The Shop => Finishing => Topic started by: kwackers on March 10, 2012, 09:01:07 AM

Title: Cast iron - how well does it polish?
Post by: kwackers on March 10, 2012, 09:01:07 AM
I'm just finishing some cast iron parts for an engine and as always am trying to get a shine on some of them.
But no matter how much I try though the finish always looks a bit 'grainy'...

Now tbh I'd expect that but some of the pics you see on the interweb show what looks like much more highly polished parts than I can obtain.
So, is this a trick of the light/side effect of the photography or is there a method to get a shine on cast iron that doesn't look slightly grainy?
Title: Re: Cast iron - how well does it polish?
Post by: philf on March 10, 2012, 09:31:57 AM

It's simple. Just ask Rob Wilson if you can borrow his camera!


Title: Re: Cast iron - how well does it polish?
Post by: mzt on June 14, 2012, 06:30:47 AM

much depends on the quality of the C.I. You're using.
The conn rod cap I used for an Elmer's cylinder was of the highest quality, it came out so mirror like I will never manage to take a picture doing justice of it.
Here's the best my camera could gain, maybe it will earn autofocusing skills in time: still, with a bit of effort, You can see the cloth texture on the valve face.



If that's enough, I got that result by putting a sheet of sandpaper (the finest grade I had) on a flat plate (plastic ikea cutting board) and slid the face on it till I
removed all the tool marks. Next, I put another sheet of the same grain, which I had already worn out while polishing aluminium. The 'final touch' came using
printer paper as a support for Dremel polishing compound (anything of that kind would do, I suppose) mixed with thin oil.
It was some time spent into useless elbow work, as both the mirror-like faces won't be visible on the finished engine. The rounded parts could be made so on the lathe,
by wrapping the sandpaper (and then the 'polishing' paper) on a lathe tool blank, but I don't think I ever bothered with them.

Removing that black powder deeply embedded into nails and skin will take days, however frequently You wash Your hands.