Tuesday, May 11, 2021

A Useful Little Tool Off the 3D Printer

Since I posted my last 3D Printer post about printing internal threads,  I made some changes in the way I'm doing things.  I've switched the CAD software I've been using from the Cura Slicer over to the Prusa slicer.  Both are freeware, and I had been getting recommendations to look into the Prusa slicer because it has more features.  Prusa is one of the big names in the field and sells printers that are very well regarded, either as completed printers or kits.  They're based in the European Union, but have dealers in the US. 

I came to the conclusion that the difficulty with the printed internal threads was caused by my design, not the slicer settings, and scaling things to the right size off the printer. When you run a tap through metal, you get some additional room around the threads from the design of the tap and the drill bit you use; tables of the drill size to use before threading have a tight fit, 75% thread, and a looser, 50% thread.  In my CAD program, I made a solid cylinder then moved a model of a screw thread into the center and subtracted everything contained in union of the two parts. Yes, it produced a thread, but it was exactly the same size as the model, so no room in any direction from the threads. It felt tight because it was. I need to think of a way to do that, but it started out as a "I wonder if I could..." project.

Following a path like a ping pong ball in a clothes drier, I ended up with a project that would be useful around the shop and fitted into some things I've been thinking of doing.  An adapter that would allow me to both test and use batteries from my Ryobi tools - all the 18V One Plus line, not their 40V line.  I found the design on Thingiverse, downloaded it and went through my process of turning it into a Gcode file to print.  On Thingiverse, designer nafis used an almost Ryobi green colored filament. 

In case it's not obvious, this is two pieces; the green printed portion and a plastic piece with metal terminals in it.  That's a Ryobi replacement part, part # 300001044, which I bought from a seller on eBay.  The terminals are a rather tight press fit into the printed part.

The print turned out less than perfect but good enough. 

The flaw is that one corner area of the cap lifted off the bed, and the cap isn't flat, like it should be.  In this use, that absolutely doesn't matter.  Here it is as it's being used and you can see the taper on the cap better. 

What do I do with this?  Aside from checking the battery capacities every now and then, when I look at the batteries I think of energy for when the grid is down, like after a hurricane.  I'd love to be able to get at that energy and the first step is getting onto those terminals.  In the case of trying to run something that runs of the 120V wall outlet, they make a product to do that for you.  I may well replace my aging 35AH AGM (sealed lead acid) battery with a handful of these tool batteries. 


  1. I LIKE the 18VPlus series. I got a set of the NiCad tools when a neighbor went into hospice. The cells went Tango Uniform, but the new LiIon thingies that I got to replace them worked perfectly. Then there was a set (Drill motor, flashlight, recip saw, circular saw, other stuff, plus 2 chargers and 3 batteries, for the price of like way cheap), all retro compatible. And then, on a very sad December day, I saw a neighbor. He seemed distressed. Just a neighbor, right? He had a son in the Navy, QM, Logistics. I got a son in the USMC, MOS 305, logistics. We both did some set building for local theatrical troupes. Some commonalities, you might say.
    But neighbor was bummed. All of his cordless power tools had been stolen. Just the tools, not the batteries and chargers. 'What brand' I asked. 'Ryobi 18v'. 'I'll be back in 5'

  2. That's a clever idea. These new Li-Ion batteries can pack a stunning amount of energy compared to Ye Olde Dayes of rechargeable batteries. There are some that would run my Elecraft K2 for quite a while if TSHTF.

    1. The only obstacle is that they're 6S strings, so the pack is 21V when it comes off the charger and around 17 when discharged. That means it's going to need some sort of DC-DC converter to get it down to something that won't blow up the radio.

      Because you need efficiency, it has to be a switcher. Because it's a radio, it has to be an EMI-quiet design. Once you start looking down that line, it has to be able to handle whatever power the rig wants while transmitting. Depends greatly on the radio.

      I've never done switching power supply design, but what's retirement for, anyway?