You’re not doing what you think you are

Powerful tools are funny things. They make it very easy to look at the outcome and forget about the process. Often the task that was the original intent of a tool can get lost by the wayside as that tool becomes used in different ways. A friend of mine once gave me a carpenter’s pencil as a reminder that construction tolerances are imprecise. They forgot in their eagerness for the analogy that a carpenter cuts to the edge of their wide rough pencil mark, pulling precision out of a seemingly coarse tool.

Without going down the rabbit hole of the technological changes to society as a whole that were writ by machine-made threading and screws, the Phillips screw is arguably one of the core technological changes that allowed for the development of assembly line manufacturing. They’re still awesome, except when you strip out a screw head because you’re driving it too hard.

That’s a very common frustration with them compared to other screw types. The Phillip screw’s development was originally to solve a couple of crucial problems with slotted screws that made them less ideal for assembly lines, and it did that very well. Slotted screwdrivers are difficult to line up with the screw, and they are very easy to

“cam out” of the slot if you are not careful. Phillips screws self-align with the tool, and can take a lot more torque than a similar slotted screw (you have about twice the surface area to apply force to). That made them ideal for early assembly lines. Better still, they do cam-out when too much force is applied, in effect self controlling the applied torque, which is very handy for consistency across an assembly line.

That annoying cam out that strips the screw was described as a feature in one of the patent filings for the fastener. Most of us have lost track of what that feature was for, and are now frustrated by a very clever design that we no longer understand.

I had a similar revelation while talking to a few other grognards about those kids these days and their Revit practices, and I think it all goes back to good documentation practices whose original purpose was forgotten.

Nearly everyone agrees that the best practice in BIM is to locate objects in their intended “real” location in the model, and that location should be such that your dimensions land at useful “construction tolerances”. In North America, this generally means that everything is located to ⅛” precision and that the part of the object we’re dimensioning to is located exactly there. There is a non-trivial population of Revit users who insist that they can place items anywhere close to that, and let the dimension style automatically round it off. This can rapidly lead to a 2+2=5 sort of overall error that can cause errors and omissions in our documents but many users won’t listen to that (2.4+2.4 =4.8 and with a bit of rounding, suddenly things are exciting).

Back in the hand drafting days, the total ink width of a typical pen was such that (at normal architectural plan scales) the thinnest ink line when scaled up is 2cm wide in real life. That is not the sort of error we want in buildings. Where the carpenter’s 4mm wide line gives them one reference edge that they can place with sub-millimeter accuracy, at architectural scales, that 2cm swath is no longer within useful tolerances. As a practice, we dealt with that representational imprecision by providing the real and exact dimension we wanted something built to. We manually added up dimension strings all the way along to make certain they were accurate. Those theoretical dimensions were exactly where the “drawing” was located, irrelevant to the fuzz of the line width. The dimensions were the important part of the data.

Then came CAD. All of our lines suddenly really were somewhere exact and were mathematically lines with width only applied for visibility. They had lost their fuzz. And dimensions were automagically created from where we put things. And they could round themselves to the precision we wanted so that we could ignore the manufacturing and assembly perfections and imperfections for a “theoretical” location, like our “flat” gypsum board walls. Many of us embraced this new precision in our representational lines and used dimensional rounding to just clean up newly available precision to useful tolerances.

Some of the hand drafting folks didn’t adopt the new precision and still thought of their lines as representational. What they missed was that with the new precision of the inherent tool meant that where the dimension had contained the key information in hand drafting. In CAD, the line itself now contained that information, and the printed dimension now had that fuzz built in. We also saw the role of Chief Draughtsman morph into CAD Manager, a role often less focused on the designed content than on the technical execution thereof. Where the prior focused more on communication, the latter had to focus on a more technical process.

As those users trained new drafters who had never worked professionally in hand drafting, and as folks self-taught themselves, it was easy for them to see that the rounding of dimensions could make up for imprecision in the drafting. This was an automatic tool after all, and you didn’t need to manually add up your dimension strings. The tool itself seemed able to clean up that imperfection, and the reasons behind manually checking those dimensions were easy to overlook.

Then we moved over to BIM, and folks who had never hand drafted transcribed the hand drafting dimensioning practices which they had learned from CAD into a brave new world. What was in many ways excellent practice in hand drafting was made easier by CAD, and the reasoning behind it was lost in the transition to BIM. Where the CAD Manager was juggling some layers and standards enforcement, the BIM Manager had to swing into workflow management and training, dealing with entirely new processes and very literal new dimensions of complexity, further stepping back from the role of finessing communication.

This has resulted in a philosophical disconnect between the idealized version of BIM as a Digital Twin, and the idea of BIM as a design cartoon, a potent tool for making representational drawings. As long as printed deliverables are the norm, using BIM tools as a cartooning tool rather than as tools for a digital twin is just fine, but that is in many ways like using a Formula 1 racer as a daily commuting car. But we’re often not using BIM tools to cartoon, we’re forgetting about that part of the process. We still need to communicate and think about how we are communicating.

If we as design professionals want to fully move into the promise of what is now decades old technology, we need to look not only forward at digital deliverables, but we need to look back and understand why we do certain things. Not just for the sake of nostalgia, but to see the underlying design practice of our tool’s intended uses, and to understand what those intended uses were trying to accomplish on a deeper level.

You should not have to be a master tool maker to wield the tools of any profession, but understanding why a particular tool is or is not the most apt for your particular task at hand, and what we’re actually accomplishing with that tool, is crucial to being able to take that tool into new and creative directions.