The Back Of The Box! Tapering And Doming The Back Of A Guitar Rim

Demonstration of a simple, low tech method of tapering and doming the back edge of a guitar rim.

[@ianbooth4255]

Hi Kevin. Love your videos and your "pragmatic" approach. Just one thought. Once you've achieved the finished shaping of the sides, why not make another paper pattern so that you can copy the finished shape to the next guitar?

[@juswoodshop]

You are the man, Kevin.

[@thepragmaticluthier]

Thank you. There are many, many others.

[@davidadecker1]

Thanks for this video. I'm going to use your technique on a replica of a 1937 Gibson L-00 that I am just starting!!

[@scottborchardt1779]

I tried this method for my build and found it to be spot on! I am using a 15’ radius on the back. I measured the depth of the radius dish and used that measurement for the center mark of the template. When I finished with the chisel and block plane, I was left with 20 minutes of sanding with the radius dish. Fantastic advice!

[@thepragmaticluthier]

It;'s pleasing to know that my presentation was particularly helpful. Thank you for watching.

[@johnford7847]

Thanks again, Kevin. Your videos are always informative and encouraging.

[@JoshWard-g5i]

I had luck on my first and only build by making a pencil on a block and sliding it around the sanding dish inside before any plates are glued on. I jack up the ribs at neck , and equalize the waists.Then I cut it out on a bandsaw (clumsy). I might use a recip saw next time, maybe clamp it in the vice and roll the ribs through it. (scary).

[@johnpeters211]

I just did this method and actually like it better than cutting the taper into the sides before bending. I got very close with the chisel/plane and then build a form to go on either side of the body with the side profile depth and taper. Used a sanding block to get the rest of the way to specs ensuring it is even on both sides as well as tail/heel block sanded smooth with taper. Thanks for the video!

[@MalenyFieldsForever]

Makes a big difference seeing someone demonstrate this technique.

[@thepragmaticluthier]

If a picture is worth a thousand words, I figure a motion picture with monologue is worth a good 10,000 :)

[@jonahguitarguy]

This will be a handy guide for sides. Thanks Kevin.

[@JohnPittman-i3s]

17:38 how do you calculate the diameter of the sanding dome?

[@thepragmaticluthier]

If I understand your question correctly, the answer is in a video i posted just two days ago. kzbin.info/www/bejne/a6TXaqqMq7CBr68

[@walterrider9600]

thank you

[@thepragmaticluthier]

You're welcome

[@earlsinstrumentsandtunes9732]

I'm going to use some of this method because it is better than what I've been doing. Thanks for sharing your techniques. Looking forward to hearing the new guitars! Reply

[@kenyonfennell5003]

Great information, Thank You

[@thepragmaticluthier]

You're welcome. thank you for watching.

[@yunowot]

Unbelievably useful video instruction, thank you.

[@thepragmaticluthier]

Thank you. I'm very pleased to know that you found this useful.

[@doakwolf]

Really enjoying all of your content! A relatively new subscriber, and many thanks for sharing your knowledge!

[@thepragmaticluthier]

I'm very glad that enjoy the content and hope that I can produce more videos that you find useful.

[@dalgguitars]

It's not the "size" of your pairing chisel that matters; it's how well you use it. At least that's what I tell myself. (Thank you so much for making and posting these videos! I find them extremely useful.)

[@thepragmaticluthier]

That's absolutely true, but i choose a wide chisel because its width is a way to help me stay on the rim, but I've used a 1/2" chisel with equal success.

[@grayd135]

Hi. I've just started trying to build my first acoustic guitar and this video has been absolutely invaluable. Thank you so much for creating and posting it. Much appreciated, Gray D

[@thepragmaticluthier]

You're very welcome! And GREAT GOOD LUCK building your guitar.

[@MrDaveKC]

Seems like a good technique to me?

[@thepragmaticluthier]

Put it to use and let me know how it works for you.

[@tomallen8527]

Thank you Kevin. That was very informative for me. I’m going to my shop right now to try it on my build. I have a question though. A friend of mine uses a 51 foot radius for his top. What do you consider when you decide the radius of your back and top? Thanks again.

[@thepragmaticluthier]

I choose a radius for top in accordance with my tonal goal for a particular guitar and the stiffness of the top I am using. For example, a midsize guitar where I want balance with a little added presence in the trebles, would warrant more doming in the top, especially if the top I have is very flexible. With respect to the back, I increase or decrease the doming in hopes of increasing flexibility (more low frequency presence, slightly mellower , flatter back) or more doming for more punch or percussiveness. I use dishes in 40 ft., 30ft., and 25 ft. I think I should make a 20ft. and maybe a 15 ft. specifically for backs.

[@Apillicus]

Thanks for sharing

[@thepragmaticluthier]

You're very welcome.

[@thefreese1]

I like this video .. nice concept... and better detail as to what to look for while driving the bus than a lot of other luthiers post ...thanks

[@guywihn1658]

Thank you for this excellent tutorial.

[@thepragmaticluthier]

You're very welcome!

[@short6691]

Very nicely done! In particular the method for quick removal of material. I mark the interior with a domed fixture that rests on the top. It is adjustable so I can adjust the neck to heel block taper angle.

[@thepragmaticluthier]

Your method sound very intriguing. I'd be very interested in seeing pictures or video of that.

[@JohnScime]

As always, a very informative video lesson. After a decade of repair and restoration work, I'm on my first build currently and this information will come in very useful in a few weeks. Thanks again from about 300km north. Js

[@thepragmaticluthier]

Thank you for your comment. I'm glad you derived benefit from the demonstration.

[@codelicious6590]

Im very interested in hearing that beautiful bass when its finished. I love acoustic basses!

[@thepragmaticluthier]

Stay tuned. I'm carving the neck tomorrow. It should be done in about a month. I'll certainly do a video on the results.

[@BobStCyr]

Why would you not use a plane to remove that material rather than wait till the end - far more controlled - if you had a 3/4 inch piece of wood with a rough edge would you use a chisel first and then a plane?.

[@GarlandStringedInstruments]

This is almost exactly how I do it too - great technique!

[@thepragmaticluthier]

It's nice to know that others employ the same or similar technique. I thought I might be the odd man out.

[@johnhannasmusicaladventure8104]

Hey Kevin what is the radius of your dome sander, also do you just one radius or different radius for different types of guitars ?

[@thepragmaticluthier]

I used a twenty five foot radius for the guitar in this video. I also use a fork foot and thirty foot dome. As I consider the body size, materials used and the intended character of the guitar I'm making, I will change that radius. Generally, a shorter radius equates to stiffer plate. Thank you for your question. I should have mentioned all of that in the video.

[@alexisakin]

Thank you! The video resolution is very good now!

[@thepragmaticluthier]

Thanks. I did some more homework on the issue and found that it isn't the camera. It's the export quality from the movie editor. I like the improvement also:)

[@bradhibbitts6901]

Exactly the way I do it with some minor variations thanks

[@thepragmaticluthier]

Good to know I'm not out there all alone. Thanks :)

[@davidjennings9253]

Excellent video - very informing.

[@thepragmaticluthier]

Glad it was helpful!

[@NeverTalkToCops1]

Straightforward, clever!

[@thepragmaticluthier]

Well, straight forward anyway:)

[@patrickoleary936]

Great video Kevin! Will the 5 /16 rule only work with a 25' Radius? Thanks again for sharing.

[@thepragmaticluthier]

As the radius decreases, say to 20 or 15 feet, that 5/16" will slight ly increase and of course, decrease as the radius increases, but the difference is very little and the dimension I gave is not critical. You could probable decrease that to 1/4" and be just fine. It's all done as an effort to put you closer to the desired shape and reduce the amount of sanding time.

[@patrickoleary936]

@@thepragmaticluthier This method ended up working out great! Thanks Kevin.

[@BlaisPianoGuitars]

It will be really cool to maybe hear them.

[@thepragmaticluthier]

Stay tuned. I expect it will be another three months until these three guitars are complete.

[@jacobthellamer]

At what point do you put on the kerfing/lining? Do you sand again to get the radius/ramp right for the back? I have been doing it before taking it down to the final dimension, should I change what I am doing? I love your alternative to turnbuckles! I did an almost identical version because of what I had on hand.

[@thepragmaticluthier]

The kerfed lining is installed as the next stepfather this video. I install it as closely as I can, following the dome of the rim, staying even with or slightly proud ( about a 1/64" ) of the rim, then touch up the doming to bring the linings perfectly flush. I Don't install the linings before doming because I'm frequently removing so much material from the back edge of the rim that I would lose the lining all together.

[@jacobthellamer]

@@thepragmaticluthier thanks!

[@andrewmazurkiewicz105]

It's also a lot less work just sanding the thin sides. It would be easy to install the kerfing and use a block plane to trim it down to the sides. Cheers Andrew

[@grandadsworkshop2455]

As all your videos to date, good content and information, thank you for taking the time Kevin. I know you said you use a 25' radius on the back but could you tell me what radius do you prefer on the top please? and why?

[@thepragmaticluthier]

The radius that I choose for an instrument top is governed in part by my assessment of its flexibility; the more flexible the top, the shorter the radius. I use 40 ft, 30 ft., and 25 ft radius dishes. My choice for a back radius is based on a similar notion, equating a stiffer back with a more percussive response.

[@grandadsworkshop2455]

Thank you for that Kevin that's cleared some of the fog 😄👍🏻@@thepragmaticluthier

[@vibrationNC]

Question.. can you put a pin in the center to make sure you are driving the bus in a perfect circle? I noticed he has a hole in the center of his. ALSO.. ANYONE in Louisville, KY ever made a guitar? 🙂

[@thepragmaticluthier]

I suppose one could do as you suggest. It might be even easier to invert the process, putting the disc on the bottom, centered over a pin, holding the rim in a registered position above it.