very badly worn extractor fan shaft about 1" diameter metal sprayed and ground back to the original diameter by a company called Deritend in Luton. Their main plant is in Wolverhampton. They did a superb job, the bearings fitted perfectly and the fan is still in use. Detritend are used to doing one offs as they offer repair rather than production services.

I am sure they may be other companies offering metal spray/grinding services.

.Eric

Linear shafting is a product I use on my flash steam engine it has a ground case hardened skin if your shaft is a common size it might be suitable.

Not sure of the material specification the core is machinable but might have to use a carbide tools to get through the case.

Paul

Frank, I'm guessing the wear 'may' be limited to a step at the end of the shaft bearing the brunt of the 1st / reverse gear cluster, if so it may be worth considering localised repairs by turning down the worn area of the shaft and sleeving it, then have the sleeve surface ground to size, that way you keep much of the original shaft intact and able to use a harder material for the bearing surface without going down the route of hardening the whole thing, it can save a lot of time and expense if needing to faff around drilling and plugging for oilways and boring out the core if it's a hollow tube type shaft!

An alternative to Nitriding if you do go down the remanufacture and hardening route is Tuftriding, which is a process using cyanide salts and probably more readily available (and affordable) as a process than Nitriding!
This is a process I've had done countless times on vulnerable crankshafts to cope with high RPM performance applications from Formula Fords to F5000 V8's and A Series Mini's to Boss Mustangs, the coating is very durable and I've never had a failure even on the infamous Triumph Stag cranks, you just need to take care when polishing the surface after treatment not to go too far and get under the coating which is relatively thin, but as a treatment, it's way more than adequate for your needs!

Check Yellow pages or run a Google search for Tuftride treatments or phone around a few performance engine builders, they'll know of a company that does it, and may even tuck your finished shaft in with another batch for the price of a pint!

When you rebuild the box, I'd highly recommend using a good anti-friction product to coat bearing surfaces during assembly and when refilling it!
Wynns and Slick 50 products are very good as is Molyslip, but that does tend to centrifuge out of the oil after a while, I swear by the stuff, and having recently driven 700 miles across France and the UK to get back home on a virtually destroyed gearbox with next to no oil in it due to something letting go and puncturing the case, I can tell you it does work!

Apologies in advance if I'm teaching Granny to suck eggs, but make sure too that the bronze bushes are in good nick or replaced, because with a damaged shaft the bushes will have wear too!

John