killemall8 Posted October 15, 2014 Report Share Posted October 15, 2014 I have always wonder how people use these for sanding guitars. Even the big companies use them from what i have seen. How the heck do you get them to sand flat? i have used one for over 8 years now and no matter which one i use, it will round over any corner or hole that you go over. Even if you run it perfectly flat across the top, if it runs over a hole or rout, it will dramatically round it deeper on the edges where it touches. How do you avoid that? Quote Link to comment Share on other sites More sharing options...
ScottR Posted October 16, 2014 Report Share Posted October 16, 2014 I dunno. I have one too, but always end up sanding by hand. SR Quote Link to comment Share on other sites More sharing options...
curtisa Posted October 16, 2014 Report Share Posted October 16, 2014 Same here. Have one, rarely use it over hand sanding. Only things I can think of are: Too much pressure being applied Favouring one side of the tool Base of the sander is flexible, or the sanding pad has a bit of give in it, and conforms to the edges of the workpiece slightly as it passes over. Grit is too aggressive for the task The problem I experience more with the ROS is when it leaves behind little "swirlies" in the wood, which then have to be hand sanded again to get out. For the extra time I have to spend trying to get rid of these little squiggles I usually find it easier to just hand sand from scratch. Quote Link to comment Share on other sites More sharing options...
sdshirtman Posted October 16, 2014 Report Share Posted October 16, 2014 When I was younger I worked for a company that did custom finishes on kitchen cabinets. We would get mirror like finishes using dual action/random orbital sanders. They used these custom made hard DA pads made from plexiglass with a thin layer of rubber between the pad and the paper. We were using the pneumatic type DA's with the nice speed adjustment levers on them. These hard disks would chatter like hell until you dialed in the sweet spot on the speed. Once you found that ideal speed they worked incredibly well and gave you a super flat and even base to paint over and get a mirror like finish. I dont know how some of these guitar companies get a decent flat finish with the ones with soft pads. I sand all the flat parts of my guitars by hand with a flat 3M block. Quote Link to comment Share on other sites More sharing options...
Ripthorn Posted October 16, 2014 Report Share Posted October 16, 2014 Using a different backer makes a world of difference. Also, the big name guys are using high end pneumatic sanders that allow for much slower orbital speeds than the little electric ones we buy at the hardware store. The closest thing to a pneumatic that isn't one is the MIrka Ceros, which I would love to have, but at close to $500, I will pass. Also, as with all tools, it comes downt to practice and dedication to perfect the technique. The guys at PRS that do it all day every day for years get to know the device so well that they can account for any kind of characteristic that we see as a problem. Much like the guys who use relatively low tech tools to produce works of art. You just learn how to use the tool with all of its flaws and soon you can compensate for them. For the guys like us that don't build that much, it can be much easier and more effective to just go at it by hand. Quote Link to comment Share on other sites More sharing options...
killemall8 Posted October 16, 2014 Author Report Share Posted October 16, 2014 The main reason i ask is because after hand sanding 80+ guitars, i am really, REALLY getting tired of having to sand out 80 grit sandpaper scratches by hand. 80 is the only thing that knocks the sides flat and gets rid of mini tearout. but after that it takes so dang long to get those out of endgrain and sidegrain. Quote Link to comment Share on other sites More sharing options...
DC Ross Posted October 16, 2014 Report Share Posted October 16, 2014 (edited) Never had a board that was so rough that it needed 80 grit that didn't go through the jointer and thickness sander first. I usually only use random orbit sanders on flat surfaces with 220 and up. Most of the downward pressure needed comes from the weight of the machine, don't press down on it much at all -- that's a sure-fire way to get rounded edges. As for the sides, maybe it's time to change that router bit if 80 grit is needed Edited October 16, 2014 by DC Ross Quote Link to comment Share on other sites More sharing options...
guitar2005 Posted October 16, 2014 Report Share Posted October 16, 2014 I use my thickness sander and finish with sandpaper wrapped around a piece of MDF with laminate on the sandpaper side. For the sides, I've never had to go to 80grit. 180 max but I take thin passes on the router and try to use a sharp bit. Quote Link to comment Share on other sites More sharing options...
killemall8 Posted October 16, 2014 Author Report Share Posted October 16, 2014 Well, most of you guys dont make extreme shaped guitars as i do. With pointy guitars, there is a lot more runout on the edges of Vs and explorers due to the angle of their points. Even with a brand new router bit and going slow you still get tearout on some areas. Quote Link to comment Share on other sites More sharing options...
guitar2005 Posted October 17, 2014 Report Share Posted October 17, 2014 Well, most of you guys dont make extreme shaped guitars as i do. With pointy guitars, there is a lot more runout on the edges of Vs and explorers due to the angle of their points. Even with a brand new router bit and going slow you still get tearout on some areas. I should show you my "off the router" V bodies. I have two right now and they both have minimal sanding/cleanup to do. Quote Link to comment Share on other sites More sharing options...
Juntunen Guitars Posted November 14, 2014 Report Share Posted November 14, 2014 Try to route with the grain instead of into it. If you keep going in one direction with the router it will always tear out. Fine Woo Working has a video on what I'm talking about but I can't post links anymore for some reason and if I try the forum freezes the link adding thing onto my screen... Google how to route end grain and the video title is "How to avoid router tearout" it's on the Fine Wood Working website. Quote Link to comment Share on other sites More sharing options...
Prostheta Posted November 20, 2014 Report Share Posted November 20, 2014 I've been using a variety of random orbital sanders the last three years and there is a BIG difference in quality across the board. Festool and Mirka sanders (CEROS and ETS 150) are right at the top for many reasons, but they cost a lot so you should expect them to be. I prefer the Mirka anyway because of the lower stance. The biggest mistakes I've seen people making with ROS is dwelling in one location for too long and using the wrong pressure or grip. In general the tool's weight and your hand restricting it from running off is all the pressure that is required. Pressing down is asking for bad results. I plan my sanding so that it starts at one end and move consistently to the other side before sweeping down a little and moving back across. Space Invaders style. As for the rounded edges, just don't go over the edge and you should be fine. Router bits....never go cheap and if you do, buy lots of them and dispose sooner. The bits are usually cheaper than the wood they could junk when worn so why go for the false economy? I use Luna Tools' router bits at the moment since I am stuck with Metric collets. They seem reasonable and not too expensive to junk and replace, but stay working well if not left together in a box clinking together.... Quote Link to comment Share on other sites More sharing options...
mistermikev Posted April 30, 2021 Report Share Posted April 30, 2021 necrobump (that's what the kids call it right?)... lamenting right now that I can't have a da sander. my compressor isn't big enough. when I was 17/18/19 I worked as a sander at a cab shop. they pretty much only used dynabrade air sanders. I used one to remove the finish on my sg90 (neck break) and it was the greatest thing ever. never had issues sanding flat or sanding the profiles using that sander. idk if the dyna brade is just better, or if they use a better pad... but it was the absolute perfect tool for sanding detail work, and it could remove material in a heartbeat with a heavier grit - just an absolute pleasure to sand a guitar with (and I hate sanding). with that in mind... my electric sander is "ok". just a black and decker - bought it because it was low profile and thought that would be the closest to a da sander. I know they make electric da sanders that are like $300... but if I was gonna go that route I'd just buy a 80gal air tank and a da sander. the decker just isn't good at sanding profiles. on a da sander... the little edge that sticks out is flexible... making it ideal. I want something like that in an electric sander. Is it a unicorn? hopeless? what sander do you use, do you like it, and why? Quote Link to comment Share on other sites More sharing options...
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