On 12 Dec 2005 10:46:01 -0800, "Marc"
wrote:

Hi There,

I've received my custom order Bi-Fold doors which I was planning on
hanging like french doors with 2 hinges on the outside edge of each
doors. I've mortised the doors and the jambs to mount the hinges and I
am now trying to figure how much space to allow around the doors for
them to open and close properly. I was thinking:

1/8" for the Top
1/4" for the Bottom
1/16" X 2 for both hinge side
1/8" for the middle where the 2 doors meet.

I know I will probably have to bevel the back inside edge of each door
so that they open without rubbing each other. How much of a bevel will
I need? How can I figure this out?

Trigonometry. Let width of the face of the door from the hinge point
to the opposite edge have dimension 'A' and the thickness of the door
have dimension 'B'. The length of the radius that the back edge of
the door swings through will be 'C'.

C = sqrt (A^2 + B^2)

You don't give the width of the doors but for example, say they are
12" wide from the hinge pin to the opposite edge and 1 1/2" thick.

Then C = sqrt ( 12 * 12 + 1.5 * 1.5) = 12.093", so with zero gap
between doors there would be 2 * .093" or approximately 3/16" of
interference between them if you tried to open them simultaneously.

With only 1/8" gap then you need to back bevel each door enough to
remove 1/32" on the back side. The required angle can be determined
by taking the arctangent of (1/32) / (1.5) or a bit over 1 degree.

Of course this kind of precision is foolish when working with wood,
and it's not quite exact if the hinge pin is proud of the face of the
door, but you get the idea.


Thanks

Marc