Making mirror-image parts

[Brian Jackson]

Howdy all.

Learned another cool trick on the table saw yesterday. While working on the engine mount for my GyroBee project, I noted that there was a slight error in my table saw's mitre gauge calibration. So cutting, say, a +50 degree angle according to the angle gauge wasn't exactly identical for both directions (-50). I discovered this slight error by mating 2 "finished" angled parts side by side and noted the angle difference... they should have been exact mirror-image opposites. Fortunately I had enough length to allow re-trimming them.

So I worked out a simple method for making sure the parts will end up exact opposites when cut. Simply use the first part's angle-cut surface to press against the mitre face, then rotate the face and part until the length of the part is exactly parallel with the guide groove in the table saw bed. Lock it down and presto.

Cheers,
Brian Jackson

[StanFoster]

Brian: Looks like you have your angles figured out. You are very meticulous...I can tell. Your gyro should be a thing of beauty. Keep up the good work and the posts.

Miter gauges are finicky to get exact. Another method you can try ....is set you miter gauge one way at 50 degrees.....trace this angle with the miter gauge slot....then swing the miter gauge to 50 degrees on the other side. Trace this angle with the miter gauge slot and then overlay these two angle recordings. The true 50 degree angle will be a line that splits the difference between these two angles. Its a dead nuts way of getting what ever angle you want very precisely. I use this all the time....but only in wood.

Stan

[Brian Jackson]

Originally Posted by StanFoster

Brian: Looks like you have your angles figured out. You are very meticulous...I can tell. Your gyro should be a thing of beauty. Keep up the good work and the posts.

Miter gauges are finicky to get exact. Another method you can try ....is set you miter gauge one way at 50 degrees.....trace this angle with the miter gauge slot....then swing the miter gauge to 50 degrees on the other side. Trace this angle with the miter gauge slot and then overlay these two angle recordings. The true 50 degree angle will be a line that splits the difference between these two angles. Its a dead nuts way of getting what ever angle you want very precisely. I use this all the time....but only in wood.

Stan

Great idea, Stan. The angular bisector would be dead-nuts on, wouldn't it. Line up the mitre face with the bisector line and readjust the angle pointer on the mitre to true zero. Thanks man! By the way I was very impressed with the photos you emailed me of your curved stairway projects. I'm in awe, and writing to a true master. "We're not worthy, we're not worthy" (in my best Wayne's World impression)

Respectfully,
Brian Jackson

[StanFoster]

Brian: Thanks for the comments......I feel fortunate to have a passion for my occupation.....just like you are showing for your gyro project.

Stan

[StanFoster]

Brian: To take the angle thing another step.....when I want to make templates of an exact angle....we can use this 50 degree example of yours again....I will make a right triangle template. This template then can be used to set your miter gauge...miter saw...or whatever.

The base of this triangle can be any length,,,but for simplicity...we can make it 10.0 inches. If I want exactly 50 degrees....I just take the tangent of 50 degrees ...and my calculator indicates 1.191753593. Multiply this by the base which is 10.0 inches and the height of the right triangle is 11.9175393 inches. So.....I would cut out a right triangle with the above dimensions and I have a very accurate 50 degree template to set my miter gauge to.

Of course this could be easily calculated to any fraction of a degree you can come up with.

Happy angling

Stan

[Brian Jackson]

Stan, you're my hero!
Yeah, it's fun trigging out angles to the n'th degree. Especially when you see the fruits of the equations as tangible objects blending ever-so-perfectly into precise unions. There's something very satisfying about it. I suppose that's a key indicator that we love what we're doing. After all, nobody in their right mind would expend such effort on tiny details like you and me unless they posessed the passion.

Yours in friendship,
Brian Jackson