Hidden Hinges

One thing I definitely wanted to do on my project truck was to delete the stock hinges and update them to hidden hinge design. There are some hinge kits in the aftermarket street rod business but they didn't fit in to my current budget so I decided to make my own.Working on a similar project in the past I knew the location of the hinge pin is very important in allowing the doors to open correctly. Problems you can get are the door not being able to open at all or it does not open enough. If the upper and lower hinge are not aligned through the pin you can also run into problems with door not being able to open. The pins vertical alignment is also important as the door could swing up or down when opening depending on how vertical the pins are.

I started off with some measurements of my doors and door jambs. Be sure to measure in different locations as with my doors they are narrower at the bottom than the top. I then transferred these measurements to a 2D drawing. I added in the stock hinge location as a reference to how the door opened with original hinges. I knew I wanted my new hinge arms to fit flush or recessed into the inner door structure. If they protruded into the passenger compartment door panels would need to be built to cover them. With this in mind I drew up the arm and moved it in place. I rotated the hinge arm and door at the pin center in several location until I was satisfied the door would open with out problems and wide open at an angle I was happy with.

I talked over the design with my friend Steve who agreed to make the hinges for me. These were made with some scrap bar stock, square and round tubing. Since these are built on the table each one is slightly different. The important part is to make sure the hinge pins are aligned when finished.

I started off with my lower hinge and cut an opening in my door jamb. The bottom of my hinge pocket will set on top of the lower brace from the cowl to door jamb. This was as low as I could go with my hinge. The body is pinching inwards at the bottom and I wanted to leave a small amount of clearance between the outer body sheetmetal and my hinge pin.

I did run into a problem I overlooked. The jamb area had a flange on the inside near the outer sheetmetal. I did not take this into account when designing my hinges. This flange ended up to be in the location of the hinge pin. I then had to go back in and trim this flange to get my pocket to fit. I also had to cut out several inches of the flange above the pocket so that the pins could be inserted and removed. This turned out to the hardest thing to do as the space is tight the right tools are not to found in my garage. You can see the uncut flange in the photo on the right.

Once all the trim work is done I had a nice fit for my hinge pocket. At this point I marked and trimmed the opening on the outer jamb side so that my hinge would open to the point I planned.

With the lower pocket fitted it was time to move up to the upper pocket. I wanted to space the hinges as far a part as I could but limitations only allow so much. I needed to leave enough room above the hinge to remove the pin. This put the pocket part way into the dash board area of my cab. This position also kept me just below the flange holding the upper and lower cowl sections together. I thought of putting the pocket just below the dash as it would be easier to install but I decided to go ahead with tougher higher location.

The flange on the door jamb created the same problem on the upper pocket as it did on the bottom. Once this was trimmed out the pocket was test fitted, or I tried to test fit it. The flange on the cowl side was causing a small problem so I needed to lower my opening a small amount.

Once I was satisfied with the fit of both pockets the distance between them was measured. I then removed the pockets and moved over to the work bench. A long pin was ran through both hinge pockets to align them, if this part is not done right the doors will never work properly. Then the hinges were spaced out to my previous measurement. A piece of angle stock was cut and welded to both hinges while they were clamped and aligned. The pockets were then slide back in place in the door jambs and tack welded in.

Now it was time to fit a door to the hinges. I had access to a pair of junk 1936 doors that have been cut for a top chop then discarded. Perfect for me to test fit with! I put them in place and marked the location of the hinges arms on the door. This area was cut out and the door tack welded in place on the cab. In the upper hinge location you can see the front widow track. The track is welded in place and left alone. The hinge arm and mounting plate fit leaving me about a quarter inch clearance.

With the hinges in place and the door tacked to the body I took some scrap steel and welded in a backing structure so the door could be bolted to the hinge. Now comes the real test, will it open?

The door was broken free from the cab and opened perfectly! The photo on the lower left shows the door gap when the door is fully opened.

The junk door was then removed and finishing work started on the door jamb. The pockets are now fully welded in place with a little extra bracing done on the inside. The gap above the upper hinge pocket was also filled back in. I cut some sheetmetal to cover and fill in the locations of the original hinges and these were welded in place. I also tacked the outer sheetmetal to the door jamb every few inches to make sure it stays in place.

With many parts of building my project truck I consider them projects within a project. The hidden hinges are a whole project and can be considered a major project. They look great when finished but will never work right if installed wrong, and there are many placed you can mess up. While I made my own, or had them made, you can buy them ready to install and may be a better option for most people. Even with premade hinges proper installation is very important.

Next up will be mounting the real door and installing a new latch.