Bushings, Washers and Spacers: The Unglamorous 3D Prints That Stop Rattles, Wear and Corrosion
Nobody posts photos of a washer. But if you look closely at where a boat actually wears out, it is rarely the big part that fails first. It is the pin that has ovalled its hole, the stainless bolt that has turned an aluminium fitting to white powder, the block that rattles against the deck every time a wave passes. Bushings, washers and spacers are the parts that sit between two things and take the abuse so neither of them has to. They are also, by a wide margin, the most useful category of small 3D prints on board: cheap, fast, and almost always a better fit than anything in the chandlery drawer.
Three jobs, three different parts
It helps to be precise about what you are asking the part to do, because it changes the material and the tolerances.
- Bushing — a sleeve that lines a hole so a pin, bolt or shaft turns or slides inside it. Its job is to take wear and to centre the pin. Think tiller pivots, hinge pins, sheave axles, rudder stock bearings on a dinghy, the pin in a bow roller.
- Washer — a flat ring under a nut or bolt head. It spreads load over a larger area so the bolt does not crush laminate or timber, and it can electrically separate two dissimilar metals.
- Spacer — a fixed-length sleeve or block that holds two parts a set distance apart: a bracket off a curved cabin side, a cleat above a toe rail, a fitting clear of a weld bead. It is not meant to rotate or wear; it is meant to be exactly the right length.
A printed part can do any of the three, but a bushing needs a controlled bore and a low-friction material, a washer needs compressive strength and a flat face, and a spacer mostly needs an exact height and a face angle that matches the surface it lands on.
Why printed beats bought for these parts
Standard washers come in standard sizes. Boats do not. The pin on your 1990s traveller car is 7.9 mm because it was made in inches; the hole in the bracket you are lining is 12.3 mm because it has been wearing for twenty years. A printed bushing is drawn at 7.9 × 12.3 and prints in ten minutes. Try ordering that.
The second reason is isolation. Stainless fasteners through aluminium spars, bronze fittings on aluminium plates, a stainless backing plate under a steel bolt: every one of those pairs corrodes when seawater bridges them. A plastic washer or sleeve breaks the circuit. Marine suppliers sell nylon isolating washers, but only in the handful of sizes they stock. Printing gives you the exact bore and outer diameter for the fastener and the counterbore you actually have.
The third is that these parts are the perfect test of parametric files. Our Customisable Bushings & Washers file takes bore, outer diameter, length and an optional flange and generates the STL for those numbers. Type in what your calipers say, print, done. The same logic drives the parametric gaskets if you need a soft seal under the same fitting.
Sizing: the numbers that matter
Measure with calipers, not a ruler, and measure the worn part rather than trusting the drawing. Then apply these rules of thumb for FDM on PETG or nylon at 0.2 mm layers:
| Fit | Bore vs pin | Outer vs housing | Use |
|---|---|---|---|
| Running (rotates) | pin + 0.2 to 0.3 mm | housing − 0.1 mm (light press) | Sheave axles, hinge pins, tiller pivots |
| Sliding (slow, occasional) | pin + 0.15 mm | housing + 0.1 mm (slip fit, glued) | Bolt sleeves, lock pins |
| Isolating washer | bolt + 0.5 mm | free | Under nuts and heads on dissimilar metals |
| Spacer | bolt + 0.5 mm | free | Standoffs, packing under fittings |
Printed holes always come out slightly smaller than drawn because the perimeter bulges inward. If your printer is not calibrated, run the test piece in our tolerance calibration guide once and note the offset; it will be the same for every bushing you print afterwards. If a bore is still tight, a drill bit turned by hand or a reamer takes it to size cleanly. Do not force a pin: PETG cold-flows and the bushing will loosen in the housing instead.
Material and print settings
PETG is the default for washers and spacers: stiff enough, dimensionally reliable, fine with sun and salt for the few years you will get out of the part. Nylon (PA6 or PA12, ideally glass- or carbon-filled) is the material for bushings that actually rotate under load, because it is self-lubricating and does not creep under a preloaded bolt the way PETG does. ASA if the part sits in full sun on deck and you want colour stability. Avoid PLA for anything under a bolt: it creeps within weeks in a warm locker and your nut goes loose. The materials guide goes into the trade-offs in more depth.
Settings that matter for these parts specifically:
- Orientation. Print bushings and spacers standing up, bore vertical, so the bore is round and the compressive load runs through solid perimeters rather than across layer lines. Print washers flat. See print orientation and strength for the reasoning.
- Walls. 4 to 6 perimeters, or 100% infill on anything under 15 mm across. Sparse infill under a bolt head collapses.
- Top and bottom. 5+ solid layers so washer faces are flat and do not dish under load.
- Elephant's foot. Enable compensation, or chamfer the first 0.4 mm in the model, otherwise the bottom edge flares and the bushing will not seat.
- No supports. Design flanges so they sit on the bed; a flanged bushing prints flange-down with no overhangs.
Fitting them
A light press fit into a metal housing is fine for a plastic bushing: warm the housing with a hair dryer, chill the bushing in the fridge, push it in with a bolt and two large washers as a press. For anything that could walk out under vibration, a drop of thin CA or a marine epoxy on the outside diameter keeps it in place without affecting the bore. Grease a running bushing once with a PTFE or silicone grease; do not use petroleum greases on PETG or ASA, they soften both over time.
Washers under bolts on laminate should be paired with a proper backing plate or a large-area fender washer on the inside; a printed washer spreads load but it is not a substitute for backing. If you are bolting a printed part itself to the boat, the heat-set inserts and marine hardware article covers the fasteners.
Spacers deserve one extra step: measure the surface angle. A cabin side is rarely vertical, and a spacer cut square will load the bolt in bending. Most parametric spacer files, including ours, let you set a face angle so the standoff lands flat on the surface and square to the fitting.
Where they show up on a real boat
- Sleeves for the axles in printed sheaves and blocks, replacing worn bronze or missing plastic bearings.
- Isolating washers under stainless bolts on aluminium masts, booms, arches and davits.
- Standoffs that lift solar-panel rails, antenna brackets and instrument pods off curved or non-skid surfaces.
- Wear bushings in tiller heads, hatch hinges and the pins of bow rollers in the anchoring collection.
- Thick washers that stop a nut bottoming on a short bolt, saving a trip to the chandlery for one 60 mm M8.
Browse the small-hardware files in Deck & Rigging and Tools for more of these; several are free.
A note on safety
3D-printed parts are not certified marine equipment. A printed bushing or washer is a wear and isolating part, not a structural one: it should never be the component that stops a load-bearing fitting from pulling out, and it does not belong in steering, rig or through-hull assemblies where its failure could be dangerous. Check that the material suits the temperature, chemicals and loads at the location, inspect printed parts each season, and keep a spare in the kit. If you are unsure whether a part is suitable, write to us at info@marinelab3d.com with your measurements.