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Die Forming

Hydraulic Die Forming for Enamelists
by Carol Holaday
from Vol. 18, No. 1, April 1999

Spring Promise

Introduction 
     The purpose of this article is to present a few basic types of dies that can be used with the hydraulic press to form metal in preparation for enameling.  I have included a brief overview of hydraulic die forming for those not already familiar with this process. 
     I am an enamelist, jeweler and teacher. As a part time instructor at Monterey Peninsula Community College, I teach Metal Arts I & II, Introduction to Enameling (basic to advanced techniques) and a variety of specialized short courses such as Die Forming and Enameling.  Along with Susan Kingsley, I have co- taught workshops at Arrowmont School of Arts and Crafts, including one at the last Enamelist Society conference.  Susan covers the hydraulic press instruction and I cover the enameling portion.  
     First, I'd like to say that everything I know about die forming (and share here with her permission) I have learned from Susan, a good friend, outstanding artist, inspiring teacher and the author of HYDRAULIC DIE FORMING FOR JEWELERS & METALSMITHS.  
     If you are considering building or buying a press, I strongly recommend that you read this book first.  There are a number of safety issues to be aware of, and much more information regarding die forming than I could possibly cover in this short article. 

A Great Tool for Enamelists 
     The hydraulic press is a great tool for enamelists.  With the press, a few tools, and simple dies that you design and create yourself, you will be able to easily form metal in preparation for a variety of enameling techniques.  When thin gauge metal is formed, structure is given to the metal and results in the metal being less likely to warp when enameled and adds strength to the enamel/metal composite. 
Hydraulic Press     Giving dimension to flat metal can be an important design element, making it more interesting; however, when using traditional metal working techniques, going beyond simple forming can be labor intensive (as with repoussé and chasing) and time consuming.  In contrast, once a die is made, it can be used to quickly form a number of identical forms.  Although die forming has traditionally been used for production work, artists making one-of-a-kind pieces will find it useful for the many unique effects possible with easy- to-make dies. 
     The hydraulic press uses power provided by a 20-ton bottle jack (or some alternative power source) and the conformability of polyurethane to gently move annealed metal into and/or around the die.  Jacks of lesser power can be used for some of the techniques described here, but are not strong enough to produce fine detail when using shallow embossing dies. 

An Abbreviated Glossary 
     COMBINATION DIE - two or more types of dies used in combination to form, emboss and/or cut the metal. 
     DIE - the tool that the artist creates to form the metal in the press. 
     EMBOSSING DIE - a die used for forming a shallow relief in sheet metal.  Can be made of wire, pierced metal, carved acrylic, etched metal, etc. 
     FLANGE - the extra metal that skirts a shape after it has been formed.  It serves to clamp the metal between the die and the urethane pad during pressing.  It can be removed or left as part of the design. 
     MATRIX - the negative or impression part of a die. 
     NON-CONFORMING DIE - a die with only one part, either a matrix or punch, which is used with urethane pads or contained blocks of urethane. 
     PUNCH - a tool that is driven into a surface. 
     SILHOUETTE DIE - a simple matrix die consisting of a thick plate (of acrylic or other non-compressible material) with the silhouette of a form cut out, used with a urethane pad. 
     SPACER - a block of non-compressible material (Plexiglas, etc.) that is used to take up vertical space in the press so that the hydraulic ram is not fully extended, this is important for efficient use of the jack. 
     URETHANE - a tough rubber-like material that becomes, under pressure, the other half of a nonconforming die.  Available in two degrees of hardness (durometer), and in a range from 1/16" to 1" thick.  95 durometer is the hardest and used most often. 80 durometer is slightly softer, moves under less pressure and has specific uses.  Colors of pads are not a consistent indicator of hardness.  Mark the durometer on the pad with a permanent marker.  Thin pads are used for embossing.  Thicker pads are used for deeper forming.  Note:  rubber is not a good substitute for urethane because it compresses, whereas urethane moves (like water in a waterbed). 

Some Tips and Facts for Using the Press 
Photo 2     ANNEALING - Metal must be annealed before forming.  If metal cracks or splits during pressing, it wasn't annealed properly or you attempted to push it too far, causing it to work harden before it could stretch the full amount.  Instructions for annealing metal are covered in most jewelry how-to books.  My own preference is to use the kiln for annealing, especially when I am working on a number of pieces at once. 
     URETHANE PADS - The harder, thinner pads are used for maximum detail.  They should be used with shallow embossing dies (including simple wire dies and thin matrix dies).  They can also be used for the first pressing with a silhouette die to assure a sharp edge on the form.  Thicker, softer pads are used to pro- duce the maximum depth of form. 
     THE JACK AND THE GAUGE - The 20-ton bottle jack may be modified by the addition of a gauge.  This gauge does not indicate how much force is actually being used or when the metal has become work hardened.  What is measured by the gauge is the psi (pounds per square inch) being exerted by the hydraulic ram.  How many psi will be required for any specific die and pressing cannot be predicted as there are so many variables.  Each die is unique in size and shape.  Also, different types and gauges of metal will affect the outcome.  It is possible to work without a gauge on the jack, but it is very difficult to judge the optimum pressure by feel or to reproduce exact results. 
     Properly annealed metal should not require pressure beyond 8,000 psi.  Shallow embossing dies will require more pressure than large silhouette dies.  Some applications will require no more than 1,000 psi.  Correct psi readings for any application are relative to individual jacks and gauges.  (This is covered in Susan's book.) 
     MAKE NOTES of what works, what doesn't.  When you have determined the correct pressure and/or the number of times annealed to achieve a desired result, make note directly on the die or on a sample pressing.  This will save a lot of wasted time, metal and frustration. 
     PRACTICE on copper before pressing silver. 

Traditional Enameling Techniques 
     Following are a few examples of how die formed metal can be used in combination with various traditional enameling techniques: 

photo 4     BASSE-TAILLE - In this technique, traditionally the metal surface is textured through a variety of means including etching, engraving, roll printing, stamping, or hammering.  Several thin layers of transparent enamels are then applied over the textured base.  The use of shallow embossing dies and the press can be an effective way to produce the low raised planes that remain below the surface of the smooth enamel.  The key here is that the die forming should be very minimal so that the enamel surface is flat.  Darker transparents will emphasize the apparent depth and detail of the shallow forming. 
     CHAMPLEVÉ - With the press, shallow matrix or punch style dies can be used to form the cells traditionally formed by etching, engraving, sweat soldering or repoussé.  Enamels are then either wet inlaid into the cells, leaving the high areas of metal bare, or sifted over the entire surface and then ground off the high areas after firing. 
     CLOISONNÉ - If wire is used for the die, narrow ridges will be raised in the metal sheet, which can give the appearance of cloisonne wires when surrounded by (opaque) enamel.  This is a kind of "faux cloisonné" because, strictly speaking, it is a variation of the champlevé technique. 
     COMBINING TECHNIQUES - It is possible to combine various styles of dies to form and texture the metal in one or more pressings.  For example, areas of basse-taille can be included within a champlevé piece. 

Other Uses 
     Complex shapes can be quickly domed without the use of hammers and their resulting marks.  This smooth "pillowing" can be shallow or deep, and the edges of the form will remain flat; this can be important for ease in bezel setting or the creation of a hollow form. 
     Die forming combines well with other metal working techniques such as fold forming and roll printing.  Additional repoussé can be accomplished easily with the use of hand tools once the die has established the design; this results in a more "hands on" appearance which can minimize the "hot off the press" or "cookie cutter" look. 

Three Dies to Get Started With 

1.  MATRIX (or SILHOUETTE) DIE 
     This style of matrix die is simply a block of material with a shape sawed out, leaving a void which metal is formed (pushed) into.  As used in this form, it is also known as a silhouette die.  Urethane, when used with a matrix die, becomes the punch that pushes the metal.  A silhouette die can be used to form softly pillowed shapes for a variety of enamel applications including traditional cloisonné, Limoges, basse-taille, etc. 

Making the Die - Some General Rules 
     A matrix die can be made from a variety of hard, non compressible materials such as Masonite®, aluminum and acrylic sheet.  Cast acrylic sheet is inexpensive and easy to cut.  A die cut from acrylic, when properly made, will withstand considerable use. 
     As a general rule the cutout part should be centered and no closer than 3/4" to the edge of the die.  A wider margin will make the die both stronger and more efficient. 

Width of
Silhouette
Thickness
of Die
1" .............. 1/4"
1-1/2" .............. 3/8"
2" .............. 1/2"
2-1/2" .............. 3/4"

     The larger the cutout silhouette, the deeper the relief can be pressed.  The deeper the relief, the thicker the die needs to be (refer to chart).  Dies that are too thin for the design can result in forms that have "bottomed out" (have flat tops).  Because it is difficult to hand saw 1/2" or thicker acrylic, you may prefer to build up the thickness with 1/4" layers.  Make sure that there are no undercuts in the added lower layers, as top layers will break if not fully supported. (Fig. 1)  The layers may be bonded together with double-sided tape.

Figure 1

Steps for Making a Silhouette Die 
     1.  Transfer your design to an acrylic sheet.  This sheet usually comes with a protective paper glued to it.  It is OK to draw your design directly onto this paper if the shape does not need to be precise.  For more exact layout, remove the paper and use a scribe to mark a line in the acrylic.  Fill the line with a permanent marker to make it easier to see.  Another option is to paint the acrylic with colored fingernail polish and scribe the design into that 
     2. Drill a hole well within the shape to be cut out. 
     3. Saw out the shape, using a spiral saw blade (used for sawing wax) set into a jeweler's saw frame.  These are difficult blades to keep on true course, so cut within the line and trim to the line with a file.* 
     4. Use a coarse file (a wax file works well) to trim up to the line.  The wall of the cut may be angled so that the hole is slightly smaller at the bottom of the die than it is at the top (Fig. 1).  In other words, the opening at the top must be fully supported (no under- cuts) to prevent the edges of the opening from breaking from the pressure of the metal being pushed into the die. 
     5. Mark the top of the die in some permanent fashion.  This is the side of the die that is placed against the metal.  Hint:  After repeated use, the edges of the opening may become rounded.  If this is a die that is going to get a lot of use, and the edges must remain hard, first cut the shape in a sheet of brass (16 gauge will do) and use this as a faceplate over the acrylic.  Use the pierced metal as a template to mark the acrylic and cut well within the line.  I use this method for most matrix dies (even when I expect them to have a limited use), because I can cut the metal more accurately and easily than the acrylic.  Very narrow areas will not need to be removed from the acrylic, as the metal will not form deeper than the faceplate. 
     6. If any area of the opening is wider than 1", you will need to cut a second 1/4" die in order to allow for the deeper forming that can be achieved in those areas.  Identify and mark the first acrylic die with a #1 and use it as a template to mark the design on the second sheet of acrylic.  Once again, pierce and cut well within the line.  Remember that the opening in the bottom die needs to be smaller than the opening in the top die so that the top die remains fully supported.  You will only need to cut material from the second die in areas where the metal is being formed deeper than the first die allows for.  Mark this die #2.  The two acrylic sheets (and the face plate if you made one) can be held together with double sided tape. 

Using the Matrix Die 
     GAUGE OF METAL - Metal from 18 to 28 gauge can be formed in matrix dies.  The correct gauge is determined by the depth of relief desired.  The depth of relief possible is in turn limited by the size of the cut out shape and thickness of the die.  Larger, thicker dies will require heavier gauge metal to accomplish the desired form.  The smaller, thinner dies may be used to form thinner metal.  The way in which the formed metal will be used should also be considered when choosing the proper metal gauge. 
photo 6     SIZE OF METAL - Metal to be formed in matrix dies should be at least 1/2" larger than the silhouette cutout.  This flange may be cut off after pressing is completed or trimmed and used as part of the final piece. 
     ANNEALED METAL - Metal to be formed should be properly annealed.  As the metal is stretched by the action of the urethane pressing it into the die, it will work harden.  If you attempt to stretch the metal beyond the point when it hardens, it will crack and split.  The piece needs to be formed in stages, and may require several annealings and pressings before it can reach the relief (pillowing) desired.  Begin with the thinner pads and progress to the thicker, softer ones.  Do not attempt to move the metal a great amount in one pressing! 
     PLACEMENT OF METAL IN THE DIE - The annealed metal is sandwiched between the die and the appropriate urethane pad and this "sandwich" is placed in the center of the bottom platen of the press.  It doesn't matter if the die is on the bottom or the top, as long as the metal is in the middle!  It is advisable to use acrylic spacers below and above the "sandwich" in order to shorten the required length of extension of the ram.  The jack does not work well with the ram at full extension. (Fig. 2) 
     CHOICE OF URETHANE PAD, PSI TO APPLY - Begin with a thin hard pad and a (relatively) high amount of pressure.  This will establish a firm edge while forming the metal to only a shallow depth.  If your goal is a shallow form, as it might be for a cloisonné project, this will be all the forming that is required.  If your goal is a deeper form, then proceed with successive pressings.  Using a thicker soft pad and very little pressure (start with 1000 psi), form the metal part way into the die.  Anneal and repeat, each time with increased pressure, until the desired relief is achieved.  If the metal cracks or tears during pressing, you used too much pressure, the gauge was too thin to begin with and/or the metal was not properly annealed. 

Figure 2

2. MATRIX STYLE EMBOSSING DIE 
     A very thin matrix (silhouette) die can be used to emboss metal in preparation for use in the basse-taille technique of enameling.  The low raised planes (or depressed areas if you use the reverse side), when covered in colored transparent enamel, will result in beautiful dark to light patterns that remain below the surface of the smooth enamel.  Note:  One of the differences between metal that has been embossed in the press and metal that has been roller printed is that embossed metal has detail on both sides.  

Photo 3

Making the Die 
     This type of die can be cut from thin (24 to 26 gauge) sheet metal, or any other non-compressible material of similar thickness.  My own preference is to use sheet metal, because I find it easy to pierce, saw and refine my design using metal working tools and methods.  This die can be used from either side making it a reversible die.  Etched metal plates will also work if the etch is deep enough, and the detail is not too fine. 
     1.  Draw a design with multiple small areas that will become the raised areas of the formed metal.  You might want to fill in these areas of your drawing with a dark marking pen to get a clearer idea of the relationship between what will be cut away and what will remain.  Both are equally important in your design, which will look much like a pattern for a stencil, with all of the background connected. 
     2.  Use a water soluble glue stick to attach the design to your previously cleaned metal. 
     3.  Pierce and saw out the design.  File and refine the cuts.  Hint:  Filing a slight bevel at the top edges of the openings will help to prevent the die from getting stuck in the pressed metal.  

Using An Embossing Die 
     Thinner gauges of metal will emboss with greater detail than thicker gauges; however, the end use of the pressed metal must also be considered when selecting the gauge for any project.  Thin gauges of metal may require creative planning in the design stage, as they will be fragile and easily bent.  Test your die using 24, 26, 28 and 30 gauge annealed metal, and you will quickly see the difference in how the gauge of metal effects the results. 
     1.  Anneal your metal. 
     2.  Using your thinnest, hard urethane pad and the maximum pressure your press allows for, press the annealed metal into the die (see earlier instructions for more details). 
     3.  Optional:  After the metal has been embossed, you may "pillow" form it in a silhouette matrix die.  To preserve detail, don't anneal it after the embossing step.  

Enamels for the Basse-Taille Technique 
     In the basse-taille technique you will want to use transparent enamels directly on the formed metal (without a base of flux) in order to take full advantage of the shallow forming.  Most cool colors fire well on fine silver and many look great on copper as well.  Previous articles printed in this magazine have listed transparent lead free enamels that work well directly on copper.  In my own trials I have found many more lead free colors (both cool and warm) that fire beautifully directly on copper, too many to list here.  You should test your colors, building up the desired depth of enamel with several siftings and firings, being careful to fire to full maturity, just as you will on the finished work. 

3.  PUNCH STYLE EMBOSSING DIE 
Photo 5     This style of die can be used to form metal for either the champlevé or "faux" cloisonne techniques of enameling.  Enamel can be wet packed into the cells created by the die, or it can be sifted over the entire form and ground off the high areas after firing.  
     In one approach, a die can be quickly and easily made with round brass wire.  The wire die may simply be placed on the annealed metal and pressed, or it may be taped to paper before pressing if there are a number of loose elements.  For a more permanent die, wires can be soldered to a thin sheet of metal.  A reversible die is one that is not soldered to aback plate.  (See back cover.)  This allows for using the die from either side, and the creation of reverse images as might be desired for a pair of earrings.  Shapes cut from sheet metal can also be used for this type of die, either in combination with wire or on their own. 

Making and Using a Wire Die 
     I use 14 and 16 gauge brass wire for most of my dies. 
     1.  Bend wires to your design. 
     2.  Tape, glue or solder wires to paper or thin sheet metal as desired.  If you are making a reversible die, solder the wires together but not to a back plate. 
     3.  Use a thin, hard urethane pad, and as much pressure as your jack will allow, to push the annealed metal into the die.  Remember that the thinner the gauge of your metal, the greater the detail.  I do most of my work using 24 or 26 gauge. 
     Note:  The metal will not form as deeply into narrow areas as it does into wider areas of the die.  On a second pressing of the same piece you may wish to add "pushers" in these areas.  "Pushers" are made from small pieces of thin urethane pad, and are stacked over narrow areas between the metal and the full sized pad. 
     You may enamel on the die formed metal as it comes from the press, or you may choose to do some additional forming using repoussé and chasing tools.  I do this forming over wood, and work from both sides without the mess of pitch.  I also use a small nylon hammer with a rounded face to slightly dome the form.  There are ways to emboss and dome in one application, but that is another article. 

To Grind Enamel Off of Raised Areas 
Photo 7     A variety of grinding stones, papers and diamond pads or files may be used to remove enamel from raised areas of metal.  My preference is to use silicon carbide belts on the expanding rubber wheels of a lapidary unit.  Beginning with a 320 belt, I progress to a 400 and then a 600 belt.  Finer grits can be used for a higher polish if desired.  I use a glass brush under running water to clean the piece between belts and after the final grinding and don't allow the grinding residues to dry in the pores of the enamel.  A hard wax (I like Johnson's Paste wax) may be used as a finish over the enamel and the metal. 

Equipment, Tools and Materials List 
     For making and using the dies described you will need to have the following items: 
- hydraulic press with 20-ton jack (preferably one with a gauge installed) 
- urethane pads (a minimum of two) one thin, 95 durometer one thick, 80 durometer 
- spacers for press 
- torch for annealing metal and soldering wire dies 
- 1/4" cast acrylic sheet (I buy in bulk, cut to 4 X 4") 
- sheet metal (brass) for dies, various gauges 
- wire for dies (brass), 14 to 20 gauge 
- jewelers saw frame and bench pin
- spiral saw blades for cutting acrylic
- saw blades for metal
- flex shaft or hand drill
- drill bit {#55 will work) 
- wax files, small and large files for metal double sided tape 
-scribe 
- permanent marker 
     Optional: 
- repoussé and chasing tools 
- chasing hammer 
- small nylon hammer with round end 
- wood blocks for forming into 

*Safety Warnings: 
     Any modifications made to a jack must be made by a qualified person. 
     Acrylic "saw dust" is very sharp.  Do not get it into your eyes.  It clings to your skin, cloths and tools.  Clean up your work area immediately after cutting and filing. 

     Address for ordering Susan Kingsley's book, 
     Hydraulic Die Forming for Jewelers & Metalsmiths: 
     20-Ton Press 
     P.O. Box 222492 
     Carmel, CA 93922 
     $25 {includes postage) to U,S. and Canada 
California residents add $1.45 for tax. {send a check made out to: 20-Ton Press) 
     For foreign orders of Kingsley's book, contact: 
     Frei & Borel 
     1-800-772-3456 
     Other suggested reading:  
     Tim McCreight, 
     Metals Technic
     Brynmorgan Press, 1992 
     To contact Arrowmont School of Arts and Crafts regarding workshops: 
     423-436-5860 or e-mail arrwmnt@aol.com 
     Web sites to check out:  
     Bonny Doon Engineering {for press, etc.) 
     http://www.bonnydoonengineering.com/ 
     Robin Casady's site for images of my work as well as Susan Kingsley's work and a tour of her studio:      
     http://www.CarmelCoast.com/ 
     Orchid, a forum for jewelers, metal artists, etc.  
     http://www.ganoksin.com/

Die for Leaf Stand

 

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