Second Caliper Battery Hack Prioritizes Simplicity

One of my early 3D printing projects was motivated by the wasteful battery usage of a cheap Harbor Freight digital caliper. I didn’t want to replace its LR44 battery all the time, and I didn’t want to directly modify the caliper in any way, so I ended with an overly complex tray to hold a AAA battery in place of the default LR44 battery.

The main goal was to avoid the wastefulness of burning through LR44 batteries, and that goal was a success. I was able to use cheaper AAA batteries and use them for longer. In fact, this caliper was able to run on AAA batteries that were too weak for much else, giving them a very useful secondary life. However, my battery tray suffered poor reliability of electrical contact points. In actual usage it was too easy to move a component just enough to break electrical connection, resetting the caliper and losing whatever measurement I had at the time. After a few frustrating episodes, I broke off the plastic head substituting the LR44 battery and soldered wires directly.

Caliper printed battery tray cracked

After years of use, the battery tray I designed and 3D printed finally cracked. And this time around I decided to go for simplicity instead: a commodity AA battery tray held to the back side of my caliper with double-sided foam tape.

Caliper commodity battery tray back mounted

Wires from this battery tray were soldered directly to the battery tabs inside my caliper for reliable operation. I could no longer lay this caliper down flat on a table, but I don’t think that will be a significant concern. I’ll know for sure after some usage and if it proves to be a problem I will re-evaluate.

In the meantime, I have a replacement battery tray allowing me to run my caliper on weak AA batteries already destined to be thrown away. And since this tray is a mass produced commodity item, using it was cheaper and it was faster to install than my previous solution.

Moral of the story: sometimes 3D printing is not the answer.

Drilling Into Half Inch Diameter Tubes

It didn’t take long before my new old drill press was put to work doing something that was difficult without the tool: I needed to drill a total of eight holes through three half inch diameter aluminum tubes, perpendicular to the tube’s axis.

Because the surface is curved at the point where drilling starts, it takes a skilled hand to perform the task via freehand held drill and workpiece. I did not have such skills in my hands. Putting the workpiece in a vise helps, but still difficult for me to keep a hand held drill on center. What I needed was a way to hold both the workpiece and the drill bit in rigid relation to each other, meaning a custom workholding solution bolted to the drill press table.

Printed V vise jaw installed

It was built using a very cheap Harbor Freight vise. Its jaws were removable and I designed and 3D printed replacement jaws with a V profile to better hold a round object. The other benefit of 3D printed plastic jaws compared to metal jaws is the reduced chance of marring workpiece surface.

Printed V vise jaw gripping tube

The next step is to bolt this vise onto the drill press table. I saw mounting slots on both the table and the vise, and their slots were in the same pattern. I naively thought this was a standard form factor and they will easily line up.

When I put my vise on the table, I found that they did not.

Vise and drill press table slots do not align

Fortunately even though they did not actually line up, they left enough room for me to use a smaller bolt to try to make things work. In this case, my stockpile of 1/4″-20 bolts.

Vise and table has room for quarter inch-20

The slots are too wide for the typical 1/4″-20 washers I had on hand for this bolt, but again I could turn to my 3D printer for custom solutions that help me bolt the vise to the drill press at the location I needed.

Drill jig for 0.5 inch tube

It took some adjustment to bolt the vise exactly where it needs to be. (Tip: double check to make sure the drill press table isn’t itself moving!) But once everything was tightened down, the jig made drilling the holes I needed very simple.

Public Onshape CAD file for this project are available here.

Old Drill Press Is New Drill Press

When local fellow maker Emily upgraded to a big floor standing Delta drill press, her old benchtop drill press was up for grabs. “Free if you pick it up” were the terms of the sale, and I was glad I could pick it up before someone else did. Taking part in countless Emily projects in the past, it shall now play a role in my projects in the near future.

Its long history in the hands of many handy creators showed clearly, with many stock parts missing replaced by either scratch fabricated or adapted parts. This is not a problem at all, a drill press is fundamentally a fairly simple machine and none of the modifications changed its ability to do its core job. Besides, with a less-than-new machine, I feel less intimidated about adding my own modifications as necessary.

The first project on the list addressed a known existing mechanical problem: the drive belt occasionally rubs against the chassis when it is installed in the lowest and slowest of four pulley slots. I inherited a workaround from Emily which I was content to leave in place, but then I saw the set screws holding the pulley to the motor shaft.

Drill press motor pulley

I thought it might be worth a shot to try loosening the set screw and move the pulley a little higher. There might be a good reason why the pulley was in its location. I thought it was possible (likely) the motor was not original and had a shorter shaft, or something along those lines. But it was worth investigating.

I put my hex wrench on the set screw and discovered it is loose now. The reason this pulley is too low is because the set screw came loose and it fell down due to gravity. I moved the pulley a little bit higher, tightened the set screw, and we’re back in business without any rubbing between belt and chassis. This was a great start to what I hope will be a long illustrious career for this drill press, enabling my project ideas in the future.

SparkleCon Sidetrack: Does It Have A Name?

spool holder with two stage straightener 1600x1200

My simple afternoon hack of a copper wire straightener got more attention – both online and off – than I had expected. One of these came as a fun sidetrack to my Sparklecon talk about my KISS Tindie wire sculptures. As part of the background on my wire form project, I mentioned creating this holder. It kicked off a few questions, which I had answered, but I had the most fun with “Does it have a name?”

I gave the actual answer first, which was that I had only been calling it a very straightforward “wire spool holder with straightener” but I followed it up with an off-the-cuff joke “Or did you mean a name like Felicia?” I think I saw a smile by the person asking the question (hard to tell, he had a beard) and I also got a few laughs out of the audience which is great. I had intended to leave it at that, but as I was returning to my presentation another joke occurred to me: “Felicia will set you straight.”

Since my script was already derailed, I saw no reason to run with it: “Is there a fictional character who is a disciplinarian? That might be fitting.” and opened it up to the audience for suggestions. We got “Mary Poppins” which isn’t bad, but things went downhill from there. The fact is: the disciplinarian in a story is almost always a killjoy obstacle in our hero’s journey. Or worse, one of the villains, as in the suggestion of “Delores Umbridge” given by a woman wearing a Harry Potter shirt. My reaction was immediate: “No.” But two seconds later I remembered to make it a tad more positive: “Thank you, she is indeed a disciplinarian, but no.” Hopefully she doesn’t feel like I bit her head off.

After the talk, there were additional suggestions interpreting my second joke “Felicia will set you straight” in the sense of personal relationship preferences. This went down a path of politically conservative zealots who believe it is their public duty to dictate what people do in private. This direction of thinking never even occurred to me when I threw out the joke on a whim.

I think I’ll leave it at Mary Poppins.

SMD LED Under Macro Lens

Several recent posts focused on small things like a damaged ESP32 module. Trying to document these projects presented a challenge because it’s been difficult to take good clear pictures of fine detail. I did the best I could with what I had on hand, but the right tool for the job is a camera lens designed for macro photography. When one such lens for my Canon EF-M camera was on sale during the holiday shopping season, I could not resist.

Here’s the LED on the Introduction to SMD kit, with the entire image scaled down to 1024 pixels wide.

SMD intro kit scaled 1024

If I crop out the center of the original picture instead, this is what I see:

SMD intro kit LED 1024

A lot of detail are visible, certainly far better than what I could get before, but I think the focus could be a little sharper. I hope the lens is limited by operator skill rather than optical characteristics, because I could learn and improve my skill.

Here is a picture of the LED array from my recent freeform SMD experiment, again scaled down to 1024 pixels wide. The solder joints – which I could barely manage with the naked eye – look really uneven at this magnification. But wait – there’s more!

Freeform SMD 7 scaled 1024

Here’s the cropped-out center of that image. Tiny beads of solder look like monstrous blobs of invading space aliens, not at all attractive. But the wire inside the left side LED is clearly visible, and multiple diffractions of the right side LED can be seen. This picture represents a combination of two novice skills: freeform SMD soldering and macro photography. I’m pretty happy with the detail and clarity of these pictures, but not at the quality of these solder joints. That’s OK, it just means I have lots of room for improvement.

Freeform SMD 7 cropped 1024.jpg