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Hi, a while back there was a link posted to a jig you could make for your table saw to cut a 14 degree scarf for your headstock.
I built this jig, tried to use it on my table saw, but got so much kickback that I abandoned the idea as unsafe, dismantled the jig and used the wood for other things.
However, I now cut my scarf by hand, but would like to give this another go because if I could get it to work there would be less clean up with the plane before glue up, and it would be faster.
Does anyone have any idea why I got so much kickback? Is there a specific blade I should be using, or a technique I'm missing? Or perhaps my saw is too underpowered? I have a Craftsman 10" that was given to me. It's a fairly inexpensive saw, so that may be the problem right there, but any help would be appreciated.
Thanks.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

Is the fence parallel to the blade? If it angles in such that the space is narrower on the outfeed side, that can cause kickback. I always cut my scarf joints on the table saw and have never had a problem. It would be scary if it did kick with the full blade exposed.

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http://www.chassonguitars.com

You're doing something wrong; it's almost certainly not the saw or even the blade although you should
be using a fine cross-cut blade.

Can you post a photo of your jig and set-up?

Thanks guys.
Runamuck, I don't have it anymore, but this is the jig I used.
http://home.comcast.net/~kathymatsushita/amateurluthier/htmlpages/scarfjigplan.html

As far as I know, there is only one way to run that jig through the tablesaw. I built it exactly like the plan, and used it exactly as described.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

Requires a lot of blade to clear the jig and the thickness of the neck blank which in my experience leaves burn marks, not to mention scares the crap out of me with that much blade exposed....IMHO much easier, and safer, to band saw then use a disc sander or plane to clean up ...plus one less jig to keep up with......

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MK5acoustics.com

+1 on what Wes said.
I like and use my table saw for much more than my band saw, but in this case I use a similar jig on my band saw, since I don't have the height on my table saw.

a band saw would be safer to use for sure. fwiw i use a dozuki saw and free hand the cut then clean up on my mill. i don't own a table saw or a band saw.

Thanks, guys. I don't own a band saw. I'm used to cutting it by hand and cleaning up with a plane, but I would like to reduce the time and more importantly the wear and tear on my hands. I have nerve damage that causes pain sometimes even doing simple things like using a hand saw to cut the scarf. I'm trying to reduce the amount of damage to my hands and hopefully extend the time I can build guitars. If I can get a pretty clean, square cut I would only have to use the hand plane for slight touch up before gluing. Sometimes this is the case when I cut by hand, sometimes it requires a lot more work with the plane to get it right. If I could figure out what I'm doing wrong on the table saw, it will improve the consistency and accuracy of my process, and help physically as well..
FWIW, I usually radius the fretboard by hand, but I'm switching to a jig for my router there, too. I'm trying to reduce the amount of manual labor that goes into a build, and improve the repeatability of my build process.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

Bandsaw. You can build another angle jig or free hand it. If you free hand it I would tack on a wide base for stability.


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Agreed with Kent -- check the blade-to-slot alignment. Other ways the neck might contact the side of the blade during the cut:
- The forward part of the neck may have pulled away from the fence during the cut. Prestress in the wood, non-flat fence, and clamping near the end could do that.
- The neck might have slid down the fence, into the blade. Some combo of light clamping, dull blade, and high vibration could induce that.
Using a different jig, we've cut at least 150 scarf joints on the TS with zero kickback. John H has another slick way of doing it: clamp the neck to the table, then raise the blade.

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David Malicky

I wouldn't use spring clamps for that operation. They have a tendency to creep a bit, probably resulting in kickback.

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Under Compensated Nut!

I don't remember which clamps I used, but it is possible I used spring clamps. I think I'm going to rebuild the jig and try it over. I'll pay particular attention to the slide that goes into the slot on the table and make certain the blank is clamped like Fort Knox.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

I made up about eight blanks two years ago. Here's the thing about getting old. I don't remember how I cut the scarf but they came out good.

Sometimes I think I was a goose in a former life, its like waking up in a different world every morning.

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Joe Beaver
Maker of Sawdust

The spring clamps jumped out at me too. If that's how you did it, I'm not surprised it kicked. I mostly bandsaw or handsaw, but I have a similar sled - comes out nearly ready to glue. Maybe I should use it more... I've got sand paper glued to the face for better traction, and I clamp it strongly with c-clamps. Make sure the clamps are well clear of the blade path going and coming. If not, I'm sure it'll get your attention.

Mike

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Mike Lindstrom

Yeah, that's why I say there's a possibility I used the spring clamps, since that's what's in the picture, and I've got 'em laying around. I don't remember what I used, but if I saw them in the pic I could have assumed they were adequate to the task.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

This is why I'm reconsidering it's use. I think I'm gonna give it one more shot. I think I have enough wood to build it in the shop, not sure.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

Pete's jig instructions do say just to push the material forward straight through the cut. It says to stop the saw once you have run the piece through, and NOT to reverse it (when the saw is running). Just want to clarify that.

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Kathy Matsushita
San Jose, CA USA
http://theamateurluthier.com
Facebook: https://www.facebook.com/kathy.matsushita

Kathy, thanks for posting the plans. I hope that I can get it working properly for me, as it would be a great help.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

yeah my first instinct was that the forward piece of wood was slipping back into the blade, and with this setup it would start pinching pretty fast. Put some "c" clamps on there and pay attention to the most forward section of the wood to make sure it doesn't tweak when the cut releases pressure that may be on the neck, (although if your jig is straight it shouldn't really be a problem)

The amazing Scarf-o-matic! It slices, it dices!

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

You can even cut a tin can with it!

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http://www.CostaGuitars.com
PMoMC

With the exception of my first guitar, where the scarf was cut freehand on a band saw, all of my scarf joints have been prepped on my 10" Delta table saw with a jig very similar to Peter's plans reproduced on Kathy's website. There's a picture of a joint set up for a multi-scale project in the first posting at http://www.luthiersforum.com/forum/viewtopic.php?f=10117&t=41115

From that experience, I would suggest:
1. Check carefully that the fence on the jig and the raised blade are both at perfect right angles to the saw table surface -- otherwise you'll be doing more work later to align the joint. Also check that your blade runs exactly parallel to the table slots. This adjustment should be described in the saw's manual.
2. If the longer rear section is secured firmly to the jig with 2 clamps (as in my picture posted in the above link), it cannot twist to cause burning or kickback.
3. The problem child is the smaller front piece. If you can secure it also with two clamps, then that piece will also stay put and not cause blade burn or kickback. BUT, I'm not able to do that with the clamps in my collection without interference with the blade, so I usually allow it to break away on its own.
4. A single clamp on the front piece can sometimes cause that piece to twist or rotate slightly, and thus become a candidate for kickback. Use either 2 clamps (if you can) or none.
5. An alternative to clamps on the front are a couple of pieces of double-sided tape as insurance to keep the front piece from shifting when it breaks free.
6. As recommended by others, do NOT pull the sled back once the cut is through. Not only will it mess up what should be a perfect cut surface finish (if you have a good blade), but you could also drag the front piece back into the blade and cause it to launch. Just stop the sled once the cut is all the way through and wait for the blade to stop before moving anything.

Have I launched any pieces? No. Use common sense, and I think this is a very good, consistent way to make the cut, leaving a minimum of work to complete prep for glue-up.

Spring clamps work just fine if you have psa sandpaper on the clamping surface of the jig to keep things from slipping.

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http://www.chassonguitars.com

To each their own. If things don't go perfectly, the last thing I want is a large metal clamp 1/4" from my blade. I've made close to 200 necks using spring clamps to hold the blank in my scarf joint fixture. They work fine. If someone's using a poorly tuned saw, a wobbly blade, a poorly designed jig, or anything else that can cause a 5500 rpm mishap, all bets are off on any clamping system.

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http://www.chassonguitars.com

Also agreed that it's safest to let the small front piece be completely free: no clamp and no fence, like Filippo's jig. If there is a fence supporting the offcut but it is unclamped, it could get wedged as it's advanced, as Todd said.

Todd, your jig is slick -- my one concern is that an inexperienced person may clamp too close to the far end of the neck, which could cause the small piece to rotate into the blade after the cut. Perhaps include some guidance on how close is too close.

We use a TS jig similar to Filippo's; I think that style is safest but we do occasionally get a ~1/64" gap in a corner, probably due to the offcut shifting slightly as it's cut. Todd's jig probably trades some safety risk for better accuracy.

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David Malicky