Got my rotating assy back from the balance shop last week.
Opened up the box and found my brand new crank rusted.
Mainly on one end. One of the rod journals was almost completely covered. (counterweight was too, but no bigie)
Probably should have taken it back to the shop and bitched, but I was in a rush to assemble the eng, so it hit it with some emery cloth.( All I had was some 180 grit that was smoothed out a little already from previous use.)
I got the rust off and assembled the bottom end.
Told a friend about it at work today, and now he's got me paranoid I may have messed it up using the rough emery cloth.
I didn't use much pressure with it.
I looked really smooth and I didn't see or feel any scratches, but now I'm worried abt it.
Guess I'll be tearing it back down,, AGAIN!

What grit emery cloth should I be using for this? 2000 grit or so??

 

One of my manuals says use 400, you could probably re polish it, better get a second opinion on that tho'

 

180 grit is like gravel.

I use 400 to size the crank, and then 600 and then 1500 or 2000 to polish it. I wrap a strip of it around the crank, lube it with ATF or thin motor oil, wrap an old fan belt around it, and go to it.

I doubt you did it any harm, but the motor will br a little more efficient and the bearings may last a little longer with the crank as smooth as possible.

 

Yeah and on my crank i used news paper because i wanted it to be blue printed.

 

Don't quit your day job just yet.

 

If you finish with crocus cloth or flint paper, the surface finish will have less granularity since the abrasive is a lot softer than aluminum oxide. If you examine the surface under a microscope, you'll see what I mean.

Then again, far be it from me to tell a guy how to polish his own crank. That may be more than we need to know...

 

damn 180, you might was well used a grinder. i use 1000, 1500, and or crocus. i chuck mine in a lathe to hold it and make it easier to turn.

 

Yeah, I know the 180 was way too rough, but it was a pretty worn-out piece. Actually the front of the emery cloth was abt as smooth as the backside.
Never-the-less, It will be coming back out tomorrow. It's been a 6 month project. What's another 6 hours?

I like the fan belt idea.

I have a pocket size 30X illuminated microscope. I'll compare a unmolested journal to the suspect one tomorrow.
Not sure if 30X will do it or not.
We'll see. (pun intended).

Should I worry abt increasing the rod bearing clearance an appreciable amount using 1500-2000 grit and the fan belt?
It's currently on the snug side at .0016-.0019".

OUCH!!

 

No, it would take hours of vigorous labor with 1500 to take a whole .001" off.

I usually bolt the crank to something where it is out in the open; I have an engine stand with some holes drilled in it that are just perfect. Cut the belt, wrap it 2 turns around the sandpaper.

 

I just picked up some 0000 Steelwool and some 1000, 1500, and 2000 grit wet/dry sandpaper.

My #1 main journal has a scratch I can hang up my fingernail on (in the right direction). The other journals have light scratches from the inexperienced mic job I did on them.

I'm not worried about anything except #1 because I can feel it. Would home polishing it with the 2000 (and ATF) probably be sufficient to take care of this?