Dobladores

Hinges - Benders

Tonight's demo is on hinge benders. Both types are found in the book Professional Smithing by Donald Streeter, 1980. These are relatively standard. I've used both types. Couldn't find the parts of either. . must of canabalized them. A common thing to do since I'm down in the country.

Often if you are short a piece you ah, "borrow" it from something else.

Figure 1 If you make these to handle thicker stock they will also work on thinner stock. However the pin size stays the same. The bending nose is best made of some sort of hardenable tool steel.

I differ from Streeter in that I make the stationary part from a piece of angle so it can be clamped in a vise. I am also using shims on one side of the bending nose rather than set screws on both sides. Remember that wide benders work on narrow hinges but no vise versa. Don't get carried away. There is a limit to what the pin can take. Bigger benders need to be made heavier too.

Figure 2

Figure 3

There are several ways to use this type bender. Streeter clamps the bending nose tight on the stock and pin and lets the stock pull through the bender.

Figure 4

Figure 5

Figure 6 The other method is to feed extra stock through the bender and clamp it to the stationary arm. Then adjust the bending nose to a slip fit and pull it around.

This method also works for ends that are pre-bent and prepared for welding.

Figure 7 Our second bender is used on an arbor press. This type is best used on thin material. It makes a wrap that goes as far as possible.

I make these benders using a mandrel that can be used to push the bent hinge out of the bender. Click to enlarge.

Figure 11 Stock can be prepreped with notches or cut later. If using a press to shear stock it is best done before hand. If hand sawing the stock you can fit the parts after bending.

Figure 8 These benders work in any arbor press big enough to get them in. You can also use a vise or tap the pusher with a hammer. The arbor press does a better job.

Figure 9

Figure 10

The pusher bridges the guide plates. After pushing the stock home the mandrel is used to push the finished part out.

Figure 12 The finished bend by this method is clean and smooth with a complete wrap.

Detail 1

Detail drawing of the lever type bender.

The tools required to make this bender are, an arc welder, drill, hand saw and files.

I differ from Streeter in that I make the stationary part from a piece of angle iron so it can be clamped in a vise. For long benders the angle iron may be extended with flat bar if needed to clamp the hinge. The angle only needs to be about 8" long. I am also using shims on one side of the bending nose rather than set screws on both sides.

The handle for this bender can be round pipe or square tube. For common hinges the length needs to be about 28" (711mm).

Figure 2

Figure 4

There are several ways to use this type bender. Streeter clamps the bending nose tight on the stock and pin and lets the stock pull through the bender as in figure 2. This requires a slightly narrower "nose" with square corners on the tool (see middle of detail). This end could be on the opposite of the nose piece if you are going to use both methods.

The other way to use the bender is to let the nose slide on the stock as it bends it around. In this case the nose needs to be round and smooth.

The bending nose is best made of some sort of hardenable tool steel.

Notice how the bending nose needs to clear the stationary part.

Although these benders are normally used cold they can also be use hot.

Be prepared to quickly drive the pin out with another slightly smaller pin if bending hot.

Detail 2

Detail drawing of the press type bender.

Tools required to make this bender, a metal working drill press, saw, arc welder and dial calipers. Optionaly it helps to have a lathe to make the mandrel and a mill or shaper to square up blocks or cut the slot.

The hole size needs to be carefully determined. The pin or mandrel wants to be an even stock size for what ever system you are using. Add to that double the thickness of the stock. Then add .010" (.25mm) to the total and find the closest drill size to that number using at least 1/64" (.4mm) drill sizes. When using gauge sizes be sure to use actual decimal size of the stock.

Detail 1 The tricky part of making this bender is the slot. My first one of these was sawed. My second one cut using a 1/16" (1.5mm) lathe cut off tool in a shaper.

The width of the slot is not critical, however it must be tangent to the edge of the hole.

Detail 2 An alternative method for making the slot is to fit pieces together as shown.

The small piece is the slot. The pieces must fit together very snugly or the drill will hang on an edge and possibly break. Cold drawn steel or ground precision bar is recomended.

The slot can also be made without the fourth "slot" piece. See below.

Detail 4

Detail 5

There are two ways to use loose pieces. One is with a piece that is removed for the slot. The other is with three pieces. When using three pieces the third piece makes the inside of the slot. After drilling the third piece is removed and cut off square then replaced flush to the edge of the hole.

Detail 3 When using loose pieces they must be clamped together tightly and welded before drilling. When using a fourth piece for the slot it should be lightly welded so that the the welds can be ground off and the piece removed. The other pieces should be permanently welded together. IF using the three piece method the third piece needs to be held tightly but not permanently welded. After drilling it is removed, cut off and then replaced by either bolting or welding.

The hole center must be very carefully laid out. Then a center drill or pilot drill used to position the hole. Note that a normal small pilot drill nay be too small for drilling across the joint surfaces. 1/4" (7mm) should be satifactory.