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What I have found, for the most part, is that the fault is on both sides.
The "draftsman" is not usually a draftsman. He is often just somebody that
learned to draw shapes with a CAD program. His knowledge of drafting
standards and proper layout are usually lacking. Often that is on top of
limited shop experience. On the other hand, people in the shop are often
not any better. They never bother to correctly learn to read a print,
thinking that a print should be like a picture and if they can't understand
it, it's the draftsman's fault. This situation is very prevalent and usually
continues this way as there is often no one that really knows any better.

are

CAD

wrote:

To cut a 54-degree angle you set the saw to 36 degrees, for the same reason that to cut a 90-degree angle you set it to zero.

-- Regards, Doug Miller (alphageek-at-milmac-dot-com)

For a copy of my TrollFilter for NewsProxy/Nfilter, send email to autoresponder at filterinfo-at-milmac-dot-com

Something (maybe) your speed:

http://www.coolmath.com/interior.htm

You might want to be a little less cocky when you're (obviously) working so far from your area of expertise.

Tell us again how the sum of the interior angles of a polygon must be 360 degrees. I get a kick out of it.

The sum of the interior angles of a pentagon is 540 degrees. Each interior angle is 540/5 = 108 degrees. half of that is 54 degrees.

If your measuring instrument is providing the right-angle compliment, then you want to cut at 90-54 = 36 degrees. Note that this is not the usual meaning of "complimentary angle" in geometry, where it refers to the 180 degree compliment:

\ \ \ 180-A \ A -------------\---------------- A \ 180-A \ \ \

Many mitre saws will provide a scale showing the angle from 90 degrees (0 is a right angle cut) and the right- angle compliment (90 degrees is a right angle cut).

In this case, you want 54 degree cuts on the legs of the pentagon so that 108 degree interior angles will be formed. And yes, 108 does not divide evenly into 360 degrees, and there's no reason why it should.

Figuring out how to use your mitre saw's dial is not the crux of the problem. It's knowing what interior angle you need in order to form a given regular polygon.

Quick, what's the required mitre cut for a nonagon?

I would build a correct pentagon. My pieces would have 54 degree angles as measured between the outside face and the cut face:

--------------------* / \
/ * \ cut face
* / \
/ * <----- 54 deg -----> \
-----------------------------
outside face

20

area of

Actually, Complimentary angles add to 90 deg. Supplementary angles add to 180 deg.

#### Site Timeline

- posted on April 19, 2004, 1:29 am

are

CAD

- posted on April 19, 2004, 1:35 am

To cut a 54-degree angle you set the saw to 36 degrees, for the same reason that to cut a 90-degree angle you set it to zero.

-- Regards, Doug Miller (alphageek-at-milmac-dot-com)

For a copy of my TrollFilter for NewsProxy/Nfilter, send email to autoresponder at filterinfo-at-milmac-dot-com

- posted on April 19, 2004, 3:35 am

In rec.woodworking
snipped-for-privacy@milmac.com (Doug Miller) wrote:

BINGO!! Swish! Nothin but net Doug. LOL!

BINGO!! Swish! Nothin but net Doug. LOL!

- posted on April 19, 2004, 4:05 am

In defense of the CAD program and drafting in general, in the old days when
one used a pencil and T square to draw, the "rule" was to not "over"
dimension. Over dimensioning would be showing a dimension for every line or
object on the drawing from more than one reference point. Proper
dimensioning requires the person reading the drawing to do some math on his
own to properly interpret unknown distances. For example, a line is 2"
long and another line intersects this line .25" from one end. Proper
dimensioned, the over all length of the line is shown and only the distance
from only one end of the line describes where the intersecting line is
located. Either a dimension indicating the intersection is .25" from the
end of the other line or a dimension indicating 1.75" from the other end of
the line is all that is required. In more complicated and detailed drawings
this is not so cut and dry. The person reading the drawings should be able
to interpret the drawings and to handle his end to make sure that the
results are a reflection the drawings. This is probably much like a
pharmacist that is able to read the prescription from a doctor. The patient
normally has no clue as to what the prescription really says. This whole
thread is a good example of why knowing how to read a drawing is essential.
Full sized plans should not be needed by any one to understand a properly
drawn and dimensioned drawing. CAD programs if anything have let some
draftsmen become lazy or sloppy as it does eliminate a lot of thinking on
the draftsman's part.

- posted on April 19, 2004, 4:05 am

In defense of the CAD program and drafting in general, in the old days when
one used a pencil and T square to draw, the "rule" was to not "over"
dimension. Over dimensioning would be showing a dimension for every line or
object on the drawing from more than one reference point. Proper
dimensioning requires the person reading the drawing to do some math on his
own to properly interpret unknown distances. For example, a line is 2"
long and another line intersects this line .25" from one end. Proper
dimensioned, the over all length of the line is shown and only the distance
from only one end of the line describes where the intersecting line is
located. Either a dimension indicating the intersection is .25" from the
end of the other line or a dimension indicating 1.75" from the other end of
the line is all that is required. In more complicated and detailed drawings
this is not so cut and dry. The person reading the drawings should be able
to interpret the drawings and to handle his end to make sure that the
results are a reflection the drawings. This is probably much like a
pharmacist that is able to read the prescription from a doctor. The patient
normally has no clue as to what the prescription really says. This whole
thread is a good example of why knowing how to read a drawing is essential.
Full sized plans should not be needed by any one to understand a properly
drawn and dimensioned drawing. CAD programs if anything have let some
draftsmen become lazy or sloppy as it does eliminate a lot of thinking on
the draftsman's part.

Imagine full sized plans for a house, sky scraper or a highway from the east coast to the west coast.

wrote:

a

at

that

miter

degrees

give

Imagine full sized plans for a house, sky scraper or a highway from the east coast to the west coast.

wrote:

a

at

that

miter

degrees

give

- posted on April 18, 2004, 9:50 pm

Something (maybe) your speed:

http://www.coolmath.com/interior.htm

You might want to be a little less cocky when you're (obviously) working so far from your area of expertise.

- posted on April 18, 2004, 10:20 pm

Please go and BUILD a pentagone to see that your MITER has to be 36
degreesand figure out what I mean. You have no clue what you are talking
about. You are the one who is "(obviously) working so far from your area of
expertise."

CHRIS

will

Use

you

3.33333333333333333

you

CHRIS

will

Use

you

3.33333333333333333

you

- posted on April 18, 2004, 10:22 pm

Sorry for the spelling forgot to run through spell checker before sending
the last post.

CHRIS

do

sell

CHRIS

do

sell

- posted on April 18, 2004, 11:46 pm

Tell us again how the sum of the interior angles of a polygon must be 360 degrees. I get a kick out of it.

The sum of the interior angles of a pentagon is 540 degrees. Each interior angle is 540/5 = 108 degrees. half of that is 54 degrees.

If your measuring instrument is providing the right-angle compliment, then you want to cut at 90-54 = 36 degrees. Note that this is not the usual meaning of "complimentary angle" in geometry, where it refers to the 180 degree compliment:

\ \ \ 180-A \ A -------------\---------------- A \ 180-A \ \ \

Many mitre saws will provide a scale showing the angle from 90 degrees (0 is a right angle cut) and the right- angle compliment (90 degrees is a right angle cut).

In this case, you want 54 degree cuts on the legs of the pentagon so that 108 degree interior angles will be formed. And yes, 108 does not divide evenly into 360 degrees, and there's no reason why it should.

Figuring out how to use your mitre saw's dial is not the crux of the problem. It's knowing what interior angle you need in order to form a given regular polygon.

Quick, what's the required mitre cut for a nonagon?

- posted on April 19, 2004, 12:07 am

Read the OP
And then try and build one using 54 I would like to see what yo end up with

CHRIS

area of

CHRIS

area of

- posted on April 19, 2004, 12:48 am

I would build a correct pentagon. My pieces would have 54 degree angles as measured between the outside face and the cut face:

--------------------

- posted on April 19, 2004, 12:14 am

20

- posted on April 19, 2004, 12:18 am

That's the setting on the miter guage.
The angle on the side of the board is 70°.

Art

Art

- posted on April 19, 2004, 12:39 am

My reply was in context with rest of the thread

- posted on April 19, 2004, 12:43 am

Exactly.

- posted on April 19, 2004, 12:23 am

On Sun, 18 Apr 2004 19:46:45 -0400, "Greg Neill"

He's mixing it up with the exterior angles which always add to 360.

Dan.

He's mixing it up with the exterior angles which always add to 360.

Dan.

- posted on April 19, 2004, 5:36 am

area of

Actually, Complimentary angles add to 90 deg. Supplementary angles add to 180 deg.

- posted on April 19, 2004, 12:19 am

I would suggest you do a little rethinking before you make yourself out to
be this ignorant.

were

were

- posted on April 19, 2004, 12:38 am

Go and make one before you start calling me ignorant and do a little of
your own rethinking as to why when you set your saw to LOL 54 degrees you do
not come up with a pentagon. By the way what is your occupation???
I will bet you are not a cabinetmaker.

CHRIS

a

CHRIS

a

- posted on April 19, 2004, 12:50 am

On Mon, 19 Apr 2004 00:38:10 GMT, "Chris Melanson"

Using the formula (n-2)*180 as the sum of interior angles of a polygon:

With n = 5, you get 3*180, or 540.

If all the same (regular) you'll get 540/5 or 108.

To have two equal cuts meet at that angle you'll have to have each 54 degrees.

Most, if not all miters turn only to 45 degrees on the scale, and are initially perpendicular to the blade, so set at the complimentary angle (90 - 54) = 36 degrees.

Dan (not a cabinetmaker)

Using the formula (n-2)*180 as the sum of interior angles of a polygon:

With n = 5, you get 3*180, or 540.

If all the same (regular) you'll get 540/5 or 108.

To have two equal cuts meet at that angle you'll have to have each 54 degrees.

Most, if not all miters turn only to 45 degrees on the scale, and are initially perpendicular to the blade, so set at the complimentary angle (90 - 54) = 36 degrees.

Dan (not a cabinetmaker)

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