80 grit scratches

[Dave Fritz]

I believe it was Robo Hippy in his video on sanding that said 80 grit scratches can be as difficult to remove as tool marks. That sure rings true for me, especially on the inside of a bowl just below the rim.

Any tips other than patience?

 

[Roger Chandler]

Try wet sanding with the next grit up, then follow with the rest of the grits. Some cheaper abrasives have inconsistent grit matrix particles, which can cause issues one should not have to deal with, as the large particles gouge into the wood deeper than the rest of the particles. I find wet sanding properly will 99% of the time give me a wonderful finish.

 

[Doug Freeman]

Use methods to get a better tool finish so you can start at a higher grit. Obviously getting better with a gouge, but shear scraping on the OD (gouge and/or scraper) and neg rake scrapers on the ID replace low grit paper for me. I can start with 150 to 320 grit depending on the situation. For flatwork, using hand planes on all visible surfaces allows me to do a pass with 220 or 320 and be done. Turning scraping does the same.

Never tried wet sanding for pesky surfaces - have to give that a try.

 

[Mark Jundanian]

A couple of lessons I've learned.

Follow the 80 grit with 100 rather than jumping all the way to 120. Be thorough with the 100, but keep a light touch letting the sandpaper do the work. Proceed through 120, 150 and 180 cleaning off the swarf between grits and changing paper when it's worn. Wipe down with MS and have a close look.

I don't spin the lathe very fast as speed encourages me to press harder, and if I sand manually I can use the 80 grit just on the spots that need it.

(At these coarse grits there is little difference between the CAMI and FEPA standards, but above 180-220 the difference becomes very important).

 

[Randy Anderson]

Realized early on that not all sandpaper or sanding mesh is created equal. You didn't mention what type of sanding material you're using, spin sander, flat paper folded, mesh, lathe spinning, etc. I try to avoid holding flat paper to the work and sanding while spinning the lathe. I also usually start at 120, depending on my tool work that day, and will spend a little more time at 120 vs dropping back to 80 just to avoid deeper scratches that I then have to deal with.

 

[Mark Jundanian]

Dremel makes non-woven abrassive pad accessories that can sometimes be used to work problem areas, especially with a flex shaft tool. Since it is a spinning tool you can get away with using a higher grit than you would with hand sanding, so 180 non-woven might take out some 80 grit scratches.

And like Randy said, sometimes you can start out sanding at a higher grit. You can always go coarser if that doesn't work out.

 

[robo hippy]

I prefer a shear scrape, both inside and outside the bowl for my finish cuts. To shear cut near the rim, this has to be done before the rest of the bowl is hollowed out, at least on bowls over about 10 inch diameter. The walls will flex with even the very lightest tool and hand pressure. This pretty much leaves about the best surface possible prior to sanding. I almost never have to resort to 80 grit any more. In the cases where I do, like Mark said, I go from 80 to 100, to 120, to 150, to 180, and up to 400. The main reason behind this progression is that it is easier to remove the grit scratches from 2 grits back if I take this progression.

One other thing, I always use oversized discs, as in bigger than the sanding interface pad. If they are both the same size, even if the disc is perfectly centered on the pad, the edge of the pad will leave 80 grit scratches.

I have heard many say to blow out the bowl after each grit. This is supposed to remove any grit particles from the previous grit. Well, I might have tried that once or twice, but it blows dust every where, even at low air pressure. So, I took to wiping down the surfaces with my hands. I never once felt any grit remaining.

I did experiment with the Abranet type abrasives. I found that the lower grits, up to about 180 or 220, would not cut as well as the standard abrasives. Guess it is because of all the open space. Above 220, there is pretty much no difference in how they cut.

Never liked wet sanding. The sludge would fill holes that I wouldn't see till I applied finish. If there is a lot of tear out, getting the wood very lightly wet, and then taking very light passes with a freshly sharpened gouge can remove most of the heavy tear out.

robo hippy

 

[Al Chavez]

If there is a lot of tear out, getting the wood very lightly wet, and then taking very light passes with a freshly sharpened gouge can remove most of the heavy tear out.

Thanks for the great advice!
Both the wetting of the wood and also the shear cutting on the rim before the rest of the bowl is hollowed out.
Al

 

[Dean Center]

Having been exactly where you are now, I can share some lessons learned.

First, my difficult 80 grit scratches were mostly caused by me pressing too hard. The paper would get hot, so I started power sanding, but I still ended up pressing too hard. Except I wouldn't know it as my fingers were not on the paper. I still struggle with it, but I'm working to keep light pressure and getting better results.

Second, under the rim is a difficult area, especially if you make an undercut rim. Recognizing this, I now am more careful when cutting that area, trying to remember that 'downhill is 2 different directions for undercut rims. Applying some back pressure on this area when cutting, scraping or sanding seems to help. A negative rake scraper is my current best solution for the problem area, but I still often have to spend extra time on it.

Last, based on comments from forum members, I now 'spot' sand that pair of tear out prone areas adjacent to the end grain by hand with the lathe off. I thought this would leave an 'uneven' feel, but wilth a little care to blend the areas in, this comes out fine, and really helps.

 

[Bill Blasic]

Let the sanding medium do the work, light pressure. The old adage is use the sandpaper as if someone else is paying for it.

 

[hockenbery]

I believe it was Robo Hippy in his video on sanding that said 80 grit scratches can be as difficult to remove as tool marks. That sure rings true for me, especially on the inside of a bowl just below the rim.

Any tips other than patience?

Patience

But work o getting a better tool Finnish.
Top inside Is a difficult area- light cuts sharp tool .

I have adopted a jimmy Clewes trick, use a 1/4” bowl gouge 3/8 bar diameter
I use a Michelson grind. Jimmy uses a traditional grind.
Get the first 1 inch and a bit more

 

[Dave Fritz]

Thank you for all the information. I am using the blue flex back disks in the 2 inch size on a 8 inch bowl. I've tried both a power sander and an inertia sander. I'm transitioning into being a seated turner due to hips and knees that are arthritic.
The truth is I think I've got the first one inch done the way I want it only to find a slight bump so I come back with a NR scraper which generally makes things much worse. I really like an undercut rim and find I sometimes dig in a little to deeply before transitioning out again. It's definitely something I'm trying to improve upon. I will be switching to the radius pad on both 2 inch and 3 inch blue flex disks. Light pressure it is. Hard to do, when learning to drive my dad used to call me old lead foot. Turing and learning - thanks again.

 

[Doug Freeman]

I have heard many say to blow out the bowl after each grit. This is supposed to remove any grit particles from the previous grit. Well, I might have tried that once or twice, but it blows dust every where, even at low air pressure. So, I took to wiping down the surfaces with my hands. I never once felt any grit remaining.

Try a microfiber towel. After wiping out the dust, hold it to your DC inlet and let it flap. One towel lasts a long time. As others mentioned, I do a lot of spot sanding with the drill, turning the piece by hand. Much faster than bringing the entire surface down and not noticeable in the finished piece if the area is feathered in. Also much less area to remove low grit scratches when it is needed. “Cool sanding” is a term I have pilfered from David Ellsworth - keep lathe, pressure, and drill speeds low , keeping paper cooler and letting it work.

 

[Aaron Harris]

Good advice all around, especially for us newer turners. As I work to develop my skills with the bowl gouge and getting better finishes through shear-scraping, I still find myself relying on the old "80-grit gouge" too often for final shaping, evening out curves, etc. I usually start out hand-sanding, and yeah, I probably press too hard sometimes. I then switch to power-sanding with 2" disks on a drill, as most of my bowls are between about 5-10" inches. Then 100/120/180/240/320 and on up to 400 or 600 depending on the wood and finish desired.

My trouble spot is usually in that pesky transition zone around the bottom, where a strong raking light sometimes reveals scratches left by the lower grits-"Damn, go back!" I suspect that part of it is the edges of the paper and disks leaving scratches as much as it is the grit themselves. Just recently, I have switched to the wave-edge disks in 80 and 100 grits, which is helping. I'm hoping that as I get more skilled with my tools, maybe I can start at higher grits as suggested, and use a lighter touch. Of course, some softer woods are just easier to scratch up (cedar, for instance!).

 

[robo hippy]

That transition area is as difficult to turn and get clean and smooth as the bottom of the bowl is. Some times it is easier to cut out high and low spots than it is to sand them out. Your hands and fingers are really good gauges for figuring out where the problem spots are. My favorite way to remove these trouble spots is with a shear scrape, and I do have one video dedicated to just that. A properly shaped and sharp NRS (negative rake scraper) works great on some woods, and not on others. Other than that, "10,000 more times!" Yes, that is what I said the last time.....

robo hippy

 

[Dave Fritz]

Lessons learned: slow down and let the sander do the work, I cut down some abranet 6 inch disks so they fit on my metabo random orbital sander with some overhang on the pad, spot treat bad spots and don't skip grits, wipe down between each grit and inspect carefully, and lastly, spend more time and don't be in a hurry. I think working from a seated position has helped me also. When your body aches it's hard to be patient. Thanks again for all the comments.

 

[Randy Heinemann]

I wouldn't disagree that a smooth finish right off the gouge or whatever you use on the bowl inside is desirable. However, for those of us, like me, who are still getting there, not skipping grits and making sure that the dust from the previous grit is removed as completely as possible contribute to removing coarser grit scratches. For example, if you start with 80 grit, thorough wiping of the 80 grit dust and then going just to 100 grit next, then 120, etc. is the best way I've found to get a smooth finish when I haven't been able to get one with my gouge. Even skipping the 100 grit and moving to 120 from 80 can make it more difficult to get rid of the 80 grit marks. I also agree that power sanding with a variable speed drill, electric or air, makes the job easier. Over the past year I have acquired the Sanding Solution passive sander. This works great with a soft, flexible pad, but it's still hard to get rid of tearout on the inside; not so hard on the outside.

 

[Charles Cadenhead]

I'll just add since I don't see it mentioned, change out your paper sooner rather than later. It's easy for the paper to get bogged down.

 

[robo hippy]

If you have 'ripples' on your bowl walls, they do cause a lot of extra time if you try to remove them by sanding them out. If you don't have the gouge skills to remove them, then this is where you use the NRS or a shear scrape. Much easier, especially at the beginner level, to remove those ripples, and more efficient than trying to sand them out.

robo hippy

 

[Kevin Jenness]

One thing to try is addressing problem areas locally with the bowl stationary using shaped card (cabinet) scrapers. Oftentimes the issue is tearout where side grain changes to endgrain, and sanding with the bowl rotating removes side grain material faster leading to out-of-roundness. Careful scraping (or even paring with a carving gouge in extreme cases) and feathering the contours can sometimes fix a problem faster than coarse sandpaper. This is a nice thick scraper I like StewMac scraper but it's easy to modify a standard card scraper with a hacksaw and grinder.

As Robo said, wetting the wood before the final cut can help get a cleaner result. This trick can be useful in flat work when planing figured wood.

I do most of my sanding with power sanders with the lathe off, rotating the piece slowly by hand. I find it easier to see what is happening and to concentrate on the areas that need it. Someday my tool control will be perfect and no sanding will be required at all. In the meantime...