An Easy-to-Read Fractional Slide Rule

These rulers are easy to use, quick, and accurate. They build confidence and familiarity with measurement, and are a useful stepping-stone in the development of applied math skills.

Step 1: Materials List

1. Plastic louvered blind.

2. Scissors.

3. Paper cutter—helpful but not necessary.

4. Clear packing tape.

5. Masking tape, clothes pins, or binder clips—some kind of temporary fastener.

6. Hole punch.

7. Fine-point Sharpie marker.

8. 12-inch ruler (with zero on the very edge of the ruler).

Step 2: Prepare the Blinds

Disassemble an old plastic blind. Cut to approximate size. These rulers will be 18 inches long, so I cut the 50-inch-long blinds in half. Each 18-inch ruler will use two 20-inch sections. Wash off any grime.

Step 3: Cut One of the Blinds for the Fractional Slide

Prepare two sections that are 8 inches long. These will be used to draw the inch rule lines on your ruler and for the slide itself. You can cut the blind with scissors but it is difficult to get a square cut because of the curve in the blind. I used a paper cutter and it still took a couple of tries. I seemed to get the best results when I pressed the blind down flat. The squareness of this cut will affect the appearance of the lines on your ruler.

Step 4: Take Another Blind and Make a Hook

This blind will be the main part of your ruler. Make a square fold about 2 inches in from what will be the zero end of the ruler. Cut the bent part of the fold so that it has a nice shape.

Step 5: Temporarily Fasten the Blind to a Ruler

Hook the blind to the end of the ruler and clip or tape in place. The ruler used here has zero at the end of the ruler. Many rulers are not like this, so be aware.

Step 6: Place a Mark at Every Inch

Space marks 1 inch apart along one edge of the blind. Depending how long the ruler is, you may need to change the blind placement. This ruler will be 18 inches long so it will have to be slid along the reference ruler. Double-check the alignment of the line marks.

Step 7: Draw the Inch Lines on Your Ruler

Use one of the square-cut pieces and a fine Sharpie pen to create the rule lines.

Step 8: Finish the Rule by Labeling Each Inch

Write the number in the upper right 1/4 of each segment.

Step 9: Create the Vernier Scale on the Slide

Depending on the type of ruler you want to make, you will be offsetting the fractional scale from the ruler by the amount equivalent to the accuracy of the fractional slide. The slide is composed of a top and bottom section that are taped together. These are the squared pieces that you used to draw the rule markings.

Step 10: Lay Out the Top Slide

Using the section of blind you used to mark the inch rule, carefully line up the previously squared end of the blind to a mark on a ruler and temporarily fasten in place. The picture shows the ruler lined up to one of the thicker lines. I used one of the thinner lines because I felt like it was easier to see what I was doing.

Step 11: Create a Vernier Scale and Determine Spacing

Here I am laying out markings that will read in 1/8-inch increments. The markings on the slide are set 7/8 inch apart. For a 1/4-inch incremented scale, the spacing would be 3/4 inch. When you begin to use your ruler, this should make more sense, but for now just decide how accurate you want your ruler to be. Given the size of the holes we will be punching in the slide, making a slide that reads in 1/4-inch or 1/8-inch increments makes the most sense.

Step 12: Draw Marker Lines

Using the other squared section of blind as a guide, draw the Vernier scale lines on the bottom half of the fractional slide.

Step 13: Punch a Hole

Use a hole punch to make a hole centered on the line. I should have drawn my lines a little longer here ... so that a mark remains at the top and bottom of the hole. Punch your holes low enough so that the numbers on the inch rule will not be visible through the openings—that is, below the upper 1/4 of the rule.

Step 14: Label Your Vernier Scale

Punch a hole in the zero of the scale, mark a line on the edge of the zero end, and draw a small arrow just touching the zero end of the fractional scale.

Step 15: Assemble the Vernier Slide

Cut and place a strip of packing tape sticky side up on the table. Place the fractional slide ruled side down on the strip of packing tape. Sandwich two long sections of blind between the top and bottom pieces—this allows the slide to move easily once the slide is taped. Carefully tape down the edges of the tape onto the bottom piece, which I like to offset from the zero of the slide so that it does not interfere with the hook on the inch rule. Rub down the tape and extract the spacer sections of blind. Lastly, punch out an edge of the slide as a thumb grip and round off the tail end of the slide.

Step 16: Test Out Your New Ruler

Connect the two parts of the slide rule by inserting the tail end of the inch scale into the fractional slide and test out the magic that is your new ruler. Here, the arrow points to the 1-inch mark on the rule and there is a line through the hole under the 1/4-inch punch hole. This means that the ruler is measuring 1 1/4 inches between the zero-hook of the inch rule and the zero-arrow of the fractional slide. Happy measuring!

Step 17: Tell Us What You'll Do With the Form 1+ 3D Printer If You Win!

As a workshop teacher for 5th through 8th graders, I would use the printer as a tool for teaching—hopefully as a means to inspire my students' creative potential.