Marble Race

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This article is from Issue 44 of Woodcraft Magazine.

Building blocks with a built-in race track

Building blocks are a cornerstone of childhood, but with most kids, the thrill is relatively short-lived. Here’s a set that’s guaranteed to entertain the young and the young at heart, and to teach you a few woodworking lessons along the way. These cleverly designed drops, chutes, and curved blocks encourage creative minds to assemble tall towers that double as marble raceways.

This simple scrapwood project also offers lessons in accurate production work. The parts must be milled precisely in order for the marbles to roll without a hitch.

With the following step instructions and jigs, you can make a starter set in a weekend. But keep the jigs handy. You’ll likely get requests for more parts, or another set, before the holiday season ends.

Mill the stock

1 From 5/4 (11⁄4") stock, mill chute stock to 1" thick. From 10/4 (21⁄2") stock, mill block stock to 2" thick. (Note: Consider milling extra chute and block stock now. If you’re short on time, you can forgo the routing and make plain-faced blocks for “stackers.”)

2 Rip the block and chute stock to 2". Crosscut the chute stock to about 121⁄4" long. Now using a stop, carefully cut all of your block stock to 2" cubes.

3 Set up your router table with a 1⁄8"-radius round-over bit. Using a pushblock for the chute stock and a handscrew to safely hold the blocks, round over all edges (Photo A).

Secure the small blocks in a wooden handscrew to keep fingers clear of the router bit.

Make the jigs and mill the parts

1 From 3⁄4"-thick plywood and block scrap, make both slotting jigs, as shown in Figure 1.

2 Using a plunge router equipped with a bearing-guided cove bit (see the Convenience-Plus Buying Guide, page 39), adjust the bit height (and set the depth stop) to rout a 3⁄8"-deep groove. Using your bench vise, clamp a piece of chute stock (A) in the straight slot jig and rout a groove (Photo B). If needed, insert a shim against the stop so that the groove is centered on your stock.

3 Continue routing straight grooves on your chute stock (A), curve (B) and drop blocks (C and D), using the figures on page 38 as reference. To make the castle-topped drop blocks (C and D), rotate the block 90°, and rout a second groove perpendicular to the first.

4 Clamp a block into the curved slot jig, and rout a groove to make the curved slot block (B), as shown in Photo C.

5 Using a mitersaw and stop, trim the chute stock to make short, medium, and long chutes, where shown in Figure 2.

Use a vise to secure chute stock and blocks to the straight slot jig, and rout the groove.
Clamp a block in the curved slot jig and feed the router counterclockwise The scrap stock controls tear-out and protects the vise.

Drill the drops

1 Using a center gauge, mark out the centers on the unrouted faces of curve blocks (B). Make sure your drill press table is perpendicular to the chuck, and then drill 3⁄4"-diameter through-holes where shown in Figure 3.

2 Clamp a starter drop block (C) into an adjustable angle vise. Using the grooves as a guide, center the bit on the top of the block, and drill a stopped hole as shown in Figure 3 and Photo D.

3 Adjust the vise angle to 26° (or the tilt of your table), and drill a second stopped hole through the front, as shown in Photo E.

4 To round the intersection between the holes, chuck the bearing guided cove bit (used to rout the grooves) into your drill press. Drilling at the slowest speed, lightly clean out the hole as needed to allow clearance for the marble (Photo F).

5 Repeat the drilling sequence for the standard drop blocks (D), making sure to adjust the hole depth and vise angle, where shown in Figure 3.

Set the vise to 90° and drill a stopped hole into the top of each of the drop blocks.
Set the angle, reposition the vise and then drill the angled hole in the front face of the drop block.

Use the router bit to shave away any tear-out and round the inside corner.

Build the box and finish the blocks

1 From hardwood and/or Baltic birch plywood, cut the box ends, sides, and bottom to the sizes listed in Figure 4.

2 Using a tablesaw equipped with a dado set, dado and rabbet the box ends where shown.

3 Glue and clamp the bottom and sides to the ends.

4 Sand the parts to 220 grit, and then apply a kid-friendly finish to the blocks and box. (I wiped on a coat of walnut oil, let it soak in for about 10 minutes, and then wiped off the excess.)

5 Give the blocks a test run. You may need to sand or plane a corner or face to make a fast rolling track.  

About Our Designer/Builder

Scott Emch, from New Martinsville, West Virginia, has been woodworking for close to 20 years. Most of his projects have been for friends and family, using wood cut directly from his farm.


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