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Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine> How to PROPERLY polish crankshaft journals yourself?
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Thread: How to PROPERLY polish crankshaft journals yourself? Reply to Thread
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Topic Review (Newest First)
02-27-2014 03:53 AM
markhansenconquest
polishing with ruby stone or arkanasaw stone

I have a turbo crank that is nitrited coated ..I want to polish ..moldmakers use ruby stones,and arkanasaw stone to polish ? thanks for all replys
05-31-2010 06:46 AM
barnym17 The recomendation from the chevy power manual is 400 grit emory cloth, lubed with a little kerosene and shoe string.They say to wrap the emory around the crank, tape then use the string to turn the cloth as described above.This is the factory recomendation so it should work.
05-30-2010 06:22 PM
crystalbluevib I dont know about the leather belt, where is the abrasive? leather belt im thinking is too wide???? Plus how would you get it to turn?? I dont know.
05-30-2010 04:54 PM
383SBC Wow thanks for all the suggestions guys....... I guess I should have explained the situation and reason for doing this in my original post. The crankshaft only has about 1000 kilometers on it (pistons detonated) and all journals look fine I was just wanting to remove the "stain" left on them from the bearings. I will be mic'ing each journal to verify the measurements but with that little usage and visual appeal being good I am assuming I won't find anything out of the ordinary. I just wanted to "shine them up" before I rebuild this engine, I wasn't hoping on removing much (if any) material. I know at work when we rebuild transmissions and reuse certain components such as main shafts and turbine shafts, all we do to polish them is soak them in WD40 and take scotch brite pads and wrap and rub . The surfaces turn out looking like they're chrome plated but I am not so sure if this is a good idea on a crankshaft. I did read somewhere that an old leather belt works wonders to just do a basic polish which is all I really need, would you recommend trying that first?

Thanks,
Keith
05-30-2010 11:39 AM
matt167
Quote:
Originally Posted by Irelands child
Matt - unless you are 'experienced' my suggestion is - don't. The engine builder (Prattsville??) will use some 400, a bit of kerosene and strop the stone marks - but has done it probably for many years and has the 'touch'. Lawn mower, other small, low load for its' size, engine, not a problem!!!
engine builder is actually in Grand Gorge a few miles away.. my small town doesn't have much of anything except a grocery store, lawn mower/ ATV shop and 2 auto repair shops.... but the builder in Grand Gorge does most all of the dirt track motors, as there is quite a few racers in the area, and a chassis shop in the paint shop of the now closed down Chrysler dealer

I'v done it the above way on a few cranks.. with the emery cloth wrapped around the journal and pull the string.. just until the crank is nice and shiny and smooth. and this is after I mic them to make sure the cranks are within spec for roundness as per the manuals.
05-30-2010 11:04 AM
crystalbluevib
Quote:
Originally Posted by cobalt327
The "proper" way of polishing the crank is done by spinning the crank and using a polishing belt to polish it in the same direction of rotation as the engine runs.



I've "polished" cranks to remove slight surface rust by hand using solvent wetted emory paper wrapped around the journals and spun w/a lace double-wrapped around the paper. This isn't meant to be a replacement for proper machining of the crank if it's needed.
Hmm, i wonder if the op owns one.
05-30-2010 10:58 AM
cobalt327 The "proper" way of polishing the crank is done by spinning the crank and using a polishing belt to polish it in the same direction of rotation as the engine runs.



I've "polished" cranks to remove slight surface rust by hand using solvent wetted emory paper wrapped around the journals and spun w/a lace double-wrapped around the paper. This isn't meant to be a replacement for proper machining of the crank if it's needed.
05-30-2010 09:42 AM
crystalbluevib
Quote:
Originally Posted by Irelands child
There is always a bit of oil discoloration between the two journal bearings. You can knock that off with crocus cloth and a lubricant which doesn't remove any metal. If the journal has a spun bearing there is more then just discoloration - like transferred babbit and gouges. Been there too many times.

Matt - unless you are 'experienced' my suggestion is - don't. The engine builder (Prattsville??) will use some 400, a bit of kerosene and strop the stone marks - but has done it probably for many years and has the 'touch'. Lawn mower, other small, low load for its' size, engine, not a problem!!!
There is a line you can see between between the two yes, thats not what i would refer too as discoloration
05-30-2010 09:10 AM
Irelands child
Quote:
Originally Posted by crystalbluevib
If you have discoloration , then you have a problem, spun bearing perhaps??? No then you need machine work. Im talking about just polishing up here, with a decent crankshaft. There is no such thing getting it too smooth. Yes you have to be ( carefull )
There is always a bit of oil discoloration between the two journal bearings. You can knock that off with crocus cloth and a lubricant which doesn't remove any metal. If the journal has a spun bearing there is more then just discoloration - like transferred babbit and gouges. Been there too many times.

Matt - unless you are 'experienced' my suggestion is - don't. The engine builder (Prattsville??) will use some 400, a bit of kerosene and strop the stone marks - but has done it probably for many years and has the 'touch'. Lawn mower, other small, low load for its' size, engine, not a problem!!!
05-30-2010 08:40 AM
crystalbluevib
Quote:
Originally Posted by Irelands child
I think that I wouldn't do that by hand unless all you want to do is possibly take the discoloration off the journal. You can buy rolls of different grit cloth, but the fact that you have to have a strop that totally goes around the journal at least once and a bit more, and the two ends passing will make for a sanding band that's very narrow, i.e. less then half of the width of the journal and will tend to dig an edge in the surface and possibly do some damage. Depending on what the journal looks like (a minor scratch that you can't "feel" with a fingernail) you might just be best off leaving it. If you can run that fingernail across and "feel" it, then it should be left for the grinder. We used to do 220/400 grit stropping on gas turbines and generators, but we had an 8 up to 20 inch diameter shaft to work with and a fair bit of allowed clearance.

Here's where you can buy rolls of paper if you are determined to do that job:http://www.mcmaster.com/#sandpaper-rolls/=7ba0w9
If you have discoloration , then you have a problem, spun bearing perhaps??? No then you need machine work. Im talking about just polishing up here, with a decent crankshaft. There is no such thing getting it too smooth. Yes you have to be ( carefull )
05-30-2010 08:39 AM
matt167 even my local engine builder polishes crank journals that don't need turned by hand.. and the above procedure is also how I was tought
05-30-2010 06:00 AM
Irelands child I think that I wouldn't do that by hand unless all you want to do is possibly take the discoloration off the journal. You can buy rolls of different grit cloth, but the fact that you have to have a strop that totally goes around the journal at least once and a bit more, and the two ends passing will make for a sanding band that's very narrow, i.e. less then half of the width of the journal and will tend to dig an edge in the surface and possibly do some damage. Depending on what the journal looks like (a minor scratch that you can't "feel" with a fingernail) you might just be best off leaving it. If you can run that fingernail across and "feel" it, then it should be left for the grinder. We used to do 220/400 grit stropping on gas turbines and generators, but we had an 8 up to 20 inch diameter shaft to work with and a fair bit of allowed clearance.

Here's where you can buy rolls of paper if you are determined to do that job:http://www.mcmaster.com/#sandpaper-rolls/=7ba0w9
05-29-2010 10:17 PM
crystalbluevib personal prefference i guess.
05-29-2010 10:08 PM
327NUT Havn't needed to do this procedure in a long time but when I did I used thinner, kerosene, even diesel on the wet/dry sand paper. Need to keep it wet just like block sanding a body panel. The grit you start with depends on the condition of the crank, but if it's real bad then just get it 10-10'd at the machine shop.
05-29-2010 08:46 PM
crystalbluevib I forgot to mention you have to cut a v like in the ends of the 2x8 stock for the crank to sit in . Its jUST HARD TO EXPLAIN. I could draw a picture if you need it , i gave my stand away, but they are easy to make.
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