TOOLS AND GADGETS

Page Updated: 2005 05 15

  1. Fret Saw Machine Design ..... by Frank Harris
  2. Sanding or Scraping a Picture ..... by James Colter
  3. Strip Cutting Jig ..... by Bruce Fairchild
  4. An Analysis of Fret Saw Blade Angles ..... by Frank Harris
  5. ... and Follow-up to Blade Angles (with table) ..... by Frank Harris
  6. Saw Table for 17" Tubular Fret Saw .....by Jim MacKeracher 
  7. Using Pins to Position Tracings and Overlays in Marquetry ..... by Tony Stuart    
  8. Picture Hanging  ..... by Jim MacKeracher  
  9. Modifying a scroll saw for marquetry by Frank Wood, written by James Colter

  Back to Canadian Marquetry Home Page


Fret Saw Machine Design

by Frank Harris

All the homemade machine mounted fret saws that I have seen and also the designs shown in marquetry manuals have a throat-piece inserted from the front. This requires you to cut into the throat-piece the first time you use it and perhaps to have two or three throat-pieces if you wish to change the angle or size of the blade. Finally the throat-piece will eventually wear to the point you start losing tiny pieces through the hole and you have to make a new one.

I believe there is a better way to design the throat-piece and it is very simple and could easily be done as a modification.

Instead of inserting it from the front, cut your dovetail groove from side to side right across the table and use two square-ended throat-pieces inserted one from each side. Where they meet is a slot no wider than the thickness of the blade and you didn't have to cut it. You don't need different throat-pieces for different angles or blades and when the inserts begin to wear just trim the ends. You will never again lose any small pieces. In order to have the slot no wider than the width of the blade when you are bevel cutting you must, of course, trim the end of one of the inserts to a slightly greater angle than you might use on the saw.

You might also consider changing the top surface of your table from wood to polyethylene. I did and am no longer bothered by the masking tape (used to hold the veneers together) sticking to the table.

You might also try the following suggestions:

  1. Melamine coated particle board is probably as good as the polyethylene and considerably cheaper.
  2. Round over the edges of the table surface. This helps to prevent your work from snagging on the edge as you rotate in the sawing process.
  3. Circles of various diameters can be cut by mounting a small diameter pin in either of the throat-pieces for use as a pivot point.

SANDING OR SCRAPING A PICTURE

by James Colter

For those of you who tuned in expecting a debate on the merits of sanding versus scraping, sorry Charlie. This is about something a little more mundane. How to hold the picture while sanding or scraping it. Well, sure, you could hold it, but what if you want to use both hands? That's the problem.

When using a good palm sander in the early stages of sanding, or using a scraper, or even a sanding block, the picture has a tendency of travelling in the direction of your force. How do you stop it, you ask? There are many ways of achieving this end. If you are not married, there is that plush carpet in the living room. Nothing will skid on that sucker. I find, however, if you are married you have to be a little more creative in problem solving.

There are still many ways to solve a particular problem. First, I tried nailing the picture to the work bench. Won't work you say? Yes it will. You just have to be sure to counter-sink the nails or the scrapper gets a little nicked. After getting tired of finding the right colour nail filler, and fixing the side of the picture (claw hammer), I decided to get smart, and glue the work to the table. Hey, you only do that three or four times (OK, four) before you realize those suckers don't come up. All was not lost, however. (See my upcoming article on Marquetry Designs for your Workbench).

It was then that I stumbled on the incredibly simple device who's design I lay before you here. It will allow you to apply pressure without the picture slipping.


STRIP-CUTTING JIG

by Bruce Fairchild

The Jig

Sundry Parts

 


Assembly

Glue 18" x ½" x 1" back stop to 12" x 18" base board.

Glue 4 corner feet in place.

Glue 12" x 18" piece of arborite on top of base board, also glue arborite strip on sides and bottom to protect the particle board.

Drill 4 - 5/16 holes with ¾" centres from each side, ¾" from the top and 2" from the bottom.

Using a 5/16" straight router bit, set router guide to centre router bit in the pre- drilled holes and cut a 5/16" slot from the top hole to the bottom hole.

Repeat for the other side.

Drill 2 - 5/16" holes in the adjustable width stop to line up with the slot in the base.

Clear a 1/8" deep slot from the bottom to within 1¼" of each end.

This gives a tunnel about 15½" wide for veneer to slide freely in and out for the jig.

Drill 2 -5/16" holes in the adjustable cutting straight edge.

(prior to this I had to cut and epoxy glue a piece of wood into the hollow portion and sand to get a solid flat surface on the bottom.) A piece of sand paper is glued to the bottom of the cutting edge to hold the veneer steady while cutting.

Place a flat washer on each ¼" carriage bolt and above through the slots from the bottom of the base. Place each the width stop and the cutting edge onto the ¼" carriage bolts, place a flat washer and a wing nut on each ¼" bolt.


Operation

The width of veneer to be cut is established by moving the cutting edge till the distance between the back stop is established. Tighten the wing nuts on the cutting edge bar to hold this setting, then move the adjustable width stop up to the back of the cutting edge bar and tighten the wing nuts on the width stop. Loosen the wing nuts on the cutting edge bar and slide veneer under the slot in the width stop and under the cutting edge bar. Tighten the wing nuts on the cutting edge bar, making sure it is tight against the width stop. You can cut your veneer using a craft knife. Remove the cut piece and repeat for as many cuts as you require of the set width.


Making a Chessboard

Using the jig set the width of the cut to 1½". Take a piece of maple or birch about 15" wide and cut with the grain nine pieces that will be 1½" x 15". Next to a piece of walnut about 15" wide and cut with the grain eight pieces that will be 1½" x 15". Now join the alternately maple or birch and walnut strips together edge to edge and tape along the joints with gummed tape. Rotate the assembly by 90 deg. and slide into the jig. It is important to position the assembly at 90 deg to the back stop (this can be established prior to the setting the 1½" width by sliding a try square under the width stop and cutting edge to the back stop and marking the 90 deg edge).

The first cut will not be 1½" but enough to establish a square cut across the assembly. Now proceed to the 8 strips across the grain from the assembly that are 1½" wide. With the 8 strips move alternate strips forward by one square, to bring the light and dark squares together and tape them together. Trim off the unwanted ninth square which protrude at the end of each now.


AN ANALYSIS OF FRET SAW BLADE ANGLES

by Frank Harris

Since joining the Marquetry Society of Canada a couple of years ago I have been puzzled by many things, and one of those "puzzlements" has been the proper angle to set the fret saw to obtain a good fit between mating parts. This puzzlement came about because I was unable to find any consensus among other members, or in books, as to the proper fret saw angle for certain conditions (different saw blade and veneer thicknesses). The few members I have asked about this say they set their fret saws to angles between 10 and 15 degrees. The Modern Marquetry Handbook by the Marquetry Society of America (page 73) says, "12 degrees will form a perfectly tight fit that requires little or no filler", without mention of either blade size or veneer thickness. The Marquetry Manual by W. A. Lincoln makes two or three references to angles, and sets out one table of angles which vary from 8 to 20 degrees and are related only to veneer thickness, not to blade thickness, (although he says in a previous paragraph that you have to experiment with practice cuts to establish angles).

It is obvious from the high quality of work done by many marquetarians that the saw settings being used are working very well, even though they may not be calculated mathematically or even well understood. It may also be, of course, that those skilled at the craft know that approximations are all that are needed, and that perfect geometrical accuracy is a waste of time. Nonetheless I have set out to do a little trigonometry to determine the theoretically-correct angles for certain conditions, if only to satisfy my own curiosity.

In order to understand why only one fret saw blade angle is correct for a perfect fit for any one combination of veneer thickness and blade size, please refer to Fig 1. In this diagram, a "plug" (shown in sawing position) is to be sawn with a fret saw blade of a certain thickness (kerf) set at an angle a, such that the resultant fit of the plug to the "body" of veneer will be exactly flush at the top face of the body. In other words, the dimension of the top face of the plug must exactly equal the dimension of the top face of the "window" cut out of the body in order for the resultant top face to be flush. If this is to be the case, it can be seen that the points shown as A on the top face of the body veneer must be directly over the matching points B on the top face of the plug after sawing. It is obvious from the diagram that, for any given thickness of "body" veneer, and a specific blade thickness, this condition can be met at only one blade angle. (If the blade angle is increased using the same blade thickness, point B on the left side of the diagram will end up to the left of its present position and will no longer be directly under point A. Similarly, too small a blade angle will move point B to the right, away from its position directly under point A.

So for any given thickness of body veneer and of saw kerf, (I am using "blade thickness" to represent the resultant kerf after sawing) how do we find the correct blade angle? From the diagram, note that the blade angle a is also one internal angle of a right triangle (ABC), of which the hypotenuse (AB) is the body veneer thickness, and the side (BC) opposite the angle a is the blade thickness. From trigonometry we know that the opposite side of a right triangle divided by the hypotenuse is the sine of the angle, so the sine of angle a is the blade thickness divided by the thickness of the body veneer. We can find the blade angle a from a set of trigonometric tables.

If all veneer were the same thickness, or very near the same thickness, only one calculation would be necessary and all marquetarians would be using the same saw angle for any given thickness of blade. Unfortunately such is not the case. In a measurement survey of 52 pieces of veneer (from the two or three hundred that I have accumulated) I found thicknesses from .019" up to .041", and a size for every .001 increment in between. This means a lot of thickness measurements and calculations to get the correct blade angle for each cut in a piece of marquetry if you want to have perfect fits. To make this easier, I have provided a table (Table 1) of blade angles for 26 veneer thicknesses (in increments of .001") and 9 different blade sizes. To use this table it is necessary only to look down the column for the blade number or blade size that you are using, to the row corresponding to the veneer thickness, and pick out the correct blade angle in degrees and tenths. For example, for a 4/0 saw blade and a veneer thickness of .032", the correct blade angle for a geometrically perfect fit would be 15.6 degrees (or 15 degrees, 36 minutes).

For the type of fit shown in Fig. 1, flush at the top face, the computation of blade angle depends on the thickness of the body veneer, not on the thickness of the plug. Any variation in the thickness of the plug will show up as irregularities on the bottom face of the assembly. This is not always desirable. For many if not most types of marquetry work, it would be preferable to have the bottom face of the assembly flush, so as to form a solid base, and the irregularities in the upper or "picture face" can be removed by sanding or scraping prior to the finishing process.

This is the situation shown in Fig. 2. In this diagram, it can be seen that, in order for the bottom face of the assembly to be flush, it is necessary for the points A on the bottom face of the body veneer to be directly over the points B on the bottom face of the plug. Once again it can be seen that for any given veneer thickness and blade size, this condition will exist for only one blade angle. However, now the computation of blade angle depends not on the thickness of "body" veneer (as in Fig. 1), but on the thickness of the veneer in the plug. Once again, the blade angle forms an internal angle of a right triangle (ABC), and the side BC opposite the angle divided by the hypotenuse (AB, or the thickness of the plug veneer) gives us the sine of the blade angle. Again, the angle can be found from a set of trigonometric tables, or you can use Table 1 . This calculation is completely independent of the body veneer thickness, and all variations in veneer thickness will appear as irregularities in the upper face of the assembly.

Finally we come to Figure 3, where I have included the cellotape that is used in the bevel-cutting technique. Note now that points A and B are separated by the plug thickness, plus a double thickness of cellotape. For a fit similar to the case of Fig. 2, where the bottom face of the assembly is flush, all that needs to be done to compensate for the cellotape thickness is to add one double thickness of tape (.004") to the thickness of the plug, and use this sum in the calculation of the sine of the blade angle (or as the veneer thickness in Table 1).

All that remains is to decide whether all this has any real practical value, and if so, how to use it. I believe it has, if only to give some marquetarians a clearer understanding of what is required to get those tight "invisible" joints that are so desirable. The mathematics and geometry involved inexorably lead us to a "theoretically-perfect method", and this is what every perfectionist wants, isn't it? Of course everyone knows perfection is impossible, so it is your choice as to how far you wish to go along this road. Perhaps you will find among these numbers only a slightly better angle than the one you have been using all along.


A Theoretically-Perfect Method
  1. Measure with a micrometer each piece to be inset (i.e., each "plug");
  2. If you are using cellotape, add .004" to this thickness;
  3. Look up the correct angle in the Table for the saw size you are using;
  4. Set the fret saw to this angle for that particular inset piece.

This method will give a theoretically-perfect fit, with a flat back face for easy and solid gluing to a substrate, and all variations in veneer thickness will show up as irregularities on the top face which makes for easy removal by scraping and sanding. When edge gluing by this method, it is important to lay the piece to be inset (the plug) face up on a flat surface, and place the window (the body) over it. If you try to place the plug into the "window" when the body is lying with its upper or picture face against a flat surface, and if the plug is thicker than the body, it will not fit properly.

The equipment required would be a micrometer or caliper capable of measuring to .001", and a means of setting a blade angle accurately on your saw. The latter can be as simple as a protractor fastened to a block of wood with double-sided tape, and stood on your saw table behind the blade while you adjust it. It might also be as complex as a built-in protractor complete with vernier graduated in increments of five minutes of angle.

To conclude, this article could not have been written (and some may wish it hadn't been!) without the able assistance of an engineer friend and former work associate, Mr. Roy Bourke, who with his knowledge of mathematics set me straight on basic trigonometry (which I had forgotten), and who provided valuable expertise and computer time in preparing the table.

Well, there you have it, for better or for worse!!


FOLLOW UP TO:

"AN ANALYSIS OF FRET SAW BLADE ANGLES"

by Frank Harris

Since writing the above theoretical article, I have had some time to experiment and try the theory. As you might expect, some of it did not work out exactly as theorized, but it did work.

To begin with, I tried cutting-in nine randomly shaped pieces using the "theoretically-perfect method". The body veneer was .037" thick, and the plugs were .021", .025", .030", .032", .034", .036", .038", and .040". Each piece was overcut such that all pieces ran into at least two others and sometimes three or four. The back surface was reasonably flat but not flush, and the irregularities did show up on the top face. Initially I was quite disappointed that the back was not flush, but on reflection I realized that I had not allowed any tolerance for working inaccuracies, e.g. inability to set the saw perfectly, slightly rough kerf preventing intimate contact, wood swelling due to the white glue, and perhaps other reasons.

I then experimented to find out how far undersize I needed to cut the angle to get a flush fit. I tried ½ degree, 1 degree, 1½ degrees, and finally settled on 2 degrees. I cut-in five more pieces, which were much better than the original nine.

The next experiment was to cut into a piece of thick veneer (which had itself been cut into the body veneer), three pieces of dyed white veneer to illustrate how a thin veneer can be cut-in so it is flush on the top or bottom surface, as you choose. A third white piece was first laminated to double thickness before cutting-in, leaving it flush on the bottom and slightly proud on the top.

Another demonstration experiment I performed was to cut-in three pieces approximately 1¼" in diameter of a veneer which had the same plug and body thickness. A perfect fit in this case should be flush on both top and bottom. This was the case with an angle two degrees smaller than theoretical, while the theoretical angle cut would not fit flush. It was slightly proud on the back, and depressed on the top. The third piece, cut two degrees larger than theoretical, would not fit into the window. This third piece illustrates why so much pressure is sometimes required to get the plug into the window and roll the edges flush. What happens is the fibres are crushed, and the main body is forced out of shape.

While doing these experiments, it occurred to me that there was another way to obtain good fits without changing the angle. I reasoned that if a double thickness of cellotape effectively increased the thickness of the plug, then I could effectively make the plug any thickness I wanted by simply putting shims between the body and the plug in preparation for sawing; e.g. for a plug .045" thick and a 4/0 saw, I would set the angle at 9 degrees (2 degrees smaller than theoretical) and no shim is required. I can now cut-in every other size of veneer without changing the angle by shimming the plugs to .045" thickness; e.g. to inset a .020" plug, use .025" shims. This effectively increases the plug thickness to .045", for a theoretical angle of 11 degrees and the saw is set to 9 degrees. When working from a minimum thickness to a maximum as in my example, the amount of shimming becomes quite large so one might set the angle to 13.1 degrees (2 degrees smaller than theoretical 15.1 degrees), and shim .013" instead of .025". Remember that with this method, whatever angle you set on the saw, this angle is 2 degrees smaller than the theoretical and only those veneers at and above the theoretical angle can be cut-in by using shims.

Shims could be anything that can be cut by a fret saw blade. I used heavy waxed paper which worked very well. It was easy to cut and also lubricated the blade. Make sure you pack and tape the assembly (body, plug and shims) tightly. Remember that whenever you apply tape to the bottom side of the body or to the top side of the plug, you are using shims and if you overlap the tape edges you are doubling the thickness; e.g. with overlapped tape on both body and plug (.020" thick plug), the plug is effectively increased to .028" which is a 40% increase, and the theoretical angle changes from 25.5 degrees to 17.9 degrees, a change of 7.6 degrees.

I considered concluding this article with some recommendations or suggestions but I have decided that, due to my lack of practical experience, this would be presumptuous. I am confident that, mathematically and theoretically, everything I have written is true and I have experimented enough to prove it to my own satisfaction.

I hope that the material in these articles is not dismissed arbitrarily as being too complicated or difficult to incorporate, but will be considered carefully to see what might be of practical value.


FRET SAW BLADE ANGLES FOR MARQUETRY

Blade Angles (in degrees) for 26 Veneer Thicknesses and 9 Blade Sizes

BLADE NUMBER AND SIZE                                                           
           8/0     7/0     6/0     5/0    4/0     3/0     2/0     1/0      1    
Veneer                                                                          
Thickness  0.0063  0.0067  0.007   0.008  0.0086  0.0095  0.0103  0.011   0.012  
  0.020    18.36   19.57   20.48   23.57  25.46   28.359  30.99   33.36   36.86  
  0.021    17.45   18.60   19.47   22.39  24.17   26.89   29.37   31.58   34.84  
  0.022    16.64   17.73   18.55   21.32  23.01   25.58   27.91   29.99   33.05  
  0.023    15.89   16.93   17.71   20.35  21.95   24.39   26.60   28.57   31.44  
  0.024    15.21   16.21   16.95   19.47  20.99   23.31   25.41   27.27   29.99  
  0.025    14.59   15.54   16.26   18.66  20.12   22.33   24.33   26.10   28.68  
  0.026    14.02   14.93   15.61   17.92  19.31   21.43   23.33   25.02   27.48  
  0.027    13.49   14.36   15.02   17.23  18.57   20.60   22.42   24.04   26.38 
  0.028    13.00   13.84   14.47   16.60  17.88   19.83   21.58   23.13   25.37 
  0.029    12.54   13.35   13.96   16.01  17.25   19.12   20.80   22.29   24.44 
  0.030    12.12   12.90   13.49   15.46  16.65   18.46   20.08   21.51   23.57 
  0.031    11.72   12.48   13.05   14.95  16.10   17.84   19.40   20.78   22.77 
  0.032    11.35   12.08   12.63   14.47  15.58   17.26   18.77   20.10   22.02 
  0.033    11.00   11.71   12.24   14.02  15.10   16.73   18.18   19.47   21.32 
  0.034    10.67   11.36   11.88   13.60  14.65   16.22   17.63   18.87   20.66 
  0.035    10.36   11.03   11.53   13.21  14.22   15.74   17.11   18.31   20.05 
  0.036    10.07   10.72   11.21   12.83  13.82   15.30   16.62   17.79   19.47 
  0.037     9.80   10.43   10.90   12.48  13.44   14.87   16.16   17.29   18.92 
  0.038     9.54   10.15   10.61   12.15  13.08   14.47   15.72   16.82   18.40 
  0.039     9.29    9.89   10.33   11.83  12.73   14.09   15.31   16.38   17.92 
  0.040     9.06    9.64   10.07   11.53  12.41   13.73   14.92   15.96   17.45 
  0.041     8.83    9.40    9.83   11.25  12.10   13.39   14.54   15.56   17.01 
  0.042     8.62    9.17    9.59   10.98  11.81   13.07   14.19   15.18   16.60 
  0.043     8.42    8.96    9.36   10.72  11.53   12.76   13.85   14.82   16.20 
  0.044     8.23    8.75    9.15   10.47  11.27   12.46   13.53   14.47   15.82 
  0.045     8.04    8.56    8.94   10.24  11.01   12.18   13.23   14.14   15.46 

 


SAW TABLE FOR 17" TUBULAR FRET SAW

by Jim MacKeracher

from Canadian Marquetry May 1998

I have made many different versions of fret saw tables.  The plans for my current model are at the end of the newsletter.  Also included are the steps I take to make this model.  I use a 17" tubular fret saw purchased from Lee Valley Tools.

Making Individual Components

CLAMP BLOCKS 
Take a 5/8" thick piece of solid maple. 
Follow the steps in the Figure 1 and 2 (not to scale).
 
SWING ARM
Cut out the shape shown in the plans from 1" thick MDF (medium density fibreboard) with a band saw.
Drum sand the edges smooth.
Drill a 1/4" hole for the Hex bolt.
 
PIVOT BLOCK
Cut a piece of 3/4" thick solid maple to 4" wide by 3-1/2" long. Grain direction is important. 
Drill a 1/4" hole for Hex bolt. See plans for location. 
Mortise the head of the bolt into the maple 1/4" deep on the hinge side.
 
ANGLE BLOCK
Cut a piece of 3/4" thick MDF to 4-3/4" by 3-1/2".
Use the plan to mark out the slot for angle adjustment.
Drill out the ends of the slot with a 3/8" bit.
Cut the rest of the slot out with a scroll or jig saw.
Drill and counter sink holes, E for #6 screws.
 
INSERT BLOCK
Cut a piece of 3/4" thick poplar to 2" wide by 3" long. Grain direction is important. 
Drill and counter sink holes, F for #6 screws. 
 
PLATE
Cut a piece of 11/16" thick PB (particle board) to 4" by 24". 
Drill and counter sink holes, A and B for #6 screws. 
 
SUPPORT 
Glue together 4 oversize pieces of 11/16" PB. 
Cut to 3" by 14" by 2-3/4". 
 
BASE
Cut a piece of 11/16" thick PB to 4" by 20". 
Drill and counter sink holes, C for #6 screws. 
 
TOP 
Cut a piece of 3/4" thick melamine to 16" by 21". 
Rout all the edges with a 1/4" round over bit. 
 
Rout a 17 degree dovetail groove 5/8" wide and 5/32" deep. 
 
THROAT PIECE 
Cut pieces of soft wood to fill the 17 degree dovetail groove flush with the TOP.
 
PIANO HINGE
Cut 3/4" piano hinge to a of length 3-1/2".
Drill extra holes for screws if necessary. 

Assembly 

Attach the 17" tubular fret saw to the SWING ARM with CLAMP BLOCKS 1 and 2 using 1-1/2", #6 wood screws. 
Attach the PLATE to the SUPPORT with 2", #6 wood screws. 
Glue and screw together the ANGLE BLOCK and PIVOT BLOCK with 1-1/2", #6 wood screws. 
Insert the 2" by 1/4" Hex bolt into the PIVOT BLOCK. 
Attach the piano hinge to the PIVOT BLOCK with 3/4", #5 wood screws. 
Glue and screw the INSERT BLOCK to the PLATE with 1-1/4", #6 wood screws. 
Attach the piano hinge to PLATE with 3/4", #5 wood screws. 
Mark the centre of the insert nut through the slot in the ANGLE BLOCK at the joint between the INSERT BLOCK and PLATE. 
Remove the screws holding the piano hinge to the PLATE and set the assembly aside. Drill and put in 1/4" insert nut. 
Reattach piano hinge to PLATE. Place 1/4" wing nut and washer on 2" by 1/4" machine bolt. 
Thread bolt all the way into insert nut and tighten. Use wing nut to secure ANGLE BLOCK in vertical position. 
Clamp entire assembly to table making sure clamps position will not interfere with installation of TOP. 
Slide SWING ARM over Hex bolt and secure snugly with 1/4" washer, nut and wing nut. 
Place TOP on plate under top fret saw arm and clamp lightly in place. 
Insert coarse fret saw blade through hole in TOP and tighten in fret saw under tension. 
Check clearance with blade tilted and reposition TOP if necessary. 
Tighten clamps holding TOP to PLATE securely. Remove clamp holding assembly to table and turn over. 
Attach PLATE to TOP with 1-1/4", #6 wood screws. 
Remove clamps holding TOP to PLATE. Attach BASE to SUPPORT using 2", #6 wood screws. 
Turn over and clamp BASE to table. 

Fine Tuning

For quick, accurate tilt angle adjustment, set the fret saw tilt to vertical by using a protractor sitting on the TOP and lined up against a tensioned fret saw blade. 
Mark a pencil line on the ANGLE BLOCK using the top of INSERT BLOCK as a guide. 
Label as 0'. Set other commonly used angles and mark for quick adjustments (10, 12, 15). 
Adjust the wing nut and nut so SWING ARM moves freely but not sloppily. 
Cut 2 throat pieces and insert from either side of dovetail until they touch the fret saw blade. 
Secure to the TOP with a piece of cellophane tape. 
Bevel the ends of the throat pieces so that they conform to the most commonly used tilt angle. As the ends wear, re-trim.

 


USING PINS TO POSITION TRACINGS

 AND OVERLAYS IN MARQUETRY

by Tony Stuart

 Register pins are used in the graphic arts for assembling film and processing printing plates.  They come in various heights, of about 1/8" to 1/4", and they are 1/4" in diameter.  A big advantage of using register pins for marquetry is the ease with which both sides of the workpiece can be accurately worked.  I happen to have a pair of these pins and have used them successfully so I thought I'd pass this idea on.

 

 

The regular 3-pin binder-punch I have makes holes just a bit too large, about 0.265" diameter.  So I use a one-hole punch (Grand & Toy $2.00) which is just a little smaller than the pins but presents no problems for tracing paper and white-card-wasters.

 

 

 

 

 

 

The technique is very simple.  If a one-hole punch is used, attach temporarily the waster (background veneer), tracing paper, and working pattern (transparent overlay) together.  Punch two holes as far apart as possible.  They should be roughly equidistant from the centre, along one edge.  The assembly must be kept flat and together while punching the two holes.  Therefore, it may be best to put a register pin in the first hole punched, then check for position and flatness before punching the second.  If a regular binder-punch is used, each item, the waster and tracing paper etc., can be punched separately.

It is best to reinforce with cellophane tape thin papers such as tracing paper in the areas which are to be punched.  If a hard veneer is to be used for the waster (background), then a strip of soft thin cereal box cardboard about one inch wide should be securely taped to one edge of the waster and the holes punched in the cardboard.  The pins are placed in the punched holes in the waster (background).

With the prepunched pattern and tracing paper placed over the pins in position on the waster (background), trace the design in the usual way.  Now each time a new section of the pattern is to be traced on the workpiece (background), just pop it on the pins and it will be accurately aligned.  To work on the back, simply turn everything over and reposition it on the pins.

However, because the pins are not a common item, and because it is more convenient if a regular 3-hole-punch can be used, I tried using wooden dowel to make a pair of pins.  They seem to work okay (maybe the dowel is a bit oversized).  To make a two-pin setup, take a punched piece of cereal box cardboard to your local lumber store and find a piece of dowel that fits the holes snugly.  Cut two strips of cardboard the same size, punch one strip in your 3-hole punch and paste them together.  Saw off two pieces of the dowel about 1/4" long as square as you can.  Chamfer one end with sandpaper and glue the other end into each of the two outside holes.

The metal pins can be obtained from a graphic arts and printer supply house.  So check the yellow pages in your area.  Canadian Graphic Supply Ltd., 133 The West Mall, in Etobicoke have them if you purchase a minimum of ten pieces.  An unmounted pin costs less than $2.00 and a pin on a metal base is $9.00.  You will need a pair of them of course.


Picture Hanging

by Jim MacKeracher

 

 

 

 

 

 

 

 

This article outlines the technique I use to hang marquetry pictures.  See Figure 1.

 The following is a list of equipment required: 

STEP 1 

   The brass plates I use have 4 predrilled screw holes.  Two more holes have to be drilled for the hanging cord to be inserted.  Mark with a centre punch on the good side of the brass plate the centre between the screw holes at both ends as seen in Figure 2.  Drill 1/8" diameter holes through the plate at both locations.  File the metal burrs off the back of the plate resulting from the drilling operation.

STEP 2

   Measure distance 'A' as shown in Figure 2.  On the back of the plate mark off (with a felt pen) distances 'B' so 'A=B'.  Draw lines across the plate at both locations.  Saw along the lines with a hack saw.  File the burrs from the newly cut ends of the two pieces of plate.

STEP 3

    The guidelines I use for the placement of the plates have their centre located 1/3 the overall length down from the top of the picture and the edge of the plate 1/4" from side edge of the picture.  The cord should stretch up to 1/6 the distance from the top of the picture  as shown in Figure 3.

 

On the top back of the picture place a piece of masking tape so you do not accidentally hang the picture upside-down.  I like to place pieces of masking tape as shown in Figure 4 to make it easier to mark the positioning on the back of the picture.  Mark with a pencil and ruler onto the masking tape the two cord holes placement with a '+' and the highest distance the cord will stretch with a '-'.  Centre a plate over a '+' and adjust it so it is parallel to the pictures edge.  Mark with a pencil onto the tape the screw hole locations with a 'o'. Do the other side with the other plate.  Make sure not mix up the plates and their markings because they may not be interchangeable.  Use an awl to dimple the centre of the two cord marks ('+') and four screw marks ('o') to prevent the drill bit from slipping off the mark.

 

Tie a knot at one end of a test piece of cord.  Trim off the excess cord leaving 1/8".  Test drill 1/4" diameter hole into a piece of scrap so the hole is just deep enough to hold the knot as shown in Figure 5.  Wrap a piece of tape around the drill bit to act as a stop indicator.  Drill similar holes at the cord hole locations marked by a '+'.

 

   

STEP 4

    Drill 1/8" pilot holes for the screws at locations marked by a 'o'.  Be extremely careful not to drill through the picture, a drill stop is advisable.  Make sure the screws are not too long.  Remove the two pieces of tape at the plate locations.

 STEP 5

Thread one end of the cord through the centre hole of one plate from the good side.  Tie a knot on the back side and trim as in Step 3.  Place a drop of glue on the knot so it will not unravel and putace.

 STEP 6

    Remove all remaining tape and residue.  Stick on the bottom corners bumper pads to prevent the picture from damaging the wall and vice versa.

Closing Remarks

    This method is similar to an article was written by Doug Denton in the October 1989 issue of the Marquetry Society of Canada's Newsletter.  Doug went a step further and mortises the plates into the back of the picture.

 


SCROLL SAW MODIFICATION

as Demonstrated by Frank Wood,
written by James Colter

Motorized scroll saws useful for marquetry are very expensive.  The inexpensive ones do not have variable speed control so are more suited for fretwork rather than veneer.

Modifying a motorized scroll saw presents a number of problems. The addition of a potentiometer or variac to an AC motor creates loss of power or torque of the saw. Clipping the sinusoidal AV wave decreases power.  The good scroll saws get around this by using DC motors.

A good source of a DC motor is a used sewing machine. This has the added benefit of having a foot peddle for hands-free speed control. The mechanism for oscillating the blade is on the AC motor, so Frank got around this by extending the shaft of the AC motor with a sleeve coupling and adding a pulley wheel to couple to the DC motor by a belt. (see photo)

Another addition is a light - also found on most sewing machines.

 

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