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Nitriding Vs Tuftriding - Crankshaft And Conrods


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#1 Inno

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Posted 13 May 2019 - 01:46 PM

I have 12G1505A crankshaft and apparently this is 1275cc - Non-S, EN16T with 1.75" dia. big ends.

 

It is already -0,020 and I will need to go to -0,040 for my engine.

 

I plan to take off big chunks of steel form cranckshaft around big ends as per Vizard's sketches and to do balancing.

 

I have a chance to do Nitriding very cheap (almost for nothing)  but the guy told me that results depends on the type of the steel and it can improve but also decrease the strength. He said if the crank was Nitrided from the factory means material is good for Nitriding and it will be stronger.

 

"T" in the number stands for Tuftriding so it means this crank was tuftrided before but does it means Nitriding will also help.

 

What is the real difference in practice?

 

And what are the chances to make it worst that it is?

 

Same question goes for conrods since I plan to lighten them and balance and Nitriding is basically for free so question is to take it or not?

 

What I found:

Nitriding
The part is heated in a nitrogen-rich environment, usually a gas (ammonia) or a powder bath (the Tenifer process) - very hard but also brittle.

 

Tuftriding
This method is similar to nitriding except that nitrogen and carbon are introduced into the surface of the work piece - very hard but much less brittle - much better shock resistance!!

 



#2 ACDodd

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Posted 13 May 2019 - 04:20 PM

You need a nitriding steel for this treatment, IE Nitroy, commonly known as EN40B.

The T in EN16T does not stand for Tuftriding. It's the heat treatment conditiin. It means the EN16 material is heat-treated to the T condition, hardness (Rockwell C) should be 25 to 31.

Tuftriding is not done anymore in the UK on cranks as far as I can tell. Most heat treatment works gas carburise the surface.

Giving a wear resistance thin skin. It works well.

Ac

#3 carbon

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Posted 13 May 2019 - 05:33 PM

+1 for above.

 

With the conrods nitriding or tuftriding is not recommended. Probably best left alone, and after checking for straightness and big-end / small-end dimensions may require a little bit taken off the balance weight on the caps to get end-to-end balanced consistent.

 

If you do polish them the next step for race or similar very hard use would to get them shot peened - this helps make them less susceptible to fatigue fracture



#4 Inno

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Posted 13 May 2019 - 05:41 PM

You need a nitriding steel for this treatment, IE Nitroy, commonly known as EN40B.

The T in EN16T does not stand for Tuftriding. It's the heat treatment conditiin. It means the EN16 material is heat-treated to the T condition, hardness (Rockwell C) should be 25 to 31.

Tuftriding is not done anymore in the UK on cranks as far as I can tell. Most heat treatment works gas carburise the surface.

Giving a wear resistance thin skin. It works well.

Ac

thanks...it is clear for Tuftridind....

....means Nitriding is also not applicable for EN16 crankshaft....sorry for my ignorance and thanks for the help.



#5 Inno

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Posted 13 May 2019 - 05:49 PM

+1 for above.

 

With the conrods nitriding or tuftriding is not recommended. Probably best left alone, and after checking for straightness and big-end / small-end dimensions may require a little bit taken off the balance weight on the caps to get end-to-end balanced consistent.

 

If you do polish them the next step for race or similar very hard use would to get them shot peened - this helps make them less susceptible to fatigue fracture

thanks, have Inno conrods that weight between 720 and 770grams.....with similar weight on caps as pre A+ conrods....plan to take off most of it to bring them to around 680g - similar as A+ conrods. Balance them all and check length and big/small end dimensions.....will check for shoot peening but as far as I understood conrods are not the most critical part of the engine. Plan to use new ARPs for conrods since I understood bolts can be the critical parts on conrods (and torque).



#6 Moke Spider

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Posted 13 May 2019 - 07:05 PM

Either process does not make the Crankshaft any stronger and in fact, (as already mentioned) can make them weaker. It gives added wear resistance to the Crank Journals so it can usually go longer between grinds.

 

EN16T isn't tuftrided but the T mans it's 'tempered'. The 12G1505A isn't Tuftrided as supplied.

 

It only takes to the machined surfaces of the part being treated and can random effect on the raw unmachined 'skin' of the part.

 

Nitriding is only very shallow, typically 0.005" to 0.010" deep. Truftriding goes in deeper. Most steels, including EN40 can be Tuftrided with varying effects, however, few can be Nitrided.

 

Tufrided cranks can go to 0.020" grind before re-treatment is needed. Nitrided Cranks need to be after 0.010".

 

As both processes involve heat treatment they relax the stresses in the Crank from Forging and this part of the process can increase Crank Life and can be done without Nitriding or Tuftriding, however, with this relaxation, the crank will also change shape, it will only likely be a few thousands, but you can be sure it won't be true and needs to be bent back.

 

Personally, I wouldn't bother with either process, it can bring about headaches.

 

Here's a little bit of factory info;-

 

PKS0hXN.jpg

 

ATBPRYY.jpg

 

One wouldn't treat Con Rods with either process.



#7 Inno

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Posted 13 May 2019 - 08:07 PM

Either process does not make the Crankshaft any stronger and in fact, (as already mentioned) can make them weaker. It gives added wear resistance to the Crank Journals so it can usually go longer between grinds.

 

EN16T isn't tuftrided but the T mans it's 'tempered'. The 12G1505A isn't Tuftrided as supplied.

 

It only takes to the machined surfaces of the part being treated and can random effect on the raw unmachined 'skin' of the part.

 

Nitriding is only very shallow, typically 0.005" to 0.010" deep. Truftriding goes in deeper. Most steels, including EN40 can be Tuftrided with varying effects, however, few can be Nitrided.

 

Tufrided cranks can go to 0.020" grind before re-treatment is needed. Nitrided Cranks need to be after 0.010".

 

As both processes involve heat treatment they relax the stresses in the Crank from Forging and this part of the process can increase Crank Life and can be done without Nitriding or Tuftriding, however, with this relaxation, the crank will also change shape, it will only likely be a few thousands, but you can be sure it won't be true and needs to be bent back.

 

Personally, I wouldn't bother with either process, it can bring about headaches.

 

Here's a little bit of factory info;-

 

PKS0hXN.jpg

 

ATBPRYY.jpg

 

One wouldn't treat Con Rods with either process.

thanks....as far as I understand this document recommend one of those hardening processes in case of regrind as stated above?

 

Guess practice showed we can regrind it 0.40 or more and crancks are still strong enough (at least up to 100HP and 6500rpm and no racing in my case) without any strengthening process?

 

just to make it clear for myself....I can lighten EN16 crank as long as I balance it, regrind it as needed (0,040" or even up to 0,060") and it shall work fine in fast road 1330 engine with up to 95 HP and not more than 6500rpm (power is optimistic but just to make a point).?

 

Also plan to cross drill mains and journals - is that ok - any special considerations for that?



#8 Moke Spider

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Posted 14 May 2019 - 07:48 AM

Grinding to -0.060" will be quite OK and it won't need any treatment.

 

Lightening the crank is a good idea as it will not only allow it to spin up faster, but it also usually moves the critical harmonic resonant frequency of the crank to a higher order (and that's a good thing). The power levels you are talking of will be fine with this set up.

 

In regards to cross drilling the crank, I'm not at all in favour of that as I've seen them crack as a result. If you are worried about oil centrifuge, fit restrictors in to the crank, however, at 6500, I wouldn't bother, especially on a road car.



#9 Inno

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Posted 14 May 2019 - 11:07 AM

Thanks a lot!

I just left two sets fo conrods at machine shop to be checked (big/small ends and lenght).
I would appareciate if somebody can share small and big end diameter for 1275 ... it is not Mini specialised shop so it may be better if I give them exact diameters...

#10 DeadSquare

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Posted 14 May 2019 - 12:55 PM

There is nothing you can do about the big ends.

 

There is not much you can do about the little ends.  They are meant to be .03mm smaller than the gudgeon pin.

 

There is nothing you can do about the length.

 

If they aren't bust, don't fix them.



#11 Inno

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Posted 14 May 2019 - 02:43 PM

There is nothing you can do about the big ends.

 

There is not much you can do about the little ends.  They are meant to be .03mm smaller than the gudgeon pin.

 

There is nothing you can do about the length.

 

If they aren't bust, don't fix them.

...at least they will check big and small ends roundness and let me know is there any difference in length....I saw on many places suggestions to check and repair conrods to be same length - now a bit confused ......at least I will also check crank stroke height and put shorter conrod at longer stroke.... :proud:

 

....guys at the shop actually confirmed they can correct small discrepancies .....but they said they will measure first and let me know if there is something to be done and can they do something....



#12 mini13

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Posted 14 May 2019 - 03:10 PM

i think they can correct a little bend or twist, length wise thy can shorten very slightly by skimming the caps ad rehoning, certainly some of the big companys "grade" their rods to get them closer.  but generally its more a case of checking them and rejecting them if they look to be troublesome.



#13 DeadSquare

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Posted 14 May 2019 - 03:18 PM

I have 12G1505A crankshaft and apparently this is 1275cc - Non-S, EN16T with 1.75" dia. big ends.

 

It is already -0,020 and I will need to go to -0,040 for my engine.

 

I plan to take off big chunks of steel form cranckshaft around big ends as per Vizard's sketches and to do balancing.

 

I have a chance to do Nitriding very cheap (almost for nothing)  but the guy told me that results depends on the type of the steel and it can improve but also decrease the strength. He said if the crank was Nitrided from the factory means material is good for Nitriding and it will be stronger.

 

"T" in the number stands for Tuftriding so it means this crank was tuftrided before but does it means Nitriding will also help.

 

What is the real difference in practice?

 

And what are the chances to make it worst that it is?

 

Same question goes for conrods since I plan to lighten them and balance and Nitriding is basically for free so question is to take it or not?

 

What I found:

Nitriding
The part is heated in a nitrogen-rich environment, usually a gas (ammonia) or a powder bath (the Tenifer process) - very hard but also brittle.

 

Tuftriding
This method is similar to nitriding except that nitrogen and carbon are introduced into the surface of the work piece - very hard but much less brittle - much better shock resistance!!

 

Is this going to be a full race engine or just a zippy road car ?



#14 Inno

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Posted 14 May 2019 - 04:14 PM

 

I have 12G1505A crankshaft and apparently this is 1275cc - Non-S, EN16T with 1.75" dia. big ends.

 

It is already -0,020 and I will need to go to -0,040 for my engine.

 

I plan to take off big chunks of steel form cranckshaft around big ends as per Vizard's sketches and to do balancing.

 

I have a chance to do Nitriding very cheap (almost for nothing)  but the guy told me that results depends on the type of the steel and it can improve but also decrease the strength. He said if the crank was Nitrided from the factory means material is good for Nitriding and it will be stronger.

 

"T" in the number stands for Tuftriding so it means this crank was tuftrided before but does it means Nitriding will also help.

 

What is the real difference in practice?

 

And what are the chances to make it worst that it is?

 

Same question goes for conrods since I plan to lighten them and balance and Nitriding is basically for free so question is to take it or not?

 

What I found:

Nitriding
The part is heated in a nitrogen-rich environment, usually a gas (ammonia) or a powder bath (the Tenifer process) - very hard but also brittle.

 

Tuftriding
This method is similar to nitriding except that nitrogen and carbon are introduced into the surface of the work piece - very hard but much less brittle - much better shock resistance!!

 

Is this going to be a full race engine or just a zippy road car ?

 

...just a road car......that will hopefully put the smile on my face every time I drive it.....and few things I am doing are more like a personal challenge than a real need since it is my first build and I want to do it right....and I have two more to build....one more standard Innocenti 1300 Cooper.....and if everything goes well with both engines my third project is lumpy 1380 with 100+HP at least or may be supecharged 140-150HP.....collecting tools, parts and knowledge for those builds.....



#15 InnoCooperExport

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Posted 14 May 2019 - 05:00 PM

I guess if you're read Vizard you already know Inno conrods are stronger than standard rods with extra strengthening ribs in there. If you're not building a full on race engine I'm not sure I would bother with lightening them. All you risk is making them weaker, getting them all balanced will probably gain you the same without the risk. 






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