How to cut a mirrored taper

[Doug Fennell]

Never ran into this before, but I'll bet someone here has - how would I go about cutting an identical taper on on both sides of my work piece using the table saw? It'll be 2.78" at the base, 1.75 at the tip and 29.5" overall length. Trapezoidal in shape.
This image isn't to scale, but gives the overall idea -

blue1.jpg

Thanks!

[Bill Huber]

If I was doing it I would just use my tapering jig.

http://www.pbase.com/wlhuber/taper

111630807.NsoMCsCN.P5205353.jpg

[Doug Fennell]

Bill, thank you for the suggestion. I have a tapering jig, but I'm just not getting my head around how to use it for this purpose, can you elaborate?

[Bill White]

I use a jig that allows me to place a center point on both ends of the work piece, determine the offset needed, cut one side, flip to the center point with the needed offset on the other side, and cut the other side.
The offset is usually placed on the narrow end.
Hope that makes sense.
Bill

[Bill Huber]

Bill, thank you for the suggestion. I have a tapering jig, but I'm just not getting my head around how to use it for this purpose, can you elaborate?

This is the way I would do it with my jig, my jig runs on the fence and not the miter slot.

Mark the angle on the board on both sides.
Place the board on the jig so the lines, line up with the jig.
Lock it down and make the first cut.
Turn the board around and do the same for the second cut and you should have it.

I have had a case where my jig was a little short to get it lined up with the one end but I just used a straight edge to extend the edge of the jig.

Drawing1.jpg

[Doug Fennell]

Thanks guys, this does help.

[Peter Quinn]

Use the tapering jig, set the offset for the first side, make the cut, save the drop, flip the piece 180 degrees side to side across the width, not the length. Put the drop against the fence, you may have to make a small cut at the skinny end, this wedge will return the tapered side to square. Set the width accurately, make the second cut.....Bobs your uncle....mirrored taper, identical angles. The centerline thing could work, but that introduces tricky stuff like finding dead center twice, transferring it accurately to the jig, measuring....things a simple guy like me tries to avoid. Rip it...flip it...wedge it...forget it.

[HANK METZ]

Funny, I just cut a coupla shapes like that this morning for my DIY- goodbye cable- antenna. I used a scrap square of ply as the base, screwed the work to it after orienting the desired angle to a square outer edge, and zip- zap, off it came on my RAS. Oh yes, got about 20 free over the air channels too, it was a good day all 'round.

Carboard And Foil Antenna.JPG

[Doug Fennell]

Yep, this makes sense to me. As long as I save the drop, it'll be exact. Set the width on the narrow end and Pythagoras will be in the drivers seat.

[Peter Quinn]

Complementary angles are your friend.

[Lee Schierer]

Use the tapering jig, set the offset for the first side, make the cut, save the drop, flip the piece 180 degrees side to side across the width, not the length. Put the drop against the fence, you may have to make a small cut at the skinny end, this wedge will return the tapered side to square. Set the width accurately, make the second cut.....Bobs your uncle....mirrored taper, identical angles. The centerline thing could work, but that introduces tricky stuff like finding dead center twice, transferring it accurately to the jig, measuring....things a simple guy like me tries to avoid. Rip it...flip it...wedge it...forget it.

This method will work just fine, but use some tape on the top surface to hold the cut off in place against the finish piece as you make the second rip cut.

[glenn bradley]

An alternate is to add a pin to your taper jig. With the stock centered on the pin you can do two or even four sides without changing your setup.

Taper Jig (13).jpg . Taper Jig (15).jpg . Taper Jig (17).jpg

If the top of the part will show drill the hole in the foot to go on the pin. If the top is hidden I drill the top but, it is of little consequence as long as you take any mortise or other joinery cuts into account. If the guide hole will bother my joinery, I just make the blank a bit longer and then cut off the tip with the hole in it ;-)

[Peter Quinn]

This method will work just fine, but use some tape on the top surface to hold the cut off in place against the finish piece as you make the second rip cut.

I would batch cut the first side then double stick tape a drop to the sled and batch cut the second assuming sizes are consistent, either way angle remains constant.

[Kent A Bathurst]

Yeah - I do it like Bill H. describes - mark the ends with a pencil, line those "ticks" up with the edge of the sled [mine looks a lot like Bill's - I wonder if I stole the design from him years back ???], and fire away.

If I am off, I am not off by 1/64" - something less than that. And I can definitely live with those results.