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BENDERS 1

For Duplicate bends


HOW TO MAKE A UNIFORM OR DUPLICATE BEND
This is a simple bender. It can be made for any type of curve. In busy architectural shops you may find hundreds of these lying about. This one is made on a piece of angle so that it can be clamped in a vise or edge of a bench. The original curve can be bent hot or cold, by eye, on a wooden form or to a template. The material is mild steel and is arc welded. You could also weld a shank on it to fit your hardy hole.

Two Scroll jigs. The first was used to bend 7/16" square, the second 3/8" x 1" flat bar. Notice that the second jig is two stage. When using both these jigs the ball, bean or scroll end is forged first and then the long scroll bent. These work on plain or tapered material.
The little universal bender above was shown to me by Peter Lindbergh of the Longship Co. The two identical parts are clamped in a vise adjusted to suit the current job.
The bender above is one of several sizes made to make ends for straps using a pinned connection. It is one stage in a multi stage process. Oblong holes were first machined in the blanks. Then the tight bends with critical tolerances were made in a simple press. The bender was the last stage before welding. It was used to produce the long and the tight (pin) bend. The finished parts are now on an oil drilling platform in the Gulf of Mexico.

The benders above were found in Josh Greenwood's shop. Some are mounted and some are not. The unmounted ones are simply clamped in a vise or to a bench. To get the necessary height for starting scrolls he forges a fishtail flare before scrolling. The smooth taper also helps produce a smooth spiral as the thinner material bends easier than the thick.


BENDERS 2

Commercial Benders


Two small dedicated benders from the M.O.T.A.T (Museium of Transport and Technology) located in Auckland, New Zealand. The scroll bender on the left is cast iron but there are similar benders made of flame cut steel that is bent (pulled out) after torching a spiral cut. The bender on the pipe stand is for bending horseshoes. Note the extra hole for the anchor bar. Images above courtesy Andrew Hooper, Kiwi Blacksmith, NZ.


This unusual little bender is from Andrew Hooper's collection. It appears to be a production product and is very similar to the cast bending jig above. What is unusual about this jig is the ingenious method of manufacture mentioned above.

The scroll is torched from a piece of 1/2" (13mm) plate and then pushed out. The end pins are knurled to help grip the bar and are mounted through excentric holes so that the jig can be adjusted for different bar sizes.



A Diacro bender. These comercial benders are no longer made by the original manufacturer.
Hossfeld Bender. These are also still manufactured. The Diacro and the Hossfeld are most often found in commercial fabrication shops and are used for cold bending. However, they can both be used for hot bending and greatly increase their capacity. Full sets of dies for these benders are expensive and rarely found with used benders. Generaly it is easier to make a special hot bender than to make dies to fit these machines.
Scroll Bender attachment and detail of Hossfeld bender. Note that this is for bending 1/8 inch flat stock without a forged end. All the leverage needed comes from the 6" (9cm) offset of the crank handle bent in the shaft.

Future articles will cover how these commercial benders are used and building similar benders.

BENDERS 3

Special Benders

Double bend pickett bender

Picket Bender

The drawing above is for a double bending setup to be used on a weld platen. It is for bending the pickets commonly used on balcony rails in Italian and Spanish style ironwork.

The bending is done in two stages. The first stage is the large radius bottom bend. It is done without the second stage bender in place as it would interfer with the sweep of the bar. The corner bend is forged first, then the part placed in the bender against the starting post. The lift off bending handle is placed over the center post and the first bend is made. The end position is shown by the dotted line in the drawing to the right. A certain amount of "over bend" will be required due to spring back.

After the first bend is complete the bending handle is removed and the second stage bending jig installed. This should have some tabs or short bars on the base so that it just drops into place on the weld platen. The bending handle is put in place and the second bend is made. The end position (for spring back) is shown by the dotted line in the drawing to the right.

Note that I have shown a flat between the two bends. This may or may not be needed according to your design.

Once the jigs are tested the bending can be done in batches, one stage at a time. However, it might be benificial to clamp the bar in place with a C-clamp after the first bend. In this case the second stage bender is removed and installed for each part. This is why the weld platten is recommended for setting up this type bender.

To constuct the bender guide surface the bending arm should be used to assure a smooth fit. I prebend the flatbar, weld the starting end, adjust the bending arm against the flat and then work around the arc with handle tack welding the part in place. This assures a smooth radius with the center pin exactly centered.

You can make seperate bending arms for the two different radii OR make the handle adjustable. It is actualy easier to make seperate handles if you have the materials. The rotating bearing may want to be longer or have two plates rather than what is shown above. See bender below for adjustment ideas.

U-bolt bender

U-Bolt bender

This is a custom made bender I built to make several sizes of large U-bolt. It has two interchangable dies and an adjustable bending arm.

A pre-threaded bar with a nut on the starting end is positioned against the inside vertical surface of the angle iron bracket. The poistioning of the nut assured that the legs of the U-bolt came out exactly the same length. In this case that was when the nut was flush to the end of the rod.


Click for enlargement
  U-bolt bender top and side views.

The bending handle pivots on two hard steel shoulder bolts. It slips inside a piece of square tubing and is held in place by two set crews.

Roller nose detail


The roller nose is made of mild steel. It had a low "V" groove but bending pressure made it fit the round bar being bent perfectly. Benders can also have a plain "nose" but they need to be hardened and polished tool steel.

The vertical tab bolted on behind the roller reacts against the bending arms to reduce flex.

This special bender was built for a production job that was quoted in the thousands of parts but only a dozen were ordered. The cost of the bender which took about 12 hours to build was built into the quote. This was done by pricing the parts on a curve where ONE equaled the cost of the bender plus the minimum stock order and single job costs (setup, purchase materials, delivery). Ten were priced at the bender cost plus actual estimated labor, then the same for 100 and 1000, each with single job costs. If I had bid on the perceived cost of one part I would have lost my shirt on the job. The result was I made money and had a nice bender left over. Anyone need some 1/2" dia. x 6 or 8 inch U-bolts?


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