limits of grit size for small belt sander (wood/bit of metal)? - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: May 07, 2019, 03:31:52 am
content: In home depot and lowes if you want to get belts for a belt sander, they typically don't go above 120 grit.I see that you can buy a 220 grit on line, but when I look at major tool manufacturers (i.e. diablo) that are widely used, they tend not to produce anything over 120 grit as far as belts go.As far as random orbital sanders go, they don't really sell anything in the hardware store above 400 grit, but automotive stores carry them to much higher grits and I have seen them used successfully on youtube for car work and metal polishing. No idea about the life time though, especially on bare metal. I assume very short.Still, is it possible to get meaningful use out of a 24 inch belt on a oscillating sander, or a 36 inch on a stationary sander (both with a flat back)?I have seen finer grits used for knife making, but they typically have very long belts. Is it just a question of clogging for a 24/36 inch belt, where past 120 does not make much sense? Are these belts considered low lifetime 'hacks'?https://www.amazon.com/Silicon-Carbide-Extra-Sanding-Assortment/dp/B01FIN7WZEGiven that I need to remove screws to change belts on the 36 inch sander, is buying these just going to be a exercise in frustration?

author: KL27x
author_rank: Super Contributor
timestamp: May 07, 2019, 10:26:13 pm
content: Grit depends on surface area of contact, especially when sanding flat surfaces against a flat platten. As the area of contact increases, you need a larger and more aggressive grit to cut, at all. This is the same for wood, metal, plastic.I use 80 grit on my disc and belt sanders. If I have to do anything finer, then it doesn't usually help that much to use a belt sander, to begin with. If i'm finishing a flat surface, even 80 grit is basically useless when the surface area of wood gets bigger than say 5-8 square inches. On a small belt sander for shaping and finishing small implements, a finer grit might be better. 220 would be plenty fine, IMO.For buffing/polishing/finishing metal, there are better tools that are very inexpensive.

author: coppercone2
author_rank: Super Contributor
timestamp: May 07, 2019, 11:31:05 pm
content: what tool do you recommend for doing something like polishing the edge of a small bracket?For metal most projects I use flap wheels of the appropriate size but they are pretty aggressive if you want to end up with a smooth surface... and I don't really see them go above 150 grit or so either (but thats fine for prime paint job and welding).Using a flat wheel on a hand tool I feel like I am going to be left with either a scale-clogged wheel or some seriously wavy texture if I use coarse grits first.Are you just thinking sand to like belt sander max and then use some aggressive compounds on a buffing wheel (i.e. sisal with emery ?). I never tried to skip all the steps and go right to compounds. In fact my sisal wheel has never been used,since it looks like some kind of medieval construct.Is it just two different ways to skin a cat, where if you can tolerate the the rouge getting everywhere or working outside, you go to the buffing wheel with a more aggressive cutting compound sooner, rather then slaving away trying to work with fine grit sand papers to work with a less aggressive cutting compound?are there grit/compound combination steps that work well to get rid of finer sand papers which seem to have a very finite life span?For instance with aluminum right now I actually go down to 2000 grit with sand paper and then use something like mothers aluminum polish. For steel I don't bother right now past whatever I can find as a flap wheel for a angle grinder but I want to get into stainless steel work.. since I paint steel its easier to use a gap-filling primer and sand that. I think the exception would be cutting blade edges. But I am more interested in fabrication. For me it kind of makes sense to leave stainless steel un painted since its cosmetically pretty, so the high polish would be nice.Can the process I use for aluminum be simplified some how? my results are high quality but the labor required is extreme and I feel like I am jumping through hoops. The tool I currently use is this:https://www.amazon.com/Makita-BO4556-Amp-Finishing-Sander/dp/B00134477O, cutting squares from hardware store paper sheets.

author: macboy
author_rank: Super Contributor
timestamp: May 08, 2019, 05:27:29 pm
content: I have a series of belts down to 6 micron (~2000 to 3000 grit) for my 1x36" belt sander. I use them for honing of blades, or just putting a near mirror finish on old tools when I'm bored. I got my belts from Lee Valley Tools. This is a Canadian company, but they do mail order worldwide. One thing I can say about Lee Valley Tools is that they don't sell junk. Everything they carry is top notch. Polar opposite to Hazard Fraught Tools, or Princess Auto in Canada.

author: KL27x
author_rank: Super Contributor
timestamp: May 08, 2019, 08:31:16 pm
content: QuoteNot necessarily. After getting the geometry you want with the belt sander, you can hand sand. Taking care near crisp edges, you can apply pressure with your fingers or a soft pad or whatnot, using a finer sandpaper. This will get things shiny faster than trying to "lap" down the entire face/facet on a power machine with a flat platten with successively finer grits. I keep up to 2000 grit sandpaper, and I even use it on occasion. But not with power tools. At that high a grit, I think the only power tool I'd want to use is some sort of buffer with a soft pad. Or a lapping wheel, if you're making optics and mirrors.Or if you're talking super tiny tools and inside corners... files, dremels, sanding blocks and machinist stones.That said, yeah, buffing wheels and hand buffing with leather and compound will get you super shiny.QuoteI dunno. I just use stones for that, mostly. Probably use the belt sander for the hatchet, simply because it has deep chips and dings from gravel or whatnot by the time I sharpen it. Or maybe for repairing a chisel after trying unsuccessfully to pull a nail with it. Heck, last time I repaired a chisel, I just clamped it to the bench and took the angle grinder to it to get it in some sort of shape. Then finish the bevel and edge with stones. Took under 5 minutes. And it still looks and works and cuts exactly like a Lee Valley store bought chisel with a razor edge.I shave with a straight razor. I use hand planes. I never needed a belt sander to sharpen anything, except for a set of very hard stainless steel kitchen knives with a really thick 90 degree edge bevel. And that was with an 80 grit belt. I dunno if I'd call that sharpening. The knives were essentially not finished.

author: coppercone2
author_rank: Super Contributor
timestamp: May 08, 2019, 10:53:16 pm
content: Quote from: macboy on May 08, 2019, 05:27:29 pmHow much life do you get from such a belt? I know its very subjective, but say you are making a new knife. How many inches of blade can you get one of one of these belts?

author: coppercone2
author_rank: Super Contributor
timestamp: May 08, 2019, 10:56:20 pm
content: the finishing sander I use kinda has a rubbery bottom but I don't know how well it 'confroms'.The paper attaches with a spring wire tensioning bar. I thought maybe I can lay some thing soft (like a used 3000 grit sanding 'pad') under neath to increase its ability to conform to irregular surfaces while it vibrates. That thing just buzzes, there is no rotation etc.I am worried the backing of the sand paper will be too thick and prevent good conforming.. I thought to weaken it with another sand paper with flat lapping then to rubber cement it onto a reusable pad to make a sanding pillow, to take the hand work out of it. The 3000 grit pads they sell in the store for hand sanding seem like a good soft substrate for other sand papers. And It could be soaked in water if the tool was low voltage to lubricate the cut a bit. I thought that emery or other super-sharp sand paper could be good for weakening paper backing on finer paper if the idea has merit.

author: KL27x
author_rank: Super Contributor
timestamp: May 08, 2019, 11:06:42 pm
content: ^Why super high/fine grit using a sanding machine... Why not polishing compound with an orbital buffer?You have a surface area problem trying to use a sander to polish things.The belt sander with the 6 micron grit? That will polish a tiny edge bevel. Or slightly convex surface. Or small facets of small things. (And you can run the small facet across the belt side to side, to use the whole surface).A large flat area of super fine abrasive grit is otherwise not very useful on that kind of a finish sander you posted, unless you are lapping a large area with a paste. Silicon carbide sandpaper creates a little bit of lapping paste, due to how it breaks down, and this is why you usually wet sand or use oil when using fine sandpaper. This is one of the reasons you can only buy fine grit sandpaper in silicon carbide. But even with a soft backing pad, you will quickly find a limit with the area being that large. Buffing wheels and compound will probably be more economical and efficient in the long run, for finishing/polishing larger areas.In general: shaping/flattening and finishing/polishing are two distinct ends of a spectrum. Other than lapping mirrors/optics, you generally transition from one to the other for the highest efficiency. A belt sander higher than 220 grit is a waste of time and money for most people.

author: L_Euler
author_rank: Regular Contributor
timestamp: May 13, 2019, 02:32:10 pm
content: Delete.

author: coppercone2
author_rank: Super Contributor
timestamp: May 13, 2019, 10:13:52 pm
content: how do you feel about scotch brite belts?https://www.3m.com/3M/en_US/company-us/all-3m-products/~/All-3M-Products/Abrasives/Industrial-Abrasives-Finishing/Abrasive-Belts/Scotch-Brite/?N=5002385+8710644+8710812+8710949+8711017+8711730+3294857497&rt=r3They seem to get rid of the flatness criterion so its a polishing tool but, is this going to wear out in 3 seconds?I only ever used that kinda stuff to like, clean a bath tub or something once a year on a polishing tool, but the non abrasive kind.https://www.amazon.com/dp/B01NA6HBZN/ref=biss_dp_t_asnThe nylon grit brushes for the dremel I like and they seem to do very nice work.Those belts have a grit specification, but like, for best results, what what kinda grit do you need with sanding to get to a grit on a belt? Do you just do a direct transition or do you need to over-sand grit wise then switch to a belt? Or are you only getting flatness?I mean, is there a hidden spec to think about, kinda like with leaf blowers you see CFM ratings all the time, but really you need to consider velocity and in the end force (newton meters) to get real results (then you see a battery leaf blower might be 500 cfm but it ends up having like only 25% of the force a gasoline one has). Do I need to know something other then grit?I am thinking of something like momentum transfer ? do you just call that an arbitrary 'aggressiveness' scale? impulse? etc, if so, how do you correct to minimize operation time per process?I feel like it would have a thermal signature. But I don't know because those scotch brite pads are airy so they will air cool themselves quickly so you can't really monitor belt heat

author: coppercone2
author_rank: Super Contributor
timestamp: May 13, 2019, 10:32:04 pm
content: Quote from: KL27x on May 08, 2019, 11:06:42 pmYes I typically do it to wood, and I do it wet. It seems to work.I don't know when to switch processes to get reasonable work times so I just do it by the book with every single grit till the friction on fresh test paper seems uniform on a surface, then I switch to finer papers and then compounds.I figured with different types of woods and stains and everything, it might be too many tests to run to figure out what is the maximum sand paper size to use before I get a mirror finish I like from compounding/polishing in a reasonable amount of time.I kinda figure this, maquires '/ultra cut' compound ranked 12 on their scale says it sands out up to 1200 grit scratches, and it goes from 12-1, and i got ultimate compound, which is a 8, so I figure just ball parking it that it will take out scratches from something like 2000 grit? But then I sand up to 2000 grit and the 3000 grit sand paper is right there so I figure I might as well.How many steps am I liable to save?I mean how do you figure you just start compounding it from 400 grit? just takes longer with the same finish? I do it infrequently enough that running the experiments would take longer then doing it (and I often try to re-use junk wood etc so it comes out hodge podge but nicely polished).

author: coppercone2
author_rank: Super Contributor
timestamp: May 13, 2019, 10:42:44 pm
content: Can you measure power consumption of the sander and compare it to mass loss of the test piece (after cleaning) on a high end scale (not sure how much material this removes but I got a big ass metler) to quantify aggressiveness and belt ware?then compare to optical reflection to get an idea of how well its conforming vs how aggressive it is? reflectometer at different incidence angles?

author: KL27x
author_rank: Super Contributor
timestamp: May 14, 2019, 12:27:07 am
content: QuoteIf you get a mirror finish on wood, then you're the expert. Looking forward to your book.Lots of wood workers will suggest or say something like 220 is the finest grit you will ever need. Or even 120. And with a random orbit sander on big, flat surfaces that might be pretty much right. You only need to go finer on weird or small shapes, by hand, when you are applying pressure over a smaller area. And there's only so far you need to go. No clue what you are doing using buffing compounds and polish on wood or why you would finish wood that fine in the first place.