Thread: Best way to cut a 7 sided heptagon

Are we talking ripping or cross cutting? size & length?

Cross cutting boards using a sled, the appropriate fence setup & toggle clamps is pretty straight forward. - on a conventional table saw.

Ripping on the other hand is not so straight forward and requires careful thought.

ps I should read more thoroughly.

Its also pretty simple using a sliding table/panel saw with a fence. Just requires an initial fence setup, then a secondary fence setup to cut the remaining angles - however - always a however, it presents significant potential for cumulative errors - similar to the multi-cut setup to test squareness of a tablesaw / fence setup.

My only thought is the first cut as its a circle. Sproing!

Could the first face be planed down, or at least made flat?

That would make the jig straight forward.

How about create the circle blank. Using a cross cut sled, cut off the first side at the diameter wanted.

Hot glue a stop block onto the cross cut sled at the desired angle.

Register the cut side against the block and make the next cut. Rinse and repeat.

Table saw or sliding table saw.

take a piece of board about 100 mm wide and trim it on the fence
turn the saw off and move the fence towards the saw so the edge of the board lines up with the other side of the teeth on the blade, lock the fence.
then put the board against the fence and on top of your workpiece and line the edge up with your setout line on the workpiece, clamp the workpiece down to the table or sled. Move the setting board away.
cut the workpiece off on the first line
proceed similarly around the workpiece
this technique works well and eliminates a lot of guesswork because you’re using a parallel board that’s set to the cutting face of the teeth with the fence, which is fixed.

Wouldn't know how to attempt this on a drop saw, Dengue, but it should be fairly straight forward on a table saw, band saw or router table with a sled. Freehanding would also be possible, but a little more difficult.

First, I would joint one edge of your plate as the reference surface.

Second, I would draw an accurate drawing of the heptagon and transfer it to the plate.

Heptagon.jpg
With a heptagon we can disect it into seven identical triangles radiating from the centre. There are 360 degrees in a circle. Thus:
First angle = 360 / 7 = 51.4286 degrees.
Second angle = ( 180 - 51.4286 ) / 2 = 64.2857 degrees.
Third Angle = 180 - ( 64.2857 * 2 ) = 51.4286 degrees.
OR: Third Angle = First Angle = 51.4286 degree.

Third: Set fence on sled as close to 51.43 degrees as possible.
Fourth: Align reference surface to fence and make first cut as close to line as you are comfortable.
Fifth: Rotate plate and make second cut. Repeat.
Finally: With hand plane, carefully trim down to lines.

If doing several of these I would much prefer to use a CNC.

But for one or two it is probably quicker to do it by hand.