deadedith wrote:Rob - so, even on soft soundboard edges, this would be a safe tool - by 'safe' of course, I mean extremely unlikely to pull a chip out of the top?
Best results are gonna be obtained with:
1. Sharp edge
2. Technique suitable to the application.
1. For most of my edged woodworking tools, I use the "paper test" to check the edge. Clean slice- ready to go. Snag/tear means more work is needed on the edge before taking it to the wood.
Follow their sharpening instructions to the letter, and you should be OK. The tool should come well-ground, but you definitely want to do a honing before first use. I mentioned use of progressively higher grit on the sandpaper, but maybe the recommended 600 followed by a stropping is OK.
Your first few honings should be needed on the back side only. After several honings on that side, you're gonna get a burr on the opposite side that needs removed. That's where it's important to follow the instructions so you don't alter the cut angle (the "grind").
Don't let the sharpening process scare you; it only takes me a minute or so. It's not like a plane blade where you have to set up in a jig, etc.
2. Technique for this would be same considerations for any edged tool- follow the grain.
On a guitar shape, start at widest part of the bout and work to the narrowest part of the waist, then stop and come back in from the other bout.
Once you have the bout-to-waist areas done, cut apex of the bout to the end (stop at centerline).
A technique that would help with the endgrain (besides obvious need for sharp blade) would be a "double pass". You have built-in "fences" on each side of the blade that limit the cut depth; when these are in contact with the wood, they serve as a backer that helps prevent tearout. So a "trick" that may help alleviate any concerns of chipout is to favor the angle on the side of the tool that contacts the soundboard for the initial pass, then come back for a second "straight" pass (45 degree angle to the soundboard). The shavings on that first pass should be very thin and narrow; if you did it correctly the shavings on the second pass will be about equal in size to the first.
By the way, the double pass trick is nothing more than reducing the radius of the cut. If you have the choice of different radiuses,
always start with the smallest radius. For this tool, that would be 1/16". Maybe you'll be happy with 1/16" and leave it at that. But if you want 1/8", do the smaller one first. Immediately starting with the 1/8" means a deeper cut, which means more pressure, which means the increased chance of "boo-boos".
I understand your concern about tearout/chipout. I get the same fear when taking off binding tape.
I haven't used this tool on spruce for this particular application, but I
have used it on balsa templates with complex curves. Balsa is very soft, open-pored, with a somewhat coarse texture. Any dullness at all in the cutting edge will cause it (the balsa) to be "fuzzy", which is a form of the tearout you mention.
I got a couple of scrap pieces of spruce in the shop; tomorrow afternoon I'll cut some curves in 'em and try things out.
Will let you know how it goes.
As a final note, don't let my long**s post scare you into thinking use of this tool is some unattainable master form of woodworking; once you understand how it works it is much quicker (and cleaner) than sanding.
Rob