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Arm Crank and Plate Height

A fantastic upgrade to kitchen cabinets is the newer soft close Euro hardware for doors and drawers. When I decided to build the kitchen for my new home (another story for another day), I knew I wanted this feature and went with the most popular brand: Blum.

So why the blog? I'm writing this because Blum hardware - like all cup hinge and undermount slide Euro hardware - is incredibly confusing. I'm an engineer who lives for reading diagrams and schematics and I still found the learning curve very steep. I spent days looking at Blum's documentation and prowling cabinetmaker forums trying to figure these things out. So I'm writing this blog to transfer some of my learnings to others and I'll start with the cup hinges. Rather than paint by numbers, I will try to explain the logic behind the system so you can make sense of the technical documentation. This entry will hit on the topics of "arm crank" and "plate height". "Reveal" and "bore distance" will be covered later.

This will be a long document so if you only read one thing, read this:

If you are a traditional American weekend-warrior woodworker, Blum hardware was not designed for you. It was designed for a production level cabinet shop producing standardized frameless cabinets in Europe.

Of course, that doesn't mean you can't use them with great success, because you can. What it means is you need to take off your craftsman/artist hat for a minute and think like an engineer to understand the design of the product. To do so, take a look at this configuration straight from Blum's documentation. It represents frameless, full-overlay cabinetry that dominates Europe and is very popular in the US today.
Rectangle Schematic Font Parallel Slope

I'd bet dollars to donuts this was the first configuration Blum's engineers dreamed up since it perfectly suits their target market. So why does this matter to you if (like me) you're building traditional face frame inset cabinets?

Correct use of the Blum hinge is based on selecting the hinge configuration and/or adjusting your cabinet design so that it reverts back to functioning like a frameless cabinet. Understanding this is "thinking like an engineer".

To get from the frameless, full-overlay style to a framed inset style, Blum engineers make two steps. First, a move of the door to a frameless, inset style.
Rectangle Slope Parallel Font Plan

Notice the shape of the hinge arm has changed. This is because the door now has to swing out and around the panel, rather than just pivot. This is referred to as the "crank" of the hinge. So we've gone from a "straight arm" hinge to "full crank" hinge. And there's a "half crank" that falls in between. This jargon is part of what makes the curve so steep.

Second, another step changes this frameless inset style into a framed inset style. The easiest way is to set our face frame on the carcass so that the panel is flush to the inside of the frame.
Rectangle Slope Font Parallel Plan

Congratulations, we now have an inset face frame style cabinet by adjusting our cabinet design to the hinge. But, we've lost some space inside the box. Doing this with a 1-1/2" face frame costs you 3/4" of space for every door assuming 3/4" thick panels. In most of my kitchen, I was ok with the loss, but I had a couple of smaller cabinets where I wanted to conserve as much space as possible. And maybe you are at the point where you can't redesign the cabinet, so we need another solution.

An alternative is to simply tuck a block-out board behind the face frame so the first three inches or so are flush like it was a panel.
Rectangle Slope Font Parallel Schematic

I found this solution to be aesthetically unpleasing, so I moved on from altering the cabinet design to altering the hinge configuration.

Now is a good time to introduce another point of confusion. The hinge is not bought as a single component. The hinge "arm" and "plate" are separate components that click together. The arm/cup attach to the door, while the plate connects to the cabinet carcass. The figures above are of a "full crank arm" attached to a "0mm plate" (notice the H=0 in the diagrams). The plate comes in 3mm increments up to 9mm. Increasing the size of the plate in this picture effectively moves the hinge and door to the left. See where I'm going with this? Functionally, it is the same as introducing a blockout board. The "plate height" needs to be the same as the amount as the offset between the panel and the inside of the face frame.
Rectangle Slope Parallel Font Diagram

As mentioned, the plates only go up to 9mm, so the face frame overhang can't exceed that unless we add a blockout board to augment. I found the combination of a 6mm plate and a 1/2" block to be the best option to use to get me out the needed 3/4" (there are 25.4mm in an inch). It looks better than a full blockout and functions just as well.

At this point, you may think I don't know what I'm talking about. If you've researched at all, you've undoubtedly seen this configuration from Rockler or Amazon or elsewhere.
Handle Fixture Wood Rectangle Household hardware

Rectangle Parallel Font Plan Diagram

It utilizes a half crank arm and a special mounting plate that attaches to the face frame instead of the carcass and provides the remaining crank needed to swing out around the frame. You could attempt to use it, but I decided against it for two reasons. First, I read horror stories about mounting the plate to the face frame and I believe them with the angle of that screw. Second, I didn't like the idea of the torque from the opening and closing of the door being applied to the face frame instead of the much more rigid panel. These Euro hinges can be a little stiff, resulting in a great deal of torque about the pivot point on a wide door. I felt the risk of splitting the face frame was reasonably high with thousands of cycles found in a kitchen and I discovered instances of this happening to professionals.

At this point, I hope the concept of arm crank and plate height are clear enough that you can now understand the technical documentation on Blum's website. In the next blog entry, I'll attempt to explain the interplay between "boring distance", "reveal", and the sizing of your cabinet doors.

Thanks for reading
You made your points very clearly. Well written and informative. I will be tuning in for chapter two.

I tend to use blocking for lower doors, and they seem fine in that application. For upper cabinets, I see your point that large blocking doesn't look the best. I tend to use Rockler self closing statutory bronze hinges for inset doors. They are full crank, H=0 by your definitions. They work well and I like them because they are black / oil rubbed bronze in appearance. The self closing feature is nice, but they are not soft closing, so they need a cork or rubber bumper. Install on the Rockler hinges is simple, but they do require blocking.

Thanks again.


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