Intro: Angle Divider for Perfect Miters No 2
In January 2016 I did an Instructable on my copy of a Stanley No 30 Angle Divider. This is another version of the Stanley No 30 Angle Divider that looks a little more like the original from 1903. (Search your favorite browser for Stanley No 30 Angle Divider to see images of the original version with a wooden handle.)
But, the chief advantage of this Instructable is a jig for drilling the center pivot hole in the body. That jig makes dead on accuracy almost foolproof. However, this version is also more work with more steps. But, some shortcuts could be taken for those who do not have access to a welder or want to avoid the extra work.
The photo shows this version of the Angle Divider in use to set a power miter saw. The other member of the miter would be set and cut by turning the Angle Divider 180 degrees and adjusting the saw to the other half of the fence. The fence on this saw had a wavy profile. I needed to catch more of the blade because I was cutting some tall baseboard molding, so I added 3/4 inch plywood to the face of the fence. That brought the work out toward the operator and caught more blade. It also gave a flat top surface for the Angle Divider, which resulted in easier and more accurate setting of the saw.
- Hardwood fully cured
- 16 gauge sheet steel
- 1/4 inch steel rod
- 3/16 inch steel rod
- 3/8 inch steel rod
- 3/16 inch nylon locking nut
- 1/4 inch flat washer
- 1/4 inch wing nut
- 3/4 inch plywood
- Wood glue
- Table saw
- Router and router table
- C clamps
- Spring clamps
- 4 1/2 inch angle head grinder with cutting wheel
- Straight piece of 3/4 inch angle iron for a cutting guide
- Drill press and drills
- Electric hand drill
- MIG welder (GMAW)
- Bench grinder
Step 1: First, the Jig
You do not make a jig unless there is no other way to get accuracy on something, or you want to make multiple copies of something. I have so come to appreciate how well these angle dividers work that I am using up scrap materials I have to make some as gifts to friends who can utilize them well.
The first photo shows the finished jig. To make it, begin with a rectangle of 3/4 inch plywood about 9 x 11 inches. This is the base.
See the second photo. Glue two strips of plywood about 1 1/4 inch wide across one end of the plywood base. This will make a fence against which you will push the arms or wings of the Angle Divider before drilling the pivot hole.
See the third photo. Fasten a piece of 3/4 inch plywood to the base and make it 90 degrees to the fence made of two layers of plywood.* Near the right side glue a spacer to the base and the fence. (See the text box in the photo.) This spacer assures space between the end of the body and the straight edges of the wings or arms.
See the fourth photo. It shows the location of two pieces of Masonite glued to the base piece. They lift the body of the Angle Divider and provide a void where the head of the adjusting bolt can rest when the jig is in use. See the text boxes in the photo. Notice the 90 degree fence. The body of the Angle Divider will be firmly against this during the locating of the pivot hole. This must be exactly 90 degrees to the fence in the second photo.
See the fifth photo. The weld on the bottom of the adjustment bolt "head" made a bump that sometimes caused the wooden body of the Angle Divider to rise, and I got some inaccuracy on one copy I made. So, I made a recessed area with a Forstner bit. See the text boxes. The steel rule also gives measurements for the area between the pieces of Masonite.
Set the jig aside until later once it is completed.
*I was getting a slight inaccuracy in my finished Angle Dividers. I discovered that the 90 degree fence was not exactly 90 degrees to the fence made from two layers of plywood. The jig works like a charm once I corrected that problem. A good precaution would be to install the 90 degree fence with screws rather than glue so some adjustment is easy later. That would mean leaving a little space between the 90 degree fence and the Masonite.
Step 2: Cut Steel for the Arms or Wings
I have some rusty scrap 16 gauge steel that works well for making an Angle Divider. It is about 2 inches wide, but has nice straight edges.
See the first photo. I cut a piece 7 inches long.
See the second photo. I marked a diagonal line across the 7 inch piece of steel. The diagonal is laid out so that one end of each 7 inch piece will be 1 1/4 inches wide and the other end will be about 3/4 inch wide (minus the width of the cutting wheel). I used a piece of angle iron as a guide to get a straight cut. The angle iron is clamped to the 16 gauge steel sheet.
Step 3: Drill Holes Simultaneously
Place the two pieces for the arms on top of one another so the straight edges align with each other. I could have clamped them together with a Vise-Grip pliers. I chose to tack weld the two pieces together in an area where each weld would later be ground away in the process of shaping the arms. See the text boxes in the photo. The holes in each piece are 3/16 inch in diameter and are 2 1/4 inches apart on center.
Step 4: The Connecting Arms
I had another piece of 16 gauge steel, also scrap and rusty, but about 9 1/2 inches wide. I used the angle iron as a guide and marked a strip 11/16 inch wide for cutting so the final piece was about 5/8 inch wide. I cut two pieces 4 1/4 inches long from the 5/8 inch strip and tack welded them one on top of the other for simultaneous drilling. See the text boxes for the size of the holes and their spacing. One set is 3/16 inch in diameter, but the other is 1/4 inch in diameter. Grind away the tack welds, round the corners, and grind away any sharp edges.
Once all four metal pieces have been made and drilled, grind away rough edges that interfere with smooth action of the parts or could cut skin. Use a power wire brush to remove rust deposits.
Step 5: Lay Out the Pieces and Weld Pivot Pins in Place
It is important to lay out the pieces properly so they slide over one another as they ought. Then one must be careful to preserve that order when welding pivot pins in place. But, it is also very easy to become confused and make a mistake.
See the second graphic. Click on it so you can see all of it. It is a cross sectional view. The gray piece is the arm or wing. The olive drab piece is the connecting arm. The 3/16 inch pivot pin is in blue. The lower red rounding is a weld to the connecting arm. The collar (blue) is a piece of 3/8 inch rod center drilled 3/16 inch in diameter. The 3/16 inch pivot pin is sized and cut to length. The collar was put onto the end of the rod and welded in place.
When assembling and welding the mirror image of the opposite half the olive drab piece and the gray piece exchange positions, as you can see from the first photo.
Shortcut--Rather than welding, #10 machine screws could be used. Use a nylon stop nut to keep joints snug.
Step 6: The Wooden Body
The wooden body is fully cured hardwood. I am using some beech that is over 75 years old. It is about 3/4 inch thick and 1 1/2 inches wide. It is about 10 inches long. I cut both corners on one end at 45 degrees.
See the first photo. I fitted the metal assembly made from the hinged arms to the wooden body to mark the approximate limits of the slot so the arms have a full range of motion at 90 degrees to the body to folded over the body and I marked the ends of the slot. I set the fence on the router table so the 1/4 inch bit will cut on a line centered between the sides of the body.
See the second photo. I set end stops to limit the sliding of the body when routing. I raised the router only a little after each cut for better control.
See the third photo. After several cuts the router bit poked through. Keep your fingers near the ends of the body so you will not be injured by the router. I lightly made a few strokes on each side of the slot with a wood rasp to make the fit with the adjustment bolt smoother.
Step 7: The Adjustment Bolt and Its "head"
The first photo shows what I wanted to make, except the smaller rod has not yet been cut and welded.. (If you want to reduce your work, just buy a 1/4 inch carriage bolt and file or grind two opposite flats under the rounded head so it fits the slot smoothly.)
See the second photo. Use a thread cutting die to make about 5/16 inches of threads on the end of a 1/4 inch rod. The threads should be 1/4 x 20.
See the third photo. Drill a 1/4 inch hole in a piece of steel bar 1/8 x 3/4 inch and cut it to about 1 1/4 inches in length. Drill a 3/16 inch hole to fit a rod as you see in the first photo.
See the fourth photo. Put a wing nut onto the threads on the 1/4 inch rod, but leave it at least one turn loose. Add a washer. Add the connecting arms. Put the rod through the body slot. Add the 1/8 inch "head." Saw to length with a hacksaw.
See the fifth photo. I drilled a 1/4 inch hole into a piece of sacrificial wood so the 1/4 inch rod would be perpendicular to the flat steel that is the adjustment bolt's head. See the sixth photo. Place the 3/6 inch rod into its hole and cut to length. The 3/16 inch rod keeps the head from turning when the wing nut is tightened. Weld both rods.
Step 8: Fitting to the Jig and Drilling.
Place the adjustment bolt through the slot. Place the connecting arms over the bolt. Add a washer and the wing nut. Place a 3/16 inch rod into the pivot hole. See the text box on the first photo.
See the second photo. Slide the wooden body against the 90 degree fence and against the spacer. Slide the adjusting bolt in the slot until the arms are firmly against the fence. The pivot hole centers itself if all is done properly as described.
See the third photo. I clamped the arms down so they cannot move. I had to use a piece of scrap wood so the clamp applied pressure as desired.
See the fourth photo. Drill by hand. If everything is locked down as it should be, the hole will be located exactly where it needs to be.
See the fifth photo. Check from both sides with a T bevel square. The setting between one arm and the body should be exactly the same on the other side. (If it is not, fill the hole with a 3/16 inch wooden dowel. When the glue is dry, locate the hole again and drill.)
The photo shows a 10 - 32 screw in the pivot hole. I used it to check the tool for accuracy. If you wish to take a shortcut, use a 10 - 32 screw with a nylon locking stop nut. I wanted a smooth rod where the hole in the arms or wings fit the pivot. So, I threaded a 3/16 inch rod with 10 - 32 threads. I sized the length of the rod in the wooden body and allowed for a collar. I did not want to burn the wooden body with heat from welding, so I removed the pivot rod and welded the collar with the rod in a vise. I used a nylon locking nut and made it snug, but not too tight.
I have found the parts of the Angle Divider move more smoothly if I rub the wooden body with a little paraffin for lubrication. It also helps to file both sides of the slot a little with a wood rasp I turn the Angle Divider over so the wing nut faces downward and use my thumb to slide the wings firmly into the corner. Then I use my other hand to tighten the wing nut on the adjusting bolt. See the photo in the Introduction to see again how measurements of the angle are transferred to the saw.
See the sixth photo. This Angle Divider will help you get miters like this on any corner with ease. (The test pieces are from an old park bench. Edges were not planed or particularly smooth, but are fairly straight. The test pieces are 2 1/8 inches wide, which is more than enough for any inaccuracies to show clearly, but the miter is tight and neat. The corner is more than 90 degrees.)
(For outside corners, record the angle of the corner with a T bevel square. Fit the Angle Divider to the T bevel square and proceed as if you were working with an inside corner.)