It's been a while siince I have done this. Please correct me if I am wrong.

I picked up a set of micrometers last week. Crankshaft is out and I decided to see where it was as far as previous machining....

Here is a main journal measurement and all 5 are the same:



I read 2.748", yes?

And for the rod journals:



Again, all 4 journals are the same size measured in three places across the face of the journal. The diameter is 2.438".....?

I need to do this more often. It's been too long!!

 

On the first one you're correct, the second looks more like 2.4385 or 6, this is where a micrometer that reads to 0.0001" comes in handy.

 

You get what you pay for with micrometers. I have a set made in China that are not accurate at all. And an old Starret set that works great. When you start looking at tenth's of mils, a cheap set isn't worth a damn. Remember that when you are reading them. Just because it has the digits, doesn't mean it is accurate to all those digits. Get a good set of tools. They may not be cheap.

 

I don't have a 2"-3" Vernier Micrometer accurate to 0.0001" though I would love one and I know they aren't cheap... I'm not building anything, but I want to verify that this crankshaft has not been machined before. This mic is plenty accurate for the task as no one would have ground less than 0.001" from this crankshaft. The best that could be said of the journal reading then can't include a guess at .0005 or .0006". I have to count the 13 on th thimble as the most precise measurement obtainable with this tool, correct?

And rest assured if an opportunity arises to pick up a more accurate 2"-3" tool I will get it. And none of my measuring tools are chinese made... I just wanted verification I was remembering how to read this tool correcctly.