Harden the camshaft and crankshaft.

[peterl95124]

Silver steel seems to be pretty good at hardening without excessive distortion in smaller diameters, as you would use for D-bits. That's what I'm making my camshaft from. You harden by heating it cherry red then quenching in water or oil, then temper it at around 200 degrees Celsius.

I plan to do the finish machining using CBN tooling on the lathe and mill, followed by polishing. We shall see how that goes on my pathetically small and non rigid mill, but on the lathe I've even been able to turn down HSS tool bits using CBN.

when I mentioned CBN I meant as a grinding wheel abrasive, yes you can turn hardened steel and I've even done it with carbide, but crankshafts and camshafts are generally too flexible to cut reliably as the deflection you'll get with the force required to make a cut will result in a very out-of-round and non-concentric set of journals. so the best way to finish a crankshaft or camshaft after hardening is with grinding, and since I've had bad results with alumina (doesn't wear evenly, and the parts I was making were too small to allow me to traverse the grinding wheel back and forth during grinding), and diamond isn't compatible with steel (as I understand it, could be wrong, someone enlighten me), so CBN seems like the next alternative to try.

 

[Nerd1000]

when I mentioned CBN I meant as a grinding wheel abrasive, yes you can turn hardened steel and I've even done it with carbide, but crankshafts and camshafts are generally too flexible to cut reliably as the deflection you'll get with the force required to make a cut will result in a very out-of-round and non-concentric set of journals. so the best way to finish a crankshaft or camshaft after hardening is with grinding, and since I've had bad results with alumina (doesn't wear evenly, and the parts I was making were too small to allow me to traverse the grinding wheel back and forth during grinding), and diamond isn't compatible with steel (as I understand it, could be wrong, someone enlighten me), so CBN seems like the next alternative to try.

Plunge grinding with alumina wheels is pretty common practice in industrial work I think. Maybe your issue is related to dressing of the wheel or speeds/feeds? Dress the wheel square before doing the last little bit of the journal?

 

[minh-thanh]

Hi Everybody !
Thanks for the comments.

Just an idea
A / The crankshaft will be fixed on the jig and hold it during hardening
B / The crankshaft is fixed in the jig and all of them will be rotated during hardening

Your opinion?
Thanks !

 

[D and D]

D and D: I understand that for (example) cam lobes, Chrome plating can suffer fatigue problems (short lifetime) as the hard plating on a relatively soft under-material, flexes as the material beneath suffers compression loadings and distorts, so the chrome suffers early life failures due to fatigue (over-flexure cycling). Big words, but simply not good for cams other than on racing engines with short lives anyway. Case-hardened steel or iron is better for long-life engines. But I am just a dumb engineer from car engine manufacturer, not the expert who decided the rules... or made things work! So "Well done" if you succeded with chrome plated cams!
K2

Yes I agree, I case harden cams, but for the crank I think it is worth a look.

 

[Steamchick]

Thanks D & D. I don't know about the chemistry of chrome plating. I doubt I'll ever need to know, but do you have some suggestions? (We all benefit from your knowledge and experience).
My only experience of "Chrome" is on Motorcycles, where it is decorative, heat and corrosion resistant, and (especially on sliding front forks) a durable bearing surface. But this is the first I have heard of Chome plated crankshafts. - Sounds good?
Thanks,
K2

 

[Steamchick]

Peter, Nerd, Both of your grinding commentrs are interesting. I worked (55 years ago?) in a machine shop doing crank re-grinds, and other refurbishment of engines and compressors. The crank grinding machine - typicall for journals of 1 1/4" wide to 4 or 5 times that had what I remember to be a 1" wide carborundum stone. very fine grit - but I could only guess at 600 - or something? The stone was redressed maybe every hour or 2? (The diamond dresser was a permanent fixture as part of the machine). The stone ran quite fast and was about 18" diameter, so the cutting speedwas correct for the grit. The whole job was flooded with oil coolant. The "plunge" to add some cut was made in the middle of a journal, then progressed left and right and back to the middle, to ensure the journal ws "true" from the sideways transition of the stone. But the dressing was necesarily "true" so any area of the journal not fully transtioned (the ends) would not be measurably tapered or otherwise out of true.
So for the "amateur" hobby machinist, I would suggest a "narrow" stone and side-to-side transition where possible, as the dressing may not be as true as the transitioning. - Just depends on how you do it.
I like your simple comment about "the pressure of cutting tools distorting shafts" so grinding is better from that aspect.
I must make a grinding attachment for my lathe now! - Where's that Dremel?
K2

 

[Nerd1000]

Thanks D & D. I don't know about the chemistry of chrome plating. I doubt I'll ever need to know, but do you have some suggestions? (We all benefit from your knowledge and experience).
My only experience of "Chrome" is on Motorcycles, where it is decorative, heat and corrosion resistant, and (especially on sliding front forks) a durable bearing surface. But this is the first I have heard of Chome plated crankshafts. - Sounds good?
Thanks,
K2

There are actually two kinds of chrome plating. One is decorative chrome, the other is industrial 'hard' chrome. The latter is what you see on hydraulic cylinder rods etc. I think the main difference is that hard chrome is thicker and bonds more strongly to the substrate.

The chemistry to make hard chrome is nasty. I don't know the details, but I do know that there is lots of hexavalent chromium involved. That stuff is extremely carcinogenic.

 

[Steamchick]

That 's worth knowing. I have had cancer in my prostate, I don't need to risk anything else.
I'll leave that to a proper company that can handle stuff safely.
K2