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Spinning Jig

Traditionally, before the on-set of digitally created models and model detail, most of the intricate work for scale models was developed by the modeler using various machinery such as lathes and mills. The modeler would also construct various jigs and fixtures to assist in the duplication of various parts.

 

For the purpose of making a scale wheel in clay for the Corvette project, we will construct a spinning jig to turn the rim and tire. The material for making the spinning jig is 1/2" and 3/4" plywood, which is available from any Home Depot, Lowes or D.I.Y. Center.

 

Engineering drawing for base of spinning jig.

To begin the construction of the spinning jig we will start with the rectangular base.

 

A. 15"x 11"x 3/4" plywood

 

On the plywood mark-out with a combination square the dimensions set-out by the illustration on the left.

 

From the right hand side measure 61/2" and square across the board, then mark a centerline along the length of the board. The resulting center will be the center of the turn table for the spinning jig.

 

From the centerline measure up 1/8" and scribe a line. This will be the position of the main body to support any templates that will be used in producing clay parts.

 

The reason for the off set is; most of the templates will be made from 1/8" masonite or hardboard. When clamped to the body the cutting edge will be on the absolute center of the part being spun therefore giving a correct overall dimension. It will also give a cleaner cut to the clay as there will be less drag from the back edge of the template.

 

Engineering drawing of body for spinning jig.

For the body we will use a piece of 1/2" plywood.

 

B. 11"x 9"x 1/2"

 

Mark out the plywood with a 6" high by 51/2" wide cut-out. A radius can be applied to the corner purely for aesthetic reasons if desired.

 

Remove the cut-out on the bandsaw and sand the edges smooth.

 

 

 

To support the main body in a vertical position a pair of support webs are made from 1/2" plywood.

 

C. 41/2"x 31/2"x 1/2"

 

Cut the plywood to the dimensions provided and scribe a 2" radius on one corner. (This will prevent a few scraped knuckles by removing the corner.)

Cut to shape on the bandsaw and sand smooth.

Engineering drawing for support webs for spinning jig.

Photograph of support webs in place on spinning jig.

 

With all the components made for the base (A) and the body (B), glue the body into position on the base board. Set the body to the far left, aligning with the edge of the base board and the 1/8" off-set line. Ensure that the body is vertical by gluing the two webs (C) to the back face and to the base board. This will provide the necessary stability for the body when spinning the clay wheel. (See above photograph)

 

Engineering drawing of bearing and spinning jig platform.

Now we can turn our attention to the turn table and bearing.

 

The bearing (D) should be of sufficient size so as to provide support for the platform (E) when spun in the bearing.

 

To make the bearing glue two pieces of plywood 4"x 4"x 3/4" together. When the glue has set, scribe lines across the diagonals to find the center. Set the dividers to 1" and scribe a circle giving a 2" diameter, reset the dividers to 1 3/4" and scribe a second circle giving a 3 1/2" diameter. 

 

The 2" diameter hole can be cut-out using several methods. The easiest is by drilling a hole and cutting out on a scroll saw. The inside can then be sanded on a spindle sander or with a barrel sander set-up in the drill press. 

An alternative method is to drill holes close together around the inside of the line then remove with a coping saw. The left over material would be filed out with a rasp then hand sanded to the line using a large diameter wooden dowel with sand paper wrapped around. Either method will give the same result, time is the only factor. 

Photograph of bearing glued in place on base of spinning jig.

Photograph of spinning jig table with plug glued on for location into bearing.

 

With the hole of the bearing cut-out and sanded, the outside can be trimmed to the line using a bandsaw or hand cut with a coping saw then sanded smooth. It is not absolutely necessary to round off the outside but it will prevent you knocking your knuckles on the corners when spinning the table.

 

With the bearing finished glue up two pieces of plywood 2 1/4"x 2 1/4"x 3/4" and allow to set. This will make the plug (F) that fits to the bottom of the table and spins inside the bearing. Once dry, scribe a 2" diameter circle, cutout and sand to fit the bearing. The overall fit should be that it spins inside the bearing with minimal play ( side movement ). This may take a little time in sanding, to achieve the best fit.

 

The table (E) is made from a piece of plywood 6"x 6"x 1/2". Find the center of the plywood by scribing across the diagonals. Set the dividers to 2 3/4" and scribe the circle on, cut-out the 5 1/2" diameter circle on the bandsaw and sand smooth. On the same center scribe a 2" diameter circle, this will be used as a guide for gluing  the plug to the turn table.

 

On the base board at the center for the turn table, scribe a 2" diameter circle, this will be the guide for gluing the bearing to the base board.

 

To assemble, glue the plug to the bottom of the turn table using the scribed two inch diameter circle as a guide to centralize the plug. Next in a similar fashion, glue the bearing to the base board using the two inch diameter scribe line as a guide to centralize the bearing. (See photographs above) With the whole assembly complete it should resemble the photograph below. To make the turn table run smoothly apply paste wax to the plug of the turn table and inside the bearing.

 

Photograph of finished spinning jig ready for turning small clay buttons, wheels or rims.

 

Spinning Jig PDF    To construct the spinning jig, download the technical illustration.

 

 

Copyright © 2004 - 16 Steven Austin

 

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