Page Update: 2005 03 13


STRIP CUTTING FIXTURE 

by John Sedgwick         

W5 PARQUETRY

Parquetry is the close relative of marquetry and can be defined as geometric veneer shapes assembled so as to form a repeating pattern. The shapes must be precision cut and identical, to do this we require a device or jig to make consistent cuts and once set will duplicate pieces exactly. Some years ago I designed and build a parquetry fixture, which is shown on the following page. It allows the quick setting and clamping of the veneer to be cut. There is of course simpler set ups that can be made for occasionally cutting veneer strips, such as two “C” clamps to hold a straight edge against pre-measured blocks. Although these simple parquetry set-ups work, they tend to be less accurate and require more attention to component set-up positioning

If you do a lot of Parquetry and have need of a quick method of cutting strips without constant clamping and set up, this fixture provides one set up and quick consistent dimensions. The cutting surface is an “Olfa” cutting mat, your purchase will dictate the size of your fixture. These self-repairing mats will last for hundreds of repetitive cuts in the same place, however eventually it will be necessary to cut a section off of the mat. Secure the mat with double-sided carpet tape on both edges prior to cutting the slot. Once built the operation of this parquetry fixture is simple.

 

Typical parquetry designs beginning with veneer strips

1    The veneer strip width is best set by positioning pre sized wooden blocks at both ends between the backstop and the steel cutting edge. An assortment of pre-sized blocks ½" ¾" 1" wide. about 2" long should be made with this fixture for future set up.

 

Fig 20   Examples of typical designs starting with veneer strips

2     Loosen the clamp mounting bar wing nuts and slide the bar forward to touch the dimension block and lock in place, repeat both sides.

3    When the toggle clamps are open there is sufficient room to slide a veneer under the cutting edge to touch the backstop.

4  Once you have set the distance each repetitive cut will remain the same as the clamping only eliminates the clearance beneath the cutting edge and does not reduce the set width.

5  The other blocks with wing nuts are to hold the cutting edge firmly in place.

The alternate cutting position is to allow for larger strips or squares to be cut using the same fixture.

When cutting strips and beginning the assembly it is important to remember the concept of “compound errors” which multiply with each successive cut. The variables can definitely be reduced but not completely eliminated. Please note the following details.

 

Additional strip cutting sequences 5 - 8

 

1   Use the sharpest edge possible, I use breakaway blades and replace the edge often 

2 Use many repetitive cuts; if you force the knife through the veneer it will tend to pull the wood fibres apart leaving a rough edge.

3    Hold the knife vertical at all times, a variable angle will make a dimensional difference when compounded or placed alongside reversed pieces.

4   Glue a piece of 180grit abrasive paper to a hardwood block and run it along the cut edge of the strip, some species such as mahogany or walnut usually leave small imperfections and prevent a tight joint.

5    Because some designs require strips to be reversed end to end or turned over there will be a build up of tape due to repetitive cutting, making it difficult to make tight seams. When you have finished an assembly sequence tape the strips and carefully remove the tape from the opposite side. Use low stick masking tape to join the strips together as it will hold the strips for cutting, but can be easily removed.

 


PARQUETRY

by John Sedgwick

This aspect of Parquetry falls in between Parquetry and Marquetry. The subject is truncated triangles or variation of the traditional fan design, - 90 deg. for corners - 180 deg. for along a base line, 360 deg. for centre pieces. The traditional fan design was and is precision cut in volume with a saw in stacked components (10 to 20) at a time - each piece is sand shaded and joined to the next piece. (see fig. 1)

Fig. 1 Intersection points are cut out. Amount increases with numbers and length

There are two basic designs:

a) Truncated triangles cut into a background

b) Truncated triangles cut convex or concave or combinations (see figs 2-5)

 

 

     


Shading

To add emphasis to each segment, it is common practice to shade the base along it's length as designated with "XXXX". The base of one triangle touching the adjacent or hypotenuse side. The sectional pieces divide either 90 deg.-180 deg. or 360 deg. in as many pieces as desired 8, 9, 10, 11 etc. This is determined by simply dividing the desired area by the number of appropriate pieces - e.g. CORNER MOTIF 90 deg. - 6 pieces required - each piece will be 90 deg. divided by 6=15 deg. The number of pieces is arbitrary, but as a rule the larger the motif the greater the number - e.g. 1½" 90 deg. CORNER MOTIF not less than 4 or more than 6 - - 6" 90 deg.

CORNER MOTIF not less than 8 or more than 12. The reasons for this ratio becomes obvious when you do this. The further out the sections go, the wider they become and the larger the cut away becomes at the radius intersect points. Either side can be shaded. However, the same side must be common for all or both sides, when alternately placing them. (see drawing)

Shading can be done using either molten lead or sand. The principle difference is not effect, but speed. The molten lead at 600 deg. - 650 deg. F. will scorch the edge of some of our species to unrecognisable cinders in a few seconds - e.g. Pear; whereas Canadian Sugar Maple is perfect for lead. It scorches without undue shrinkage in a couple of seconds. Using hot sand at 350 deg. F., however, will allow for Pear to be scorched without damage and limited shrinkage. Any shrinkage will re-expand during gluing with white glue. Maple on the other hand will shrink and even curl and harden without noticeable or sufficient scorching. The lesson to be learned here is experiment with different veneers at different temperatures. Lead can be obtained by melting fishing sinkers in a piece of 1" pipe sliced in two and capped (see fig. 7)

 


The Non-scorching Method

Any of the fan designs can achieve a similar, but uniquely different effect by using my method, which I shall refer to as the L.B.D. Method - paraphrased from - "My Fair Lady" and I quote - - - with a "Little Bit of Dark" With a Little Bit of Dark you can have it all and not Sand Shade! --- with a Little Bit --- and so on. This requires a little bit more mathematics --- now hold on --- I did not say this requires you and Mr. Pythagorus to be on a first name basis or that your library include works of Newton, Einstein or Steven Hawking. If you understand that when a clock hands point to 3:00 o'clock, that is 90 deg. and at 6:00 o'clock they are 180 deg. and 12:00 o'clock is 360 deg. and can use a calculator - you are home free.

The principle of the L.B.D. Method is to insert 3 deg. or 5 deg. of dark veneer between each triangle - for example: If a 5-piece were to be cut for a corner, each piece would be 5-piece x 18 deg.=90 deg.. The 18 deg. pieces would be reduced to 15 deg. and a 3 deg. segment placed beside it for a total of 18 deg.. Of course 15 deg. and 18 deg. are whole angles and easy to measure - other segments will require fractions of a degree - - - don't panic now. Although dividing the 180 deg. in say 11 pieces, you will require segment of 16.36 deg.. When making your cutting template consider it 16 deg and a bit, less than half, but more than 16 deg.. There is, as the lawyer would say, some "Wiggle Room" in this procedure during assembly.

Well you heard the magic word - "Template". Templates are for people like me, who cannot make the same measurement twice.

 


Cutting Templates

So here is how you make and use them. Like most people I make a jig to suit the job required, then when I need it again, two years later, I cannot find it. The writing of this article has prompted the making of a series of angle jigs at once, so that I could make the designs shown. If after reading this you want to try these designs, I recommend making a set using the angles shown, sooner or later you will use them. To my knowledge this method of cutting angles has not been documented before, so for the record, I shall lay claim to it and name them J.A.C.'s (John's Angle Cutters).


HOW TO MAKE JAC's

MATERIALS


  1. Cut - 8Pc - 8" long 2" wide.
  2. File, grind or plane a chamfered edge equal to approximately 2/3 the width on both sides
  3. Cover under side with double sided tape.
  4. Place on Bristol board and cut around.

7PC. JAC'S TO BE CUT

  1. 3 deg & 12 deg 15 Pc
  2. 5.deg & 12.86 deg 14 Pc
  3. 13.85 deg & 15 deg 13 Pc - 12 Pc
  4. 16.36 deg & 18 deg 11 Pc - 10 Pc
  5. 20 deg & 22.5 deg 9 Pc - 8 Pc 180
  6. 25.71 deg - 30 deg 7 Pc - 6 Pc 180
  7. 36 deg & (Special) 5 Pc 180

Cutting Angles

Pleated Design

Tape 18 deg angle sections securely with veneer tape to desired size. Because a point is not required, cut the pieces to allow a ¼" to 3/8" cut off as shown. However, all pieces will be cut to the same width.

Pleated JAC

For pleated design:

  1. Cut 18 deg wedge with JAC.
  2. Place on JAC & mark with pencil
  3. Remove Bristol board and glue film.

Turn over and slide all other pieces in - cut off where shown

Having assembled the angle segments either a circle or oval shape can be selected.


Dimension Variables

When deciding to make any of these patters, it is important to remember the potential problems. The jig will cut the exact angle every time. However, the angle may be slightly out, in which case the more pieces, the greater the compound error - e.g. (11Pc for 180 deg.) angle is 16.36 deg. - if the error was 1.5 deg. the compound error would be 11 x 1.5 deg.=16.5 deg. In general the pieces you cut will be slightly bigger than the measured angle, principally because you cannot place each piece so tight that no gap exists. If only .2 deg. error exists due to placement, then at 11Pc the compound error is 11 x .2 deg.=2.2 deg. Such things as the angle of your knife or how sharp it is will generate small errors. Fear not - the answer is - be consistent, use a sharp knife and make the angle slightly negative rather than positive. "SMALL" negative template errors will usually offset positive cutting errors. Finally, test the segments through 180 deg. and adjust your cutting template accordingly.


Sand/Lead Shading

Previously I mentioned the shrinking effect due to heat. This will obviously vary with the degree of scorching and the veneer species. However, all will shrink to some degree. If only one edge requires shading, cut the angle after shading. This will do two things. First the angle will be correct - Second the point of the segment will remain intact.

If you are familiar with sand shading, you will know that any point of veneer tends to distort and burn off. This is because the heat cannot dissipate as with a larger area. With the traditional production saw cutting method the angle must be made to compensate for shrinkage and each different species and tonal variation requires adjustments to the pre-cut angle. In addition, because the points burn and distort they are replaced with a full or part circle of black veneer.

This does not look unattractive and you may wish to cut the points off and be traditional - the option is yours.


Variations

Another variation of this design shown previously is a pleated or folded fabric design. This can be used in conjunction with banding as a corner motif. Veneer pieces are cut at a low angle, preferably 12 deg., as it is part of the recommended angle templates to be made. For veneer, I prefer "YEW" as it is very stable during shading joined to A pear or a cherry border stringer

3 to 5 or 7 pieces can be used as desired - tape them together after cutting one motif to the desired shape - position over each of the remaining pieces and mark around with a pencil. Cut in using a saw or knife. If a saw is used the waste from the sections can be simultaneously cut along with the waste from the corners.

Using the J.A.C.'s will give you quick precision cuts with no set-up time. If you keep them together in a box they will always be available to make up a quick inlay motif.


PARQUETRY DESIGNS AND METHODS

The technique of combining geometric wood pieces into flat surface decoration is very old. The early Egyptians were masters of the art. French furniture makers incorporated parquetry in elaborate ways in their fancy furniture. Most of us today think first of wood floors when the term is mentioned.

To relate the art of parquetry, we will define it as the art of geometric marquetry. Parquetry procedure borrows some of marquetry's methods but limits itself to straight cuts. Veneers are cut into squares, triangles and diamonds. Usually the cut pieces are assembled into a sheet which is laid as a single piece on a flat wood surface. Large cut pieces intended to cover a table top or to decorate a sizeable panel are sometimes laid individually to avoid the hazard of handling an oversize taped assembly of veneer pieces. The primary tools for parquetry are a craft knife or a single edge razor blade, a steel straight edge and an assortment of metal triangles providing 45, 60 and 30 degree corners.

If you cannot buy suitable triangles, cut them from sheet metal. Six-inch triangles are handiest and are large enough for most work. You need a 90 degree steel square and a simple bench hook. The best veneers for parquetry are those having straight grain. A parquetry pattern is inherently busy and would become bizarre if composed of veneers having wild or strongly irregular figure. In general a selection of only two or three colour tones - light, medium and dark - will work best. For your first parquetry experiment it is best to start with a simple design of squares such as those required for a chess board. The next easy step to try is to cut triangles.

Gradually you will find ways of creating interesting design patterns by alternating the grain direction of every other veneer strip in an assembly of two colour strips, or by turning over every other strip, or shifting every strip by a distance of one square to left or right. Cutting an assembly of squares on diagonals and varying the cutting angles can produce some wholly unexpected results. The possibilities are endless. If you enjoy simple parquetry, you will want to experiment with more complicated switches of cuts and variations of assembly.

The progression from cutting squares is to move into diamonds. At its most simple, providing the grain direction is correct, simply turn the square onto its corner. However, a more useful diamond is the 60 deg. one and is made by cutting across the strip assembly at 60 deg. You will note that grain direction becomes important; now the planning begins in earnest. A good example of the use of the 60 deg. diamond is the Louis Cube. To produce equilateral triangles, cut the 60 deg. diamonds, and then cut across in the other direction.

You will appreciate that the assembly will require taping back together between the first and second cut. Before devising fiendishly complicated patterns with pieces of veneers, making a 'map' using graph paper (with he small squares) can be a great help. As mentioned earlier, it is easier to produce parallel strips if you use a simple jig. The intention is to produce pieces of identical width by: a) locating the edge of the veneer against an end fence, and: b) having the cutting line (along the straight edge) a fixed parallel distance away. Your jig may look like this:

shown or hold in place with brads.

Now mitre the ends of the (E) and (F) pieces respectively. Be sure to apply glue to the mitres as well as the flat surface of the door stop. Clamp or hold the place with brads. Note that one of the (E) pieces is supported only at the ends.

After the glue is dry, sand and finish the frame. You can apply the finish of your choice. Thoroughly clean the glass. Insert the mounted art and drive the screw through the centre of the top (A) piece to prevent the art and glass from accidentally sliding out of the frame. Install the screw eyes and braided wire for hanging the frame to complete the job.


CUTTING MULTI-POINTED “STARS”

by John Sedgwick

From Canadian Marquetry December 1997  

Some time ago, a fellow Marquetarian, text book and pieces of veneer in hand, asked me to explain why the pieces he had cut to make a star would not fit according to the instructions. It was then that I realized that my method was not known, or at the very least, not documented. So for the first time in print, as far as I can tell, here is my method. The triangular pieces used in this article are cut using a “Jac or J.A.C.” ( my method of cutting angle wedges of veneer). The end of this article describes how to make and use a Jac. The number of star points which you can cut is related to the degree angle of a veneer piece. For purposes of simplicity, I will choose a 15o Jac. This will produce either a 12 or 24-point star suitable for a clock face. 

Step 1  

Cut 12 pieces of dark veneer and 12 pieces of light veneer using your Jac. Choose straight and tight grain veneer, such as: Dark - rosewood, walnut, mahogany. Light - maple, birch, cherry. 

Step 2 (see FIG 1) 

Place a dark and light piece together making sure they are even at their points. Temporarily tape them together with masking tape.

 Repeat the process for the remaining pieces. 

Step 3

     

Place a piece of masking tape, sticky side up, on your work surface. Make it over twice the length of the veneer pieces. The tape is used to hold the pieces to make up half of the circular assembly (180o). 

Step 4  

Place the first pair of pieces with their points along the bottom edge of the masking tape, at the centre point of the tape. 

Step 5

Place a second pair of pieces beside the set already on the strip of masking tape, so that their points line up evenly and the colours alternate. 

Step 6 (see FIG 2)  

Now fill in the rest of the pieces to make up half a circle (180o). If your half circle turns out perfect, your Jac angle is exactly 15 Go onto the next step if this is the case. More likely, your Jac angle was either too big or too small. If this is the case, I would suggest that you recut your Jac angle and begin again. If your points and pieces are not tightly joined or lined up, you can re-trim to fit or reposition them. 

 

Step 7

   

Repeat steps 3 to 6 for the other half circle. Join the two half circles to make a full circle assembly (360o), as shown in FIG 3. 

Options  

There are several options you can choose from to make different star patterns from the circle assembly manufactured in the previous steps: 

Option A -    12 points the same size. 

Option B - 24 points the same size (FIG 6). 

Option C - Star Burst, with 12 points at the furthest position and 12 points closer to the centre (FIG 4). 

I will describe in detail how to make the star in Option C and in much less detail the one in Option B. 

Option C (see FIG 4) 

Step C1  

 

I have chosen a ratio of 1/3. You can choose any ratio you wish. Each point of that ratio is represented by a circle as shown in FIG 4 as Rl, R2 and R3. 

Step C2 

Piece #1 shows the shape to be cut. Piece #2 shows the cuts having been made using a straight edge and a sharp knife along lines marked A-B and A-C. When this is done, the corners of the adjacent pieces will be clipped. This will ensure sharp points of the stars’ outer points, so be careful and cut at the intersection points. 

Step C3  

Remove piece #2. You can either leave it as a 12-point star as shown by piece #2 or continue on to make a 24-point star as shown by piece #4. Flip over piece #2 and return it to its original position in the star and tape it in place. You will notice that the arc lines are now on the underside and as such need to be reestablished on the face side. 

Step C4  

The new cut lines, as shown by piece #3 are D-E and F-E. Do not cut the entire length of D-E and F-E only that portion of the line indicated. 

Step C5  

This will now reveal the finished section as shown by piece #4. Do not discard the cut off pieces. These can be reassembled to form another star as described Step C11 and shown in FIG 5. 

Step C6  

Tape one side of the completed design with veneer tape and leave it to dry completely. 

Step C7  

When it is completely dry, place the star, veneer tape side down on the back of the field veneer you wish to cut it into. Tape it securely to the field veneer with short tabs of masking tape and cut around the perimeter using a straight edge and sharp knife. Remove the tape on a small section at a time replacing it as you move to another section. 

Step C8  

When you remove the star, it is more than likely that some of the cross grain field veneer will be lost at the points. Temporarily place clear tape over these areas and stab both sides of each point before trying to remove the cut out. 

Step C9 

Tape the star in position.  You have finished. 

Step C10 

Should you wish to inlay the star in a solid field, follow step C7, only place the star, veneer tape side up.  Use a router to remove the area covered by the star.

Step C11  

(see FIG 5) The waste pieces can be used to make another star. Using the window method, cut a piece of contrasting veneer to fill the 8-point star in the centre. Draw a circle big enough to encompass the remaining veneer assembly. The small missing sections can either be cut away or filled with the same veneer as the centre. This design can be used as an inlay in a coaster, etc. 

Option B (see FIG 6)

   

FIG 6 is accomplished in the same way as FIG 4. You can either leave it as a 12-point star as shown by piece #2 of FIG 6 or continue on to make a 24 point star as shown by piece #4. 

How to make a “Jac or J.A.C.” 

In a previous newsletter, I described how to make a “Jac.” However, if you do not have this information handy, the accompanying diagrams show how to make one.

   

After making the Jac, you will need a cutting board and a hold down clamp. Mount the hold down clamp to the cutting board in the middle of the longest side, close to the edge. The Jac is placed under the hold down clamp and locked in position with the piece of veneer underneath, taking the place of the cut away. In this manner the veneer and the Jac are held secure. The straight grain should be in the direction of the cut. It is also essential to use a sharp knife to get clean edges and good points. A small utility knife with snap off blades is the best tool for this job. Rotate the veneer 180o after each cut to keep the grain in the same orientation for each triangular piece.

   

Turn the Jac over after cutting the area shown above. Cut along this line with the veneer clamped between the Jac and the cutting board.

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