●DIY pen holder

Take one piston (in this case a Honda B18 piston, 81mm). Wash off all the crusty deposits off and you should end up with something like this:

Get some sand paper and start smoothing off the rough cast surfaces and markings. Polish with an aluminium polishing paste and you should end up with something like this:

You really need a Dremel to get into the hard to reach places but I think the result is ok considering it was all done by hand. Anyway it's a very nice pen holder:

...or if you want to see your hard work you can always just use it as a paper weight or something nice to look at