Topic: Normal crankshaft wear?

[maxheadflow]

While you can harden them, don't think that they typically are.  No reason to.   Do you have a reference?

I think I read this in HondaMan's book and the hardness penetrating to about 0.005"   I may be wrong in the cranks being hardened, however, the crank material is going to be harder than the bearing shells.  One of the materials (either the journal or the shell) has to be soft enough to embed any foreign particles so it avoids grinding the particles.  You naturally make the shells (replaceable) softer than the journals on the crank.  https://.com//

-P.

I don't see any reference to hardening of the crank in Paris' book.  If you have a page number that would be good. Only place I found referenced to polishing was small rod ends with 400 grit emery.

You're link is good for bearing material but says nothing about shaft finish.

Again, the link I provided talked about using 320-400-600 grit to motor polish a crank after grinding.  Using 600 wet and dry by hand is not that aggressive.

In Mark's book, page II-23  While discussing the crank journals..."the journals seem to be deeply hardened"  Granted this is not the same as saying the crank journals are case hardened or quench hardened.  On page II-25 Mark makes note that the bearing shells being purposefully made soft to embed foreign material.  Given that the oil film in the bearings is on the order of 1-300 microns.  On a hot engine the film will be on the low end of this.  I would not use any aggressive sandpaper on the journals where you run the risk of causing cuts greater than the oil film thickness.  even 600 grit (13-16 micron) wet dry paper will remove material quickly and for each 1/2 thou. you take off the journal you have increased the clearance of the bearing by 1 thou.  If you think about the journal-bearing and the soft bearing vs the harder journal it makes sense to want the journal polished and any oil retaining groves to be in the softer bearing surface.  Hard very smooth surface will not wear into the softer bearing and the soft bearing will not wear the hard journal.

I rebuilt my cylinder heads for my GL1000 and turned the camshaft in my lathe and used crocus cloth to polish the journals and cam lobes.  I carefully measured them before, during and after polishing and I could not detect any removal of material.

-P.

Well, I'd believe that "seems hardened" can mean about anything. The cranks are forged with good steel so I'd expect that the surfaces are hard.   

While 600 grit is 13-16 micron cutting into a hard surface will be about 1/2 that maybe less. 

Again, not trying to remove material but frost the finish.   The main reason is to allow the crank to bed itself in the bearings without sticking.   The bearing material is soft and does conform but may have imperfections. The slight finish helps to keep the bearing from sticking to the shaft at the imperfection.  With this bearing fit can be a little tighter without worry of galling.

Anyway I guess we have different philosophies when it comes to assembly.   I don't have any problem with polishing cams or rockers with 600 grit either. 

[maxheadflow]

BTW, I found where Paris mentions The 0.005" hardness in his book.  Section IV B-5 Crankshaft #4.  Still not sure I'd take that to the bank unless he cross sectioned / polished and etched a few cranks. 

I mentioned the cranks were forged, Paris say die cast. Don't know. The stuff I had was 3rd hand. Still I doubt the cranks were flame or induction hardened. Too expensive for the time IMO.

Won't get in his discussion on oversquare/undersquare and more stoke making more torque theory here..

[HondaMan]

The main reason I suggest mic'ing them to find out their depth is: I just rebuilt a K0 near-sandcast that came to me with 2" of water in the crankcases, sitting 25+ years that way. The bottom sides of the main journals were all rusted, so I took it to my machine shop and asked them to polish it to the minimum size for the journals (per data in my book). Then I installed new Black bearing shells and the final clearance after some hand-spinning of the closed cases on the new bearings came in at 0.0012"-0.0014" across the set. This will make a long-lasting. smooth engine that will require 20w50 oils on days over 40 degrees F, not too far from Honda's OEM spec.

In this process, the crankshaft guy mentioned that the journals were much harder than he expected - and they looked like mirrors, outside of 2 tiny pits on the center one.

[sammon287]

This sounds like a good idea, if I could find someone to do that sort of thing. I don't like the idea of me polishing one spot and making the journal less round. I did already buy the main bearings too. For what it's worth, it is just a low power Hondamatic that won't be stressed much.

I would like to measure the depth of the mark, but the flat spindle/anvil on my micrometer spans the sides of it. I need a pointy spindle.

[kmb69]

.....
On page II-25 Mark makes note that the bearing shells being purposefully made soft to embed foreign material.
.....

Mark is not always correct with his "assumptions".
Crank journal surfaces are hardened, usually only a few thousandths deep, typically nitrided, and bearings are soft to prevent galling NOT to "embed foreign material". Like hardnesses of material will usually gall and unlike hardnesses of material usually will not. There are exceptions to the rule depending on the two materials' chemistry.

BTW, I found where Paris mentions The 0.005" hardness in his book.  Section IV B-5 Crankshaft #4.  Still not sure I'd take that to the bank unless he cross sectioned / polished and etched a few cranks. 

I mentioned the cranks were forged, Paris say die cast. Don't know. The stuff I had was 3rd hand. Still I doubt the cranks were flame or induction hardened. Too expensive for the time IMO.
.....

Sprocket and gear teeth on the cranks are either flame or induction hardened. Not sure which. The cranks are forged, you can usually see the parting lines, maybe from castings, but, for sure from junk material.
See: http://forums.sohc4.net/index.php/topic,171740.msg2078814.html#msg2078814

[maxheadflow]

kmb69,

Thanks for the info.

[754]

 A few things.
 Honda has pretty good grasp on metallurgy. and they build longivety into a lot of their parts.
 they may have put extra effort into the early  750s and once tested may have backed off on say the crank spec.
   I seem to recall you can see the evidence of flame or induction treatment on the sprocket teeth.
  There  is a link in eBay section to stroker cranks from OZ, they claim chrome-moly, they must be new forgings or billet.

  In machinist School we were taught that plain bearings had imbedability, to save the rotating assembly from scoring.

[kmb69]

.....
Honda has pretty good grasp on metallurgy. and they build longivety into a lot of their parts.
.....
In machinist School we were taught that plain bearings had imbedability, to save the rotating assembly from scoring.

Honda did have a good grasp on metallurgy as you said. They specified material equal to their design criteria for a particular application. Their crankshafts would run forever, if the engine was properly serviced, only subjected to it's intended application.

Plain type babbitt bearings do generally have decent embedability properties, but more important is their conformability properties. I'm just saying that if the plain bearings are collecting debris in your Honda engine, you probably have bigger issues to deal with and that embedability is not their primary function.

[HondaMan]

It's also important to note: after the K1 engines, almost none of the cranks I have seen indicate heat-treatment on the sprocket(s) with the color (blue) signatures seen on the early ones. But, beginning in the K2, the crank journals and rod journals are distinctly blue and it is VERY difficult to mark the counterweights with things like a common pencil vibrator etcher. In the early engines I can usually mark those weights with the vibes. I currently have 5 bare cranks in the garage, one from a K0 and the rest from K4-later engines, and this is consistent with this collection, too.