The Veritas Steam-Bending System is very versatile in the fact that an endless variety of shapes can be made using the various components alone or in combination with each other. From simple bends to "S" bends to change-of-plane bends the same three somponents are essential: and adjustable end stop, a fixed end stop, and a steel strap.

Simple Bends

The adjustable end stop, in conjunction with the strap, and a fixed end stop allow you to do simple bends as shown below. All these bends are in one direction and in one plane.

"S" Bends

The adjustable end stop, fixed end stop, and two steel straps in conjunction with the S-bend unit allow you to reverse the direction of the bend to make "S" bends as shown. All these bends are in two directions but in one plane.

Change-of-Plane Bends

The adjustable end stop, fixed end stop, and two straps, in conjunction with the change-of-plane unit, allow you to change the plane of the bend to make the shapes shown. All these bends are in two directions and two different planes.

Combination of Bend Types

Each system can be used in conjunction with each other to give you an endless variety of combinations of bends. Shown are a couple of examples of combinations that can be put together to form more complex designs. Your imagination is the limit.

Single Bends

It is very important that the requirements for steam bending air-dried hardwood be followed, as outlined in the introduction. If you have not read the introduction, do so before attempting to bend. Damage to your equipment may result if the guidelines are not followed. To simplify your introduction to steam bending wood, we will first walk you through the process of bending a 3/4" × 1-3/4" × 24" piece of air-dried hardwood (approx. 20% moisture content) around a 6" radius 90? bend. The last section will provide some general information for bending a wide variety of single-plane shapes.

Building the Bending Form and Drying Jigs

Laminate three pieces of 3/4" × 12" × 12" plywood. Mark off the radius, bandsaw the curve and prepare the face so it is free of bandsaw marks. Mark out the inside curve and bandsaw. This face does not have to be finished in any way; it is just providing a clamping face that is parallel to the form face. If you have built a bending table, then the form can be secured to the table with 3/4" pins. Otherwise, the form can be screwed to your work surface.

If you want to try more than one bend, the blanks can be dried on individual jigs or frames as detailed in the introduction.

Assembling the Strap and End Stops

In addition to the components in the Veritas System, you will need a wooden end stop and a lever.

CAUTION: As it is coiled, this strap is under tension and care must be taken when cutting the restraints. First, cut the tape holding the outside end down, and then clamp this end to a fixed surface. While holding the coil, cut the remaining tape, and slowly unwind the rest of the coil.

Attach the strap to the adjustable end stop as illustrated in Figure 15. Adjust the end stop so that there is at least 1/2" between the end stop and the thrust plate. (This space will allow you to back off the end stop in certain applications.) Measure off the length of the bending blank and mark the strap. Because most bending situations involve blanks of different lengths and cross sections, making a hardwood fixed end stop with a series of equally spaced holes is recommended. Making the fixed end stop (as shown in Figure 16) will accommodate most conditions. However, in some instances a custom-made fixed end stop will have to be made.

The width of the fixed stop should be equal to the strap width and not less than the thickness of the blank to be bent. For this specific bend, the fixed end stop dimensions are 7/8" × 2" × 9". The position of the two 13/32" holes is measured from the mark on the strap to the center of the first hole that is at least 3/4" away, then on center to the next hole.

The bending lever is the next part required. This lever will be 1-3/4" × 1-3/4" × 36". It is extremely important that the lever extend past the fixed end stop by at least 4" on thin (<1"), narrow stock to as much as 8" on thicker stock as shown in Figure 17. Drill the two holes in the lever (remember to drill the first hole back far enough to accommodate the lever extension). Take care to drill the holes perpendicular through both the end stop and the lever for good hole alignment.

Assemble the fixed end stop, strap and lever as illustrated in Figure 17. By clamping this extension to the bending blank, local compression at the fixed end stop is eliminated. Before steaming, lay a blank on the strap assembly and bring the adjustable end stop to within 1/8" of the blank. Once the hot blank is removed from the steamer, you will have to work quickly, so it is best to be prepared beforehand. Remove the unsteamed blank and swing the lever in the approximate path that it will travel as the wood is bent. Clear any obstruction that will interfere.

The Bending Procedure

Before inserting the blank in the steam chamber, go over the safety instructions in the introduction. After the appropriate steaming time (in this case 45 to 60 minutes), remove the steamed blank. The blank will be uncomfortably hot, so wear gloves. The strap clamp is designed to lay on its side for easier handling. Install the blank in the strap clamp and lightly clamp the blank to the extended portion of the lever. The clamp should be close to the extension end with the handle of the clamp on the lever side of the strap as shown in Figure 17.

With the blank held tight to the strap, tighten the adjustable end stop so that the blank is in contact with both the fixed and adjustable end stops. Continue to tighten the adjustable end stop until the strap just begins to arch away from the blank. Tighten the clamp on the extension lever. The assembly should now be stiff and can be put in place up against the bending form as shown in Figure 18. Securely clamp the steamed blank to the face of the form with the adjustable end stop up against the end of the form.

Slowly bring the lever around, applying clamps as necessary to keep the blank tight to the form. The very first clamp applied while the assembly was flat on the bench will soon come in contact with the form face. This clamp can now be removed and the blank can be brought tight to the form, secured and allowed to cool.

In other applications, if there is excessive compression wrinkling on the inside face of the steamed blank, the adjustable end stop can be backed off a turn or two before continuing with the bending process. Back off too much and the wood will tear on the outside face.

Removing the Bent Blank

If this is a one-off bend, then it can be left on the form; however, it is best to remove the metal strap after an hour or so. If a number of bends are to be completed one after the other, then the bent parts have to be removed from the strap. However, it is extremely important that the individual bends be allowed to partially set until cool on the bending form before being transferred. This allows the lignin to begin to bond in its new position. The time varies for this according to the mass of material and the severity of the bend. The piece that has been bent for this demonstration should be allowed to set for 20 minutes. The setting process (in this example) can be reduced to 5 to 7 minutes if a jet of compressed air is directed at the bent part. As with a lot of the elements of wood bending, experience is the best teacher.

Once the blank is cool, the adjustable end stop can be loosened and the clamps removed. One thing is certain at this point, and that is the necessity for speed while transferring the parts from the bending form to the drying jigs. Failure may occur if the part is allowed to straighten out too much while being transferred. The wood fibers may unsuccessfully attempt to stretch as the part is reformed to the drying jig.

Once a bent part has dried thoroughly, a measurement of the inside face will reveal the amount of compression that has taken place. In this instance, the compression will be approximately 1-1/4", most of which has occurred at the curved portion of the inside face.

RECURVE OR "S" BENDS

The addition of the S-bend unit and a second strap to the single bending strap assembly opens up a number of design possibilities. You can either cut the 10' strap included with the 2" Strap Clamp (will leave approx. 8' bending blank capacity), or purchase a second strap. The purpose of this parallelogram assembly is to enable you to transfer the strap (the restraining force) from one side of a blank to the other, ensuring that a bend reversal still keeps the entire blank under compression. The maximum size of wood that the S-bend unit is designed for is 1-1/4" thick × 2" wide. Although a thicker piece can be placed within the unit, doing so will position the linkage in such a way that the loads it experiences rise dramatically and may break the unit.

It is strongly recommended that the novice user gain some experience in bending wood by completing a variety of curved pieces with the single bend strap assembly before attempting "S" bends. The bending forms and compressive forces at work are more complicated when using the recurve hardware.

As with the single bend hardware, it is easier to get the basic information across if specific instruction is given on completing a typical recurve using the parallelogram hardware package.

Building the Bending Form and Drying Jigs

In this case, we will be bending a symmetrical "S" of two 8" radii. The bending blank will be 3/4" thick × 1-1/2" wide × 76" long. The bending table previously described would come in handy; however, a piece of 3/4" plywood 28" × 36" can be used. Laminate two three-piece stacks of 3/4" plywood 12" × 6". Mark out the 8" form face radius and 4" inside clamping face radius on both pieces, bandsaw to shape, and smooth the outside face as shown in Figure 20.

On your bending table or plywood, draw two centered perpendicular pencil lines, as illustrated in Figure 21. This forms an axis that will assist in keeping your two forms in alignment when they are attached to the table. Lag screw the parallelogram securing bracket to the bending table (as shown in Figure 21) or, if you are using a piece of plywood, the bracket should be bolted in place using two 1/4" × 1-1/2" flat-head bolts. The head of the bolt should be countersunk into the underside of the plywood so that it can rest flat on the work surface.

Assembling the Strap

Attach the S-bend unit to the securing bracket with the hex socket head cap screws and hex key provided. Attach the two straps as shown in Figure 22 to the inside face of the jaws of the parallelogram.

Mark off half the length (38" for this demonstration) on an unsteamed blank and slide it into the S-bend unit parallelogram until the halfway mark meets up with the center of the fixed jaw of the parallelogram. Lightly clamp across the jaws to hold everything in place. Depending on the size of your work surface, a stand or support at either end will assist in keeping the long strap assembly manageable while attaching the end stops.

On the strap that will bend to the left, attach the adjustable end stop. The thrust screw will have to be adjusted until the flat-head machine screws line up with the holes in the strap and square tube. In this and other applications, always maintain the 1/2" minimum space between the adjustable end stop and the thrust plate. At the same time, it is not recommended that the thrust screw be extended out to the maximum. In some instances, the length of the bending blank will have to be adjusted to meet these requirements.

Before the square tube can be assembled, a predrilled lever arm (as shown in Figure 23) must be inserted into the square tube. The washers and nuts can then be tightened in place. Temporarily clamp this assembly to the blank.

The fixed end stop is attached to the other strap next. This end stop is brought up against the end of the unsteamed bending blank and the corresponding strap holes are marked on the fixed end stop. The lever

arm is added next. Do not forget to accommodate the extension part. Securely bolt this assembly together and lightly clamp it to the bending blank. The S-bend strap assembly should now be rigid and in line with the axis previously laid out on the table.

The center line of the left form (or the beginning of the curve) is positioned 1" from the end of the movable parallelogram jaw as shown in Figure 24. This is a minimum dimension; otherwise, the strap will pull away from the inside of the jaw and damage the retaining pins in the parallelogram.

The position of the right bending form is also 1" (minimum dimension) from the end of the fixed parallelogram jaw. Both forms must be securely fastened to the work surface, either using 3/4" pins (at least two per form) or several wood screws per form. The adjustable end stop should be backed off 1/8" to allow for easy installation of the soon-to-be-hot blank. The unsteamed blank can now be unclamped, removed from the set-up and put in the steam box.

The Bending Procedure

After the appropriate steaming time (in this case 45 to 60 minutes), carefully remove the steamed blank. The blank will be uncomfortably hot, so wear gloves. You have about 3 or 4 minutes to complete the bend before the wood cools too much.

With the end stops resting on the supports and held slightly to one side, slip the steamed blank through the parallelogram assembly. Bring the strap into place and lightly replace the three clamps from the earlier set-up. Tighten the adjustable end stop thrust screw until the steamed blank is in contact with both end stops, then give it one more turn so that the whole assembly is under slight tension. A bit of experience is useful at this point. Too little tension and the wood fibers next to the strap will tear, too much and compression wrinkles will occur along the inside face of the bends. The three clamps can now be firmly tightened.

Start bending the side with the fixed end stop first. The speed at which you should be bending is difficult to describe; it is medium (steady, taking about 10 seconds to go through 90?). Once 90? has been reached, a judgment call is made whether or not to back off the end stop thrust screw a turn. This radius and wood thickness generally do not require it at this point. However, a clamp or two may be necessary to hold the blank tight to the form face as the bend progresses. Extra pins can be dropped in the appropriate table holes to restrain the lever while the clamps are applied. Once the first bend has been completed, it is left clamped in place.

Whether or not you released any pressure in mid-bend, for sure you will have increased end stop pressure substantially by now and you should back off your end stop thrust screw to a point that re-establishes the same pressure as when you first started to bend. Complete the second half of the bend in the same manner as the first half, using the same speed and clamping methods.

The Drying Jig

The procedure for transferring the recurve bent part to the drying jig is the same as for single bends, except the part should be left on the bending form for 40 minutes (without extra cooling) or 15 minutes if bathed in a jet of compressed air. The recurve parts are more difficult to handle during the transfer and thus require more intermediate setting time.

To extract the bent part, the two upper bars across the parallelogram jaws must be removed. Do not forget to re-install them before the next bend. This fixture is subject to an incredible amount of stress during the bending process and will fail if all four bars are not in place.

The drying jig is exactly the same shape as the bending form; however, it can be a single layer of plywood cut to shape and screwed to a larger backing sheet (see Figure 25). Because it is against plywood, it does not have to be centered. This applies to most recurve bending applications.

CHANGE-OF-PLANE BENDS

The addition of the change-of-plane (C.O.P.) fixture to the Veritas Steam-Bending System allows the user to bend wood in two planes. The purpose of the fixture is to transfer the strap (the restraining force) from the outside surface of one bend to the outside of another bend in a different plane. This keeps the wood under compression at all times. For example, the back rail of a chair might continue into the armrest and on to form the front leg. By using two 90? transition fixtures on one strap assembly, both front legs, both arms, and the back rail could be bent at one time.

The freedom gained by being able to bend in two planes is only compromised by the necessity to build somewhat more complicated bending forms that will both accommodate the shapes you wish to create and withstand the considerable forces that come into play as the bending blank is compressed around the form.

As with S-bends, C.O.P. bends require two straps. You can either cut the 10' strap included with the 2" strap clamp or purchase a second strap.

It is strongly recommended that the user first gain some experience in bending wood by completing a variety of pieces with the single strap assembly before attempting C.O.P. bends.

As with the single bend hardware, it is easier to get the basic information across if specific instruction is given on how to complete a typical two-plane bend using the C.O.P. fixture.

Building the Bending Form and Drying Jigs

A typical two-plane bend would have one bend in the horizontal plane and one in the vertical plane. In this example, we will make each bend 90? at a 6" radius. This is half of the chair back-to-arm bend sequence mentioned earlier.

The bending blank will be 1-1/8" × 1-1/8" × 42". Air-dried ash or oak (at 25% moisture content) is a good choice for a novice steam bender. The bending blank, at 1-1/8" sq., is narrower than the 2" wide strap. This is often the case, so the following form construction instructions will tell you how to accommodate such a difference.

Because of the three-dimensional nature of this bend and the orientation of the curves, it is easier to assemble the bending jig on the right-hand front corner of the work surface.

A piece of plywood 3/4" thick and 15-3/4" square will form the base on which to fasten the various components of the bending form. In this case, as in most cases involving two-plane bends, the bending form is also the drying jig. (If multiple bent parts are required, then enough bending/drying jigs have to be constructed to allow the individual bent parts to set before removal.)

Two bending forms (12" × 15" × 2" thick) will be required. Due to the nature of the transition fixture, your forms must always be 2" thick. Two pieces of 3/4" ply and one piece of 1/2" will provide the correct thickness. The inside and outside radii and the two different corner cut-outs should be carefully marked out.

The two forms must be screwed and glued in position to the plywood base, as shown in Figure 26. The transition portion joining the two curved forms must be a minimum of 7" long. There must be at least 1" on either side of the transition fixture before the curves begin; otherwise, there is a risk that the strap will pull away from the fixture and ruin the locating pins on the fixture.

Glue and screw the two 7/8" × 1-1/8" spacer bars to the inside corner of the straight portions of the upper bending form, followed by the four smaller spacer blocks that fit around the curved portion of the form.

For simple bends and "S" bends, keeping the blank centered on the strap was emphasized. That can only be done with change-of-plane bends when the blank is the same width as the strap. When a blank is narrower than the strap, it has to be blocked up so that it fits snugly in the corner of the change-of-plane fixture. Otherwise, part of the blank would inadvertently be put under tension during the transition from one plane to the other.

Attach "fence posts" (as shown in Figure 26) to the side of the lower bending form. These should protrude above the surface of the form by a little over the thickness of the blank being bent; 1-1/4" projection here is about right. If the blank being bent is less than half the width of the strap, the stop may show a tendency to slip off of the blank. Small blocks the same thickness as the bending blank should be attached to the face of the bending form. This will support the edge of the strap that is not over the blank.

Once the bending form is complete, it can be attached to the right-hand corner of the work surface. If clamps are used, they have to be located where they won't interfere with the bending blank or lever as it is pulled into position. Sandpaper glued to the underside of the base (grit out) will stop it from slipping as leverage is applied to the steamed blank.

Assembling the Straps to the Transition Fixture

Assemble the two straps to the transition fixture as shown in Figure 28. Place the center mark (23") of the 46" long unsteamed blank on the center of the transition fixture. Snug the blank into the inside corner of the fixture (as shown in Figure 27) and temporarily clamp it in place.

On the strap that bends around the vertical form, attach the fixed end stop up against the end of the bending blank. Do not forget about the extension on the lever when locating the position of the fixed end stop. The length of the lever extension in these applications should be about 6" to 8".

Temporarily clamp this to the blank (the handle of the clamp should be on the strap side).

Follow the same procedure for the adjustable end stop. The thrust screw will have to be adjusted until the bolts line up with the holes in the strap. However, before assembling, the adjustable end lever with predrilled holes should be inserted into the square tube. Once assembled, lightly tighten the thrust screw so that the whole assembly is in tension. Temporarily clamp this end to the blank.

To become familiar with the placement of the clamps, a dry run is in order.

Remove the first clamp holding the transition fixture and place the entire assembly into position on the bending form as illustrated in Figure 29. A stand can be used to support the portion of the assembly that is extending off the work surface.

The transition fixture should be clamped to one or both forms. (In some applications the securing bracket will suffice here and can be attached to the table with lag screws or bolts, with the machine screws being used to mount or unmount the strap assembly.) The blank should be shifted in the strap so that it runs along the outside edge of the straps. Several small clamps can be applied along the strap to stop it from "snaking" during the bending process. The handles should be on the strap side.

Remove the clamps and the unsteamed blank and lay the strap assembly out flat on a surface that will accommodate the length.

The Bending Procedure

After the appropriate steaming time (in this case, 80 to 90 minutes), carefully remove the steamed blank. The blank will be uncomfortably hot, so wear gloves. You have about 3 or 4 minutes to complete the bend before the wood cools down.

The strap should easily receive the steamed blank (positioned as in the dry run) and the thrust screw tightened until the blank is pressed up against both end stops. Give the thrust screw an additional 1/2 turn or until the assembly just begins to arch under compression. The clamps at hand should be placed on the strap as in the dry run. Place the assembly on the form and securely clamp the transition fixture in place as shown in Figure 29.

The table top bend (horizontal) should be completed first. As the bend progesses,
replace the small clamps spaced along the strap with the larger clamps to secure the blank to the form. The adjustable end stop should not have to be backed off until the first bend is done. The thrust screw should then be backed off to the original tension level and the second bend completed.

The blank can be tapped or clamped to the spacer blocks to keep it true during and immediately after the bend. The strap can be removed after 20 minutes of intermediate setting or 7 minutes if the form is bathed in compressed air. Watch for wood fibers that lift off the surface, apply a clamp as necessary and leave the blank to set a little longer before removing the strap. Once the strap is removed, immediately reclamp the bent blank to the forms/drying jig for full setting.

Booklet Main

Part 1

Part 2

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