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Flattening a scarf joint w/o a planner
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Author:  Dolmetscher007 [ Fri Mar 01, 2019 1:24 pm ]
Post subject:  Flattening a scarf joint w/o a planner

I have been an avid woodworker... so I thought, anyway... for 20+ years. Now, however, that I am trying to build guitars, I am really starting to realize how often "good enough" will work for building furniture, but simply won't work for guitars. At least, that is the impression I get from books, videos, and forums.

I have a really really nice neck blank on my bench right now. I've already cut off 7.5" at an 11-degree angle to create the scarf joint for a back-angled headstock. I used an angle jig that I made, and ran it over my nice 3 HP table saw. The cut looks smooth, with no real gnarley saw tooth marks, or burns or any other blade marks... but, in every video I've seen on YouTube, when the guy cuts the scarf joint, he always flips it around and sticks it to the neck using double-sided tape, and then uses a block plane, or sometimes even a jointer, so make sure that the cut is exactly the same angle on the headstock off-cutt, and the neck. I don't have either of those things.

Even if I did have a block plane... I have tried to use planes before, and I end up wrecking the surface way worse than it was before. Last night, I tried to double-sided tape the headstock to the neck, and run it up along my buddy's oscillating belt sander that has a steel plate behind the belt that is square to the table. I absolutely ruined it!!! Even though the belt was tracking correctly, and the oscillating bit was perfectly 90 degrees to the table... somehow, I must have pushed with uneven pressure (even though I was barely pushing at all), because it just sanded everything all out of wack. And the more I tried to correct and fix it, the worse it got. I think I can run it back across my table saw blade and get the two pieces at least back to where they were before, albeit 1/4 shorter or so. But what can I do then?

Do I really HAVE to do anything? Can I not just take some 220 sand paper, stick it to the bottom of a 1.5" dead flat MDF sanding block, and just kiss each of the pieces individually, and then just glue the dang scarf joint? Is the whole, jointing across the two planes, really necessary considering wood moves so much anyway?

Author:  dpetrzelka [ Fri Mar 01, 2019 1:56 pm ]
Post subject:  Re: Flattening a scarf joint w/o a planner

In my limited experience with scarf joints, if you don't joint the two together, you'll have more work to do flattening the peghead face after glue up. You'll have to surface that face anyway, it will just be a little more work that may have an impact on final peghead thickness.

- Same angle ensures a coplanar peghead face.
- Faces square to the side before glue-up, helps ensure a straight (not twisted) peghead.

It may be slower, but it should totally work to use a flat sanding block (MDF, stone or other) the same as you would a plane. You can work each piece separately using an angle gauge to check they are staying the same angle—its quicker sanding them at the same time with the double stick tape technique.

I haven't done a ton of these, as I used to use one-piece necks, so take it with a grain of salt.

Author:  Bryan Bear [ Fri Mar 01, 2019 2:16 pm ]
Post subject:  Re: Flattening a scarf joint w/o a planner

I have done it with sandpaper before. It worked okay but once I bit the bullet and decided to learn to do it with a block plane it got a whole lot easier and faster. Even if you use sand paper, I recommend doing them at the same time. It is just a whole lot easier to make sure they match that way. You can watch to make sure the edges are parallel as you work. That will make clamping it up much easier and save you a whole lot of work cleaning it up afterward.

If you have access to a decent block plane, I encourage you to learn to sharpen it properly and get it well set up. That is the biggest part of the fight. Once it all clicks, it is a pleasure to use.

This may be obvious but it is worth mentioning. If you lose too much neck length while you are getting the process down, you can lengthen or shorten the neck by thinning the neck or peghead (assuming you have sufficient thickness in the blank you started with). If the angle is too close to the heel end of the neck blank for the scale you want to use, thinning the neck blank from the top of the fretboard gluing surface will move that angle back towards the peghead end. Thinning the face of the peghead will effectively shorten the neck length.

Author:  sdsollod [ Fri Mar 01, 2019 3:00 pm ]
Post subject:  Re: Flattening a scarf joint w/o a planner

Before you make your scarf joint cut, you want to make sure that each side is flat. A drum sander is good for this. After the cut, you will "invert" the headstock and glue it to the other side. Here is where the hand plane comes in. You use it to ensure that the surface of the headstock is "true" to the neck. Sorry if I'm stating what you already know... The hand plane is really good for this and can be accomplished pretty quickly. Trying to sand it might be doable, but... Perhaps you can borrow one from someone...

Bryan's comment is worth noting. The neck length, relative to the fingerboard, is an adjustment the plane really helps out with. BTW - That adjustment should be made after you have cut the tenon (dovetail), fit the neck to the body and established where the neck will join the body. Then you can adjust the length as necessary as Bryan pointed out.

I had heard many times how much folks love to use their hand plane. I never understood until I got one and started using it. It really is enjoyable...

This photo is actually of a one piece neck, not a scarf joint, but the concept is the same.

Author:  johnparchem [ Fri Mar 01, 2019 4:08 pm ]
Post subject:  Re: Flattening a scarf joint w/o a planner

Everything I sand comes out curved, it is a lot easier to get a flat surface with a plane. When pushing a sanding board forward the leading edge of the sanding board ends up with more weight because there is a lot of friction. Unless countered more wood is removed on the leading edge. That tendency needs to be countered to keep from rounding the ends. I am sure with care one can clean the scarf joint surfaces with sandpaper, but I would end up like the OP and make things worse. Edge tools can be your friends.

Author:  Bryan Bear [ Fri Mar 01, 2019 4:22 pm ]
Post subject:  Re: Flattening a scarf joint w/o a planner

Be careful with hand planes. Once you get the hang of using them you'll find yourself buy every second hand bench plane you come across to restore. I finally had to stop myself. I still have a #5 and a block plane that I am going to "one day" de-rust and get working again. I never do because I already have more of them in working order. . . :)

Author:  Dolmetscher007 [ Fri Mar 01, 2019 5:43 pm ]
Post subject:  Re: Flattening a scarf joint w/o a planner

I have a super fancy, Veritas, Low-angle Jack Plane. I just suck at using it. And it is a bit big a unwieldy for flattening such a short distance of wood. Oh well... guessyou cant just pretend to build guitars; you gotta get in there and DO IT! Looks like I’ve got some practicing to do.

Author:  SnowManSnow [ Fri Mar 01, 2019 6:08 pm ]
Post subject:  Re: Flattening a scarf joint w/o a planner

I’m also a new builder.
I can say, though, that after I became “proficient” w my hand planes things got a lot better:)

With blades tools I was able to achieve a degree of accuracy I just couldn’t with other methods.
Your OP IS exactly right “close enough” doesn’t cut it with guitars. The turn around with me and planes came

When I actually learned how to achieve a decent edge on the thing.

My first plane was a Veritas smoothing plane which I do still use quite a bit but the one I use for almost everything is my Veritas block plane.

Sent from my iPhone using Tapatalk

Author:  Freeman [ Fri Mar 01, 2019 8:12 pm ]
Post subject:  Re: Flattening a scarf joint w/o a planner

After planing my joint as flat as I can get it I put some sticky back sand paper on an aluminum carpenter's level and stand it with that.

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