Hello, I am Chris Cosentino, an engineer (mainly) and fabricator (less mainly) with a small engineering design and prototyping company in Jersey City, NJ, USA. In my spare time from designing and building roadrace motorcycles I try to run my business, finding engineering consulting gigs and small manufacturing jobs. Whatever brings the rent in is welcome! A while back I was enticed to start a cool project that eventually went nowhere reeeeeaaaaaallllly slowly. Fast forward a couple of years, I am in a meeting and my client saw a rough version of the product and wanted one. His interest rekindled the project’s flame and after trying and failing to get the old plan back together I started out a new with hope that others would find it as interesting as I did.
Please forgive the roughness of this kickstarter presentation, the doing of something is what I really love to do and am good at. The documenting and computer editing of a multimedia sales tool, not so much! So, while the presentation may not have all the slickness of an Apple ad, you can be assured the end product more than makes up for it.
What, you may ask, is this end product? Why a pen, of course! Not a first for a kickstarter project by any means, but this is a good one. At first glance what first takes your attention is the beautifully machined and electropolished hexagonal body and sculpted pocket clip.
Whatever the name, you have to pick it up, it just looks that good. And you find it feels that good as well. The lines and edges are super crisp yet no uncomfortable sharp edges will take away from the writing pleasure. For crosswords or a quick note, opt for the aluminum or titanium versions. For words that carry weight, stainless, brass, and folded Damascus steel options provide gravitas appropriate to any written situation.
After cradling it for a minute or two you think, ‘hmm, how does the cap come off?’ There is no give when you try to twist it. A light tug results in nothing. Feeling brave? A decent pull and you are rewarded with a clean cap release. No obvious detents or clips can be seen, the design is clean. Knurled finger area and smooth tapered tip. Why complicate things? KISS, baby! But how is the cap held on? It is only as you go to put it back on that it becomes obvious. When the cap is still about 1/4″ away from seating it is suddenly pulled from your fingers and seats itself, self aligning on the flats.
A magnetic cap! Living inside the top of the cap, beneath a rubber tip seal, is a custom molded Neodymium tube magnet. The magnet is pulling on the small tool steel tip that every material pen has. Now you can’t stop playing with it. Pull cap, let it be pulled back, repeat. Repeat. REPEAT!!!!!! Click, ring, click, ring, CLICK, RING!!!!!!!! Your co-workers will hate me.
You may not be like me (not many people are, or admit to being), but once I have something in my hand, the second thing I do it try to take it apart. This pen obliges. All the parts are joined with fine pitch 0.5mm threads, providing a low profile, precision look, and precise fit.
Once the barrel is off you examine the tapered collet system that retains the ink cartridges. It is an effective system adapted from the machining world, where tapered collet holders are the workhorse of the industry.
This system allows the user to adjust the amount of tip protrusion to their preference while holding the tip firmly in place. Because the collet grips the middle area of the ink reservoir, the overall length of the cartridge is not important in keeping the tip located and restrained. Cartridges too long to fit into the body can be trimmed without a need for an exact length fit and short cartridges can be installed without spacers.
As mentioned above, the plain tapered collet holder can accept ink cartridges with a reservoir diameter of 5.2-5.6mm, but with the addition of 3D printed inserts that fit into the collet mouth, cartridges with ink reservoir diameters down to 3.0mm (.118”) can be accommodated. This adapter system allows many other gel and ink roller ball cartridges to be used. A set of these inserts is available as a separate reward.
Now we have covered the functionality of owning and using the Gladiator Magnetic Pen. In this next section, I explain the design and manufacturing process. Iteration is the key to a quality design, and repeatability is the key to a quality manufacturing process. Once you have a great design that attracts customers, getting a lot of orders is great unless your manufacturing process is not repeatable. I do not intend to get into that situation.
When making any product, especially a handheld one, iteration is key to achieving a comfortable and functional design. Looking back over the 4 years since this project started, I realize the just how much iteration we’ve gone through!
The first problem to overcome was to get the magnetic cap design to actually work! I worked up a small jog to test magnetic strength and was off testing.
We tried all the off-the-shelf magnets out there but nothing could meet our main requirements of size and pull force. Unless we wanted to add extra spacer parts and lose force, the magnet would also need a center hole to clear the tip, which further limited our stock options. Another contributing problem is that the tip of a pen wants to be small to provide minimal visual obstruction to the writing area which is in conflict with the magnet wanting as big a piece of steel as possible to pull against. We could not put a small magnet near the tip of the pen to help pull at the cap magnet. We tried, but a lot of table surfaces have a steel surface or subsurface. Any magnets in the tip of the pen pulled the pen tip to the table top when writing and was very disconcerting. This would happen when writing on any metal surface, definitely a no-go. This left us with a small tip that could be of any material.
The only option was a custom magnet, which has associated mold and minimum order quantity costs. I bit the bullet, wrote a check, and waited for the first round. The first round was unsuccessful but the second round was a direct hit. No spacers or back up plate we could achieve positive cap retention! Once we got the magnet pull to be good, the next problem of the cap ‘sticking’ when getting pulled up, showed up. We want the magnets to pull the cap on and have it self align on the flats. With a strong magnet pull, the cap was tending to stick when not perfectly aligned. That gave our next hurdle to overcome and we did it by machining lead-in ramp geometry on both the end of the barrel and the inside of the cap to help self-align them. Many programs later we got it to work!
Small tapered end mills for the cap’s inside ramps were tricky to program but are a repeatable way to create the needed geometry. They now work great, and look good too.
The last piece of the puzzle was getting the correct material for the tip. In my various quests to find the way to create the most magnetic force in this small area it surprised me how little assistance magnet manufacturers could provide on such a simple system. Using the magnet pull force jig, I tried exotic magnetic alloys, simple carbon steels, and whatever else I could find with middling results. Then I tested some tool steels. Somewhere on the web I read that their high percentage of alloying elements was similar to a magnet so would provide the best target for a magnet to pull on. They clearly showed a large increase in pull-force, with O1 Tool Steel performing best. Finally, it really works! And amazingly, someone on the internet was right! Another benefit is that the O1 is a hard, durable material, unlike some of the softer specialist magnetic alloys I had tested. The last cap detail is a small rubber seal at the top to keep the ink cartridges nice and happy when not in use. The magnetic cap design was finalized!
Now that the main grab of the pen, the magnetic cap, works, we could proceed to the rest of the details of the design.
The grip area is one place that design can run amok. We had a bunch of fancy designs for the grip area but they all looked contrived and in the end not as functional as a good knurl.
Getting the knurling to run true is a labor of love. And requires the right tooling. And I love tooling. My bump knurler works decently, but again, the long, slender aspect ratio of these parts made getting consistent knurls difficult. I had to upgrade to a straddle holder and some new knurl wheels.
The new Dorian knurling tool was impressive, and by straddling the part instead of bumping up against it, the knurl was immune to the flex and inconsistent depth that bumping can introduce with thin parts.
OK, cap closing and the grip area are now done, what next? How to repeatably create the cap split slot. For this shape, as in prototyping, for production the only option is Wire EDM. It works like a hot wire foam cutter, but for metal. By nature, these machines are precise and repeatable, so using this technology for the pen does not present a problem for production quantities. It is an expensive technique but with no alternatives we are forced to accept the cost. The clip is much more durable that it looks and can be bent outwards slightly if needed to accommodate thicker shirt materials.
A last detail is what to do with the cap when using the pen. When writing, the pen body is long enough to be used without the cap. The cap can be stood vertically on any magnetic surface. I usually leave mine standing up on end and the magnet keeps it stable. If desired, the cap can be slid over the stepped-down end of the barrel where it is retained with a friction fit. We tried very hard to also have that be magnetically retained but the distances are too great using only the cap magnet and any reasonably sized second magnet in the end of the barrel was not enough to even be noticeable to hold the cap on the back. And it made the pen very tail heavy, which felt unpleasant. So, friction fit. Function must reign supreme!
One option for the main pen body is a version with no stepped down area at the end of the barrel. The cap would not have a place to be stored while in use but the pen itself looks a bit sleeker when closed. If you would like a pen with the plain end, please let me know when choosing a reward.
Covering those details finalized the physical shape of all the components of the pen and how they are to be manufactured.
Getting the machining of the individual components consistent was another iterative process. As work allowed, and my multi-axis CNC lathe was idle, I was iterating the geometry and testing revisions while saving every program change. At this point I am very happy with how the pen works and have the updated CNC programs to repeat it.
After getting the program to create the correct geometry once was done, getting the programs to run consistently somewhat of a challenge, again, due to the long, slender profile of the parts. Small changes in tool sharpness as it wears leads to changes in cutting force, which on long, slender parts (again!) can greatly affect tolerance and finish quality. For creating the main hexagonal profile with a fine finish I ended up with an 8 flute end mill machining axially.
The large number of flutes ensures that at least 2 are always engaged in a cut so there is less vibration and cutting load is more consistent, resulting in a fine surface finish and high accuracy. There is less slapping of the material against the cutting edge, which keeps the cutting edge sharper for longer.
Why machine a hexagon instead of starting with one from scratch, you ask? First, try finding hex stock with no imperfections along the length. There is also a slight radius on the corners. Using hex stock would also not help machining of the one-piece cap. That is made Lastly, it fixes you into a specific size. 3/8″ stock was close, and good for some initial testing, but the flat to flat measurement ended up at around .408″. Why? It felt good. Not too big, not too small. Think Goldilocks with a nice war helmet.
Since we were testing the pen body before the cap design was finished, wanting to make the hex an odd size led to the one-piece clip design since if we were machining the full hex, there was no reason not to machine one less flat, leaving a nice chunk of material perfectly positioned to be a clip. Now if there was only some way to cut metal like a how wire cuts foam. Wait, there is! Wire EDM! Add a stress relieving hole at the root of the clip and the rest of the clip design falls out of manufacturing requirements! And wow, looks like a Spartan helmet. How did that happen?
That is almost the last step, as we don’t want a machined finish as the final look, so need to find a repeatable finishing process.
Having the parts processed to a desired surface finish is the last potential landmine. A fine machined finish, while nice for engineers, just won’t cut it for this pen. It needs to be polished, but normal polishing tends to blur edges and blunt overall part crispness. During my years in the custom door hardware industry I learned how unforgiving finishing can be and how hard it was to generate a quality polish on various geometries without subtly altering them. It is amazing but necessary how much effort is put into a good final finish stage. No sanding and polishing rigs I worked up had good results so needed to look further afield. A brief search found electropolishing, an automated non-contact finishing process used to give a high quality, even finish to parts of any shape. For our shapes, the non-contact approach preserves the flat planes and crisp edges of the design. I was able to send in several of my scrap parts for testing to determine how much removal was necessary to achieve the desired finish. The final parts then had to be machined with several thousandths of an inch stock allowance so that after electropolishing, both parts fit together and align properly.
Now that the performance of the pen is more than acceptable I am ready to make larger runs and finally get somewhere in the economy of scale to actually afford to make them! The machines I use take a considerable amount of time to set up and dial in, as these are complex parts that have turning, milling, and drilling both with and without live center support from the subspindle. Another issue driving towards larger production runs is the electropolishing process, while repeatable, needs relatively large minimum orders to be economical. These parts require special handling and racking so small runs disproportionately add to the overall cost. So all together this means I can’t make 10-20 at a time in any economical way. I need to make a lot. The more, the better, as they say.
The available materials are as follows:
6061-T6 aluminum. This particular alloy was chosen for having the best electropolishing results. This light alloy results in a featherweight pen that looks great and is potentially the base canvas for a stretch goal of an advanced PVD finish. Rose gold color is one favorite.
360 Brass. Brass, what else is there to say? A classic material that ages. Patinas. Gets dirty. However you like to look at it.
303 Stainless Steel. The modern classic. Provides a substantial feel. Perfect for signing expensive contracts.
6Al-4V Titanium. Light weight and strength. A complete pain to machine but the end results are worth it. Titanium has that lustrous grey color that is instantly recognizable.
Folded Damascus Steel. Exotic. Gorgeous. A sure conversation piece. These pens are very difficult to make and require the highest quality folded Damascus steel to start. Due to this sourcing difficulty, reward delivery is longer compared to the other materials.
Hopefully you will agree that this pen is a beautiful creation of function and form and worth supporting. Thanks for looking at my campaign. Please ask any questions and I hope you pledge for something.
The main risks on this project is keeping the scrap rate low. The high finish requirements and simple design leave little room for errors and refinishing. Most of the machining is already optimized and the last item is to finalize the processing parameters for the electropolishing operations. I am working with a quality vendor and in the coming weeks expect to have these items resolved.