Hello,
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?
Replies
I assume, when you say that you mounted the door to a masonry wall, you actually mounted the jam to the masonry wall. It is typical that masonry walls are not perfectly flat; particularly over that distance. I'm guessing that mounting the jam to the wall forced it over a slight hump or high spot and put a bow in it. So, now the hinge pins don't line up. You may have to shim the jam so that it stays straight. You also need to make sure the jam is perfectly plumb after it is mounted.
Assuming that all 3 hinge pin are in a perfect line, having them offset from the door as you explain shouldn't matter. The door will just swing in a wider arc.
Thank Bilyo,
What you say about an uneven masonry surface certainly could cause the problem. But the jam is actually a 2x6 piece of redwood, so it's not very bendable. The wall is reasonably flat and plumb and I don't see any bending going on with the jam. But you raise a good point about the alignment of the hinges. Does the fact that the swag line on one hinge is different than the other means its swinging arc is different and I'm going to get binding? I hadn't considered that.
Yes. you should be able to sight through all 3 like a gun sight.
If my approach isn't going to work, I'm still stuck with how to fix the problem. I am convinced the problem is torque pulling the door away from the jam and partially opening the hinge a few degrees.
If you think about it, there are only a few possibilities:
1. The door frame is not square
2. The screws are not holding the hinge flat against the jamb
3. The screws are not holding the hinge flat against the door
4. The jamb is not flat
5. The hinge pin is loose.
These are in order of probability.
It is actually quite likely that the problem is you mounting such a heavy door on only 2 screws per hinge. Even very small opening of the gap between the wood and the hinge can cause doors to drop. You will probably find the issue goes away when you put in the other screws.
Don't neglect no 4 - there is a phenomenal amount of force exerted by masonry fixings and even a 2x6 will follow a wall some. It is important to shim behind even large members to ensure they are not being forced to follow the wall. Shims need to be close to the fixings.
5 Is unlikely but it's on the list.
I suggest checking that the jamb is flat, checking the frame is square, and then seeing if you can lift the door into position - put a lever under the opening end of the door - if it can be lifted into position then the position of the hinges is ok, but you need to put in the screws. If that fails, you can either shim out the bottom of the jamb or in a pinch, shim the bottom hinge.
Thanks everybody for the input. The problem is solved with a 1/8" gap now. I think it was an accumulation of several issues. I'm still convinced that a 4" hinge on a 1.5" thick door puts to much torque on the hinge. But as Rob suggested, four screws (I used an inch and a quarter long screws on the top hinge) snugged the hinge up to the door edge and jam better than just two.
If the door is 50 pounds and 3 foot wide, the torque created is the product of the weight and the distance from the center of gravity to the holding point, in this case 50 lbs X 1,5 ft = 75 ft*pounds . To counter this torque, the upper hinge will see a force trying to pull it from the jamb, the farther apart are the hinges, the lesser the force will be needed. If the top and bottom hinges are 6 ft appart, the 75 ft*pounds applied will be exerting 75/6 pounds on the upper hinge, so about 12 pounds, not very much. Of course the door should withstand some abuse so if your 150 pounds kid wants to hang on the door and swing out, he will be exerting 150 X 3 = 450 ft*pounds and the hinge will have to resist to a 87 pounds force horizontally, and 100 pounds vertically assuming that both hinges are supporting the vertical component.
I hung doors for a living and a fifty pound door was a lightweight.First and foremost check that the jam is straight and plumb.Then check that you did not bend the hinges with so much proud of the door.Put all the screws in the door of the lower two hinges.Then drill and drive 2 1/2 inch masonry screw through a remaining hole in the top hinge.If that does not solve the problem then send me a ticket to wherever you are
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