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Thread: From Rough Carving to Finish Sanding

  1. #1

    Default From Rough Carving to Finish Sanding

    I've built three flattops now and am pretty happy with the result, so I decided it's time to try a carved top. Armed with a couple of nice gouges, a 12mm Ibex arched sole finger plane, and a good scraper, I have the outer side of an A-style plate looking pretty reasonable. Rough carving with sharp tools is a lot of fun, so I didn't feel the need for power tools for that phase, at least for a spruce plate. I'm now carving in the recurve. So my question is, what's the best way to get from here to finish sanding, meaning blending in the various areas to get nice smooth curves and transitions? I tried a sanding disk in the drill press and found it hard to avoid grooves from the edge of the disk. Is it worth investing in a random orbital sander? Sometimes it feels like a large riffler file would be really handy (if there is such a thing), especially compared to my results with the Ibex or scraper going cross-grain. Obviously, hand sanding is an option, but I don't mind turning to a little mechanization if it makes sense.

  2. #2

    Default Re: From Rough Carving to Finish Sanding

    I don’t sand. I use scrapers.

  3. #3

    Default Re: From Rough Carving to Finish Sanding

    Maybe it's just this particular piece of spruce, but scraping cross-grain, such as around the bottom of the recurve, gets pretty ratty. Same with the Ibex even after sharpening through stropping. I can go back and smooth it with the grain I guess. Scraper is a sharp "Ultimate Scraper" from Stewmac. I have a couple of traditional card scrapers, but this is the only contoured one I have.

  4. #4

    Default Re: From Rough Carving to Finish Sanding

    Different areas of the plate require different angles of attack with your tools. You’re learning this. Keep going. I’m unfamiliar with an “ultimate scraper.” I make mine from .4mm spring steel stock or old saw blades. You can get premade shaped sets from places like Metropolitan Music or International Violin. James at Red Valley Mandolins also recently made a custom set that he sells. Try not to get too frustrated with this and remember that tool marks can look quite nice under varnish.

  5. #5

    Default Re: From Rough Carving to Finish Sanding

    If you prefer ‘mechanization’, concave areas can be done smoothly with flap wheels and a portable drill. These items (hardware store sometimes) come in different diameters and grits. Ones that start out cylindrical tend to develop rounded corners with use that might nicely fit the shape.
    As a general suggestion for using sanding disks and avoiding edge grooves, in my other universe, we cut deep notches in the edges of disks just for this, and use undersized backing plates or soft ones. Random orbital sanders, I think, are not that useful in small areas, but help eliminate swirl marks in finer sanding. The orbits are large. Considering that it’s soft wood and not much to remove, scrapers and sanding blocks are probably more than sufficient.

  6. #6
    Registered User sunburst's Avatar
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    Default Re: From Rough Carving to Finish Sanding

    With sharp gouges, finger planes and scrapers you have all the tools you need (along with sandpaper). Now you need practice and experience. As Partick said, you have to learn how to work with the direction of the grain.
    For checking your progress, use side lighting in a darkened area. Roll and turn the plate in the side light. High and low areas will be revealed.

    Edit to say; even though you have all the tools you need, that doesn't mean you won't find other tools very useful and there might be other tools that you prefer. Keep at it and you'll find your own way.

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  8. #7

    Default Re: From Rough Carving to Finish Sanding

    Thanks for the encouragement, guys, and for not calling me Grasshopper. When I first posted this morning, it was after struggling with my first recurve on one edge. I've since pretty well completed that one, which gave me a little more confidence for going after the other side. I was being a little too cautious with my gouge, expecting to scrape or sand away a lot of material to sneak up on the desired contour. This time I got a lot closer with the gouge in terms of carving away almost to the bottom of the contour holes. And of course, it took less than half the time.

  9. #8

    Default Re: From Rough Carving to Finish Sanding

    As usual, Sunburst's wisdom is spot on. Carving compound curved surfaces into something with grain is a learning curve. John's tip of using a strong sidelight is a lifesaver (or wood saver). I also turn off the general lighting and do it in the dark to really see what's going on.

    The "ultimate scraper" referred to is the Carruth scraper and it is an awesome tool and time saver, especially for working in figured maple. It's thick and hollow ground like a skate blade and doesn't need to have it's hook renewed all the time. It shaves figured maple like no tool I've ever tried. The original one has the perfect curve for getting a smooth transitional recurve.

    re: power tools- At my age, my finger joints give me grief if I spend very much time with the Ibex plane, particularly in maple. Being a cabinetmaker as well as a luthier, I already have a lot of power tools including an awesome Bosch RO sander and dust collection. To save my knuckles, I put a 1/2" thick soft foam interface pad on the sander and put an 80 grit disc on it to even out the tool marks, then progress through finer grits. The soft foam conforms to the general curves you've roughed out, knocking down high spots. This is where the sidelighting trick John mentioned becomes important. You can also use your fingers to feel the surface, sometimes they reveal things the eye doesn't see. Barring power tools, you can get the job done with what you have. You'll need a toothed blade for your finger plane to avoid tear out if your doing a figure maple back (then scrape down to the V grooves). To even out tooling marks, I make small (2-3") oval shaped sanding blocks with a cork face glued to them and put sticky-back sandpaper on them. The oval shape helps you to angle them into the recurve area. Welcome to the curvey world of f holes!

  10. #9
    Teacher, luthier
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    Default Re: From Rough Carving to Finish Sanding

    It never hurts to err on the side of caution when you're doing an unfamiliar job.
    As your skills grow, you will get a better sense of when to go easy and when to dig in.
    Lutherie is an unforgiving craft. Sometimes you only have one chance to get a job right. This is especially true if you repair valuable old instruments. Building is more forgiving, because if you mess up a piece of work, you can start over with a new piece of wood.

  11. #10
    Registered User j. condino's Avatar
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    Default Re: From Rough Carving to Finish Sanding

    Remember that you don't have to pay hundreds of dollars for those fancy pre made scrapers, even the big heavy one from Stew Mac. For $3 of scrap steel & an old belt sander you can easily make your own into any shape you desire.

  12. #11
    Adrian Minarovic
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    Default Re: From Rough Carving to Finish Sanding

    Quote Originally Posted by Parker135 View Post
    I'm now carving in the recurve. So my question is, what's the best way to get from here to finish sanding, meaning blending in the various areas to get nice smooth curves and transitions?
    I carve recurve together withthe rest. I just use the gouge from edges towards centeline nicely scooping the recurve. Thumbplane just removes any leftover ridges between gouge strokes and smooths any visible bumps. Well set plane will do this quickly. I made larger "thumbplane" with 1" iron to alow faster material removal but I will likely use it just for insides.
    After thumbplane the plate should be pretty smooth and IMO scraper is equivalent of sandpaper in material removal. I prefer square-edge cabinet scrapers of slightly flexible steel (0.5mm old fretting saw) that will conform to curvature of plate and help smooth any imperfections. By changing angle of blade and using slicing action I can remove material quite fast and also get very smooth finish everywhere. I finish with thin scrapers (0.3mm steel from artist spatulas) that will leave no trace of other tools. Carving top from sawed out shape to this almost finished outside takes 1-1.5 hours including final checking of topography with "pencil gauge".
    Adrian

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  14. #12

    Default Re: From Rough Carving to Finish Sanding

    Adrian, you put me to shame. Maybe if I make a few hundred carved top mandolins I'll get back to you with my time. I've only ever held a carved top mandolin in my hands a couple of times, and I'm working from drawings and photos while I figure this out. I'd love to try making some scrapers as you and others describe but I don't have the right sort of steel remnants around, nor do I feel comfortable right now with the virus, to go on a scrounging mission. Maybe someday.

    I'm intrigued with your "pencil gauge." Care to explain?

  15. #13
    Adrian Minarovic
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    Default Re: From Rough Carving to Finish Sanding

    "Pencil gauge" is my home made thickness caliper with the dial unit removed (pulled out) and pencil inserted (I use some masking tape so the pencil holds well in the hole but not to much so I can set the exact distance to be marked). The pencil has to be a bit blunt not to dig into the wood when you drag it along the surface carefully, marking topo lines.
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    Adrian

  16. #14

    Default Re: From Rough Carving to Finish Sanding

    Got it. Great idea. That reminds me.... I need to make a new gage (much like yours) for carved tops. I made mine for flattops and it doesn't have enough clearance.

    Thanks,

    Parker

  17. #15

    Default Re: From Rough Carving to Finish Sanding

    Quote Originally Posted by HoGo View Post
    I carve recurve together withthe rest. I just use the gouge from edges towards centeline nicely scooping the recurve. Thumbplane just removes any leftover ridges between gouge strokes and smooths any visible bumps. Well set plane will do this quickly. I made larger "thumbplane" with 1" iron to alow faster material removal but I will likely use it just for insides.
    After thumbplane the plate should be pretty smooth and IMO scraper is equivalent of sandpaper in material removal. I prefer square-edge cabinet scrapers of slightly flexible steel (0.5mm old fretting saw) that will conform to curvature of plate and help smooth any imperfections. By changing angle of blade and using slicing action I can remove material quite fast and also get very smooth finish everywhere. I finish with thin scrapers (0.3mm steel from artist spatulas) that will leave no trace of other tools. Carving top from sawed out shape to this almost finished outside takes 1-1.5 hours including final checking of topography with "pencil gauge".
    I love the idea of scrapers flexible enough to conform to the curve! I guess I'm going to have to build another mandolin to try this out. :-)

  18. #16

    Default Re: From Rough Carving to Finish Sanding

    Without an old thin saw blade to shape into a scraper, or some appropriate shim stock, the old everybody’s got a few standby, the used hacksaw blade, is a curve-conformable scraper just about as-is, but the back can be sharpened flat or hooked. The other side is a glue spreader if you attach a handle. Pieces of used bandsaw blades are also useful. Back in the day, when cars were amenable to human tuneups, hacksaw blades were used as point and plug setting gauges if you had nothing better.

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  20. #17
    Registered User sunburst's Avatar
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    Default Re: From Rough Carving to Finish Sanding

    By the way, it seems that you've started carving the top and will be moving on to the back. Assuming the back is a hardwood like maple, it will scrape much differently from the spruce of the top. You'll basically have to ignore what you've learned scraping spruce and learn to scrape hardwood. That's the bad news. Here's the good news. Scraping hardwood much easier than scraping spruce!

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  22. #18
    Adrian Minarovic
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    Default Re: From Rough Carving to Finish Sanding

    Here are few pics of my latest carving sessions... (I hope the pics will show in correct order)
    1. plate cut out and drilled to my topo map (I drill 0.5mm ~ 1/32" shallower than final arching height)
    2. plate carved with gouge everywhere including recurve, (sometimes I'm braver and cut closer to bottoms of the drilled holes, I probably carved a bit more after the pic was taken)
    3. plate with gouge marks smoothed with small thumbplane to stage when bottoms of the holes start to disappear (notice the flattened edge just hair over final height)
    4. few passes of the scraper on one quarter of plate, notice the nice shavings, no dust or torn wood when you are careful
    5. whole plate scraped to smooth surface (after this I use the pencil gauge to find any unevenness, those are usually small enough that few extra passes of scraper will remove them) I'm using elliptic scraper for recurve, sometimes I clean the bottom of recurve with cork sanding block and 100-120 grit paper - in the few parts where scraping may tear some fibers.
    6. scraped plate after grain raising (wet towel and drying)
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    Adrian

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  24. #19

    Default Re: From Rough Carving to Finish Sanding

    Sunburst, John, I'm actually building Graham McDonald's Celt model, which uses a flat back. It seemed appropriate since my interest is in Irish music, plus I thought one carved plate might be a good start. I guess I'll have to jump to a carved back at some point. Either Graham's #4 design or I'll pull out the Gibson A4 plans I have here.

    Adrian, I really appreciate seeing your photos. That looks terrific. How many mandolins have you built now? I'm working with a pretty mediocre piece of spruce from Old Standard, sold as practice wood, but I'm going to continue all the way through to a finished instrument so I'll have the new jigs and such ready for my next one. I'm sure there will be another.

    Time to go rummage through my old hacksaw blades. I never had to resort to one for setting points, nor did I ever use a piece of cigarette paper pulled through the points to set the timing.

  25. #20
    Adrian Minarovic
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    Default Re: From Rough Carving to Finish Sanding

    This is one of my latest batch of tops/backs numbered 20 through 26. I will not build that many mandolins at once but during the corona times I had some extra time and prepared few more plates...
    I've carved about 30 plate sets so far (some for other guys as "kits") but I had some prior experience with hand tools. There's nothing magical, just understanding tools wood and shapes you want to get.

    And, BTW, the spruce you see there is piece from free firewood... Our foresters often leave odd/damaged parts of trees at country roads for firewood if it is not enough to be worth loading onto truck and selling. I found such bunch of cutoffs from half rotten spruce that had 6 or so inches of healthy wood under bark and big hole in center. I cut it to length and split into wedges and got some 30 tops with somewhat wider grain, but nice straight split and good stiffness. I've traveled around the place many times and the rest of the logs just rotted over time.
    Adrian

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