Saturday, September 13, 2008

Brass Guitar Nut Making Pt. II: Google SketchUp

You would think that since I have been getting paid to work with computers for over fifteen years and use a dizzying array of software over the course of a week that picking up a new application would be easy for me. You'd be wrong.

Google SketchUp is a 3D modeling and design program. A basic version of it is available for free. A payware "Pro" version includes a presentation tool called LayOut and other enhancements. Both versions are available for Windows and Macintosh and, between them, seem to be developing quite a following. My brother-in-law, a partner in an engineering firm, says many of his fellow engineers use the free version for most everything that doesn't need to be done in a dedicated engineering app. To show me the plans for the firm's new offices (what he really wanted to talk to me about) he opened SketchUp on his laptop.

This is an example of a SketchUp design I swiped directly from

As I mentioned in earlier posts I'm making a brass nut for my baritone hack. I'm building a guitar part, not a stadium, so my SketchUp screen is more likely to look like this.

Since previous nut modifications I have done have never come out right I decided to make "real plans" for this one before I started cutting into my brass stock. With everything good I had heard about SketchUp it seemed like an obvious choice.

What is obvious to others is not always obvious to me. After hearing how Ableton Live was easier to use than a spoon I had to take three or four good hard runs at it before I got anywhere. So it was with SketchUp. Although the controls and tools all make sense very simple tasks such as changing the length of a line took me some time to figure out.

That said I was able to do some very cool things. In sum, I was able to make a correctly proportioned 3D model of the nut I am making, right down to the fine differences in string spacing.

First I created a solid object representing my over-sized brass blank. I did this by creating two identical rectangles representing the faces of the blank and connecting their corners with straight lines. I then used the push/pull tool to make the blank 1/8" thick. I used the tape measure and protractor tools to reassure myself that I had right angles and parallel lines.

I simply drew lines on the top face of the blank to represent the fret slots and final hight of the nut. I used the numbers from the "center-to-center distances between strings" section of the string spacing calculator spreadsheet to draw the exact lengths of the lines separating my slot markers. I used SketchUp's tape measure tool to make sure the slot markers for string one and string seven were both 1/8" from the outside edges of the nut. The math works out perfectly and I didn't need to worry about how sharp my pencil was.

Because I was working with short, precise distances it was important to me to be able to specify line lengths down to the thousandth of an inch. The precision of these measurements is set in the app's preferences, not preferences for the line tool as I had assumed. This makes sense as they have implications for the whole model, regardless of how lines or objects are created.

Eventually it dawned on me that what I needed was not actually a 3D model of the nut. I'm probably not going to change its thickness so all I really need is an accurate guide for cutting it to length and precisely locating the string slots. So, maybe I could have done this in a drawing program, but having used Sketchup I know my distances are right and that it will print exactly to scale.

Something like this.
Speaking of printing, that was a bigger adventure than setting distance precision. SketchUp has fairly flexible printing features so I had some decisions to make. As it turns out people want to print their designs in all sorts of interesting ways and from various perspectives. I wanted to print the top face of my design from directly above it in 1:1 scale. This meant turning off Perspective under the Camera menu and setting the scale to "1" to 1"" in Document Setup under the File menu. Also I needed to make sure I did not print the background, among other things.

Before I figured these things out I printed:

1) The nut blown up to about 2 1/2 times its intended size
2) The nut from a viewing angle almost but not quite straight down
3) A white renctangle proportioned like the nut centered on a tasteful gray background
4) Only the nut slots
5) Only one nut slot
6) A completely blank page

But I'm from Iowa and I was raised to believe that God gave humans dominion over software so I persisted. Eventually I got this.

It looks more impressive printed out but you get the idea.

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