How to Magnetize 3D Printed Miniatures for Weapon Swaps and Loadouts
Magnetizing printed miniatures so arms, weapons, heads, and turrets swap cleanly. Magnet sizing, drilling brittle resin without cracking it, and a polarity system that stops you gluing a magnet in backwards.
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Magnetizing is the step that turns one printed model into several. A captain with a magnetized weapon arm carries a power sword this week and a plasma pistol next week off one body. A vehicle with a magnetized turret covers three loadouts off one hull. The printer already removed the cost of extra models; magnets remove the cost of committing to one build.
It is also where printed parts get destroyed, because it means drilling into brittle cured resin with a bit nearly as wide as the part. This guide covers joint selection, magnet sizing, drilling without cracking, and the polarity system that prevents the one mistake you cannot undo. If you have not printed a miniature yet, start with the complete beginner’s guide to resin printing.
One scoping note before the steps. This guide is about magnetizing joints so parts swap. Magnetizing bases so models stick to a steel storage tray is a different job with different magnet sizes, and magnetizing terrain so tiles clip together is covered separately in the dungeon terrain tiles guide.
What Is Actually Worth Magnetizing
Every magnetized joint costs roughly ten to fifteen minutes and two magnets. Cheap on a vehicle, expensive across forty infantry, so decide deliberately rather than magnetizing everything you print.
Magnetize these:
- Weapon arms on models where the weapon is a real in-game choice
- Backpacks and jump packs, which are large, flat-faced, and trivially easy joints
- Vehicle turrets and sponsons, the highest-value magnetization on any model
- Heads, where the head signals a loadout or a rank
- Monster and character weapon options on a model expensive enough in print time that a second copy is not appealing
Skip these:
- Joints under about 4mm across. There is not enough material around the socket to survive drilling.
- Load-bearing joints. A magnet holding a leg to a base will fail during a game. Pin those instead.
- Anything you will only ever build one way. Most DnD character models fall here.
- Thin, gracile parts. Staffs, spear shafts, extended arms on gracile sculpts: the socket takes out most of the cross-section.
I use one test before picking up the pin vise: if I cannot name the second loadout I want off this model, I do not magnetize the joint. “Might be useful later” produces a lot of half-finished models with holes in them. On a Warhammer army, where loadout flexibility is the whole reason to print rather than buy, that calculus flips and most weapon arms earn it. The printer comparison for Warhammer 40k covers the build-volume side of printing at that scale.
Magnet Sizing
Neodymium magnets are sold by diameter and thickness in millimeters: a 3x1mm magnet is 3mm across and 1mm thick. Grades run N35 through N52, higher holding more strongly for the same size. N52 is common in hobby sizes and worth the small premium here.
| Joint | Magnet size | Notes |
|---|---|---|
| Infantry arms, small weapons | 2x1mm | Barely fits most 28-32mm arms; check the joint face first |
| Larger arms, backpacks, monster limbs | 3x1mm or 3x2mm | The most generally useful size to keep in stock |
| Heads, small turrets | 3x2mm | Enough hold for a part that gets handled often |
| Vehicle turrets, sponsons | 5x2mm or 6x2mm | Heavier parts need diameter, not just thickness |
| Movement trays, base-to-tray | 6x2mm | Different job; see the basing guide |
The rule that overrides the table: the magnet has to leave at least 1mm of resin around it in the joint face. Measure the smallest of the two mating faces and size down from there. A 3mm magnet in a 4mm arm socket leaves half a millimeter of wall on each side and blows out sideways the moment the drill bit wanders.
A mixed pack of small neodymium discs in 2mm and 3mm is the sensible first purchase, since you will not know which sizes a model needs until you are holding the parts. For vehicles, N52 discs in 5mm and 6mm neodymium discs cover everything above infantry scale. Buy more than you think you need; losing one to the carpet is a normal part of this hobby.
Step 1: Plan the Joint Before You Slice
The easiest magnetization is the one where you do not drill at all.
Check whether the STL already has sockets. A growing number of miniature files, especially vehicle and kitbash-oriented sets, ship with magnet sockets modeled in at standard sizes. Print those as designed, wash and cure the parts, and press-fit the magnets. No drilling, no wandering bit, no blowouts.
Separate the parts on the plate. If you plan to magnetize a joint, do not print the arm attached to the body. Split the parts in the slicer so both mating faces print as accessible, reasonably flat surfaces. A joint face that printed against a support forest is a rough face, and a rough face means a socket that is off-center before you start.
Orient with the joint in mind. Faces you plan to drill should not carry the heaviest support scarring, since you will be centering on them later. The orientation guide covers the general trade-offs; the extra rule here is just to keep joint faces clean.
Watch out for hollow interiors. If you hollow the model, the wall at a joint may be only 2-3mm thick. A 1mm-deep socket in a 2mm wall is fine; a 2mm socket breaks through into the cavity, and a magnet glued to a hole holds nothing. Check wall thickness at every joint you plan to magnetize, or leave those areas solid.
Step 2: Set Up Your Tools
The kit list is short and mostly overlaps with the repair kit:
- A hand-turned pin vise with bits matched to your magnet diameters. Buy a bit for each magnet size you stock, not a “close enough” bit.
- Gel cyanoacrylate glue. Gel, not thin. Thin CA wicks straight past the magnet and into the joint face, where it cures as a lump that stops the parts sitting flush.
- A hobby knife for marking centers and scraping paint off magnet faces later.
- Flush cutters for trimming any plug or rod you use in a repair.
- Nitrile gloves. CA bonds skin instantly, and a recently printed model can still hold uncured resin in recesses. Handling rules are in the resin safety guide.
- Magnification, optional but useful. Centering a 2mm socket in a 4mm wrist is guesswork at arm’s length.
Do not use a power drill. A powered bit grabs brittle resin, torques the part, and cracks it. Hand-turning is not a limitation, it is the mechanism: you feel the resistance change as you approach the far wall, which is the only warning you get before breaking through.
Step 3: Mark and Drill the Socket
Work one joint at a time and finish both halves before moving on.
- Dry-fit the parts and note how they align. Some joints only sit right at one rotation, and the sockets need centering relative to that alignment, not to the geometric center of the face.
- Mark the center of each face with a knife tip. Press hard enough to leave a divot. The divot is what stops the bit skating across a smooth cured surface on the first turn.
- Start the bit perpendicular to the face. Not perpendicular to the model, perpendicular to the face you are drilling. An angled socket seats the magnet at an angle and the joint sits crooked forever.
- Turn slowly and back out often. Every three or four turns, pull the bit out and clear the resin dust. Packed dust in the flutes generates heat and pushes the bit sideways.
- Check depth against the magnet itself. Drop the magnet in the socket. You want it to sit flush with the surface or a hair below it. Deeper than that and the hold weakens noticeably; shallower and the joint stands open.
- Repeat on the mating face, matching depth and center.
If a bit breaks through into a hollow cavity or the socket wall blows out, stop. Fill the hole with a short length of brass or plastic rod and gel CA, trim it flush once cured, and re-drill into the solid plug. It is the same rod-and-glue repair used for snapped weapons in the broken miniature repair guide, applied preemptively.
Step 4: Polarity, Before Any Glue Comes Out
This is the step that separates a magnetized model from a ruined one, and it takes ten seconds to get right.
Two magnets glued in with the same pole facing out will repel each other. There is no way to tell which pole is facing out once a magnet is cured into a socket, no way to see the difference on a loose magnet, and no realistic way to pull a CA-glued magnet out of brittle resin without destroying the socket around it. This mistake is permanent at the part level.
The fix is a convention plus a stack:
- Pick a rule and never break it. Mine: magnets in the body present north, magnets in the removable part present south. Which way round does not matter. Consistency does, because it means any arm you magnetize fits any body you magnetize.
- Work from a stack, not a pile. Every magnet in a stack has the same pole facing the same direction along the column, so taking from the same end every time handles polarity structurally rather than by attention.
- Mark the exposed end. A dot of permanent marker on the free face tells you which end you are taking from. Re-mark after each magnet.
- Seat directly off the stack. Bring the socket to the stack and let the end magnet separate as you pull away. More reliable than picking up a loose magnet off the bench, where it may have flipped.
For a joint where the two halves must also line up rotationally, magnets alone will not do it: the parts are free to spin. Either use two magnets per side, or use one magnet plus a short pin in a second hole to key the rotation.
Step 5: Glue the Magnets In
Put the glue in the socket, not on the magnet. A small drop of gel CA at the bottom of the hole, then press the magnet in from the marked stack.
Three things to watch:
Flush or slightly below. A magnet standing proud holds the parts apart. Once painted, that gap reads as a visible seam. If the magnet will not seat flush, deepen the socket rather than pressing harder.
Wipe squeeze-out immediately. Gel CA that squeezes onto the joint face cures into a bump that does exactly what a proud magnet does. A cotton bud clears it in the first few seconds and nothing clears it afterward.
Keep the two halves apart while wet. Bringing a magnetized part near its mate before the glue cures can pull the magnet straight back out of the socket. Gel CA sets in seconds but reaches strength over minutes, and the first swap test puts direct tension on the bond.
Step 6: Test, Then Paint
Fit the parts together and pick the model up by the removable piece. If the body drops, the magnets are undersized for the weight and the joint needs a larger diameter, not a thicker magnet. Test every swap you actually intend to use, not just the first one.
Then paint the parts separately, and keep paint off the magnet faces. This matters more than it sounds like it should: magnetic force falls off sharply with distance, so at 2-3mm scale a couple of coats on both faces is a real gap, and a joint that held firmly bare will sag once painted. Mask the faces or angle them away from the spray, and scrape overspray off with a hobby knife before final assembly. The full sequence is in the painting guide for 3D printed resin miniatures.
Common Problems
The joint holds, but the part spins. One magnet per side is a pivot. Add a second magnet, or drill a small pin hole alongside the magnet and glue a short brass rod into one half to key the rotation.
The magnets repel. One of them went in backwards. The practical fix is to drill out the smaller or less visible of the two, plug the hole with rod and CA, re-drill, and reseat from the marked stack. Prevention is genuinely cheaper here than repair.
The hold is weak on a heavy part. Diameter contributes more than thickness. Go from 3x2mm to 5x2mm before you reach for a thicker magnet of the same width, and make sure both faces are actually meeting flat rather than resting on a raised paint edge.
The socket blew out the side of the arm. The magnet was too wide for the joint. Plug, re-drill at the next size down, and accept the smaller magnet.
The magnet sank too deep. Glue a second magnet on top of it, oriented to attract so the stack stays together, and file it flush. This is a legitimate fix, not a bodge, provided the top magnet ends up flush.
Magnetized Bases and Movement Trays
Same tools, different job. A 6x2mm magnet in the underside of a 32mm base, paired with a steel sheet in a movement tray or transport case, keeps ranked infantry aligned and stops a unit sliding around in a bag.
The detail that matters is timing: the magnet goes in during basing, before basing material and paint, because retrofitting means drilling up into a finished base. The basing guide covers the sequence, and the magnet recess slots in at the start of it.
Is It Worth the Time?
For infantry, honestly, only sometimes. Fifteen minutes per model across a unit of twenty is five hours, and printing a second unit with different weapons costs a few dollars of resin and no attention at all. That is the trade-off nobody buying models has to make: magnets buy flexibility, but a duplicate print buys the same flexibility with time you are not sitting at the desk for.
Magnetization clearly wins on the expensive stuff: a vehicle, a monster, a centerpiece that takes eight hours to print and a weekend to paint. There, magnetizing the turret or the weapon arms means one paint job serves three loadouts, and the paint job is the part you cannot print a second copy of.
That is the line I would draw. Magnetize where the painting is expensive; print duplicates where only the resin is.