|04-14-2016 10:51 PM|
|knobi1||Random +1 Reb CrystalBlueVib Stumbled across a video then this explanation. Genius! Not for reviving a busted pice of metal but actually laying a finish on the old one. I'm doing this too my 1993 Subaru Justy tomorrow morning and I really needed to see this explanation, rawhide seems better than a shoe string initially.|
|02-27-2014 03:53 AM|
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|
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?
|05-30-2010 11:39 AM|
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|
|05-30-2010 10:58 AM|
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|
|05-30-2010 09:10 AM|
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|
|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|
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.|
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