[jlhaslip]

Mine is marked like that too...

titled: Is the 31.6 reading something special?

yes. that angle is used when cutting crown mouldings flat on the mitre saw table... there is another angle on a compound saw (39 deg???) which is used in conjunction with the 31 deg mitre angle

 

[woodnthings]

This you tube explains the 38 degres and 31 degrees

bill :thumbsup:

 

[woodnthings]

for further explantion of miter saw settings

Go here:
http://www.woodworkingtalk.com/f2/equalateral-triangle-36923/#post316355

 

[Outlander]

I gave up when doing moldings since I had inside and outside compound cuts. So I spent some time to make myself some templates that were nicely labelled that I used to rough in the mitre saw. BIL stole them when he was stuck

 

[Al B Thayer]

I paid a couple thousand for my table saw and it still came with a cheap miter gage no one could use. But that was more than 25 years ago. Oh but I see they still sell the same crappy miter gage. Some things never change. Even when they should.

Al

Friends don't let friends use stamped metal tools sold at clothing stores.

 

[cabinetman]

I paid a couple thousand for my table saw and it still came with a cheap miter gage no one could use. But that was more than 25 years ago. Oh but I see they still sell the same crappy miter gage. Some things never change. Even when they should.

Al

Yes, and that's unfortunate. When I bought my first new Unisaw, it came with a miter gauge similar to this. A replacement gauge (OEM), is somewhere between $30 and $50. At the time there were no alternatives like now. It was a matter of not trusting the numbers. The gauge got improved slightly by adding a shopmade fence which gave it a bit more usability. Gauges were shop made set at 90° and 45°, like this 90°.

Accuracy and versatility lead to the use of shop made sleds.

.

 

[WillemJM]

Thx Bill

Thanks for starting this thread, found it interesting.

Outside of the US, we covered most of this by the 6th grade in trigonometry and by 8th grade we would be working fluently with radians and degrees, the Sin rule, the Cosine rule, etc.

I never understood why one needs a computer program to calculate segments for a segmented bowl.

Using grade 7 math (overseas) for calculations including a miter saw:

Using a miter saw, for cutting segments of a segmented bowl:

Outside diameter = 15", the radius is 7.5"

If we decide to cut the pieces into 15 degree segments, we will set the miter saw precisely at 7.5 degrees, which is the angle it will actually cut into the one side of the segment.

We need a wood strip, or board approximately 1" wide.

We convert 15 degrees to radians by multiplying with Pi/180 and if we multiply that by the radius of our circle, we have the arc length (outside) of our segment.

15*Pi/180*7.5 = 1.963" which is slightly longer than what our stop should be set.

360/15 = 24, so we need 24 segments, the circumference of the bowl wil thus be 24*1.963 = 47.124"

To calculate the exact long (outside) length of the segment, for setting the stop on our miter saw, we use the Cosine rule.

a2 = b2 + c2 -2bc Cos A

b and c are the radii, while A is 15 degrees, so it follows that the exact length is 1.958"

In short, for a 15" diameter bowl (it will be slightly less than 15"), 15 degrees will give 24 segments, set the miter saw to 7.5 degrees (the angle it actually cuts onto the segment) which is half the angle of the segment it will actually cut and cut the outside length to exactly 1.958" measured with a vernier (dial) caliper.

 

[Al B Thayer]

Thanks for starting this thread, found it interesting.

Outside of the US, we covered most of this by the 6th grade in trigonometry and by 8th grade we would be working fluently with radians and degrees, the Sin rule, the Cosine rule, etc.

I never understood why one needs a computer program to calculate segments for a segmented bowl.

Using grade 7 math (overseas) for calculations including a miter saw:

Using a miter saw, for cutting segments of a segmented bowl:

Outside diameter = 15", the radius is 7.5"

If we decide to cut the pieces into 15 degree segments, we will set the miter saw precisely at 7.5 degrees, which is the angle it will actually cut into the one side of the segment.

We need a wood strip, or board approximately 1" wide.

We convert 15 degrees to radians by multiplying with Pi/180 and if we multiply that by the radius of our circle, we have the arc length (outside) of our segment.

15*Pi/180*7.5 = 1.963" which is slightly longer than what our stop should be set.

360/15 = 24, so we need 24 segments, the circumference of the bowl wil thus be 24*1.963 = 47.124"

To calculate the exact long (outside) length of the segment, for setting the stop on our miter saw, we use the Cosine rule.

a2 = b2 + c2 -2bc Cos A

b and c are the radii, while A is 15 degrees, so it follows that the exact length is 1.958"

In short, for a 15" diameter bowl (it will be slightly less than 15"), 15 degrees will give 24 segments, set the miter saw to 7.5 degrees (the angle it actually cuts onto the segment) which is half the angle of the segment it will actually cut and cut the outside length to exactly 1.958" measured with a vernier (dial) caliper.

Thanks Willem

Posted like a true "outside of the US" snob. In short. Glad we woodheads could post something of interest to you. Any chance you could post some pics of your segmented bowl.

Al

Friends don't let friends use stamped metal tools sold at clothing stores.

 

[woodnthings]

Thanks Willem

Posted like a true "outside of the US" snob. In short. Glad we woodheads could post something of interest to you. Any chance you could post some pics of your segmented bowl.

Al

Friends don't let friends use stamped metal tools sold at clothing stores.

Coming to Willem's defense here. Al that "snob" remark is totally uncalled for. Willem is a very smart guy, smarter than me for sure and is providing some information to the forum in a civil way and does not deserve any personal attacks. You are also a very smart and ingenious fellow and I respect both of your opinions and ideas, so let's not get into that kind of response...OK? :smile: bill

BTW our educational system used to be at the top compared to other nations, and is now near the bottom and I think that was the basis for his comment..."from outside the U.S."

 

[WillemJM]

Coming to Willem's defense here. Al that "snob" remark is totally uncalled for. Willem is a very smart guy, smarter than me for sure and is providing some information to the forum in a civil way and does not deserve any personal attacks. You are also a very smart and ingenious fellow and I respect both of your opinions and ideas, so let's not get into that kind of response...OK? :smile: bill

BTW our educational system used to be at the top compared to other nations, and is now near the bottom and I think that was the basis for his comment..."from outside the U.S."

Bill, thanks for the post, but did not take any offence. Wifey is from Michigan and I always upset her when I talk about math education in the US. :shifty:

Don't think I'm a snob, but "Social Education" (Debate, state of the nation, economy etc.) in the US is way ahead of anyone else, the reason for this being such a great country. "Technical education" (Math, applied math, etc.) is not the best though.

I work with a lot of Engineers, and they think I'm crazy because we were taught to to design and calculate everyting from a fundamental basis, while they use software to get to the same answers, without really understanding the concepts.

Perhaps just getting old. :laughing:

 

[Al B Thayer]

When calling someone a "true snob". It's not said to be a total put down. It comes from the movies. Like Steel Magnolias had a line much like this one. It went, "spoken like a true smottass".

Nice to see you get it Willem. I'm glad to be from the stupid side of the pond and be the biggest wood snob on the forum. Which is easy to see at the bottom of my posts. Also glad I've got the smartest hands in town. Women never cared about my math skills or the lack there of.

Al B Thayer

Friends don't let friends use stamped metal tools sold at clothing stores.

 

[liquid6]

Currently working on some other none wood related stuff and took a break to read a little. I think the problem with a compound miter saw lies in the semantics of the base plate.

So, you notice on the base plate that the number perpendicular to the fence is 90. Technically, this should read zero. But, those engineering folk set it to 90 because the saw blade is perpendicular to the edge of the board or fence.

If the base plate read zero, then the cut at 22.5 degrees would make total sense. As someone else said. I picture my cuts what I am removing, not what is remaining.

 

[woodnthings]

an interesting article

If reaffirms my position that the angle markings were designed for non woodworkers, rather roof and framing contractors according to the author.

http://www.thisiscarpentry.com/2011/07/29/miter-angles-miter-saws/

The use of a protractor to measure the included angle is the source of some confusion, however it is the accurate measurement of the included angle. The setting on the base plate is the amount of the difference from a 90 degree angle. You must "do the math" to arrive at the protractor setting. :smile:

 

[FrankC]

Bill,
I'm sure that you remember "Complementary Angle" from school. That is the subtract from 90° thing.

Think of it this way with your miter saw.

"I need a 62.5° cut. So I'm starting with a square cut (90°) and I need to cut off 22.5° to make my 62.5° cut."

Simple, Right?

Not too simple when the cut is 5 degrees off. 62.5 + 22.5 = 85 :smile:

 

[Alchymist]

Sorry you fell for that drawing. A quick look may appear to make sense. I didn't say it was a right triangle. I didn't say anything. It represents a lesson I learned when reading plans. It's a drafting illusion so to speak where a drawing looks correct, and may be clad with dimensions that appear to support the drawing.

For example: Do the numerical dimensions match what the details show? If dimensions are in feet and inches, are they mistaken for inches?

This is a good lesson to pay attention to details.
IOW, just because something looks right, doesn't mean it is right.

Somtimes it is just plain obtuse. :laughing: