Author Topic: Nitriding  (Read 912 times)

Online Brian

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Nitriding
« on: 21.03. 2013 23:24 »
There have been quite a few mentions of nitriding and other processes of hardening spoken about on the forum over time and as I have just had a job done I thought I would put up a post just to give some idea what it is all about for those who have never come across it.

I had to make a new big end pin for a 1910 Triumph I'm restoring. The big end is a pin with a bronze bush running on it.

The first thing I did was research just what material to make it out of (thankyou, Markus). I decided on 4140 which is also the preffered metal by the company that did the nitriding.

Nitriding is a surface hardening process, I wont go into just how its done as you can easily research that on the net. You can specify just how deep you want the hardening to go, in this case I went .005" as I didnt want to go too deep and risk the possibility of the pin fracturing.

The good thing about this method of hardening is it doesnt effect the finished surface of the item, there is no need to get  the part ground or anything else afterwards. I will simply polish up the bearing surface with some very fine wet and dry.

I've added a couple of pics, the top, or first pic is before hardening and the second as it came back from the nitriding.

My next thing is to look into grinding the face of cam followers for the A10's. If I can build a machine to accurately grind them then I can get them nitrided and re-use them. That should be a very cost effective way of getting new cam followers, it would cost about $20 AUS to get a set nitrided.
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Offline Topdad

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Re: Nitriding
« Reply #1 on: 22.03. 2013 11:04 »
Brian, the effects aren't anyway as i remember them being when I used nitrided cams for Fords back in the 70's ,when fords first ohc engine came with what could have been a plastic camshaft when standard !!
That looks quite clean whereas my memory seems to register something much heavyer in colour ,very grey but it certainly worked ,i did hundreds of replacements and never had a failure, my own Mk3 cortina went through it's first cam @ 25k miles from nearly new fitted a nitrided cam and it was still going with 230k on the clock (twice round and abit )when it went to the breakers .I've got a nitrided cam and followers in my A from SRM, can't for the love of me remember the finish now but is working fine after 8 -9 yrs and i'm confident that it will continue to do so. I hope your big end pin works for many yrs ,utilising a more modern technology within a veteran can't be bad , best wishes Bob.
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Online muskrat

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Re: Nitriding
« Reply #2 on: 22.03. 2013 19:30 »
 Very nice Brian. Why the nut as well?
A tool & cutter grinder should be able to do the job on the followers. Sounds better than building up with stellite and grinding back.
Cheers
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Online Brian

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Re: Nitriding
« Reply #3 on: 22.03. 2013 21:29 »
This is probably one of those areas where technology has improved to our benefit. I remember case hardening was very messy and the item had to be ground afterwards. As you can see nitriding has virtually no effect on the finished item.

This was the first thing I had ever had nitrided so it was all new to me. Also the first thing I had made out of 4140 steel and that was also a learning curve, difficult to machine as it work hardens as you machine it but like most things once you understand whats happening its ok.

Musky the only reason I had the nut done was because the original one was hardened, it may  not have been necesary.

With the cam followers I am thinking about ones that are not badly worn. I have several sets that I have taken out of motors over the years, some are totally worn out but lots only have about .010" wear or maybe a bit more. These are the ones that I was thinking of grinding the face and getting hardened. They would end up about ten or fifteen thou shorter but I dont think that is enough to cause any problems.
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Offline MG

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Re: Nitriding
« Reply #4 on: 23.03. 2013 16:55 »
Hi Brian!

Great job, glad to see it worked for you!

I've had a lot of followers reground and nitrided, works a treat. I'm always having the camshaft nitrided with the followers, btw.

For regrinding I've knocked together this little device some time ago:
The follower is held in place by two brackets and is clamped down by the M8 bolt, the whole lot can then be clamped in a circular grinder, a crank grinding machine or even a lathe with an electrical grinder mounted on the tool support (with the grinding disc dressed perfectly square to the chuck axis I hasten to add!)
The large diameter of the tool is 68.5mm, the follower is clamped down so that it will only just protude over the outer edge by a few tenths of a mm a mm, resulting in a total swing of approx. 69mm (34.5mm radius). I found that original followers were ground exactly to this very radius of 34.5mm, while most pattern ones I've seen had smaller radii on the cam contact surface, resulting in (slightly) less valve lift duration. Think about that one for a second, Musky  ;D
No problems with follower length so far, I guess you can give a new lease of life to those followers by regrinding for a few times actually.

Cheers, Markus
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Online Brian

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Re: Nitriding
« Reply #5 on: 23.03. 2013 21:22 »
Brilliant ! I'll get busy making one and grind all the followers I have.

Thanks, Markus.
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Offline a10gf

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Re: Nitriding
« Reply #6 on: 23.03. 2013 22:14 »
Congratulations for an excellent topic. Gotta love that follower regrind invention.
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Re: Nitriding
« Reply #7 on: 24.03. 2013 08:28 »
G'day MG, yes I commented on the radius on another topic. Make them a little flatter to give a bit more valve opening.
Cheers
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Offline MG

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Re: Nitriding
« Reply #8 on: 25.03. 2013 07:23 »
Well, when it comes to finding another tenth of a hp in those engines, there is nothing Musky doesn't know it seems.  *smile*

I didn't know you had commented on that one already, I was well surprised when comparing some old to new ones. And even more so when I found one made from stainless steel in a brand new set of four... (been ranting about that for years, I know  *rant*).
Reground originals for me any day!

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Online gavinoz

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Re: Nitriding
« Reply #9 on: 25.03. 2013 10:11 »
Musky, I absolutely defer to your experience, but I cant quite work this out.

I assume you mean by "more valve opening" the duration. Why is this so? Surely the duration as well as amplitude is driven by the cam itself?

Would not a flatter follower just change the pattern of opening i.e. square-top full open / full  close?

And doesn't this lead to potential 'bounce'?

re reading the previous posts, maybe its not as extreme as I am implying, and is a pursuit of every particle of extra hp.

(Mind you, I will never get to that state of tune: I have a big fat yellow speed limiter down my spine!!!)

gavinoz
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