Tuesday, January 25, 2011

Exploding Hinge Bearings and Fallen Doors

I was called to a retail store in an emergency as the dogging was not working on the front latch lock. The key had opened the place but the latch would not stay in to allow customer access. They had moved a floor mat into the door and put up a sign to ask everybody to leave the mat there. It worked but with freezing temperatures it was a short-term solution.

The problem turned out to be strangely minor as the door had a one inch mortise cylinder and it was wound ALL the way in without any rings. There was a protective plate mounted over the rim of the cylinder so this was visually good. It also prevented using tape to hold in the latch or see the problem found later. However, the cam on the back of the cylinder was operating the very end of the dogging lever on the FAR side of the latch lock. Surprising to me it was not interfering with the cam unit for the inside lever handle but it must have been very close. Some strong staff member had turned the key hard enough to bend up the dogging lever and after that is was not in place to work. The solution was to move the outside cylinder out with a trim ring under its face. Since the dogging levers are "L" shaped and extend from the side, they are strongest if the cam acts on them close to the lock body wall. Simple and done.

Not so quick. In a routine way, I put the face place back on and let the door close. When I looked with a flashlight at the strike the latch was coming in low. It was the small Adams Rite strike as shown above. The latch was riding on the metal around the lower screw and was catching on a tiny lip along the face of the strike. (This drawing does not show this detail well. Those who know this hardware can look at one to see this.) The strike was previously filed down to get the latch to fall in but it was now lower still. In fact it was touching the screw itself. At the same time, the tops of the doors were touching although not as much as we sometimes see. This points me to the hinges.

This is a difficult customer service case. We were called to solve the one problem as identified by the customer. And now I see a bigger and more complex problem but this door could have been pulled open with a good strong tug and not mentioning it to the manager is not a good ethical solution either. I spoke to the manager before doing more and showed what I was seeing with my flashlight.

One solution on the short term had already been tried and that was to file down the hole in the strike and there was room to go lower. However, with the latch hitting the lower screw, you can not go that low. Given it was a double door set and I did not have hinges with me, I pulled one hinge from the centre of the inactive door and put it in the middle of the active door to lift it some and also did some filing to lower the strike hole. This was enough to lift the door on a very cold day. (A bit of nasty work in cold weather but they did give me some free coffee. Yeah!)

We are booked to get back and replace all three hinges to lift the door a bit more.

What did I see?
This is the one removed hinge closed next to a new hinge for comparison. The rust is clear but not really the problem itself. However, you can see the two leaves are no longer at the same height. The door leaf is about 1/16 of an inch lower and under of the door even a bit more.

This is a detail of the failing hinge. You can see the bearing has bulged out and I have seen cases where they have shards of metal breaking away from them. Also on the next joint down you can see the gaps developing as the bearing let the door drop. I could not find a way to show two other failures happening here. The hinge pin thins as it rusts or else the inside diameter of the knuckle increases or some of both and the two hinge plate can move left and right as well as up and down. This also means they can angle and twist compared to each other too.

Another feature of a failing hinge is that the metal wears away on the part of the swing the door passes through most. This has the effect of making the hinges into little ramps. And since this problem happens fastest if the hinges are not lubricated you get raw rusted steel on rusted steal so the door is harder to pull open and the closer must work harder. You can usually must slow the closer down once you change out worn hinges.

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Laux Myth ... Thoughts From a Locksmith
By MartinB, Found @ http://lauxmyth.blogspot.com/