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jmrentis

Cavity Cover Conflict

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Hey guys,

Today I finished taking off some thickness from my Zebrawood body blank using a router thickness jig. Basically, I needed to take 3/8" off in order to keep it at 1 3/4" once the top is glued on. Routing went decent, no problems and only just a little sanding or scraping left.

Anyhow, I figured that I would leave an area untouched around where the cavity cover will go and route the thickness off the rest. So, now I've finished routing and have this area the size of a (big) cavity cover which is 3/8" tall left on the blank that I want to cut off. Once cut, I can level it out and have a perfectly matching cavity cover, which will be cool with zebrawood.

So, my question is what should I cut it with to keep maximum thickness on the cover and not gouge further into the body (though this is of little worry)? I have a japanese saw, but its a medium fine and actually seems more like a rough cut( I think its a cross-cut blade) and wouldn't work well on this. I like japanese saws for this type of cut because I can bend it flat against the body to get a closer cut. So, would that be my best bet, like go buy a very fine cut or are there better ideas, like a coping saw or something else ?

I just wanted some input on what you guys think would work best. Right now the raised section is at 3/8". After just recently reading the wooden cavity cover thickness thread, I want to make sure to keep as much thickness as possible to avoid complications and possibly employ some magnets, but that would just be a bonus, no worries on that.

Also, I can rough cut the body shape on my new bandsaw before cutting the cavity cover piece, which might make cutting the cavity cover easier for certain tools. I just wanted to add that in case it makes any difference in tool suggestions. Well, I think that's about it. If no one understands what I am talking about I can post a couple pics, I ended up taking a couple before packing up tonight. Thank you very much everyone for the help. J

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I would saw of the cavity cover with a normal handsaw the give the body another levelling off to take care of any saw marks!

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I would saw of the cavity cover with a normal handsaw the give the body another levelling off to take care of any saw marks!

Mainly, I just want to keep as much thickness as I can on the cover. Russ was talking about 1/4" for his wood covers with the magnets, which is what I'd like to shoot for regardless, mainly because there isn't a replacement for this matching cover, this will be a one time deal and the thicker I can leave it the safer I would feel so I don't somehow end up splitting it or whatever.

I had been thinking of the japanese saws because of the very thin kerf and ability to make sure the blade is cutting flat against the body. Both of those traits should save some thickness. A handsaw would work just fine, but I'd imagine would probably take off more thickness and would likely be rougher cut which would require a deeper sanding to clean up. I'm sure it would work fine, I'm just worried about thickness of the cover I would really like to keep as much as possible.

I appreciate the response Wez. I do have a fine cut handsaw on hand that I have yet to try, but I know the kerf is quite a bit thicker than the japanese saw I have and the fine cut japanese saw would be even less. Again, thanks for the help, I'll definitely throw that saw into my choices, though I'll would likely go for one with a thinner kerf, unless there are reasons I should not in this situation. J

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I would saw of the cavity cover with a normal handsaw the give the body another levelling off to take care of any saw marks!

Mainly, I just want to keep as much thickness as I can on the cover. Russ was talking about 1/4" for his wood covers with the magnets, which is what I'd like to shoot for regardless, mainly because there isn't a replacement for this matching cover, this will be a one time deal and the thicker I can leave it the safer I would feel so I don't somehow end up splitting it or whatever.

FWIW, my zebrawood cavity cover is 2mm, and it seems plenty strong enough. Of course thicker can only mean stronger though, so if you can get extra thickness its probably sensible.

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Thanks for the info. Zebra does seem plenty stiff which is good in case I run into issues. Its not a huge issue, but I would like to try and keep it close to 3/16-1/4" if possible so I can try magnets possibly and so I don't make some lame mistake when screwing it in and split the wood and such. As I said if I screw the pooch on this, I won't have another matching cover which is why I would rather try to save as much thickness as possible, plus I can always take a little thickness off if I feel comfortable doing so. If this was just a random cut of zebra or other wood I wouldn't care, but since I went to the trouble to make this match, I would prefer to keep it thicker if possible. Well, thanks again both of you guys for the info and help, much appreciated. J

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Seriously, for a hardwood that's not too wide (how big's the cavity, is the question?) 2-3mm is plenty thick. Besides, you can always sand it thin, and add a lamiante or two (odd numbers of lams for stability, look at how plywood is put together) to make up for any thickness/stiffness issues.

I cut mine off with a Japanese handsaw. I don't actually own any other handsaws that actually get used these days, just various Japanese varieties.

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Cool, cool. Thanks guys. I'd like to keep it a single piece with magnets and considering my skills I'd like to leave myself some room for error, so I'll shoot for around a good 5 mm for now and see from there. I'm not really worried about how thin I can get it and would actually prefer to have it a little thicker than normal. That why I was wondering what the best tool to use was, in order to lose as little thickness as possible when cutting it off.

I think I'll use the japanese saw, I used it on my scarf and that turned out nice, though I found better saws after I cut the neck, which I might buy at my local Rockler. I think I should be able to save enough thickness with the japanese saw I have, though I still might buy the finer one (I want it anyway). I do appreciate the info on how thin cavity covers can go, since I'm sure most of the time I will usually be doing thin ones, plus if I mess up I can just forget the magnets and go thin or I can just throw on some laminates, either way. Thanks again guys, very much appreciated. J

PS: As far as scrapers go is the brand Bahco fine? Its what Rockler carries and if I can go pick it up that would be better than paying and waiting for shipping. Thanks.

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J, you should be fine with just a few mm. When I say 1/4" or 3/16", I'm thinking of things like ash, mahogany or limba. Plus, it can't be really thin because I need to set the magnets into it. Were I using something like ebony, or rosewood, I'd probably go with less than 1/8" thickness. I've no experience with zebrawood, but you can glean from that what you will.

Also, what's wrong with just leaning towards the safe side, making the zebrawood cavity cover thin so you don't gouge the body, then laminating some other wood onto the back of the zebrawood cavity cover? It's not like anyone will ever see it.

peace,

russ

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Seriously, for a hardwood that's not too wide (how big's the cavity, is the question?) 2-3mm is plenty thick. Besides, you can always sand it thin, and add a lamiante or two (odd numbers of lams for stability, look at how plywood is put together) to make up for any thickness/stiffness issues.
Yeah, what Mattia said.

That's exactly what I have done on both my guitars. Just gluing a thin veneer on the backside of the cover will give you tons of added strength.

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If you're going to glue something to the back, it might as well be a thin piece of metal. That gives you way more strength than wood (although it's admittedly more strength than you'll likely need) and as a bonus, you're saved the bother of shielding the cavity cover.

peace,

russ

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Just a thought, but what about putting the magnets in the body as opposed to the cover? If you reinforce it with a thin piece of metal like russ suggested, then the thin metal could be what holds the cover to the magnets?

Ciao,

Garth

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I wouldn't want a solid wood cover any thinner than 1/4" - you're asking for all sorts of warping/cupping issues. I've had best results taking a sawn cover down to 1.5mm thickness and using it as the surface ply on a 3 plywood cover, laid up from an other 2 constructional veneer pieces, with the center ply at 90 degrees.

I cut my covers off with a bahco hardpoint saw, it takes a relatively narrow kerf since there is no set to the teeth, but it still rigid enough to not wander.

Don't forget, for best results you should leave the cover a tad oversize, this lets you shuffle it around a bit to get *perfect* grain alignment. On a quartered blank you won't need to adjust it much, but on a flatsawn blank the grain will move quite a bit.

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I wouldn't want a solid wood cover any thinner than 1/4" - you're asking for all sorts of warping/cupping issues.

Hmmm.... I may have to consider reinforcing mine then.

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Just a thought, but what about putting the magnets in the body as opposed to the cover? If you reinforce it with a thin piece of metal like russ suggested, then the thin metal could be what holds the cover to the magnets?

Ciao,

Garth

Don't see why not, although you'd need to get a ferromagnetic sheet of stuff in there. I don't think copper or brass or, so I'm guessing stainless would be the way to go, and that can be a little expensive.

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I cut my covers off with a bahco hardpoint saw, it takes a relatively narrow kerf since there is no set to the teeth, but it still rigid enough to not wander.

That sounds like a good answer.

I used a thin kerf pull saw for cutting down a Tele style headstock. This isn't an identical application to what you want to do but not entirely dissimilar either. Because the saw blade was fairly flexible, I had to take care but in the end got a nice even and straight cut. So, if you want to try your pull saw, it should work.

th_Teleheadcut.jpg

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Again thank you everyone for all the help! Part of the reason I wanted the thickness I mentioned is that I did want to try magnets on this cover. As stated though, I could always laminate if need be.

Anyhow, I cut it today with my little pullsaw. It worked just fine though it did take a while. It actually seemed much tougher to cut than the scarf on my maple/jatoba/maple neck blank for some reason. As someone pointed out I left an area quite a bit bigger than the cover will actually be, mainly for alignment issues. I ended up having a tad bit of wander toward the end of one side, my fault likely. As I mentioned I wanted to buy a nicer handsaw that I had seen at Rockler, but I figured this one would work and it did fine really, the wander was just ever so slight and it was only at the very end of one side, so if I don't use the last 3/4"-1" or so of the cover it will all be 1/4" thick. As I said the cover is also way over sized, so there is a good chance that little thinner piece will be cut off anyhow. I tried very hard to clear out the dust often and watched my cut, no worries though. I think at the very thinnest I got 3/16" with more than 3/4 of the cover being 1/4". So I'll probably just pull out the router jig and thin it and laminate. I have enough thickness for what I want I believe, but I still need to smooth both faces and as I said I prefer to be safe and avoid complications, so I will likely laminate as suggested for some extra stiffness.

All in all it came out just fine. I really appreciate all the help with this. This weekend I will thin it, smooth it and laminate it and see how it turns out. I'm going to start a progress thread probably beginning of next week. It's a slow process for me for a few reasons, so I wanted to wait to start the thread until I had certain tools like my bandsaw and I had more done. This weekend I should get the body cut to shape and more depending on how quickly I can take care of my homework and I'll get a thread going. Just wanted to say thank you everyone again, I really appreciate all the great information and help. Each project I do, I plan on using wood covers, so all this information is extremely useful. Thanks again. I'll probably put some pics up of the cavity cover progress in my build thread when I get it going next week. J

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John,

I found my pullsaw tender to get drawn off by the grain because it's so flexible. I think I'll pickup one of the double sided pullsaws with a fine toothed egde and a coarse toothed edge, and try that. I think part of the problem is the fine teeth on the pullsaw, and I suspect the coarse teeth will be less inclined to wander. IIRC the two edges are intended to be for crosscutting and ripping respectively.

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Double Sided Saw

Were you thinking something like this? I must admit I spent a lot of time trying to pick when I wanted to do my scarf. I picked a very nice one and then realized when I got home that I could get a deep enough cut to do the scarf because it was a supported blade. I ended up getting one somewhere else that I never really liked, though it works fine. I definitely plan on buying a couple more. The double sided ones like this one are big, surprisingly big, I'd like one like this one and a couple smaller ones as well. My local Rockler actually had a bunch of them and the guy said they all worked really well for him. Thanks again for all the input guys. J

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John,

I found my pullsaw tender to get drawn off by the grain because it's so flexible. I think I'll pickup one of the double sided pullsaws with a fine toothed egde and a coarse toothed edge, and try that. I think part of the problem is the fine teeth on the pullsaw, and I suspect the coarse teeth will be less inclined to wander. IIRC the two edges are intended to be for crosscutting and ripping respectively.

Setch, that little saw in my pic does tend to wander (nothing to do with my skills :D ). I got one of the double sided pull saws last Christmas but haven't used it for much yet.

jmrentis - glad things worked out.

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