Wikipedia:Reference desk/Archives/Science/2018 January 1

= January 1 =

sanding/filing/grinding stainless steel
I have some stainless steel parts with burbs and burn marks on them that I want to clean up. Googling around I found three ways of accomplishing this easily at home without any heavy power tools:

1. Sand with sandpaper

2. File with a file

3. Grind it with a grinding attachment on a dremel

Cost wise all three are about the same (I have a dremel already, just no grinding tools). Which of these three methods is the least time consuming? Which produces the best results? Mũeller (talk) 03:15, 1 January 2018 (UTC)
 * For an professional a file is the fastest because there is not need for any tool preparation. The result depend on your skills in every case, especially with a file, which needs allot of practice for best results. For an amateur i would recommend sand paper and i would not, no matter what tool, expect "best results". In case of some "hidden skills" the result may end up being ok ofcourse. --Kharon (talk) 05:33, 1 January 2018 (UTC)


 * Once you have the equipment, a dremel will almost certainly provide the quickest execution. However, it is also the most prone to accidentally removing more material than you intended.  It takes a fair amount of skill to handle a dremel with precision.  A small metal file is likely to be the most precise approach.  Professionals can use a file in a manner that is both fast and precise; however, I generally find that even amateurs can do a decent job with a file if they take it slow.   I'm not a fan of using sandpaper for removing large imperfections on metal (e.g. burrs), though very fine sandpaper may be appropriate for cleaning / polishing.  Dragons flight (talk) 08:45, 1 January 2018 (UTC)


 * Agreed. In particular, it seems that cleaning up the holes with a dremel would lead to unwanted beveling unless great care was taken. Matt Deres (talk) 16:52, 1 January 2018 (UTC)


 * I do a lot of this. I would usually polish it with a Garryflex block - a rubber block impregnated with abrasive powder. Several grades are produced, colour coded, and they're produced worldwide under several different brands. As usual, start coarse and work through to fine.
 * If it's too discoloured or damaged to start with these hand tools, smooth it first by machine, using a foam-backed flap disc on an angle grinder. Use a foam-supported one, to avoid making more machine facets.
 * If you have the equipment, and especially for many small parts that are mostly corners, then the best way could be to grit blast it.
 * Stainless steel should be passivated after finishing, to avoid it self-passivating naturally and possibly discolouring in blotches. This can be done by wiping it with citric acid, or even just lemon juice. Andy Dingley (talk) 20:51, 1 January 2018 (UTC)
 * The best and most used method was not mentioned: Sandblasting! The results are usually superior and you dont have to worry about overdoing or doing it wrong. Its like painting with airbrush, actually a very satisfying, fun task to do. And economical and fast aswell.
 * In case you count yourself proud member of the Do it yourself-club and do all sorts of work, you may even want to check out how easy it is to build your own little sandblasing cabinet. There are many videos on youtube unter "sandblasting DIY". --Kharon (talk) 12:59, 2 January 2018 (UTC)
 * Of course it was already mentioned.
 * Don't use sand for this though, use an abrasive grit, manufactured for the task - probably a silicon carbide grit, maybe glass beads, depending on the grade of stainless, the dirt to be removed and the amount of edge rounding that's acceptable.  Sand has very few appropriate uses left for literal sand blasting, as it's not the best medium to work with and it also has safety hazards (the dust hazard from sand blasting is far worse than grit blasting). Andy Dingley (talk) 13:07, 2 January 2018 (UTC)
 * Oh sorry, i oversaw you mentioned "grid blast". Regarding the hazards was why i mentioned building a cabinet for that. Most professional shops have one and if build and handled right it is very save work. --Kharon (talk) 13:22, 2 January 2018 (UTC)
 * Most grit blasting cabinets can't be used for sand (if you're bothering to follow the appropriate regs). The exhaust air needs filtering too. You can't allow sand-shard-laden air into a workshop. Andy Dingley (talk) 20:36, 2 January 2018 (UTC)
 * Some even use glass perls and good cabinets have a circular system where the abrasive is reused. A vacuum cleaner needs a filter too. Never heard that kept anyone from using one in a workshop. --Kharon (talk) 04:37, 3 January 2018 (UTC)
 * They all need an air outlet (if they don't, or it's not enough, the door can fly open and whack you in the face!).  If the interior air is full of silica shards, that air outlet needs to be filtered.
 * Sand isn't re-used. It's cheap and it wears out too quickly.  One of the few things sand is still used for is when it can't be captured and recycled like this.
 * If you're cleaning up some hazardous powder materials, like silica dust or asbestos, your vacuum cleaner filters need to be maintained, with change schedules and records keeping, as much as your breathing gear does. Andy Dingley (talk) 11:36, 3 January 2018 (UTC)

What is this, the Wikipedia advice column? It depends on the type of SS, the size and depth of the defects, etc., and usually involves more than one type of polishing material. Why are you asking this here??? Why is answering this part of an encyclopedia? --2600:387:6:80D:0:0:0:C1 (talk) 07:42, 8 January 2018 (UTC)

Split rocks on Theodore Roosevelt Island
I am wondering if anyone might shed light on these three rocks that were photographed on Theodore Roosevelt Island? Is this splitting possibly the result of a natural process? If so, please describe ... Many thanks in advance -- P999 (talk) 18:29, 1 January 2018 (UTC)


 * By definition it is the result of a natural process. ;) The question is which.  What I know is that the description given of gneiss and schist doesn't obviously match with the basalt of the most dramatic formation with this appearance I can think of, which is Giant's Causeway.  On the other hand, they are metamorphic rocks, which raises a bit of a question of how metamorphic and metamorphed from what ... I wish I could say more, but I certainly don't know presently. Wnt (talk) 19:03, 1 January 2018 (UTC) Sorry, I realize the dramatic top photo on that site probably is just a bannerhead and not about this location at all.  Though List of places with columnar jointed volcanics does list a site in Virginia not too far from the Potamac. Wnt (talk) 19:11, 1 January 2018 (UTC)


 * Such "erratic" rocks were certainly carried by glaciers. Ruslik_ Zero 19:08, 1 January 2018 (UTC)


 * I regret that I was unable to provide a link directly to the photograph of the split rocks in question, but the website where it resides, being a blog, does not seem to allow individual links to the images; however, I have tried to improve the description of the rocks to which I am referring in my query. Thank you very much for your responses, Users Wnt and Ruslik. These rocks are of particular interest to me because they are either on, or a short distance from, the eastern limit of the Atlantic Fall Line which passes through the southern tip of TR Island ... P999 (talk) 20:11, 1 January 2018 (UTC)


 * You mean this link to these rocks? --76.69.117.217 (talk) 20:54, 1 January 2018 (UTC)


 * Yes, thank you very much! I will change my query to include it.


 * Yes, it's likely a glacial erratic, but that doesn't explain the breakage. My guess would be frost weathering; if you check out the photo in that article, the broken rock there is quite similar to the one in question. Matt Deres (talk) 02:38, 2 January 2018 (UTC)


 * I find it very hard to believe that it is a glacial erratic. The last glacial maximum did not reach as far south as the Roosevelt Island . (Great Falls is a few miles upstream) — Preceding unsigned comment added by Addisnog (talk • contribs) 04:34, 2 January 2018 (UTC)


 * Much more likely to be a boulder carried down by the river, but I agree about the frost shattering as the likely explanation for the splitting. Mikenorton (talk) 11:11, 2 January 2018 (UTC)


 * It may not be the last maximum. Ruslik_ Zero 13:24, 2 January 2018 (UTC)
 * Fixed your confusing typo. --76.69.117.217 (talk) 21:26, 2 January 2018 (UTC)
 * For a simple explanation of the process, see Frost Wedging.  Alansplodge (talk) 11:43, 2 January 2018 (UTC)