How to Make an Acoustic Guitar Series – Part Ten – Blocks and Tapering

This is part 11 of How to Make an Acoustic Guitar, and in this post I’ll cover head blocks and tail blocks, as well as tapering the sides in your mold. This will secure the sides, get them tapered down to be ready to be ready for installing kerfing. Enjoy.

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Blocks and Tapering

How-to-Make-an-Acoustic-Guitar-Series--Part-Ten--Blocks-and-TaperingIn order to hold the sides together at the head and tail of the guitar, you need two pieces of wood that cover over the joints at each end. At the top of the guitar this is called the head block, and at the bottom it’s called the tail block.

The head block also provides a little bit of beef to mill into for a mortise and tenon, or a dovetail joint between the neck and the body. The tail black adds a little bit of weight to the bottom the guitar, and provide some meat to drill for the end pin.

The back plate of an acoustic guitar tapers from the bottom area up to the shoulders, making the thickness of the guitar smaller near the shoulders than the belly. This is a common feature, and it’s pretty easy to put on the guitar.

I’ll cover everything that I just mentioned, including lots of tips and tricks along the way, and you’ll see exactly how to put in the head black, tail black, and use a cool template/jig to create the back taper.

If you Missed Last Week, Check out How to Make an Acoustic Guitar – Part Nine

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Cutting the Sides to Fit the Mold

How-to-Make-an-Acoustic-Guitar-Series--Part-Ten--Blocks-and-Tapering-sides-in-the-mold-with-the-jigAt this point in the build, the sides are clamped into the outside mold and they are drying and cooling. This will set the bends in place, and greatly reduce the amount of spring back that the pieces will experience when you pull them out of mold.

The pieces of wood are also a little too long, so there’s overlap at the head and tail sections that needs to be trimmed down. This is a really easy process, and you can do the whole thing with the bandsaw or a handsaw.

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Overlap the pieces, ensuring that they are flat against the sides of the mold, and flat against the surface that the mold is laying on. That will keep the boards nice and straight. Add some clamps for insurance, and you’re ready to start marking.

Using a square, marked straight line on one of the sides right where it meets the center line on the guitar mold. Do the same thing for both the head and tail area, and then pull that side from the mold and cut along the line.

This line is a 90 degree line that travels about 5 inches across the height of your sides, and you can easily mark this with a square.

Put that side back in the mold after you make the cuts, and then use that side as a guide to mark the other side. Remove the second side from the mold, and make your cuts like the first. Put both pieces back in, and see how well they fit.

You will more than likely have to do a tiny bit of sanding to adjust the fit, but a snug fit is exactly what you are looking for. It will help hold the pieces against the side of the mold really well, even in the absence of clamps.

See Also: The Biggest Thing I Wish Someone Told Me About Making an Acoustic Guitar

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Making the Head and Tail Blocks

How-to-Make-an-Acoustic-Guitar-Series--Part-Ten--Blocks-and-Tapering-head-and-tail-blocksNow it’s time to make your head and tail blocks. These only need to be a few inches wide, and the height of the blocks needs to be the same height as the final guitar will be with the taper or arch in place on the back plate.

The tail black is the easiest, and you can just cut it to be the same height as the sides at the bottom of the guitar. Especially if you are planning on leaving that at full height, then just make the black the same height and you’ll be fine.

If you are trimming down the tail area height, then make your block the final height, and glue it in place so that way it’s flush to the bottom of the mold, which would be the top plate of the guitar.

For your head block you need to do a little bit more work. Install your arching template, which I cover later, and cut the block so that we are perfectly fits the template. It’s kind of a pain in the butt to hand plane a tall block to remove a couple inches.

In contrast, it’s a lot easier just to do the cutting and shaping by hand before you actually glue the thing into your outside mold. Finish it first and get it prepared completely to match the taper, and then you can glue it in place.

See Also: 10 Important Questions to Ask Yourself Before Making an Acoustic Guitar

The Book Store is Now Open!   Happy Building!

Make a Template for the Taper

How-to-Make-an-Acoustic-Guitar-Series--Part-Ten--Blocks-and-Tapering-tapering-jig-on-the-outside-moldThe taper on the back plate of your guitar is a predefined size and shape. You’ll either find this in your plans, or in your book, so take a look through that section before you make a template. Making your template is easy, and it will make the tapering process easy too.

Once you know your sizes, create a couple of tapered batons that can sit on top of your outside body molds, and skin them with a piece of MDF that’s really thin on the top. Cut a hole that matches the profile of the sides, and you have a template.

The next thing that you do is sink some inserts into your outside mold, and create some corresponding bold holes in the arching template for the top. Whenever you need to use the template, all you have to do is tighten a few bolts in place and you’re ready to go.

See Also: 1,001 Acoustic Guitar Making Tips for Beginners

Plane or Chisel the Sides to Shape

How-to-Make-an-Acoustic-Guitar-Series--Part-Ten--Blocks-and-Tapering-planing-down-the-side-height-in-the-jigWith your sides in the mold, install the arching template. Make sure it’s lined up really well and tighten the bolts down so it doesn’t move.

From here, all you need to do is reduce the height of the sides to match the tapering jig and you’re all done.

Depending on which tool you’re more familiar with, you can choose between a chisel, or a hand plane to make this work.

Which ever one you are better with is the one I recommend, because it’s very thin wood, you don’t want to remove too much.

Typically going from high to low is the best practice, and take very thin passes with either edged tool. This will help avoid gouging out too much, or potentially taking a chunk or creating a crack that you can’t fix.

Get your sides down to final height, working one of them at a time.

In the end, you can use a sanding stick with light pressure to ensure that you are 100% even with the mold, and that there are no dips or valleys that you’ll need to address later.

See Also: 10 Helpful Tips on How to be a More Productive Guitar Maker

Check Your Work Carefully’s important to really make sure that this joint is good when you’re done. Yes, you’re going to add kerfing later and increase the size of the gluing surfaces, but you still don’t want a poor looking joint.

If you have to, use the block sander a little bit more aggressively, even if it does wear off a tiny bit of your template. You’ll be able to use this several times, so even if you have to re-skin it one day, it’s not the end of the world.

Do what you have to to make sure that the taper is very even, and that it’s nice and straight. The amount of effort that you spend at this point will definitely return itself later on, it will be much easier to attach the back plate.

See Also: 9 Easy Ways to Know When to Take a Break From Your Guitar Build

Coming Up Next Week

Coming up next week will take a look at kerfing. You can buy kerfing, or you can make kerfing, just depends on what you want to save. One of them will save you lot of time, and one of them will save you a lot of money.

The point of kerfing is to increase the surface area between the butt joint of the sides and the top and back plates. The top, sides and the back are all really thin pieces of wood, so there really isn’t a whole lot holding the guitar together without the kerfing in the joint.

Getting the kerfing in place is super easy, and it’s actually kind of fun to work with. If you’ve never worked with wood that is bendable before, you’re in for a real treat.

If you have any questions on how to make an acoustic guitar the series, please leave a comment and I’ll be glad to answer them. Happy building.

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Next Post: How to Make an Acoustic Guitar Part Eleven

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4 thoughts on “How to Make an Acoustic Guitar Series – Part Ten – Blocks and Tapering”

  1. Hi Brian,

    I have your book and have made several jigs and am making more in preparation for my first solo build (I made my first in a school and it turned out great and I can’t wait to make one on my own). Question: I have built an outside mold and am wondering what way you recommend clamping the top and back? Any input appreciated! Thank you! Rob

  2. Thank you Rob. I am honored that you bought my book, and I thank you very much. I hope you enjoy using it as much as I enjoyed writing it.

    Depending on the size of your mold, you need to find clamps that can reach the sides with your mold in the way. These can be cam clamps that you make, or other clamps that you buy.

    You can also use longer boards for batons or cauls that spread out the clamping pressure around the rim. I typically use a variety of clamps and it works out really well.

    Another thing you can do is trim down your mold a little. Anything more than a couple to three inches for wall thickness is plenty. Mine is a monster, and could use a trim as well. I just left it square when I made it.

    If you have any more questions please let me know and I will be glad to answer them. Happy building.

  3. Hi Brain
    Just wanted to say how much I appreciate everything you have done to reach out to people like myself to encourage and explain how to build a acoustic guitar. I have your book acoustic guitar of making and have been keeping up on all of the emails that you have been sending out on guitar builds I turned 60 years old last month and I am excited to start my first guitar. I’m still collecting a few tools and waiting for the weather to warm up in my little shop but can’t wait to get started. I just wanted to take the time to tell you how much I appreciate your openness in helping people with guitar building .

  4. Thank you Jerry for all the kind words and encouragement. It’s been a life passion of mine to share woodworking with as many people as will hear it, and I am really happy that I have in some small way inspired you to make your first guitar…and at 60 no less!

    You are going to fall in love with the process, and when you hear your first instrument play for the first time, you will not have words. It’s a magical experience, and I promise you will love it.

    Maybe a little space heater might get you out in the shed a little early? All you need to do is bring your guitar parts in the house after each session and they will be fine. I live in Arizona, so I bring them inside because of the heat.

    Best of luck on your build, and if you have any questions along the way please feel free to email me and I will be glad to help. Happy building.

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