Let's talk about sheet goods joinery

Having read Make: Designing for CNC it strikes me at just how much the authors skim over joining your pieces together.

When you study the Handibot or most anything designed by Bill young there is just a bit of mad scientist thing going on.

Furniture bolts and extrusion style T-nuts in the case of the handibot, and furniture bolts and slip in pieces containing hammer in T-nuts. I've learned a lot just studying these but it would be great if Bill or Bryan would do a full blog post just on this sort of thing.

Check out my YouTube channel where I've documented a few of the joints I use or have come up with:

[www.youtube.com]

That would be a fun article! I'd definitely like to put something together about what we've learned from using so many different strategies at handibot.

Many times, design of joinery comes down to trying to predict what will be the first thing to fail--either due to excessive stress or fatigue. HDPE is a relatively stable plastic...but its properties do change with age. It's important to figure out where the stresses will come from on a joint and avoid sharp corners where stress will concentrate along those lines. Sharp edges will always act as fracture points if the plastic is fatigued.

Fun topic to think about!!

Thanks for the kind words but I'm not sure I have much in the way of insights. There are lots of very cool CNC joinery techniques and when I first started out with my ShopBot I tried to be very clever and come up with lots of new ways to connect parts and panels. As I get older I've tended to simplify things and try to be more material and fastener agnostic. I'm just as likely these days to stick things together with titebond glue and a brad nailer than a fancy CNC-cut connection!

I think part of it is the increasing number of projects I work with like Shelter 2.0 and the Global Humanitarian Lab, where resources are scarce and equipment can be sketchy. They are just as likely to have a bag of shoelaces as a box of screws, so the simpler the connections the better. If you follow the evolution of the Shelter 2.0 design you can easily see this transformation. The connections that used to be tight-fitting (and slow cutting) half-lapped puzzle joints are now thru-bolted splice plates, and lots of bolts and t-nuts have been replaced with deck screws into inserts to avoid screwing into the edge of plywood.

I've posted a bit on Medium.com about some of these changes and have very intermittently been working on writing a booklet about the Shelter 2.0 design and how its construction details have changed over the years. Not sure if I'll live long enough to finish it though..it's slow going!

Eric: thanx, your channel is quite the treasure trove of what I was looking for.

Bryan: I hope you do it sooner than later. Post a link if/when you do.

Bill: I think you are too modest for your own good. I'll continue to study your stuff and glean what I can. If you ever do decide to do a full blog post on this I'll be tickled.

Alright Mark--I tried to start writing about joinery but I didn't even get out of the intro and had already written something way too long for a blog! This is gonna have to be a multi-part thing... but here's a start:
[handibot.com]

Brian, that is a great write up. Well done. Lot's of very useful information and very clear explanations. Russ

Brian Owen, ShopBot Wrote:
-------------------------------------------------------
> Alright Mark--I tried to start writing about joine
> ry but I didn't even get out of the intro and had
> already written something way too long for a blog!
> This is gonna have to be a multi-part thing... but
> here's a start:
> [handibot.com]

Wow, Brian,
This is like asking to borrow a cup of sugar and being handed a cake! If this is one of several and the rest are as good as the intro then the finished series will be the go-to for non-engineers wanting to do joints in sheet goods. Thank you so much and I'll be looking for the next installment.