A 12 Inch Divider

I always believed I could measure something and divide it into equal segments using a calculator and a rule. But, something usually goes wrong. After I plot the segments, they are not equal or I do not have the right number of segments. Finally, I made a divider. I have used it several times to achieve equal segments on a project. I have also used it to measure something difficult to reach otherwise. This Instructable will show how to build one like the one I made.

Materials

• 5/16 inch steel rod
• 1/8 x 3/4 inch flat bar
• 1/8 x 1 inch flat bar
• 1/8 x 1/2 inch flat bar
• 3/16 inch steel rod
• 1/4 inch threaded rod
• 10 - 32 self locking nut with nylon insert
• Washer
• Grease
• 1/4 x 20 hex nut

Tools

• Metal bandsaw
• Measuring rule
• Grinder
• Vise
• File
• SMAW (stick) 230 volt arc welder
• Spring clamps
• Vise-Grip locking pliers
• Vise-Grip locking welding clamp
• Tap and die
• Drill
• Wrench

Cut two rods from the 5/16 inch stock to a length of 11 inches each.

I chucked each rod in a handheld drill and ground a taper on the last couple of inches of each by holding it lightly against a spinning grinding wheel. The first photo shows grinding a point to one of the rods after grinding the taper. Simply make it so it looks right to your eye. The second photo shows the tapers on the two rods and their pointed ends.

In the third photo the vise is partially closed so the rod rests on the vise jaws. Spin it with a drill while holding a metal file to the tapered area in order to smooth it.

Cut two pieces of 1/8 x 3/4 inch flat bar to a length of 1 3/8 inch each. Clamp them together with a locking pliers and drill a 3/16 inch hole through both. Use spring clamps to position one of the rods and one of the spacers. Notice the hole is away from the 5/16 inch rod, not next to it. Weld the two pieces together. (I have a stick welding project in the future, and am using a stick welder for this project in order to get more practice. Also, Some who have access to a stick welder, but not a MIG welder, may want to make this divider.) Repeat for the other pair of pieces.

When the welds have cooled, clean the slag from the weld and grind as desired for smoothness. Grind away any sharp or rough edges.

Place a 3/16 inch rod in a vise. Slide the two welded rods and spacers onto the rod in the vise. Use a spring clamp to hold the two welded assemblies together. Observe how well the points of the divider align. Note that how the spring clamp is used can give a false indication. Place the flat bar portion in another vise and push or pull to correct. Check again to see if the points of the divider align better. Some final adjusting can be done later, too.

Use a 10-32 thread die to thread about 1/2 inch on the end of the 3/16 inch rod. (The photo shows my homemade die holder for six sided dies.)

See the second photo. Hang the two rods with welded flat bar spacers on the 3/16 inch rod. I do not want the hole in one of the spacers riding on threads, but on smooth rod. Slide both welded pieces until the smooth rod is just disappearing. Use a hacksaw to cut the rod flush with the backside of the spacers.

Drive the short piece with threads into the hole in one of the spacers. Make its end flush with the backside of the spacer. Weld the short rod with threads to the spacer. (I ground the mill scale away before welding for all welds for better results.)

I greased the surfaces which will slide over one another. Add a washer and a self-locking hex nut. Tighten so there is no looseness, but the movement of the divider legs is smooth.

I used a locking pliers to bend a curved piece around a piece of steel pipe. The curve in the rod is not as tight as the pipe itself. I chose to work with a vise to close the curved piece so it fits the pipe more closely. This is not a perfect process and adjustment can be done later.

Use a compass to draw some arcs on a piece of paper to determine what the actual radius of the curved rod is. I determined mine is 1 15/16 inch.

Measure the radius (1 15/16 inches) from the center of the axle bolt and mark on the two legs of the divider. I used a turnbuckle as a temporary spacer to support the curved rod and clamped it down in preparation for welding. I welded the end of the curved rod nearer the bottom of the photo to the leg of the divider. Grind and smooth after the weld has cooled.

I placed my thumb against the leg of the divider that is not welded to the curved rod. Open and close the divider. Notice if and where the curved rod pushes the thumbnail away and where the curved rod moves away from the thumbnail.

Catch the area of the curved rod where the deviant curving begins with a corner of the vise jaws. Tap with a hammer to adjust the curve in the rod. Test again. When finished, the curve in the rod will be very precise and right where it should be.

I cut a piece of 1/8 x 1 inch flat bar 11/16 inch long. Drill two holes in the flat bar piece on 3/4 inch centers. See the photo.

Cut two pieces of 3/16 inch rod so each is 5/8 inch long. Drive on end of each rod into each hole in the flat bar. Drill a hole slightly larger than 1/4 inch midway between the two 3/16 inch holes. Move the pieces to a welding table and weld the 3/16 inch rod to the sides of one of the 5/16 inch legs. Remove slag and grind smooth after the welds have cooled.

Place a 1/4 x 20 hex nut over the latest hole. I used a very short piece of a wooden 3/16 inch dowel rod to center the nut over the hole. The wood did burn some while welding, but its purpose was to position the nut with something easily removed. Too often when I weld a nut the threads become distorted. Using a 1/4 x 20 bolt would result in damaged threads when I tried to remove it. Notice the nut is held by a spring clamp and ready to weld. The ends of the 3/16 inch rods are welded in the flat bar during the same operation. (Note: Welds sometimes pull together and reduce tolerances when they cool. The curved rod no longer moved smoothly through the cage for it. I opened the divider and lightly ground the surface of the curved rod to thin the rod a little until the divider opened and closed again smoothly.)

I chased the threads in the nut to make them work smoothly again.

I placed one leg of the divider into a vise and made a small bend in each toward one another. This is a good time also to bend the legs as needed so the points align and are equal in length. One side of this divider was a tiny bit longer than the other. Placing a very slight bend near the curved rod made them equal in length again.

I made a locking screw by welding a piece of 1/8 x 1/2 inch flat bar across the end of some 1/4 x 20 threaded rod. Grind the corners smooth and round.

My wife wanted to hang Christmas stockings for children and grandchildren from a fireplace mantel. I marked off how much should remain between the ends of the mantel and the first hook on each side. Then I used the divider to space hooks equally. The job was much easier and less prone to mistakes.

A divider like this may not get used everyday, but it is certainly handy when needed. I thought about an attachment to hold a pen, a marker, or a pencil. I decided for the rare occasions when I might want to do that, I can simply use duct tape to attach the writing tool to a leg of the divider and then cut it off when finished.

I recently used this with a welding project. The spacing I needed was wider than 12 inches. I set the divider for about half of what I needed and marked off two spacings to get an accurate mark wider than what this divider can normally handle. Of course, I needed to make some fine adjustments and repeated tries until I had the division markings I needed.