Please tell me if this crank looks OK

[Ian928]

I just received a remanufactured crank from one of our vendors. It should be machined, hardened and polished. I am surprised that the bearing surfaces don’t look polished. I have compared it to my old crank for reference. The remanufactured one is more rusty so it is possible to tell them apart. Should it look like this?

[richardthestag]

where did it come from? assuming that it is the top crank in the last photo it doesnt look hardened, difficult to tell but it should be black

IMAG1096.jpg

this mine that I sourced from Faversham classics

re polishing can you feel any imperfections across the journal with your fingernail?

[mole42]

Neither of the journal pictures look good to me so if one of them is reground then something doesn't look right.

[richfield]

The radius of one of the pictures does not match the healthy radius shown on the other photo-on a crank the radius is the angle at both ends of the journal,if you receive a crank back or buy one where this angle is 90degrees or near-dustbin job,the crank will break at this point!!!

[Phil S]

looking at the "new" crank you can see whst looks like at bearing oil track in the centre of the journal this would not be there on a ground crank.
Phil

[Motorsport Micky]

It looks like a crank that's been ground, hardened and polished...and then left on a spares stillage for a year so the balance webs on the crank have to some extent corroded.

The journals look fine to me ( I assume you've measured them for dimension AND roundness to confirm somebodies not selling you an old one in decent condition ?). If you check the journal condition they are a dark grey underneath which has been polished...a standard preparation which has removed their dark finish to a large extent.

If in doubt ( why do you?) why not ask them. I agree with Richfield above, the journal grind doesn't look to have a radius into the corner ( or even an undercut) which will help relieve the stresses there which cause breakage, but I can't tell definately on a photo, the journal on the first picture doesn't look like it has a radius on the corners either ! And as a final comment the " teardropping" on the holes on the first photo of the journals looks much nicer than on the rusty crank where it's been done half heartedly.

Micky

PS which hardening process was used ? There's a number of them which leaves different finishes.

[Ian928]

where did it come from? assuming that it is the top crank in the last photo it doesnt look hardened, difficult to tell but it should be black

re polishing can you feel any imperfections across the journal with your fingernail?

Yes it is the top one that is new. Compared to yours it does not look neither hardened or polished shiny as I expected.

I will not say who I received it from, sorry about that. I am sure it something is not right we will find an agreement.

[Ian928]

It looks like a crank that's been ground, hardened and polished...and then left on a spares stillage for a year so the balance webs on the crank have to some extent corroded.

The journals look fine to me ( I assume you've measured them for dimension AND roundness to confirm somebodies not selling you an old one in decent condition ?). If you check the journal condition they are a dark grey underneath which has been polished...a standard preparation which has removed their dark finish to a large extent.

If in doubt ( why do you?) why not ask them. I agree with Richfield above, the journal grind doesn't look to have a radius into the corner ( or even an undercut) which will help relieve the stresses there which cause breakage, but I can't tell definately on a photo, the journal on the first picture doesn't look like it has a radius on the corners either ! And as a final comment the " teardropping" on the holes on the first photo of the journals looks much nicer than on the rusty crank where it's been done half heartedly.

Micky

PS which hardening process was used ? There's a number of them which leaves different finishes.

It may be correct that it has been sitting on a shelf a long time, it is looking surprisingly rusty. I am worried about corrosion on the bearing surfaces. The nose has quite a lot of corrosion underneath the timing sprockets, I am not sure if this matter to much, but I am wondering how it could become corroded there, that is inside the engine.

I have not measured anything. I unwrapped it and it did not look the way I expected. I have never seen a remanufactured crank before so wanted to check with those with more experience.

I took some more photos of the radiused corners. My old crank definitively have a bigger radius. Are there a minimum number for this radius?

I will contact the vendor with my concerns and also ask what hardening method was used. That may be the reason it is not looking black like Richards. I see that the snout of Richards crank is all black VS the one I received is not. Neither is my old one by the way.

[flying farmer]

Looking at the pictures above, the old crank looks like it has been ground at some point as there looks to be a step on to the radius which is not present on the new crank, although the radius looks to be a touch smaller.
It is very easy to tell whether a crank has been hardened, just apply a file to the journal next to the oil hole. If the file skates off the surface it is hardened, if it removes metal it isn't.

In my collection of used cranks I have one that is hardened on the big ends, but is soft on the mains. I suspect it has needed a regrind on the mains that has gone through the hardened layer. The big ends have not been ground and the hardening is still present.
Neil

[Motorsport Micky]

The photo of the new crank shows the radii has been undercut ( correctly) so as long as the bearing ground crank surface extends beyond over the undercut ( ie: you can't feel an edge there with a nail so it "drops off " the bearing surface ) it will stress relieve the crank and help prevent breakage.
In contrast the photo of your old crank shows it despite having a larger radii that the bearing surface grind ends abruptly with what looks like a shoulder and I'd be getting that reground and the radii undercut there before using.

Micky

PS: Neil is quicker typing and beat me to the post I agreei with what he said.

[trunt]

For reference, here's my hardened and polished crank.. I'm not sure I would be happy with your one!

[flying farmer]

For reference, here's my hardened and polished crank.. I'm not sure I would be happy with your one!

Your crank actually has considerably more shine on the journals than most hardened cranks I have seen which tend to be a slightly duller finish.

There may well be a difference in colour depending on the type of hardening. I have had both nitrided and tufrided cranks in the past, and I think Nitrided ones have a slightly more shiney surface finish but it is quite a few years now since I saw my last one so I may be wrong on this.
I got lucky with my last crank, it was a good ebay purchase that had been hardened correctly (file test), but I don't know by what method.

[richardthestag]

I must say that when I stripped my engine back down after HGF back in 2013......

err "why strip the engine down for HGF?"

yeah because one bolt broke flush with the block and one stud refused all persuasion techniques for removal. the block had to go for engineering.

anyway the crank looked like this

IMAG0928.jpg

note colour and also the badly scored journals, these were the best on this crank!!

my issue dispelled two rumours.

1. that factory hardening would allow for one grind. big ends and mains on this crank were 10thou
2. that when the crank is sold as hardened it might not be. This was supplied by a known part supplier. fitted by me!

I presented this back to the original supplier but alas over a decade and 30k miles made my case a weak one. No name and shame, put down to experience.

so off I toddled to local machine shops. 100% of whom responded with no need to harden it, never heard of that etc etc.

So I started to phone around. Oselli and a number of other engineering shops concurred with the local shops but Oselli did say that they could harden the crank after cutting it.

I ended up phoning my old chums at Faversham. they provided me with the crank, correctly hardened by a shop on the same estate as they are. were happy to exchange the above crank for another 10thou. The cost was about the same as Oselli quoted me, Rather give fabulous Trevor at FC my money

I can confirm that after hardening the whole thing was satin black, the journals were polished up by the same engineering shop when I collected it. Also the crank bolt thread needed recutting.

[Ian928]

Got an answer from the vendor:

The crankshaft has come out of an oven where it has been tuftrided. The tuftriding generates oxides which leave deposits all over the crankshaft, hence the black/brown appearance. It is always the responsibility of the end user who is putting the engine together to ensure the crankshaft it cleaned. This should be done using parafin or petrol and a plastic abrahsive, such as 3M Scotchbrite. All oil ways must be cleaned using wire or a small screwdriver, or even a twist drill bit of the correct size. Regarding crankshaft journals, these would have arrived with you having been partially polished by our crank grinder as one of the extra services we put into our crankshafts is to ensure they have not been bent by the heat generated in the tuftriding oven. Our crank grinder ensures that they are within 2 thou tolerance from end to end.

What we do in the workshop when building an engine is to fine polish the crankshaft journals using 2000 grit wet and dry paper with parafin, just to tidy the final appearance prior to installation.

When the crankshaft is fitted to the cylinder block with an oil film on all the bearings and all of the main bearing caps torqued down to 70 pounds feet, the crank should be easy to spin by hand.

If you are not using a specialist to carry out your engine work, please be very careful to follow correct procedure for the Stag engine and always ask us if you have any queries or need advice.

So, whatdo you say? I am leaning towards doing what is described over and use the crank.

[Motorsport Micky]

I'd be a bit disappointed if the crank as only within 2 thou of straight !
The hardening or tuft riding processes stress relieve the cranks and they sometimes take on banana shapes, the worst I had on a 3 main TR Crank showed a 10 thou bend from centre bearing to the nose of the crank ! Returned to the engineering firm and it was represented 48 hours afterwards straight...absolutely straight with no run off at all on my DTI ( clock) I had to check it was still working ! Apparently they hit them with large hammers at strategic places to remove the bend, the crank was checked for straightness after 3 seasons racing and it was still straight.
Why not fit the crank roughly to your block with bearings fitted to front and rear main and check the crank for straightness before working at it to clean out all surfaces etc. Drop the crank into the bearings without the caps fitted and clock up the crank main journals as you spin it, you can swap the mains bearings fitted so you can check front through to rear for straightness. Then you can decide which option to go for, if you use the search box there is a thread about bent cranks no more than a year ago, it had a firm mentioned who will recover the crank to within a thou of straight if you needed it.

Micky