I need a very rigid flush-cut saw to cut a 13" scarf joint


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I am building electric guitars, and need to cut a 13 degree scarf joint, reliably, and repeatably.  I do not have a band saw, and I will not be able to afford one for quite some time. I have a wonderful 3HP 22V cabinet table saw. But it's blade is not tall enough to make the cut. And you'd have to make the cut in one pass. There is no way to flip the board etc. 

So... I set out to create my own... 13 degree angle sawing guide. I got the idea from the David Barron dovetail magnetic hand saw guides. They have a strong magnet that the saw rides along as you cut the dovetail. Makes it kind of idiot proof apparently. So, I went and bought some aluminum angle. I carefully measured it. I cut pieces at 13 degrees, and I even used aluminum brazing rods to braze it all together, before I bolted it down to a double layer of 3/4" MDF. I even added some hold-downs, and drilled for these screws that come in from either side of the wood, so that once it is in the jig, I can fine tune it square with the aluminum "rails" that are at 13 degrees. 

I used a dead flat metal file to really make sure that the two aluminum rails are on the same plane with one another, dead flat, and dead square to the board. I plan to find and order some neodymium magnetic bars to epoxy to the rails. And the grand idea is that I will be able to just put the maple board between the rails, clamp it square with the side-screws, and the clamp the whole thing down with the hold-downs. Then I can slap a hand saw to the magnets, and just carefully saw the perfect 13 degree angle through the board. In theory... it's aweseome! But here's what is really happening.

I have several hand saws. One is one of those double-sided Japanese Gyokucho 9-1/2" ryoba pull razor saws. Then I also have a really think and flexible flush cut saw for trimming dowel plugs flush. I also have two huge Lynx E. Garlick and Son Sheffield Eng. saws that are like 3 ft long. And finally, I have a Gyokucko Dotsuki Japanese pull-stroke saws with the metal spine along the back of the blade for rigidity. 

NONE of these saws will work. They all have a "set" to their teeth, even the really fine Japanese ones. So after trying this just 2-3 times, I can already see where the teeth scraping along the aluminum rails is wrecking them and will force them out of plane if they haven't already. Also, the saws that have a spine cannot ride flat along the rails, so it tips the blade into the wood at a slight angle due to the spine itself. AND... the saws with no spine are too flexible to stay straight between the two aluminum rails that are 4" apart from one another. 

So... I need a... dead flat, super rigid, long enough saw, that also have NO set to the teeth. OR... I need to rethink the whole idea. Can any one of you guys help me?

Edited by Dolmetscher007
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I think the first sentence of your post is missing.  Even so, I think I get the gist of it - enough that I can offer some comment.

The reason the dovetail guide with the magnet works is that dovetails are rarely so deep that a saw with a spine will interfere with the magnet.  The teeth fall below the magnet and the spine remains above it.  I'm gather that you're trying to run your saw in a vertical fashion in which case the teeth (and spine) will interfere with your magnet line.  The best solution I could think of would be one of your Japanese saws - make your jig thinner by the depth of the set of the teeth and then added a surface to the side of the saw, above the teeth, that acts as a consistent spacer moving the teeth of the saw away from the jig.

The other comment I'd offer is that you can get a more consistent cut from your bandsaw if you combine using a blade with a higher TPI and by moving significantly slower when you make the cut.  You're still going to have some clean up but this may prove easier and quicker than hand cutting with a jig.

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Maybe the way to go is to not worry about getting the perfect angle and surface on the cut. Cut it close to what you want, say within 1/4" of the final dimension. You could then have a jig that used a router to surface the cut and bring it perfectly into plane, kind of like the slab planing jigs, just much smaller. I think this might be easier than trying to achieve your perfect cut right off the saw, and you might even be able to use the jig you built, with some modification.

I'm with @drzaius though - a couple of pictures would be very valuable here.

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One of my favorite ways to make a difficult cut perfect is to initially make the cut using whatever I have that will chop through the wood. That can be a hand saw, circ saw, jig saw, or even a hatchet if you're so inclined. Just be sure to leave a little extra on the line. Then use a straight edge & pattern cutting bit on the router to clean it up. Take very small passes & for the final pass, a very, very light cut. Be sure to clamp the straight edge very securely.

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For some reason that I don't understand, You're making a scarf cut to be difficult.  It's a simple connection, and not at all difficult.  Whatever degree you determine to use to make it, making the matching piece is as simple as the piece your having difficulty with.   Mark your line. Make the cut leaving room for clean up, then clean up with a plane, chisel, or a  pocket knife. It's not a hard problem .

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I assume this is the scarf cut that is used to tilt the head stock backwards? If so, ditch the saw jig. Mark the wood leave the line, and use a router sled as suggested, or a variation of this hand plane thicknessing jig. (one of many videos). You should only need to clean up one side, the other gets flipped around and glued to the surface you just made, right?

In fact, the jig can me constructed to hold the work such that you can saw and then plane without removing it.

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Yeah i can't help but think of what Shannon Rodgers always says. Saw to the line and clean up with a plane. Ditch the guides get practice at sawing to a line and clean up the cut with a hand plane.

We're talking about this guy right?

15115d1413490071-what-purpose-scarf-join

If it were me I'd make a shooting board that hits that angle perfectly. The top angle is easy to clean up after with a block plane or what ever. I doubt this angle needs to be accurate to the fraction of a degree if it's 12.9 or 13.1 everything is going to be ok.

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40 minutes ago, Chestnut said:

Yeah i can't help but think of what Shannon Rodgers always says. Saw to the line and clean up with a plane. Ditch the guides get practice at sawing to a line and clean up the cut with a hand plane.

We're talking about this guy right?

15115d1413490071-what-purpose-scarf-join

If it were me I'd make a shooting board that hits that angle perfectly. The top angle is easy to clean up after with a block plane or what ever. I doubt this angle needs to be accurate to the fraction of a degree if it's 12.9 or 13.1 everything is going to be ok.

Yeah... I hear ya about the, "saw to the line and clean it up with a plane." And if this were a but joint, dovetail, mortise and tenon, or even a miter joint for furniture, I'd be fine with that. But when you are dealing with a very expensive hand-selected piece of perfectly quarter sawn and milled hard maple that has been seasoned and dried slowly to the perfect moisture content for stringed instruments...  AND... you have already ruined 4-5 "test pieces" of poplar... I just don't see it working out without some kind of jig. 

The main problem is the length of the cut, the width of the board, and the thickness of the board. It sounds easy, in your head, to just use a combination square to strike your lines, prop the board up, clamp it to a bench or in a bench vice, and saw to the line. (maybe even use a sharp chisel or exacto knife to start yourself a little knife wall to get started.) But... the board is 4 inches wide and 1" thick. 13 degrees is a very shallow angle. The saw has to go through so much wood at that angle, that it just simply drifts every time. And it drifts BIG time! I've ended up 1/4" off the line by the time the saw exits the other side of the board. Again, I know it probably sounds like I'm being a baby and just don't want to put in the work to get good. But honestly, this whole post is me trying to balance great results with skill, and expense. I don't own a band saw, which sucks. I also don't own a plane. The only plane that I own is a low-angle Jack Plane from Veritas. It's a beautiful plane, but it is huge! I've tried using it on my test necks, and I just end up making things worse with it. 

I mean... I guess it is possible that I just suck at hand tools, and that any woodworker worth a squirt of piss could snatch my low-angled Jack outta my hands and true up my scarf joint in just a few seconds. I guess I could just keep practicing. Do you guys think this low-angled jack plane SHOULD be able to do this?

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There is another way to do this: saw as close to the line as possible, and then clean up with a rasp and file. 

If you are dead set on a jig, then get rid of the aluminium and just use MDF or, better still, a hardwood. The teeth will remove a smidgeon from the lower edge of the hardwood jig, but from there on it will be fine.

Regards from Perth

Derek

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Even after you saw it you still have to clean up the cut. So you are goign to need a shooting board or something. If you have the device to clean up the cut you still need to practice making the cut. It's probably going to take some effort. As with anything difficult in life you aren't going to nail it the first try or maybe not even the 10th try.

As far as all that about wood and seasoning you guitar people are crazy.... I don't get how there can be a perfect moisture content when the MC of wood depends on the humidity in it's environment. Does this mean the wood is junk if it gets transported out of it's perfect environment? How is it any different that all other QS maple? I read a double blind study about the famous Stradivarius violins and the professionals couldn't statistically identify them from the cheapest violin on the market. The pros did better than a common person but  still weren't far from 50% in a 50/50 guess.

*edit i don't mean the above as offense, I just feel like you need to learn to walk before you run. Jumping into some exotic guitar wood when nailing the technique is difficult seems bit like putting the cart in front of the horse. Thouhg i don't understand the whole seasoning and perfect MC thing ... how would they stop the MC form changing?

Edited by Chestnut
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If you only have access to a handsaw, why not build a mitre box, but with the correct angle (use your table saw to get the initial cuts)?  The cut face of your work piece will still have to be cleaned up, and that plane you have should be absolutely fine to do that.  To get the angles perfect, the hand plane jig shown above could be used.

Practice with some maple to get used to how the wood reacts.

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1 hour ago, Art said:

If you only have access to a handsaw, why not build a mitre box, but with the correct angle (use your table saw to get the initial cuts)?  The cut face of your work piece will still have to be cleaned up, and that plane you have should be absolutely fine to do that.  To get the angles perfect, the hand plane jig shown above could be used.

Practice with some maple to get used to how the wood reacts.

F*****G GENIUS!!! 

Done!!! 

 

Thanks man!!!

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