Camshaft scoring?

[Tekime]

I did my valve cover gasket last week and noticed that both camshafts have scoring - not on the lobes but on the shaft, and it looks machined.

Is this machined for balancing or is there a problem somewhere? I've seen this on other camshafts from the FJ1200 but I don't really know what's going on so it's kind of alarming!

[fj1289]

That looks normal to me.  Maybe it's done to smooth a seam to prevent cracking or breaking?  I don't know - but I wouldn't worry about it!

[Tekime]

That would make sense, my initial thought was for balancing but your explanation makes a lot of sense! Actually, my initial initial thought was "holy *&#$!" haha 

[racerrad8]

I did my valve cover gasket last week and noticed that both camshafts have scoring - not on the lobes but on the shaft, and it looks machined.

If you are referring to the grinding marks between the lobes, that is just the removal of the casting slag. Here are two brand new cams in the box ready to ship out.

Randy - RPM

[Tekime]

I did my valve cover gasket last week and noticed that both camshafts have scoring - not on the lobes but on the shaft, and it looks machined.

If you are referring to the grinding marks between the lobes, that is just the removal of the casting slag. Here are two brand new cams in the box ready to ship out.

Randy - RPM

Genius. Exactly that - thank you!

[Charlie-brm]

Hi Tekime. I was just browsing the depths of the forum and saw this thread.
I inspect camshafts for a living as they come off the line - about 700+ per 12 hour shift. I didn't say it was exciting but it pays for FJ tires.

As already mentioned and I can confirm, nothing to worry about with those marks in the rough casting area. The only thing that we pull them for in the unfinished casting area is porosity that is too large in diameter or too deep. Think of air bubbles in the molten metal when it's cast and they make it to the surface or get revealed when the mill and lathe start cutting away to shape the shiny bits.

If I bought a camshaft across the counter, I'd be inspecting it visually for abscesses over a certain size or in a critical location. I would also look for chipped off bits or tiny hair like burrs of metal, usually left at the edges of lobes or in machined notches or drilled holes. If I saw concentric lines around the journals instead of an even surface almost like chromed parts, or a change in colour or brightness/dullness, it would tip me off to run a pencil lead across them and if I could feel hesitations or the pencil lead catching, I'd ask to see another part and suggest the dealer put the other one aside.

The rest of this post is a backgrounder on the manufacturing process.

When a camshaft gets to the end of the line, the surfaces and drilled holes have been machined to spec'd dimensions +/- 0.02 mm (typical), put through grinders to bring those tolerances even finer and more consistent around the diameter and across the surface (i.e. concentricity, cylindricity, roundness). I did that job for about a month. Then they move on and get deburred by large brushes, then  polished with 15 micron (0.015 mm) abrasive tape which is about the same grit size as P600 to P800 Wet/Dry paper. All of those things are done in a wet wash environment. Then they get a final wash and dip in an anti-oxidant fluid. They are engraved with a date/time and now on some lines we now etch on a QR code.

We inspect for tiny pinholes, crack lines, tooling roughness or errors and other deficiencies that got by the people up line from me, with specs from each manufacturer on what's a pass or fail. Another line inspects my work once more (double inspection) unless the first inspector is "certified" for that specific camshaft line. I'm not certified (insert joke here).
All the stations down the line are constantly micrometer gauging samples with hand held and bench gauges, doing full gauging of every machined surface entered in a report at least every two hours,  sending parts to Quality Control for tests too fine to perform on the line such as surface roughness and lobe and sensor angles.
Really sometimes I'm amazed at the diligence. And at the vehicle manufacturer's plant the parts get the third degree all over again and randoms are run in test engines at RPMs my cars will never see and for 100 hours then torn down to inspect each part.