Nitriding or not ?

[Exminiman]

Got a couple of inline EN 40B cranks, both ground more than +10, Assume I need to get them re-Nitrided ?

Not something I have ever had done, but I am assuming EN 40B was chosen as crank material because of its ability to accept a hardening treatment such as Nitriding(for bearing surfaces) rather than its actual strength? So it might follow to not have them re-Nitrided, would be false economy, wouldn’t it?

Assume treatment is ok after grinding? Or wouldn’t it potentially be ground away .....

Have found this company, http://www.longwear-nitriding.co.uk/ any one know them or have some one they use ?

I am struggling with doing what I think needs doing, but actually wondering in practice, if anyone ever gets anything re-Nitrided...and am I being just a bit anal.......

It may be with modern oils, its not so necessary........?

[snoopy64]

Try https://www.nitriding.co.uk/dvportal.as ... ortal=1541

Ask for Jamie Payton just finished a batch for another classic car i believe

Its not all about wear, the contribution to fatigue strength is not insignificant

[mk1]

Nitriding is easy to get done, but can be expensive if you just have an odd bit to do. You also need to get the crank checked for true, as well as the journals size checked & polished afterwards.

Also, bear in mind what the crank is going to be used for. If it is going to be thrashed mercilessly for hour on end, then Nitriding will be well worth while, if on the other hand it is going to get an occasional blast but for the most part be driven like an old lady on her way to Church, then it is probably wasted money.

[Exminiman]

Thanks a-lot for info and advice guys, its really appreciated.

Makes we wonder how many EN 40B cranks get ground without being re treated.....

So, check crank straight, grind, treat, polish.....

[Dearg1275]

The first regrind to 10 thou under is not a problem as the initial factory nitriding was good to a depth of at least 20 thou. Beyond 20 is unknown territory.

D

[Spider]

These are the factory regrind limits and when they suggested re-treatment




Be aware - Nitriding makes the parts of the Crank extraordinarily hard to the point of being brittle. It takes well on a Forged Crank to any machined surface and is 'hit and miss' on the parts that retain the raw skin from the forging process. The factory Cranks only have a depth of Nitriding to barely 10 thousands, in fact at 10 thou, the hardness is only half of that at stock size. The Process can (and usually does) cause the Crank to warp and twist. It also causes the surface to grow in size, so some shops make a guess on the growth and grind them under, the have the Nitrided with the hope of it coming back to size, others and the more expensive way, is to grind the crank to approx on size, have it Treated, then straighten it and do a final grind back to size. As Nitriding Forged Cranks is only effective on the machined surfaces, it doesn't increase the strength of the crank, but allows it to go for longer between grinds. From my experience, because it makes these machined surfaces brittle with and edge somewhere around the Webbing, this is where they snap and I've seem probably around 3 times more Broken Cranks that have been Nitrided then those that have not.

Personally, I would not have it redone on a Forged Crank.

It's far better on Billet Cranks as they have no skin from forging, so it will be much more even in depth across the crank.

[snoopy64]

Having nitrided tens of 1000’s of forged OEM cranks that would be the least of my worries... a crank will not distort during nitriding if the forging was hardened and tempered correctly, the nitriding carried out at the correct temperature (at least 20C below the final temper temperature) and the regrind process was carried out correctly (not too harshly and inducing stress) The increase in fatigue strength comes from the compressive stress induced by the process in the fillet radii...these and the journals need polishing after nitriding.

If you don’t know all of the above and or don’t need the performance then leave it alone..would be my view.