Bigger On the Inside

Last time I gave you a tip at the end of the post about completing this model which might need some clarification.  After all, you'd thing a measured drawing would give you very accurate results if you followed it to the letter.

Well: if you were using dimensional lumber as your building material, I'm certain this would be the case.  I could set the scale of the pieces to the industrial standards for material thickness, and every joint could be accurate to 0.1mm, every edge could be perfect, and every inner diameter and every out diameter would be without any questions.

However: as I tested the materials I had on-hand at home after completing my prototype, it turns out that mat board is not the most consistent material for thickness on earth -- I found boards in my garage which were as thin as 0.8mm, and some as thick as 1.8mm, which is a huge variation at this scale.  You also may find that you like something thinner than mat board to use for your building material.

That's why I suggested, back in the Bill of Materials, that you have a digital caliper for measuring.  The one I use is very inexpensive and easy to use -- I got it for less than $10 USD.

Cheap 6" Digital Caliper, as found at HarborFreight.com

If you've never used a caliper before, it's like a ruler -- except that it measures using its jaw rather than your eyes and the hashmarks on a ruler.  If you are measuring the outer distance of an object -- say, the real thickness of the body of the model -- you close the caliper all the way, press the "ZERO" button to calibrate the tool to true zero, open it to clamp in the object, and close the inner-facing jaw (which is called the "outside jaw" since it measure the outside diameter) to get an accurate reading.  If you need to measure the inner diameter of an object -- say, the inside of the mouth of a jar, of the distance inside the corner joints of the main panels of this model -- you close and zero the tool, insert the outer-facing jaws (which, you have already guessed, are called the "inside jaw") and open until the jaw is touching the inner wall of the object.

This tool is probably more accurate than you can cut to with hand tools -- but it is way better to have excessive accuracy than it is to have deficient accuracy.

Consider this snapshot from our model so far:

CLICK TO ENLARGE

It's a picture of the top section of the model, right?  In this drawing, I have assumed that the building materials as exactly 1mm thick, so the assmebled panels are 2mm thick, and it generates the results pictured.  That is: the 90mm-wide panels, when assembled accurately, create a box with an outer diameter of 92mm and an inner diameter of 88mm.  This is important because if I want to build a roof for this model, and I want it to fit inside the corner details snugly, it must be about 92mm wide.  If it's 93mm, it won't fit in the corners; if it's 87mm, it will drop into the body of the model.

Because we don't have materials of a consistent thickness, your model is going to vary in inner and outer diameter.  Measuring before you make cuts and assemble the upper section of this build will help you avoid a lot of frustration do-overs and funny-looking results.