I have a technical question about door hinges. It involves a lot of background, so if you’re not interested I understand.
I just built an outside garden door out of solid redwood. It’s hefty, roughly about 50 pounds. I am using three 4 inch butt hinges. The jam is a 2×6 and the door is 1.5″ thick. (The 37″ wide door is made up of seven jointed panels of 2×6 redwood.)
I’m using solid brass, 4″ butt hinges with a removable pin.
I mortised the hinges on the jam and door and then installed the jam in the shop to make sure everything lined up. The gaps were all perfect on the hinge side.
Then I mounted the door outside to its masonry wall, using two of the four screws on each hinge leaf. I didn’t want to drill out all the holes in case I needed to make adjustments.
What I found was the gap at the top of the door had widened to about a 3/8″. The hinge screws were holding tight. The hinge actually opened a bit.
I decided I didn’t really understand enough about the forces acting on a hinge to diagnose the problem. After a lot of reading, I learned that the hinges support the vertical load of a door, but also resist a torque that pulls the upper hinge away from the jam and compresses the lower hinge into the jam.
So why is my upper hinge opening a bit when the door is in the closed position and how do I fix it. I think my problem is related to the fact that my door is only 1.5″ thick and I am using a 4″ hinge. That puts the swag line of the hinge further back behind the door than what you would have with a typical 1.75″ thick exterior door.
I think that’s my problem. The hinge can’t resist the torque, because the pivot line is too far behind the door, even if the screws are good and tight.
My solution that I am going to try is to buy another solid brass hinge and attempt to cut the width of the leaf on my band saw. I’m figuring on cutting about 3/8″ off each leaf. That should bring the pivot point closer to the door and strength its resistance to sag.
What do you all think? Is there an easier solution or something I am missing?