License plate, trim and small automotive screws
Plate and trim screws look trivial until one snaps off in a bumper. A few minutes on size and material saves an hour with a drill.
License plate fittings
Vehicles vary by market and maker. Metric-market cars commonly use M5 or M6 machine screws into a captive nut or clip, while many others use a self-tapping screw of roughly 4.2 to 4.8 mm outside diameter driven into a plastic insert in the bumper.
Always check what is already in the car. A machine screw will not hold in a plastic plug, and a self-tapper forced into a threaded insert will ruin it.
Length is usually 15 to 25 mm — enough to pass through the plate and frame with a few threads to spare.
Choose stainless, not plated steel
Plate screws sit in road spray and salt for years. Stainless A2 is the minimum, A4 if you live near the coast or where roads are salted.
Nylon or plastic screws exist for plate frames and never rust, but they are only suitable where the plate is also supported by a frame.
A smear of anti-seize or grease on the threads means the next person can undo them.
Interior trim and small fittings
Interior panels mostly use thread-forming screws into plastic bosses, plus push clips. Reuse the original screws where you can — they have already formed a matching thread.
Where a screw is missing, match the outside diameter of a neighbouring screw rather than guessing, and never go up a size to fix a loose boss.
Snapped or seized screws
Penetrating fluid and patience first. Heat is risky near plastic bumpers and paint.
If the head shears, a screw extractor or a left-hand drill bit usually gets the shank out of a plastic insert. Replacement plate-mount inserts and rivnuts are inexpensive.
Do not over-tighten the replacement. Plate mounts are thin and strip easily.
Common questions
What size are license plate screws?
It depends on the vehicle. Metric fittings are commonly M5 or M6 machine screws into a captive nut, and many bumpers instead take a self-tapping screw of roughly 4.2 to 4.8 mm into a plastic insert. Check the fitting on your own car before buying.
What length license plate screw should I buy?
Long enough to pass through the plate and any frame and still engage the mount — 15 to 25 mm covers most cars. Too long can foul what is behind the bumper skin.
Should plate screws be stainless?
Yes. Plated steel screws rust into the mount within a couple of winters, and removing them then usually damages the mount.
Can I reuse the old screws?
If they are clean and not corroded, yes, and in plastic bosses reusing them is actually better because the thread already matches.
Keep reading
Tools and screws for this job
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Metric screw assortment kit
One box covering the sizes in this guide
Precision driver and bit set
The right bit is what stops rounded heads
Digital caliper
Measure before you buy anything