Clay, Application to Refinement

 

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Scribing Mouse

The scribing mouse is used to mark horizontal lines and vertical lines onto the model when using traditional methods for duplication. When used with an angle bracket it can quickly mark positions for the transferring of information.

 

The photograph on the right shows the basic make up of the scribing mouse. The materials are plywood and 1/16" steel plate. The star shaped pointer enables the scribing of lines into internal and concaved shapes.

 

 

To make the star shaped scribing tip, a piece of steel plate 4 1/2"x 2"x 1/16" is required to develop the shape.

 

Start by scribing a centerline down the length of the steel plate. Next scribe lines at 90 to the centerline, measure from the right end 5/8"(A). This is the length of the first point of the star. From that scribe line mark the center of the next two points. Measure 5/16"(B) for the center, then 5/16"(C) for the end of the scribing tip. Mark the position where the body of the scribing mouse meets the steel plate (D).

From the left side of the plate measure 3/8"(E) and scribe a line 90 to the centerline. This is the position for the first fixing of the plate to the body of the scribing mouse. From the left again scribe a line 11/8"(F) from the end of the plate, this represents the second screw fixing.

 

Continue by marking parallel to the centerline, two lines, 5/16"(G) either side giving a width of 5/8". You now have the three tips of the blade marked out. On the left hand side, mark 1/2"(I) either side of the centerline, this will give you the overall width of the body of the blade (1"). Where the width of the body intersects with (F) scribe an angle to meet point (D)

 

The mark-out for the scribing tip should look the same as the illustration on the right.

 

Now that the blade has been marked out, cut the shape out on a metal bandsaw or with a hacksaw, then hand finish by filing to the scribe lines. With a pair of dividers scribe a 1/16" parallel line around the star shaped tip, from this line file a 45 angle to produce the cutting edge for the scribing tip.

 

In the marked positions (E) and (F) drill (5/32" or 4.0mm) and countersink for No.6 woodscrews, making sure to countersink on the bottom face of the blade. Check the depth of the countersink by using the screws as a gauge.

 

With the blade complete lets continue with the main body of the scribing mouse.

 

The quickest solution for the body is to use plywood as it is already reasonably stable. 

 

For this particular scribing mouse cut two pieces of 1/2" plywood 3/4" wide by 24" long. Glue the two pieces together using wood glue or 5 minute epoxy resin, making sure that the bases remain flat. Once the glue has set, sand off any excess glue. Check the base once again and flatten if necessary.

 

For extra strength mark-out the dowel locations. From the right measure 3" for the first dowel then five sets of 5" for the centers of the other five dowels. Intersect those lines by scribing a line 3/8" from the base.

 

With the center of the dowels marked out, set-up the drill press with a 3/8" drill bit and drill through the six dowel positions. Glue the 1"x 3/8" diameter dowels into the six positions using wood glue or 5 minute epoxy resin. After the glue has set, sand both sides to remove any excess glue.

 

To set in the scribing tip, mark a line 2" in from the end of the body and rebate to a depth of 1/16" (1.5mm) This can be done on a bandsaw, filed with a rasp or cut with a chisel. Check the depth with the scribing tip, it should be flush with the base. Before fitting the scribing tip to the body, taper the nose to give it a streamline appearance.

 

To fit the scribing tip to the body, first cover the screw holes with a couple of pieces of masking tape, this will stop the resin from seeping through.

 

Mix up enough 5 minute epoxy resin and apply to the scribing tip and the rebate on the body. Place both pieces on a flat surface and then position the body onto the blade. Once the resin has set, the pilot holes can be drilled for the No.6 woodscrews (No.47 or 5/64") Take care when screwing in the screws so as not to split the plywood. To finalize the scribing mouse coat the body with a shellac or polyurethane sealer.

 

    

To make the scribing mouse, download the technical illustration.

Scribing Mouse PDF

 

 

Copyright © 2004 - 16 Steven Austin

 

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