A standard starting item in some packs is "a bag of 1000 ball bearings." Now, I am still a D&D newbie, but it seems to me that the cart is way before the horse here. Heavy-load-bearing rotating shafts did exist in the pre-industrial world (e.g. water wheels, capstans, trebuchets), and there were apparently crude wood-and-wax or plain brass bushings that served the purpose.

But whence ball bearings? I suspect that the minimum technology to make a ball bearing possible is a lathe, as they are machined down from slugs cut from rod stock. Lathes have existed for millennia, but were certainly not widespread until the last few centuries. Likewise the technology to make ball bearings necessary, i.e. heavy machinery rotating at high speed, does not appear until the industrial revolution. Furthermore the size at which they would be useful for trap-laying indicates small-scale, high-speed applications. There is also the matter of the implied mass production of steel, such that a thousand of these things is just something one can get with relative ease (emphasis on the relative).

I understand the artificer class may find some use for them, but I believe the bag of ball bearings have been around since 1e. Their availability (not to mention their canonical naming) indicates a level of industrialization that I just don't see in the Forgotten Realms. Yes, they could be magically created yada yada, but magic is relatively rare and expensive, so why use the magic to make bearings when you could use it to do the thing?

To me, the economics of it just don't indicate the plausible widespread existence of ball bearings. Is there a canonical answer of which I'm unaware? I haven't seen this raised anywhere before, so I've seen no such answer.

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    \$\begingroup\$ Why are ball bearings so common in the Forgotten Realms? Someone screwed up a production run of bowling balls for gnomes and they are still knocking around the FR. \$\endgroup\$ Commented Sep 10, 2021 at 19:09
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    \$\begingroup\$ They wrote a specification in inches and we thought it was millimeters! Everyone knows gnomes use the metric system! \$\endgroup\$ Commented Sep 10, 2021 at 19:40
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    \$\begingroup\$ Ball bearings were used by ancient Romans: scirp.org/journal/paperinformation.aspx?paperid=92941 \$\endgroup\$
    – Vorbis
    Commented Sep 11, 2021 at 12:31
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    \$\begingroup\$ @yesterday true story: some people say "mil" and mean "millimetre" others say "mil" and mean "thousandth of an inch" so sometime the size is out by a factor of about forty. \$\endgroup\$
    – Jasen
    Commented Sep 12, 2021 at 8:14
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    \$\begingroup\$ Point of detail if I may. Ball bearings are not produced using a lathe, they are typically ground by an arrangement that preferentially removes any high spots. Since our own pre-industrial technology could produce telescope mirrors figured to within the wavelength of light, it's reasonable to assume that adequately-accurate ball bearings could also be produced: possibly by tumbling with an abrasive in the same way that semi-precious stones are rounded-up and polished. \$\endgroup\$ Commented Sep 12, 2021 at 20:41

5 Answers 5


I believe crude ball bearings would be made the same way as shot - by dropping rapidly cooling lead down a tower, so it solidifies mid-air as tiny spheres. Well within the tech range for D&D.

They would be useless at 5000rpm in my grinder, but perfectly fine for tripping orcs.

As for why they’d be common, if they’re effective for tripping orcs, then people would make them.

However - the name “ball bearing” is what we’d call them. In-universe, they’d almost certainly not be used as bearings (too crude), and would probably have been invented for use in combat, so would probably be called something like “goblin trippers”…

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    \$\begingroup\$ The information about ball bearing being made in shot towers is almost certainly correct - it's the easiest way imaginable to make round metal spheres. However, your argument that "if it's useful, people would make it" isn't a very satisfying explanation for their existing, because it would also justify everyone in the Forgotten Realms owning a smartphone, and they don't. \$\endgroup\$
    – GMJoe
    Commented Sep 10, 2021 at 23:08
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    \$\begingroup\$ @GMJoe No. it's a partial answer, which is bad. But the question included "aren't ball bearings too high tech for FR?", so this partial answer saying "no, they're fine at the given tech level" is on point and correct. \$\endgroup\$
    – fectin
    Commented Sep 10, 2021 at 23:31
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    \$\begingroup\$ According to Wikipedia, the shot tower is a far more recent technology than the lathe, invented only in the 1780's. Before that it's not clear how shot was made...maybe by casting? \$\endgroup\$
    – The Photon
    Commented Sep 12, 2021 at 2:46
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    \$\begingroup\$ @ThePhoton sure, but there’s nothing to stop people discovering it earlier, it doesn’t depend on loads of other technologies. \$\endgroup\$
    – Dan W
    Commented Sep 12, 2021 at 6:40
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    \$\begingroup\$ This is a common-sense answer that plausibly satisfies both the technological and economic aspects of the questions. Marking correct. \$\endgroup\$
    – Drew R
    Commented Sep 13, 2021 at 14:12

Gnomes are pretty famous throughout various editions and worlds of D&D for creating clockwork devices of greater or lesser complexity, which probably would involve developing various forms of bushing or bearing. Depending on the specific game, rock gnomes often function in a sort of quasi-industrial/magitech/mage-punk conceptual space. I wouldn't be surprised if they're the source of ball bearings in the Forgotten Realms, though I can't say I know of a specific source that states they are.

As far as mass production goes, it's worth remembering that fabrication magic can easily render a bar of raw steel into any form you need, including bazillions of BBs. 4th level spells may not be common, but how many casters would it take to get enormous numbers of these things hanging around?

That said, in prior editions, this item was called a "bag of marbles", and I suspect the change to "ball bearings" was primarily made for real-world reasons, to avoid the constant arguments about whether or not a giant would actually slip on glass marbles or just crush them into powder with its weight.

In general, a question like "why do ball bearings exist in D&D?" is probably in the same broad grouping with questions like "how can a thousand-year-old trap still be functional?" or "how does the ancient south american temple in Raiders of the Lost Ark have pneumatic dart guns?" where we invoke the MST3k Motto:

Repeat to yourself "It's just a show, I should really just relax."

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    \$\begingroup\$ That's fair enough, I suppose. I can stifle my innate objection-I-was-told-pedantry-was-an-accepted-practice-around-here in the face of MST3K's wisdom :D \$\endgroup\$
    – Drew R
    Commented Sep 10, 2021 at 20:04
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    \$\begingroup\$ Well, for what it's worth, the pedantry that usually circulates around here is of the "what the rules technically say" sort, rather than the "owlbears just don't make sense!" sort, which tends towards the opinion-based and "complaint disguised as a question" that we try to avoid. It's more rules lawyers and less Cinema Sins. \$\endgroup\$ Commented Sep 10, 2021 at 20:14
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    \$\begingroup\$ I don’t think “Gnomes are pretty famous throughout various editions and worlds of D&D for creating clockwork devices of greater or lesser complexity,” is true. As far as I can tell, only the Forgotten Realms has that property. Greyhawk gnomes are friendly, communal pranksters whose biggest engineering project is a dug-out burrow, Eberron gnomes are bureaucratic schemers whose greatest success in artifice is elemental binding, in Dark Sun the gnomes were all killed off by the Cleansing Wars and we know almost nothing about them prior to that. Ravenloft gnomes are extremely rare. Etc. \$\endgroup\$
    – KRyan
    Commented Sep 11, 2021 at 13:42
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    \$\begingroup\$ Tinker gnome of Krynn/Dragonlance are far more known/famous for this, and had the trait before it started to show up in Forgotten Realms in 3E \$\endgroup\$ Commented Sep 11, 2021 at 18:37
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    \$\begingroup\$ Fair enough, forgot about that—though to my mind, that’s just more proof that 5e is actually defaulting to FR no matter how much they protest that they are not. Planescape—you know, the D&D material that actually describes generalities across multiple D&D worlds and planes—does not describe gnomes that way, nor do literally any other D&D setting that I can find. \$\endgroup\$
    – KRyan
    Commented Sep 11, 2021 at 19:05

Dungeons & Dragons has always been anachronistic

Let’s leave to the side the philosophy of whether a fantasy world can even have anachronisms. If it’s there at this time then by definition it’s time appropriate in the fantasy, right?

Notwithstanding, the default setting of D&D is European late Medieval with magic. Sort of. Only not really. There’s plenty of stuff on every D&D price list that is Renaissance or Early Modern and a few that are obsolete by the late Medieval. Not to mention that the exhaustive (and exhausting) pole arm list in the AD&D PH covers over 500 years of military technology - it’s like having an M4 carbine next to an arquebus and calling them both guns; it’s correct but also very misleading.

The people who created the game engine that is D&D were not interested in cohesive and anachronism free world-building: partly because that it is the DM’s job to make the game but mostly because they didn’t care and put in whatever they enjoyed.


Notably, this is probably true only in the Forgotten Realms, among official D&D settings. Because the Forgotten Realms has Gond, deity of engineering and technology, and Lantan, the center of Gond worship and a gnomish nation of clockwork and smokepowder. Lantan has higher technological standards than is typical in D&D, and it is entirely plausible that the Lantans would have a use for, and the ability to create, ball bearings. Due to the fact that Gond is a major god known the world over, that wouldn’t be strictly limited to Lantan, either. As Dan W’s answer discusses, crude ball bearings could have been created even in lower-technology parts of the world, and due to Gond’s or Lantan’s influence, might term these “ball bearings” even if, say, they aren’t used for that purpose at all and are just meant as a tripping hazard.

But other settings don’t have Gond, and most lack any kind of equivalent. Eberron, maybe, produces and uses a certain number of them, but I doubt they’d be ubiquitous—the artificers there would generally prefer magic for that sort of thing.

So why is this item in the Player’s Handbook? That, I think, more than anything, reflects the way 5e kinda-sorta-but-not-really-we-swear defaults to the Forgotten Realms for things.

Contrast this with earlier editions. For instance, D&D 3e didn’t offer bags of “ball bearings” for use as a tripping hazard; the comparable item was a bag of marbles. Unlike ball bearings, marbles have been known for thousands of years (archaeologists identify what they believe to be some marbles from a site dated to 4,500 years ago). And unlike 5e which kinda-sorta defaults to the Forgotten Realms, 3e kinda-sorta defaults to Greyhawk. Greyhawk doesn’t have Gond, and its gnomes are friendly pranksters who aren’t known for any engineering more complicated than digging out their burrows.

Greyhawk’s gnomes form sort of the default for most settings, including 2e’s Planescape “meta-setting” that details all of the other planes beyond the Material, in which all of the other settings are found. Even Ravenloft’s gnomes—though rare in the extreme—follow a similar vein, though Ravenloft being what it is, they are known for what the book calls “graveyard humor.” We know nothing about the gnomes in Dark Sun—they were wiped out by the Cleansing Wars—but odds are good they would have roughly followed in the same mold, and even the ancient Rhul-thaun, who were non-magical masters of the world and all it contained, focused heavily on “biological” technology, and did little with machinery.

And, as mentioned, while Eberron could make and use ball bearings, they probably wouldn’t bother most of the time—they could more easily make a magical joint or axle that is just magically low-friction, if not actually frictionless. Consider that their answer to trains—the Lightning Rail—is a magical maglev train with no notable moving parts. Eberron’s gnomes are certainly industrious, and no small number of gnomish artificers exist, but they aren’t the place for artifice in that world—that would be House Cannith, which is based around the dragonmarked human d’Cannith family and its Mark of Making. The gnomes are known for being bureaucratic schemers—the gnomish d’Sivis family has the Mark of Scribing—and even their greatest accomplishment in artifice—elemental binding—is arguably as much a contract as it is a device.

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    \$\begingroup\$ You're forgetting the thinker gnomes of Mount Nevermind, in the Dragonlance campaign setting, whose penchant for way-too-complex-for-what-it-does machinery was a big part of their hat in that setting - they also made ball bearings, along with a bunch of other machine parts. That being said, your point that ball bearings are not appropriate to all settings is a good one. \$\endgroup\$
    – GMJoe
    Commented Sep 11, 2021 at 23:09
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    \$\begingroup\$ @GMJoe Not forgetting so much as not knowing, since I know little about Dragonlance (and the little I do know—primarily the kender—make me want to never go anywhere near it). But I’ll amend this answer to address that. \$\endgroup\$
    – KRyan
    Commented Sep 11, 2021 at 23:53

Since this is tagged as a lore question, I would like to highlight that the technology of the Forgotten Realms does not need to follow the same development path as the historical Earth; as the laws of physics are not the same. From the 1e FR campaign setting, DM’s Sourcebook of the Realms, page 9:

The physics of the Realms are slightly out of sync with the rest of the planes, so that gunpowder and many technological devices which operate on electronics do not function. Equivalent devices may be developed by player-characters. DM’s judgment is advised as to what may be allowed into the world.

A very similar statement can be found on page 9 of the 2e FRCS book Running the Realms. On a similar vein, 2e sourcebook Forgotten Realms Adventures states (pages 11-12):

Smoke powder, a magical powder similar to our gunpowder, functions in the Realms and has done so for hundreds of years, as evidenced by Kara-Turan rockets and small magical thundercrackers made for children. ... During the Time of Troubles, however, the Lantanese, whose state religion is the worship of Gond the Wondermaker, were taught how to make reasonably safe and accurate smoke powder weapons. As a result, examples of their new technology are now drifting into the heartlands.

These differences in the laws of physics, interference and limitations from the FR deities like Gond, as well as the presence of magic in general (as discussed in Is there an official reason the Forgotten Realms is stuck with “medieval” technology?), significantly change how and which technologies get developed and adopted when in the Forgotten Realms.

I find nimblewrights as an interesting example of this "different" technology tree, humanoid-shaped constructs which are quite agile unlike the older bulky golems. It is not hard to imagine that nimblewrights would benefit from ball bearings.


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