I would like to cut a 9-in.-wide octagon on the tablesaw. How can I do this safely?
Stewart Levine, via Knots online forum, None
Answer:
For a 9-in. octagon, start with a blank that is 9 in. square. For the jig, begin with a plywood base 3/4 in. thick by at least 9 in. long. To determine the width, multiply the side of a square by 1.41 (in this case, 9 × 1.41 = 12.69 in.). Subtract the 9-in. width from 12.69 in., and you get 3.69 in. This is the sum of two opposite corners of the square blank that will be removed to create an octagon. Divide 3.69 by 2 to get 1.84. Add 1.84 to 9, and the result is 10.84 or a hair less than 10-7/8 in. This is the width of the jig and the distance from the fence to the sawblade.
Cut a pair of 45° triangles. Attach them to the jig as shown in the drawing. Use a backsaw to open a sawkerf gap where the two points touch. Place the blank in the jig, and cut off a corner of the workpiece. Turn the workpiece 90º and repeat three times to leave a perfect octagon.
Cutting the octagon. The first cut and the second are made with the opposite 90º corner fully nested in the jig.
Final cuts. Before the third cut and the fourth cut, the opposite corner is already cut, so the workpiece doesn’t reach fully into the jig.
Fine Woodworking Recommended Products
Veritas Precision Square
This precision square is incredibly versatile, from checking squareness to dialing in machine setups.
This is the saw I want in my shop. For one, it’s easy to use. All of the controls are easy to reach and manipulate, and the glide mechanism is both robust and smooth. The handle works well for righties and lefties. Then there are added bonuses that no other saw has. For instance, its hold-down is superb, as it can move to different locations, hinges for a greater range of coverage, and actually holds down the work. In addition, the saw has two points of dust collection, letting it firmly beat the rest of the field. The one downside was the saw’s laser, which was so faint we had to turn off the shop lights to see it. Still, all these pluses in a package that fits tight to the wall? That’s a winner for me.
With its graceful curves, cabriole legs, and ornamental back splat, a Queen Anne side chair is a bucket list build for many woodworkers. Dan Faia had a very specific Queen…
Become an UNLIMITED member and get it all: searchable online archive of every issue, how-to videos, Complete Illustrated Guide to Woodworking digital series, print magazine, e-newsletter, and more.
Log in or create an account to post a comment.
Sign up Log in