Sanding Q: angle drill style vs. ROS style Results

[Clay Fails]

I have been using a Milwaukee angle drill with 2 inch pads. Seems to work fine for me. I've been wondering if the pneumatic random orbit style sanders do a better job of removing sanding marks on the piece? Is there an observable difference? I'd consider getting an air unit if i knew the results would be significantly better.

[robert baccus]

Try the HF air sanders-straight or angled. Great for inside bowls, leveling epoxy repairs and many others chores. They are very cheap and last forever. Also called die grinders.

[Faust M. Ruggiero]

Clay, Since no one seems to want to tackle this question I will tell you my opinion. I use both systems on literally every bowl I make. I have a CP 2"-3" pneumatic ROS as well as several angle sanders and a straight drill I use in deep bowls. I always do my course grits through 180 with the drills. They remove wood faster. I believe the main reason we find scratches late in the finishing process is because we do not remove all the scratches from the prior grit before advancing to the next grit. Sometimes they are too difficult to see since all the scratches follow the same circumference around the bowl. Now by introducing the ROS with the bowl not spinning, the scratch pattern is different and any left going around the bowl will become apparent. I usually use the ROS beginning with 220. I sand till all previous scratches are removed then go back to the drill for the next grit. Alternating scratch patterns helps assure me that scratches from the previous grit are gone before advancing to the next grit. I usually do my very last grit with the ROS or by hand following the grain.
The down side of an pneumatic ROS is the volume of compressed air and henceforth the compressor size needed. It is an added expense.

[Bob Bergstrom]

I'm as guilty as anyone at using a heavey hand when sanding. I feel it is more me, than the sander I'm using that causes left over scratches. I try to lighten up on the pressure at the last passes of each grit. There are certain area on bowls that sand paper will dig into the wood to maximum depth of the grit ( like at the apex of the exterior curve of the bowl). Those with a gentle touch have more success with finish cuts and sanding.

[John K Jordan]

I have been using a Milwaukee angle drill with 2 inch pads. Seems to work fine for me. I've been wondering if the pneumatic random orbit style sanders do a better job of removing sanding marks on the piece? Is there an observable difference? I'd consider getting an air unit if i knew the results would be significantly better.

Clay,

I go a different route for bowls and platters. I remove the tool marks with small hand scrapers, both with the lathe running and with it stopped. This lets me start sanding with finer grits. I seldom use grits coarser than 220 or 180, sometimes much finer. This avoids much of the clouds of dust from power sanding on the lathe. I do much of my sanding by hand with the grain, with the lathe turned off. This completely eliminates the circular scratches I see in a lot of poor work. It also avoids dished areas of unevenness common from heavy sanding with coarse disks - you know, the kind you only see from reflected light when the piece is off the lathe and a shiny finish is applied.

Since I got a Grex pneumatic ROS that will take 1" to 3" disks, I haven't used the angle drill. The ROS is small and lighter in weight and much more controllable. It can be much gentler than the angle drill. They have extension that can get deep inside a turning.

I know some people just hog out a bowl without much regard for fine tool control and fix everything with the 80 grit gouge. More power to them, this is a hobby. For me the ROS is a great asset for the way I like to turn. It does take a significant air compressor.

grex_ROS.jpg

BTW, the Grex was recommended by turner Rudy Lopes, a demonstrator at the TAW last year.

JKJ

[Reed Gray]

Yea, the main reason for scratches is not getting all of them out before stepping up to the next grit. I have found that 80 grit scratches are some times more difficult to remove than tool marks. Good light, good glasses, and patience. I do use 3 inch discs on just about every thing because they have more than twice the surface area of 2 inch discs. I sand at slow drill and lathe speeds because at slower speeds, you get better traction so the abrasives cut better. The alternating scratch patterns really helps too, so for one grit sand with the top or one side of the disc, and the next with the bottom or other side of the disc, so one scratch pattern is (, and the next is ). The ROS is better for finish grits, 220 and up, and slower for the coarser grits, but I don't use one, just the angle drills.

robo hippy

[Clay Fails]

Thanks for the input guys. I may try John's idea of using a scraper; that sounds interesting. The need for a large compressor has been holding me back on the pneumatic ROS route. My pancake does everything else i need in the shop, and buying a big compressor just for sanding is hard to swallow.

[Reed Gray]

I have a 60 gallon Campbell compressor, and my Sioux pneumatic angle drill would keep it running non stop. I prefer electric, but still can't find one that I can't wear out. I need one more similar to the Milwaukee Hole Hog (bearings mostly), but same weight as the standard angle drill..... I would think that a screw gun would have the bearings to handle being used as a grinder instead of a drill, but it would need to be hard wired rather than rely on a battery pack...

robo hippy

[John K Jordan]

Thanks for the input guys. I may try John's idea of using a scraper; that sounds interesting.

These are some of the scrapers I use. I've been using these on bowls and platters since the third bowl I ever made, close to 15 years ago. I cut the curved end off a bigger scraper and liked the way it worked I eventually added more scrapers.

scrapers_.jpg scraper_PB054025_s.jpg

I recently found some thicker scrapers made from higher quality steel, sold to guitar and violin makers by Stewart Macdonald. They have worked very well in a test but I haven't used them on a turning yet.
http://www.stewmac.com/Luthier_Tools...e_Scraper.html

JKJ

[John K Jordan]

...I have found that 80 grit scratches are some times more difficult to remove than tool marks.

Have you ever heard about sub-surface deformation? I learned to deal with that when polishing metals for examination with a microscope in a metalography lab. The grit particle causes damage even below the bottom of the groove it cuts - you grind away the scratch completely with finer grits then find the scratch reappears in polishing. I've always wondered if a similar thing happens with wood, fibers below the bottom of the scratch compressed or deformed with the huge 80 grit particles only to magically reappear near the end of the finishing.

One thing I always do: when sanding in one direction with any grit I sand (by hand) perpendicular to those scratches with the same grit before moving to the next. Kind of like the alternating pattern you mention except I alternate with the same grit before moving on. I figure if I can't remove the 220 scratches with 220 paper I'll have a real hard time getting rid of them with 320 paper. This way the dreaded circular scratches from a coarser grit are never hiding in the circular scratches of a finer grit.

JKJ

[Dave Bunge]

I recently found some thicker scrapers made from higher quality steel, sold to guitar and violin makers by Stewart Macdonald. They have worked very well in a test but I haven't used them on a turning yet.
http://www.stewmac.com/Luthier_Tools...e_Scraper.html

JKJ

John, those 1/8" thick scrapers look very interesting. I'd be curious to hear what you think after using them on bowl interiors.

Are you veering into the world of making musical instruments? I skimmed their Luthier Tools catalog and it looks like a pretty powerful and deep vortex.

Dave

[John K Jordan]

Are you veering into the world of making musical instruments? I skimmed their Luthier Tools catalog and it looks like a pretty powerful and deep vortex.

No, I'm interested, but as my son responded years ago as we were in a music store and I pointed out a small guitar, "I don't think I have an opening." (He was learning piano and cello at the time!)

I do have intentions of building a bowed psaltrey or two: this guy has great instructions (and I bought the book): http://www.apsimplepsaltery.com/

I have a lute kit I might put together, to, and maybe another native american flute/spirit whistle or two.

I did use the scrapers on some curved edges of some "flattish" turnings recently and they took off nice shavings. And Ken Rizza told me he got some of them; didn't get to talk to him about how they work. Ken may have been the one who told me about them in the first place, I don't remember.

JKJ

[robert baccus]

One good about the very high speed die grinders turn is that even 80 grit does at scratch at that speed. Also it leaves no scratches like a phono record has due to not repeating linear grooves like hand sanding with the lathe turning. I never sand finer than 220 while power sanding with the lathe going and my finishes sell well.

[John King]

I have a CP 2"-3" pneumatic ROS as well as several angle sanders and a straight drill I use in deep bowls.

CP = ? - John

[Bob Bouis]

Chicago Pneumatic, I assume.

I would recommend 3" discs first and foremost, for 99% of bowls. You might even go bigger.

Second, ROS sanders often don't work well on concave surfaces like the inside of a bowl. The pressure it takes to make the pad conform to the surface will cause the clutch on the sander to skip the orbits. At least the ones I've tried.

The best way to sand bowls is to inspect the whole piece with the lathe off and spot sand out (again, with the lathe off) any remaining defects before moving up to the next grit. Yes, it can leave slight divots in the surface, but so do scrapers...