I trying to install some crown molding. There will only be outside
corners, and all corners are 45 degrees. The crown molding must be
installed upside down so that the 38 degree angle is at the top and
the 52 degree angle is at the bottom. It has to be installed upside
down so the top can span a certain distance out. I am having a heck of
a time getting this.

The corner I'm testing on is exactly 45 degrees, left outside corner.
The book I'm working with says 33.85 B and 31.62 M. Because I'm
installing upside down do these numbers mean anything in my situation?
Should I toss them and just figure it out with trial and error? Should
I swap the numbers? Is there a formula I could use to figure this out?
I've burned through a lot of rough stock and I'm no closer.

Any help is appreciated.


Greg

On 19 Jul 2003 17:28:04 -0700, (Greg
DeBacker) wrote:

snip. It has to be installed upside
down so the top can span a certain distance out. I am having a heck of
a time getting this.

Have you considered building up the moulding with another piece in
order to span the area needed. For instance a piece 1/2 " thick by a
width that would allow say a 5/8 " exposed area under the crown. You
could mill the exposed area with say a 1/2 " cove bit creating a nice
"built up" custom moulding. Just a thought.

The corner I'm testing on is exactly 45 degrees, left outside corner.
The book I'm working with says 33.85 B and 31.62 M. Because I'm
installing upside down do these numbers mean anything in my situation?
Should I toss them and just figure it out with trial and error? Should
I swap the numbers? Is there a formula I could use to figure this out?
I've burned through a lot of rough stock and I'm no closer.

Any help is appreciated.


Greg

I trying to install some crown molding. There will only be outside
corners, and all corners are 45 degrees. The crown molding must be
installed upside down so that the 38 degree angle is at the top and
the 52 degree angle is at the bottom. It has to be installed upside
down so the top can span a certain distance out. I am having a heck of
a time getting this.

The corner I'm testing on is exactly 45 degrees, left outside corner.
The book I'm working with says 33.85 B and 31.62 M. Because I'm
installing upside down do these numbers mean anything in my situation?
Should I toss them and just figure it out with trial and error? Should
I swap the numbers? Is there a formula I could use to figure this out?
I've burned through a lot of rough stock and I'm no closer.

Any help is appreciated.


Greg

Use those numbers...do'nt swap them, swap the part...if you would normally
put the lower edge of the molding to the fence, put the upper edge to the
fence instead.

Mike

(Bruce) wrote in message ...
In rec.woodworking
(Greg DeBacker) wrote:

I trying to install some crown molding. There will only be outside
corners, and all corners are 45 degrees. The crown molding must be
installed upside down so that the 38 degree angle is at the top and
the 52 degree angle is at the bottom. It has to be installed upside
down so the top can span a certain distance out. I am having a heck of
a time getting this.

The corner I'm testing on is exactly 45 degrees, left outside corner.
The book I'm working with says 33.85 B and 31.62 M. Because I'm
installing upside down do these numbers mean anything in my situation?
Should I toss them and just figure it out with trial and error? Should
I swap the numbers? Is there a formula I could use to figure this out?
I've burned through a lot of rough stock and I'm no closer.

Yes, there is a formula but you do use those numbers. I have a program
I've written that will spit out the right numbers for any angle. If you
want it, email me at intmain AT yahoo dot com



Thanks everyone for the help. I guess it is because I'm a newbie at
this but I got very little out of the information given here. Maybe if
we try the old "teach a man to fish..." approach. My book also has a
chart for compound mitres. I'm sure every one has seen it. The far
left column is labled "Pitch Of Side" and starts at 0 degrees and
increments 5 degrees until it gets to 90. What exactly is this
refering to? What is "Pitch Of Side"?

If I find the 33.85 B and 31.62 M for standard American moulding on
the chart it falls somewhere between the 50 and 55 degree "Pitch Of
Side". So it would seem this relates to the 52 degree angle of the top
of the moulding. So if I flip the moulding over so the 38 degree angle
is the to top would I then locate that on the chart and use those
numbers. A 38 degree "Pitch Of Side" works out to be a M of 38.20 and
a B of 25.79.

Greg

Lenny wrote in message . ..
Greg, How large a crown moulding are you working with? Will it fit
under the saw blade when held against the fence and table at the
proper orientation. Cut a small section off a piece and hold it up to
a square to determine what the projection is out from the wall and
down from the ceiling. Transfer these measurements to your compound
miter saw with some masking tape just to use as a reference. The
moulding will lay top edge against the table, wall edge against the
fence.
If this doesn't make sense to you maybe you should have a look at this
site http://www.crownmoulding.com/cutting.htm
HTH
Lenny
On 20 Jul 2003 09:03:26 -0700, (Greg
DeBacker) wrote:

(Bruce) wrote in message ...
In rec.woodworking
(Greg DeBacker) wrote:

I trying to install some crown molding. There will only be outside
corners, and all corners are 45 degrees. The crown molding must be
installed upside down so that the 38 degree angle is at the top and
the 52 degree angle is at the bottom. It has to be installed upside
down so the top can span a certain distance out. I am having a heck of
a time getting this.
snip


The molding is 1X3. I'm restoring an 1895 Victorian home (my home) and
the molding goes under the outside window sills. Back in the 40s or
50s some of the ornamental woodwork was removed and cement/asbestos
siding was put on. As some would say, the house was "Eisenhowered".
Last summer when I removed the cement siding you could see images of
what was removed. The outside windows sills were fairly elaborate.
They are made up of a total of 7 pieces of wood with 4 compound
miters. They didn't mess around back then. When I was under the house
working on some plumbing I found a six inch long piece of crown
molding that matched the ghost image left behind when they ripped it
off 50 years ago. I sent it to the mill to get it reproduced.

In order to span the distance from the backing board to the edge of
the under side of the window sill the molding must be installed upside
down. This is what has caused me all of the problems. Once I
recalculated the bevel and mitre for this it works. The M of 38.20 and
a B of 25.79, as I figured out earlier are the magic numbers. That and
also the fact that I now know how to position the trim on the saw
(thanks to the web site you mentioned) means that the trim fits. I
just finished the first window, and it looks pretty damn cool, if I do
say so myself.

I have cut some compund mitres by holding the piece at an angle on the
chop saw but this cusotm milled redwood is too expensive for my skill
level to be trying that for more than 80 cuts.

Greg