ausmini :: View topic - Interesting read on tuffriding and nitriding

It is interesting that once a crank has been ground any benefit of the hard surface giving good wear resistance will be lost. The fatigue improvement that takes place in the journal webs will also be lost.

Having a component re-nitrided is quite difficult as a 'white layer' is produced during nitriding and this MUST be removed before use. It is normal to remove this white layer by grinding and an allowance must be left on the component before surface treatment. It could be done but it would need thinking about carefully as you may need to partially re-grind, nitride, then finish grind. As grinding not only removes the 'white layer' but also reduces surface hardness allowances need to be worked out carefully.

I've been told by various people that BMC in the 60s managed to get the nitriding on the EN40B S cranks lots deeper than .010".
My spare Mk1 S crank is now -.030" on the mains and -.020" on the rod journals, the guy who regrinds GR's cranks (Spiro, at St George Crankshafts) says it is still hard as hell.

Whether crank is still hard on not is apparent during the grinding process.
Yes I'm sure if you want it re-nitrided, Spiro can arrange it.

Beware though, cranks have been known to bend after re-nitriding. One ausmini member had to get the crank changed in his reconditioned motor because of this.
:wink:

<edit> typo

Author:	suffolk [ Mon Jul 02, 2007 10:47 pm ]
Post subject:	Interesting read on tuffriding and nitriding
http://7faq.com/owbase/ow.asp?SurfaceHa ... OfSteel#h5

Author:	Matt68 [ Tue Jul 03, 2007 9:24 am ]
Post subject:
Quote: It is interesting that once a crank has been ground any benefit of the hard surface giving good wear resistance will be lost. The fatigue improvement that takes place in the journal webs will also be lost. Having a component re-nitrided is quite difficult as a 'white layer' is produced during nitriding and this MUST be removed before use. It is normal to remove this white layer by grinding and an allowance must be left on the component before surface treatment. It could be done but it would need thinking about carefully as you may need to partially re-grind, nitride, then finish grind. As grinding not only removes the 'white layer' but also reduces surface hardness allowances need to be worked out carefully. So if I have a cooper s crank (EN40B, Nitrided) that is ground 20 thou under, the hardening will be lost? So I have to get it re nitrided? Can it be tuftrided instead? Basically, how far can they be ground before the hardening is lost?

Author:	suffolk [ Tue Jul 03, 2007 10:16 am ]
Post subject:
May be a engine reconditioner could answer your questions,,someone on here is bound to know....Just think of all the cranks out there that have been reground,,ive seen a few and there didn't seem to be a problem with them,,I think 0.20 might be safe any more and i think they need treating...but i'm not sure on this.. it will be interesting what people on here say about it.....

Author:	Matt68 [ Tue Jul 03, 2007 10:49 am ]
Post subject:
Yeh, I thought I had heard that 20 thou was safe, any further needed redoing. Anyone actually KNOW this for sure, or if there is a test that can be done to see if it is still alright? Cheers matt

Author:	Smarty [ Tue Jul 03, 2007 6:33 pm ]
Post subject:
Ive got a crank that was ground 60thou the bearings are huge!! the crank is not being used though...

ausmini https://www.ausmini.com/forums/

Interesting read on tuffriding and nitriding https://www.ausmini.com/forums/viewtopic.php?f=2&t=33498	Page 1 of 1

Author:	Convertible Mini [ Tue Jul 03, 2007 7:16 pm ]
Post subject:	Nitriding
I have had many cranks nitrided and I was always told the nitriding itself is only about .010" or so when crank is finishes. Usually when they do the Grind they have to leave the crank still unfinished as they always have to re grind them after the process because of distortions and to get a good finish. If a crank is re ground after that it should be Nitrided again.

Author:	drmini in aust [ Tue Jul 03, 2007 7:20 pm ]
Post subject:
I've been told by various people that BMC in the 60s managed to get the nitriding on the EN40B S cranks lots deeper than .010". My spare Mk1 S crank is now -.030" on the mains and -.020" on the rod journals, the guy who regrinds GR's cranks (Spiro, at St George Crankshafts) says it is still hard as hell. I've also been told by various engine reco people that nitriding EN16 cranks to `harden' them is a waste of time- that article (and others) bears this out. It really only works on nitriding steels, eg EN40B or other steels containing aluminium or vanadium. Tufftriding is very hard to get done in Oz now, apparently the EPA jumped on all the heat treaters that were doing it, for health and safety reasons. it is a hot arsenic salt bath process. There is supposed to be one place in Melbourne that still does it, for the aero industry.

Author:	Matt68 [ Wed Jul 04, 2007 9:06 am ]
Post subject:
drmini in aust wrote: I've been told by various people that BMC in the 60s managed to get the nitriding on the EN40B S cranks lots deeper than .010". My spare Mk1 S crank is now -.030" on the mains and -.020" on the rod journals, the guy who regrinds GR's cranks (Spiro, at St George Crankshafts) says it is still hard as hell. So it can be tested to check if the hardness is still there? Spiro can do this? Can he get them re-nitrided etc if needed? Cheers matt

Author:	drmini in aust [ Wed Jul 04, 2007 7:33 pm ]
Post subject:
Whether crank is still hard on not is apparent during the grinding process. Yes I'm sure if you want it re-nitrided, Spiro can arrange it. Beware though, cranks have been known to bend after re-nitriding. One ausmini member had to get the crank changed in his reconditioned motor because of this. <edit> typo

Author:	gafmo [ Wed Jul 04, 2007 8:15 pm ]
Post subject:
I wont be touching mine since Spiro said it was perfect

Author:	Matt68 [ Wed Jul 04, 2007 11:13 pm ]
Post subject:
drmini in aust wrote: Whether crank is still hard on not is apparent during the grinding process. Yes I'm sure if you want it re-nitrided, Spiro can arrange it. Beware though, cranks have been known to bend after re-nitriding. One ausmini member had to get the crank changed in his reconditioned motor because of this. <edit> typo The crank i have is already reground to 20 thou under. Can it be checked without more grinding?

Page 1 of 1	All times are UTC + 10 hours
Powered by phpBB® Forum Software © phpBB Group http://www.phpbb.com/