This piece is a commission for a mantelpiece. The client wanted something subtle, mysterious, and scientifically interesting. I had been reading a book called "Other Minds" by Peter Godfrey-Smith, that covered the parallel evolution of humans and cephalopods, tracing back to our nearest common ancestor, a sort of proto-planarium. Modern cephalopods share many of the features of their much earlier ancestors, almost as if they reached the pinnacle of their evolution 500 million years ago and said "Cool, we're done". Kind of like the Amish of the pelagic zones. So the octopus was in. 

I was also fascinated by the orthocones, an ancient sort of nautilus that hadn't figured out how to wrap its shell into an Archimedean spiral yet. The theme I chose was for a couple of these cephalopods to be reaching out across time and space: orthocone and octopus.  

The dimensions of the installation space was 4 feet wide by 6 inches tall, so I kept thinking the rendition would be a lot like a banner ad except without the animated gifs. heh. 

The first stone I chose was a two inch thick black granite, which meant it was super heavy but also made an interesting pattern on the octopus pelt after polishing. After mostly completing it I realized I somehow got the wrong depth measurement, and 2" would be standing well proud of the mantel frame. After some misguided attempts to shave the back of the piece down, I decided to re-do the whole piece. 

Attempt #2 went really well for about a week, then one of the corners broke off. While I was deciding how to glue it back on I re-measured and found I was ¼" short.. aaugh! That went on the heap. Well, actually it's turned upside-down and pretending to be a stepping stone in my front walk. 

Third times a charm: this one was going to be much thinner and made of two pieces rather than one large one. I started carving it at the socially distant stone carving symposium, and actually got pretty far. The orthocone has like a million arms and it took forever to get those carved and rounded without snapping them off. 

There remained two challenges to meet: level and align the two pieces and match texture and finish across the gap; and how to hang it up. 

For the first challenge I had to build a special easel to hold it and allow me to slide the pieces back and forth to gauge their fit together. This was a lot of sub-millimeter adjustments until it aligned perfectly. 

The second challenge was a doozy. The piece would be bordered on three sides, top/left/right, so there was no way to mount it where the idea was to have a hook (think: French cleat). Putting in on a ½" shelf was good, but I needed a way to keep it there without tipping and without showing any obvious clips. 

And this is where it got really interesting: I never knew that magnets will lose their magnetism when heated too much! Each magnetic material has a Curie point where it will stop being magnetic, and in theory the temp is in the thousands, but in practice with the materials in hand I found it would lose its zing at about 100° C, which is well within the range of the fireplace insert's capabilities. I was able to locate some Samarium Cobalt magnets which will survive a much higher temp (700-800° C), but I had to get twice as many since they weren't as sticky. If the fireplace got hotter than that, the house is actually on fire, and the mantelpiece would be the least of their worries.

I'm really pleased by the composition in situ. It's very hard to get a good picture, but the effect is a very subtle relief with just enough shine and texture to define, without being overly insistent.


Mini Angle Grinder

I'm a fan of the Foredom Mini-Angle Grinder for lots of my smaller work. It comes with a lot of accessories that make it useful right out of the box, but it was missing a simple blade, probably for good reasons, but I decided to make my own. 

First off, the Foredom is a frickin' amazing tool and you can get multiple interchangeable handsets for it that'll give you lots of options. I bought my first one twenty years ago, loaned it to a friend who never gave it back, so I had to buy another. I was able to find lots of them on eBay, and some were going for a song ($86 for a practically new unit with handpiece). These are built to last and are easy to service: I'd get a new set of brushes, blow out the motor case with compressed air, clean and re-grease the shaft, and it's like a brand new device. I picked up multiple handsets ($46 for a set of four) on eBay, too, and those are fairly easy to service if you know how to press bearings. If not, Foredom's repair service is fast and reasonably priced. Anyway...

The angle grinder kit is either "just the kit" or "comes with handpiece". If you don't have a spare H-30 handpiece, I recommend getting the "comes with handpiece" option because installing and unstalling the head is a drag. You may also want one of their manual speed controllers to limit the speed if you don't have a light touch on the foot control. To set it up, you put this nub thing in the H-30 chuck, tighten, and then clamp the angle head on it. Snap it on your Foredom shaft and you're ready to go.

Tiny Diamond Pads
It comes with wrenches, a bunch of sanding discs, flap wheels, and assorted mandrels: a velcro pad, a ⅜" arbor, and a screw-lok / roloc.  It comes with some aluminum oxide sanding discs, but I got some silicon-carbide discs to replace them. The roloc mandrel is great because you can spin on and off various grits of pads super quickly, and I bought some tiny diamond pads and some buffing wheels to go along with it. It also comes with a few sticky backed velcro pads, so you can make your own velcro-backed wheels.

I wanted a blade for cutting tiny frets and details in a basalt mantelpiece I was doing. So I looked for a 2" diamond blade for it, but nothing was immediately obvious. I decided to hot rig a 2" diamond blade onto the mini angle grinder and was pretty pleased with the results. 

Inside the ⅜" arbor is a screw hole. You're going to want to take the unit with you to the hardware store to get an exact match because whatever size I thought it was, it isn't. The picture of the machine screw should give you a close idea of the length, I ended up buying a few different lengths in case I had something else come up later. The head type is rounded (also called button or domed) to minimize chance of hitting the piece with a bolt. Getting the screw through the blade was hard -- it was just slightly too small -- but once in there it's a good tight fit for no slippage.

That's about it. I've been toying with a way to get a tiny water drip working on this kit, if that happens I'll post about it here. 


Dust Extraction

I used to worry about dust collection, now I just worry about dust extraction.  Rock dust is so small that it will clog any decent filter pret quick, and then the whole operation comes to a halt while you clean the filter. 

If yr not going to work wet — which really cuts down on the dust and keeps your tools cool — then the other option is to extract, that is: move the dust from where you are at over to where you are not (and, hopefully, neither is anyone else you like). 

My extraction system is based on a small harbor fright dust collector, a cyclone separator, and a vent out the back into the shrubbery. The shrubs seem to like the attention, and the rock dust enriches the soil. The blower used to have a filter bag, but it just clogged. The unit sits in the ceiling space, and I have it hooked to a wireless remote switch (amzn). It sucks air thru a 4” aluminum duct hooked to the cyclone separator, which is then hooked up with transparent venting (via blast gates) to a couple different workspaces and tools.

Overall it’s fairly quiet at 72dB, way quieter than any power tool I might be using. The sucking power isn’t enough to slurp heavier pebbles or chips, but does get rid of the sandy stuff that grinding tools knock off, and yes, all the dust. 

I went through a few iterations over time: initially the dust extractor was just sitting near the work and sucking all the things into the vent and occasionally dinging the fan blade with a larger chip. The filter bag got clogged all the time and cleaning it was a chore. My first foray into extraction was when I forgot to zip the bag after cleaning it: I wondered why it was sucking so much better until the dust come back around. Oof. 

The cyclone separator was an attempt to save the fan blades from rock damage, and it’s done a great job. I had the extractor running on the floor and venting out the door for awhile, but I kept tripping over it so I finally mounted it in the ceiling joist space and ported it out the back. With it mounted higher the chips tend to collect in corners and low spots of the venting ahead of the separator, but that’s easy to dump when it sounds too gravelly. 

I have a reducer and vacuum hose attachment so I don’t have to have a separate shopVac taking up space. For non-stone detritus like sawdust and general shop cruft the separator works wonderfully. Another advantage to the separator: when you inevitably slurp up something you meant not to, it’s way more appealing to rifle thru the separator than a vacuum bag (I mean, if you’re going to split hairs). 

Since it’s modular, I’ve got designs to upgrade the sucker with a simpler plastic vaned blower for bouncy houses. As long as no chips get into the impeller it should be fine. It has about twice the CFM for about half the price.

The main thing it’s hooked to is a box that’s conceptually like a blasting cabinet. The box, at 18x18x24”, is somewhat portable so I can have it in a couple places in the shop depending on whether I want to stand or sit while working. There’s a hardware cloth screen over the exhaust port to keep the big chips from getting away. The plexi works both for eye protection and to increase airflow, slides up or down as needed. There’s a light in the top, too. I use Dremels for small work (⅛” bit or smaller) and Foredoms for the heavier work (¼” bits). The Foredom is mounted on an IV stand so I can roll it around the garage. I’ve used the box for spray painting as well, the fumes just go!

I hope this helps anyone else who has dust problems, let me know if you have questions. 

[2022-03-23] Edit: some feedback about the difficulty of attaching to the bouncy blower led me to find a different (better?) air sucker. This inline duct fan looks interesting at $125 and 760 CFM and 39dB (!)