The Self-Closing Mock Ring (SCMR) Holder came about through a request from my mom, an experienced tatter. We were talking one day after I got home from my day job, and she mentioned that creating SCMRs when tatting can be tricky for a variety of reasons:
- Holding the loop open with the pinkie finger can cause cramps and is difficult for people with arthritis or limited hand mobility
- If not held open, the loop used for SCMRs can close accidentally, and reopening it is is difficult at best
- Other methods of holding the loop open, like hanging a sewing machine bobbin or paper clip in the loop, still allow the thread to twist and get tangled with itself
- The bobbin or paper clip method also doesn’t allow enough space to easily pass the shuttle back through the loop when needed
After a bit of research, neither of us was able to find any product designed for this purpose. So… off to my CAD software and 3D printer!
Solving the problem
Initial concept
My solution was a tool that:
- Holds the thread in a natural-shaped loop (like the base of a teardrop)
- Has enough space inside it to comfortably pass most smaller tatting shuttles through
- Doesn’t require the tatter to hold the tool
- Can be easily placed and removed
The first design that occurred to me was a horseshoe shape with a channel groove running around the perimeter to hold the thread in place. The cross-section of the tool is a flattened V-shape.
The first prototype, while it met most of my design goals, was a bit on the chunky side. The smoothed edges (fillets) decreased the contact surface with the print bed, which made it more difficult to print without issues. The thread also slipped out of the groove a bit too easily, and nothing prevented the tool from falling out of the loop if the ends of the horseshoe slipped off the thread.
Improving the design
I tried increasing the contact surface of the tool against the print bed, making the channel deeper and at a sharper angle, and adding a notch that ran along the length of the channel to help capture the thread a little better.
With injection molding, this likely would have been fine, but on a 3D printer, it needed support scaffolding inside the channel to print correctly. As a result, the surface the thread is in contact with was too rough even after removing all the supports, and the thread caught on the little burrs left over.
I was able to use sandpaper to smooth out the inside of the channel, but that added a lot of post-processing to the tool. Adding labor time to any 3D printed piece increases the production cost. I wanted to keep the end product as affordable as possible, so ideally I’d have a tool I could set to print, remove from the 3D printer, pack, and ship with minimal effort on my part.
Return to initial design, with new tabs
Given the issues with the second prototype, I chose to revive the first design I did and modify that instead. I adjusted the angle of the channel to 45º from vertical, which means it can print without supports. I also removed some of the fillets along the edges so that it printed more easily.
Small catch tabs turned out to be the best way to keep the thread from escaping the channel. I tried two different options: straight tabs, and tabs that had a small nub pointing inward in the hopes that it would catch the thread more effectively. We found through testing that the two designs were functionally the same, so I decided to go with the straight tabs that were simpler to 3D print.
Jump ring loop
Now that the basic functionality was dialed in, we worked on how to attach it to a lanyard, chatelaine, or other type of tool organizer with a jump ring. The jump ring loop needed to be positioned out of the working area in a way that it wouldn’t affect functionality, and be easy to print and attach a jump ring to.
The first prototype I made for this step had it on the side of the base of the tool. This proved effective but not ideal; having the attachment loop on the side meant that the loop was pulled slightly off-center, as the center of gravity of the tool was no longer in line with the lateral midline of its main body. We sketched out a few options and decided to try each of them with the next batch of prototypes.
Improving printability
I removed the remaining fillets since their 0.5mm radius didn’t have much effect on the appearance or functionality of the tool when 3D-printed on my Prusa. It might be more noticeable when injection molding or using a resin printer, but for my purposes, it was negligible. I also widened the catch tabs on each end slightly for better stability and so that they were less likely to snap off. Last, I made the base contact surface wider again for better adhesion, and to potentially allow for text debossed into the surface.
Adding text
My mom mentioned that some people may wish to customize their SCMR tools. For example, using them as a giveaway freebie for conventions with the convention name debossed into the tool. I could fit roughly 29 characters when I tried this, but resolution and printability was less than satisfactory on my Prusa.
Having crisp, legible lettering will likely require printing via an SLA process on a resin printer. Since the resins are decidedly caustic and the bright ultraviolet light used to cure the resin can damage my eyes, this wasn’t something I was interested in exploring. Perhaps in the future… but only once I have a dedicated workshop space where I won’t be breathing the fumes.
Jump ring position
In an attempt to maintain the symmetry of the tool, I removed the loop on the side of the tool. I added two other loops instead, one on either end of the horseshoe pointing inward. The intention was for the jump rings to connect to a chain with a clasp on one side. This proved to be clumsy and, even without any jump rings attached, prevented working with the thread effectively.
The final placement of the loop is back on the base of the horseshoe, except now it’s inside it instead of protruding from the edge. We tried out two positions: the jump ring aligned with the horseshoe as seen in the picture, or perpendicular to the horseshoe. The first option proved to be easier to work with, so that’s what we decided to keep.
Patent Pending
The final change to the design of the Self-Closing Mock Ring Holder was to add Patent Pending to the inside surface of the tool! I filed for a patent in February of 2023. Once I have a patent number, I’ll replace the Patent Pending text with that.