This was my entry in the Pens and Pencils Contest at Prusa Printers (https://www.prusaprinters.org/contest/21-pens-and-pencils), which did not place. But the upside is that I made it at all, since it probably would never have been a thing without the contest pushing me to do it.

This thing is just a pen like any other, but also has the following features:

• 135mm Metric Ruler (the first 10mm at the bit holder end are not marked)
• Metric Nut and Screw Sorter (M2, M2.5, M3, M4, M5 and M6 sizes)
• 4mm Bit Holder
• A magnet (optional)
• It also has a groove in the ruler to help with marking filament to calibrate e-steps.

Parts Needed:

• 1x pen “refill” pulled from a generic BIC pen (see the pics)
• 1x 8x2 or 8x3mm cylinder magnet (Optional). I used these:
  https://www.harborfreight.com/10-piece-rare-earth-magnets-67488.html

Printing Suggestions:

I printed some of my initial version with 0.1mm layer height, but found that 0.2mm works as well. I would stick to those however due to the pen having a ruler. This will not need supports, but I recommend using a brim, unless your printer has fantastic adhesion. This is because the parts are set up to print in the tall orientation, and there is not much to hold it to the bed unless a brim is used. It will also help to print this slower than normal, since that will help with minimum layer times and vibrations since it is printed in the tall orientation (I used 30mm/s).

I added a small test part to print prior to printing the whole pen, this will test that the pen refill will fit the print. Please print this quick model first to make sure your pen refills will fit, it is called “Pen_Tool-7B-REFILL-TEST.stl”

Due to the necessarily snug fit of some parts, it would be a good idea to calibrate flow prior to printing this, unless you are familiar with the filament being used, and know what flow to use.

If you want to use the magnet, please print the cap named “Pen_Tool-7A-MAGNET-CAP.stl”.

Assembly:

Not much to this, just take the pen “refill” from the donor pen and put it in the printed pen body. If you use the magnet, I suggest gluing it in with superglue (Gorilla SuperGlue Clear is what I use and it works well). The 4mm bit was a snug fit which is necessary, but not so tight it cannot be removed by hand. It will help to clean up the brim and trim any flash from around the hole where the bit is held. I also found that cycling a bit a half dozen times in the holder helped make it a perfect fit.

Other Stuff:

I was able to test the pen using nuts and bolts of all the sizes, except M2.5, which I don't have, so I used the dimensions I found for M2.5 hardware online.

I have an idea for a remix which will work with this pen, it's a sliding clip to help hold the filament when doing the e-steps calibration. I have used this pen/ruler already a few times for e-steps calibration and it has worked, well but keeping the filament in the groove can be tricky (but it's still a bit easier than using calipers or a ruler), and I think a clip would help with that.

I spent quite a while testing fit and getting the design right, so I hope it's useful to some folks, but if there is a problem related to the model, please let me know.

If you find these models useful, please post a like or a comment with some pics of your prints.

I regularly update my current projects and other things I'm working on at my blog.
And if you like some of the stuff I design, you can follow me here or on Printables, to see what new stuff I post.

Thanks for looking!