Why we use PLA
A router jig has one technical job: hold geometry under load. When a router passes over the template, the material has to resist bending. Any flex in the jig is a bad radius in your fretboard. That single requirement drives the entire material choice.
This is how we evaluated the options, what the data said, and why every tool in our catalog is 3D printed in PLA.
The three specs that mattered
For a precision routing jig, three material properties matter more than the rest:
- Stiffness (flexural modulus and Young's modulus). How much the material resists bending under load. For a jig riding under a router, this is the single most important property.
- Dimensional stability. Whether the material holds its shape over time, through temperature swings, and under ambient humidity.
- Workability. Whether we can manufacture it consistently in-house at a price point that works for the catalog.
Impact resistance, ductility, and heat tolerance are secondary for this application. A jig lives on a workbench. It doesn't get dropped in traffic or baked in an engine bay.
What we compared
We tested PLA against the four most common FFF alternatives. Spec ranges are pulled from published filament data and confirmed through our own print testing.
| Material | Tensile Strength | Young's Modulus (stiffness) | Glass Transition | Moisture Absorption |
|---|---|---|---|---|
| PLA | 50–60 MPa | ~3,000 MPa | 55–60°C | Low |
| PETG | 40–50 MPa | ~2,000 MPa | 70–80°C | Low |
| ABS | 30–40 MPa | ~2,300 MPa | ~105°C | Low |
| Nylon (PA6/PA12) | 50–70 MPa | ~2,500 MPa (dry) | 50–70°C | High |
| PLA-CF | 70–80 MPa | ~6,000 MPa | 55–60°C | Low |
Sources: Ultimaker filament comparison · Protolabs Network PLA vs ABS data · 3DSourced FFF strength guide · Snapmaker mechanical property summary
Why PLA won on stiffness
Tensile strength measures how hard the material is to pull apart. That number gets quoted everywhere because it's easy to test. But tensile strength is not what a router jig needs to resist.
A router jig needs to resist bending. The relevant number is Young's modulus, or flexural modulus. At roughly 3,000 MPa, PLA is the stiffest of the common FFF filaments. PETG sits around two-thirds of that. Nylon drops further as soon as it picks up ambient moisture. ABS lands in between.
Stiffness determines whether the template stays flat or deflects under the cutter. More deflection means the bit cuts slightly off the intended path. The effect is small per pass and compounds across a full fretboard radius. The less the material flexes under working load, the more accurate the cut.
PLA's reputation as "brittle" is correctly reported and frequently misapplied. Brittleness means it fails by snapping rather than bending. For a jig, that's the desired behavior. The tool either works or it's obviously broken. A material that flexes 0.3mm under the router and springs back looks fine and produces bad work.
Why the alternatives didn't beat it
PETG and PLA+. Both materials trade stiffness for ductility. They survive drops better. They also deflect more under load, which is the exact failure mode a precision jig needs to avoid. "Tough PLA" and related products are engineered for applications where flex is tolerable. Jig work isn't one of them.
ABS. Higher heat resistance and better impact survival than PLA, but lower stiffness and a warping problem during manufacture that would hurt our dimensional tolerances. The heat resistance advantage is academic for workshop use.
Nylon. Strong and stiff on paper when dry, but hygroscopic. PA6 can absorb up to 3% of its weight in water from ambient humidity. That water changes the material's dimensions and drops its stiffness. A template that measures to spec in a dry shop and grows over a humid week in July is a template that stops doing its job. Nylon is a great material for gears and impact parts. It's the wrong material for precision geometry.
PLA-CF (carbon fiber). The one candidate that beat standard PLA on stiffness. We tested it and chose not to switch. Here's what we found.
The chopped carbon fibers that make PLA-CF stiffer also physically interfere with how the polymer bonds between layers. When a fresh layer extrudes on top of a previous one, the carbon fibers disrupt the polymer chains from diffusing across the layer interface. The result is reduced interlayer adhesion. Peer-reviewed FFF research has confirmed this: carbon-fiber PLA prints are stronger in the X and Y directions (along the layers) but weaker in the Z direction (across the layers) than standard PLA. A jig that's stiffer in plane but weaker at the layer line is a worse tool, not a better one.
On top of the layer-line problem, PLA-CF runs roughly triple the filament cost. Nozzle wear is a factor in general with CF filaments, which is why hardened steel nozzles are standard on our printers regardless of what we're running. For the tolerances our jigs need to hold, standard PLA is already inside the window. We tested PLA-CF, documented the results, and stayed on standard PLA.
Where PLA has real limits
No material is without tradeoffs. PLA has two.
Heat. PLA's glass transition sits between 55 and 60°C (approximately 130 to 140°F). Above that threshold, the material begins to soften. A PLA jig will deform if left in a hot car or near a heat source. For indoor workshop use at standard room temperature, it's well below its working limit.
Cold brittleness. Below freezing, PLA becomes more prone to cracking on impact. A dropped jig in an unheated garage in February is more likely to chip than the same jig dropped in July. If you're working in those conditions, handle the jig accordingly and know that our warranty covers the outcome either way.
What PLA is not
PLA is not metal. Machined tools made from cast iron, tool steel, or aluminum plate hold tighter tolerances over longer timeframes and survive punishment that a printed jig won't. Lie-Nielsen, Woodpeckers, and Veritas use those materials for their tools. That's an honest engineering tradeoff. Machined metal tools typically cost several times what a printed tool costs, and that pricing reflects real material and manufacturing cost.
We're not going to pretend PLA is what it isn't. It isn't cast iron. It isn't tool steel. It isn't aluminum. It is a precision-capable thermoplastic that holds the tolerances a luthier jig needs to hold, printed in-house, at a price point the machined-metal tool market doesn't serve.
Where we match or beat the established tool brands isn't on materials. It's on the things around the product: a lifetime warranty that covers accidents, direct support from the people who built the tool, and the speed at which we iterate and improve the design based on what customers tell us. The material choice is one piece of the product. The warranty and service are the rest.
How the warranty completes the picture
Material selection answers the engineering question. The warranty answers what happens if the material's limits matter to you anyway.
Every tool we ship is covered by our lifetime warranty. Not defects-only. Not with a time limit. If it breaks, we fix it or replace it. That includes drops, cracks, accidents, and age. We built the tool, we know what it is, and we stand behind it without fine print.
That warranty exists precisely because PLA has a failure mode. We're not pretending it doesn't. We're making sure that failure mode isn't your problem.
The short version
- PLA is the stiffest of the common FFF filaments, and stiffness is what a routing jig needs.
- PETG, PLA+, nylon, and ABS all flex more under load, or absorb moisture and lose dimensional accuracy.
- PLA-CF is stiffer in plane but weaker at the layer line. The fibers interfere with interlayer bonding. We tested it and rejected it.
- PLA's heat and cold limits are real but don't apply to most shop conditions. Warranty covers outcomes in the ones that do.
- We're not competing on material. We're competing on warranty, service, and iteration speed.
If you have more technical questions, reach out. We built the tool. We'll know the answer.