3D Printable Micrometer Stand

This is a 3D printable micrometer stand that is capable of holding a variety of makes and sizes of micrometers, while allowing for a sturdy enough base to prevent moving and wobbling while making measurements. This is far cheaper than a professional grade tool, and can be quickly assembled with only three non-printed parts, available at any hardware store.

Building this project requires three printed parts: the base, the knob, and the press head. The non-printed parts are simply two standard 5/16" hex nuts, and one 5/16" x 1.5" long hex bolt.

I have a 2000 Mazda Miata with a 1.8L BP4W inline 4 engine that serves as my personality and the consumer of my free time. Late last year, I began noticing some serious oil consumption and overheating issues. After performing a number of tests on the engine, the decision was made to pull it out and refresh it. New engines are not available for this car, used engines run around $1200 for parts pulled out of salvage cars, and paying an engine builder to do the work would be extraordinarily expensive, so, in order to expand my horizons and give me another layer to my personality, I decided that a rebuild would be done by myself.

In order to rebuild an engine with any level of confidence, many careful measurements must be taken during a process called "blueprinting". This is simply measuring all components that interact with one another to ensure that the tolerances between the parts are within the original manufacturer's specifications. The problem, however, is that these measurements are often in the range of 1/10,000 (one ten-thousandth, .0001") of an inch- far smaller than what can accurately be measured by a pair of calipers. These measurements must also be taken multiple times in each position, and in other positions, to ensure a complete understanding of the parts at hand. (Notes are taken from the 1999-2000 Mazda Miata Engine Service Manual)

Micrometers, not calipers, are the correct tools for this job. These are somewhat expensive, limited in measurement range, rather fragile, and somewhat difficult to take measurements with, but they produce accurate, repeatable results within the tolerances needed for accurate engine building. Measurements are often taken "free-hand", in the air, for 0-1" micrometers, but this becomes difficult for anything larger than 1".

Most of the cons of a micrometer are simply problems that must be lived with, but one, the difficulty of use, can be addressed. The micrometer stand addresses that issue by providing a stable base for the tool to be used and read from, while staying out of the way of the parts being measured. Off-the-shelf stands exist and are excellent, but they cost money, which I do not feel like spending. 3D Printing, however, allows me to spend much less money and produce a tool that will tend exactly to the needs at hand.

There are other printable options available, but they all have their flaws. The base may be too small and prone to wobbling, the design too restrictive for use with other sizes of tools, or simply too difficult to quickly insert and remove a micrometer from the stand.

My "wish list", in order of most to least important, was:

-3D Printable with minimal additional parts

-Usable one-handed

-Usable without external tools

-Stable (through base size, weight, or a combination of the two) enough to hold a 3-4" micrometer

-Buildable with as few adhesives as possible

-Good looking (because, come one, if it doesn't look good, it isn't good, right?)

I initially made attempts that had a large loose platen head with a 3D printed adjuster screw- 100% printable, but rather weak, especially due to the low layer strength of prints, relative to other options. A move was made to off-the-shelf bolting components, but the loose platen still serve as a weak point due to the lever action of the clamping loads.

A new design was made that had the adjuster pressing directly on the micrometer arm, rather than the previous models using a large platen. This decreased the contact area, requiring higher clamping forces, but the amount of force required to keep a micrometer from moving is rather small and easy to deal with. This also allowed the model to be made simpler, with only one section of print overhangs, short enough to be overcome by any decently setup printer.

A number of test prints were made (and should be made by anyone who replicates this project) to perfect the fitments. The goal was to have press fits for the hexes rather than glued in parts, so a number of test prints at various scale sizes were made to ensure acceptable tolerances. Simply change the scaling on the slicer .5% at a time until a good snug press fit is achieved for the different components.

1. Press the bolt head into the knob hex. This should be a tight fit- it should not be easy, in fact, it may feel impossible right before it slips on.
2. Push a hex nut into the slot in the base. This should also be a snug fit, though not as tight as the knob. Push this nut until it bottoms out in the part and the threads are concentric with the holes in the base
3. Press the other nut into the clamp end. This should be a tight fit just like the knob was. Apply a drop of thread-locker to the threads on the nut.
4. Screw the knob/bolt combination into the nut in the base.
5. Finally, spin the clamp end/nut combination onto the bolt. This will be the most difficult part of the assembly, from an alignment point of view. A pair of pliers helps immensely in lining up the threads.
6. Let the assembly sit for the recommended cure time of the thread-locker manufacturer. I used Loctite 271 (Red threadlocker- this is never coming apart!), and as such, I had to let my part sit for 24 hours.

Simply turn the adjuster counterclockwise, drop a micrometer in the slot, and snug the hand knob down. Not a lot of force is required, just gently wiggle the micrometer until it no longer moves. That's it!

The finished build is one I am quite proud of. The tool is very stable thanks to the heated glass print bed. It does an excellent job of holding each of the micrometers in my collection. It is very easy to insert a micrometer with one hand, tighter the knob with the other, made a measurement on a part, and remove the micrometer for reading. The only adhesives required was a drop of thread-locker on the tip of the bolt to be attached to the press head. This is, unfortunately, a requirement for this build, but it prevents the press head from unscrewing, and is far easier to implement than some sort of locking mechanism.

-Material choice is not hugely important here. I used PLA+ due to availability. I cannot comment on the filament's resistance to solvents and liquids that may be present in a workshop, but measurements should always be made on dry, clean parts to avoid incorrect measurements or damage to measuring tools, so this should be less of a concern.

-Use 40% + infill on the base- the heavier the base is, the more difficult it will be to slide around while making measurements.

-The knob can be printed at whatever infill you like. I used 15%, and was able to print in around 45 minutes.

-Use 100% infill for the clamp head. Any voids in this part will collapse when clamping against a micrometer.

-Do test prints of all parts prior to the full build. Print just the clamping section of the base to get the hex sizing right. Print half the knob to make sure the bolt fits.

The biggest improvement someone could make to this design is some sort of bearing surface that allows the clamping screw assembly to rotate, while allowing the clamping load on the micrometer arm to remain in a single direction. This would have to be some kind of flat Torrington bearing, or an extra flat bearing surface between the current head and the arm, but this design works more than well enough, especially for a home hobbyist with a useful time range of a month or two.