Knife Hinge Installation

The latest Guild projects are nearing completion and I wanted to bring you up to speed on the latest happenings in the shop. Lately, I’ve got hinges on the brain! Of course, there are lots of ways to hang a door. But I have yet to see anything that matches the understated elegance of a knife hinge. When properly installed you barely know they are there, yet they are capable of supporting a remarkable amount of weight.

Now just to be clear, this isn’t a full how-to on knife hinges. I was only able to get a few shots that depict just part of the process. But I thought it would still be worthwhile to share my methods with you.

And so it begins….

Like other hinges, the knife hinge needs to be placed into a mortise: one in the case and one in the door. Our story begins with the case. The hinge leaf is located and scribed during a dry assembly. The key to success with this process is using shims. I don’t want to have to THINK about where the hinge is going to go. Instead, I want physical barriers that prevent the hinge from being anywhere other than where its supposed to be! This allows for a very systematic approach which is right up my alley i.e. “Marc-proof”! A card scraper makes a great shim and helps establish the gap between the door and the case. My small adjustable square helps me establish the set-back. A couple of steel screws hold the hinge in place while I scribe around the perimeter. Do NOT use your brass screws for this. Save them for your final installation. The case is then disassembled and the mortises are routed and cleaned up with a chisel.

The CA Glue Trick

The door mortise is fairly straightforward since the goal is to have the hinge flush with the outside edge of the stile. As long as the long part of the leaf is centered along the thickness of the door, you’re good to go. In order to keep the hinge in place while I scribe around the perimeter, I use a little CA glue to hold it in place.

With the hinge locked down, scribing around the perimeter is a piece of cake! I take light passes at first and eventually increase the pressure so that I end up with a nice deep scribe line. “But what about the glued hinge?”, you ask. A quick tap with a hammer pops it right off. The residue is easily scraped off the hinge and the glue spots on the wood will soon be routed away. I only use this glue trick on end grain. On face grain, there is a good possibility of tearing out the wood fibers (this is why I used screws previously).

Routing the Mortise

Now its time to do some routing. Obviously, this is a dicey proposition if you don’t add supplemental support. Two pieces of scrap stock clamped to the door work wonders. Also notice that the scrap is longer than the door is wide. Its a good idea to provide that extra surface area so you can approach the mortising full supported.

A 1/4″ spiral bit does all the grunt work, cleaning out the bulk of the stock. I do this part free-hand, making sure I don’t get too close to my line. This way I can come back with the chisel, drop it into my scribe line, chop down, and call it done. The end result is a perfect mortise for out hinge. Don’t underestimate the importance of a good fit here. An improperly mortised hinge will result in extra pressure on the screws, and over time could lead to the door sagging or even complete failure. So you always want to take your time with this mortising step.

The End Result

Like nearly all things in woodworking, what initially looks complicated is really just a simple series of steps. Once you know the steps, you know how to do it. And if you can mortise for a butt hinge, you can certainly install knife hinges. As you can see in the photo, this wall-hanging cabinet is nearly complete. I just need to work on the drawer and apply the finish. By the way, thanks to all of you for the great suggestions on what to do with those incredible quilted maple panels. You can see where at least some of the stock ended up.

Category: Shop Journal

Comments

  1. noumenon February 22, 2011

    Can’t wait to see it after the finish goes on and those quilted maple panels light up :)

  2. Eric R February 22, 2011

    No doubt about it Marc, you do nice, crisp, clean, delicate work.
    Always a pleasure to witness your talent.
    Thanks for sharing your abilities with us who are still getting better.
    Thanks

  3. TomB February 24, 2011

    The QM looks fantastic. Thanks for the sneak peak into the guild-build. I’ve been intrigued by the knife hinge installation ever since the Gadget Station (part 5 if I recall) for Leo. Was there any additional considerations made in the design for knife hinges, or are the gaps between the door panel and carcase as per usual? It looks from your write-up that other than the card scraper shim on the case piece, you set the depth (from the front edge) to about the the midpoint of the pivot pin? Any special tricks for final hinge assembly/door hanging?

    •  

      Hey Tom. The gaps are actually dictated by the knife hinge itself. There is a small spacer on the hinge, right near the pin, that prevents the two leafs from rubbing. So you can use that as your guide for the perimeter gap. So when you use a shim for spacing, ideally you want the shim to be the same thickness as that little spacer on the hinge.

      And yes on the pivot pin spacing. The goal is to have it on the centered on the front edge. Using this hinge and door thickness combination, that should result in a perfectly flush door front.

      And there are TONS of tricks and tips. Too much to go into here though. I just about devoted an entire 40 minute Guild video on the topic. Takes some patience, but the systematic approach means anyone can do this stuff.

  4. Iain February 24, 2011

    I have to say it lookes a bit like the gadget station project.
    But over all it lookes sweet!!!
    LOL
    ROTFL
    I am really not funny!

  5. Pat February 26, 2011

    I was thinking what Iain stated

  6. Kevin April 7, 2011

    will these Knife hinges work on a cabinet that is curved, and the doors are curved also?
    The top of the cabinet angles upward also??
    The cabinet ressembles the Broken dresser with a crack down from the top about 18- 22″

  7. Michiel December 16, 2011

    Perhaps a strange question but….

    Where can i find projects as described here ? Guild (?) projects ?

    Found a lot from you on youtube but i hope there’s more and more :)

  8.  

    Hi Michiel. You can find more information on the Guild here: http://WoodWhispererGuild.com

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