Surface corrosion on crank

[ursus]

Re: Surface corrosion

Why is it called "Crocus" cloth? Are there little crocuses embedded in the paper or something? How about "Emery" paper? Named after some guy in Michigan at the turn of the century?

(How many here know for example grease Zerks are actually named after the inventor, Oscar Ulysses Zerk? It's true.)

Thus concludes today's installment of interesting, but probably useless information.

Oh, but there's more:
ROCUS CLOTH: A very slightly abrasive cloth which contains the mineral ‘crocoite,’ lead chromate, PbCrO4. The mineral was named in French in 1838 by Berthier crocoise, from Greek krokoeis, saffron-colored, from krokos, saffron (crocus is another name for saffron, an orange-red condiment consisting of the dried orange-colored stigmas of Crocus sativus and used to color and flavor food); altered by Dana in 1844 to crocoisite, and in 1868 to crocoite (American Heritage Dictionary, Random House Unabridged Dictionary, Oxford English Dictionary)

 

[nkaminar]

Brent, you may be right that there will be some out of round if you measure it close enough. Next time I am in your shop I will bring some crocus cloth and we can do a test. Like you say, there is no substitute for facts.

 

[Crankster]

Re: Surface corrosion

Oh, but there's more:
CROCUS CLOTH: A very slightly abrasive cloth which contains the mineral ‘crocoite,’ lead chromate, PbCrO4. The mineral was named in French in 1838 by Berthier crocoise, from Greek krokoeis ...

Yes! Your google-foo skills far exceed mine, I couldn't find anything. Or did you use an actual meatspace disctionary? Thank You!

 

[ursus]

Re: Surface corrosion

Yes! Your google-foo skills far exceed mine, I couldn't find anything. Or did you use an actual meatspace disctionary? Thank You!

Google WordWizard - lots of obscure stuff there. Also:

CROCUS: 1) A dark red powdered variety of natural iron oxide [[ferric oxide]], Fe2O3, used as an abrasive for polishing (American Heritage Dictionary). 2) The name is applied to the peroxide of iron obtained [[artificially]] by calcination of sulphate of iron, and used as a polishing powder. (Oxford English Dictionary)

A friend that restores antiques told me that 2000 grit emery cloth (carborundum) cuts metal and is actually more abrasive than crocus cloth having same 2000 grit. Crocus cloth polishes and leave a smoother surface. And, as another poster has mentioned, you should use WD-40 when polishing a crankshaft with it; water will cause the crocus to wash off in a gooey paste.

 

[Pete]

Using an Arnold gauge measures all the way around and all the way across a journal. It will measure to "zero". It tells size, out of round and taper.
Any use of free hand abrasive material no matter how fine is NOT recommended by most people that grind cranks.
Normal polishing after grinding is done with a rigid mounted belt and no more
than .00005 is taken off.

On the other hand, for a back yard salvage job, a piece of 400 wet or dry will do fine.