Yes, you can reuse self-tapping screws in many situations, but the holding power drops every time you remove and reinsert one. How much it drops depends on the screw type, the material you’re driving into, and how many times the screw has been removed. In some cases, a reused screw holds nearly as well as a fresh one. In others, it barely grips at all.
Why Holding Power Drops With Each Reinsertion
A self-tapping screw works by creating its own threads in the material as you drive it in. Once you back it out, those threads are already carved into the hole. When you drive the same screw back in, it’s no longer cutting fresh material. Instead, it’s sitting in a channel that’s already been shaped, and the fit is slightly looser each time.
Research on screws reinserted into synthetic bone gives a clear picture of the decline. A single insertion produced about 1,167 newtons of pullout strength. After just one removal and reinsertion, that dropped to 768 newtons, a roughly 34% loss. By the fifth insertion, pullout strength collapsed to just 154 newtons, about 13% of the original. The pattern held across different materials: each cycle widened the hole slightly and reduced the screw’s grip.
Thread-Forming vs. Thread-Cutting Screws
Not all self-tapping screws lose grip at the same rate. The two main types behave differently when reused.
Thread-cutting screws have small flutes or notches that slice material away, producing tiny chips as you drive them. They go in easily with low torque, but the threads they create in the workpiece are weaker because material has been removed rather than compressed. That makes them more prone to stripping on reinsertion.
Thread-forming screws don’t cut material at all. They push it aside, cold-working the hole and creating compressed, work-hardened threads. This produces a tighter fit and higher pullout strength. Thread-forming screws generally create the strongest reusable threads, especially in metal, because the displaced material springs back slightly and maintains contact with the screw.
If you know ahead of time that you’ll need to remove and reinstall a screw, thread-forming types are the better choice.
Reuse in Metal vs. Plastic
Metal
Metal is the most forgiving material for screw reuse. The threads formed in the hole tend to hold their shape well, especially in softer metals like aluminum or mild steel sheet. A thread-forming screw driven into metal can often be removed and reinstalled a few times without serious loss of grip, as long as the hole hasn’t been visibly enlarged or the screw threads aren’t damaged.
The key factor is whether the hole has started to oval out or the threads inside it have deformed. If the screw still feels snug going back in and requires real torque to seat, the connection is likely still sound. If it spins freely or pulls in without resistance, the hole is stripped.
Plastic
Plastic is far less forgiving. Engineering guidelines for materials like acetal resin (commonly used in housings and enclosures) warn that backing out a fine-pitch screw will shear most of the threads in the plastic, making reuse of the same size screw impossible. The plastic doesn’t spring back the way metal does. Once the threads are destroyed, the hole is effectively smooth.
Coarser thread designs fare somewhat better in plastic because they engage more material, but the general rule is that self-tapping screws in plastic are good for one or two removal cycles at most. If you’re designing something that needs repeated disassembly in a plastic housing, threaded metal inserts are a far more reliable solution.
How to Tell if a Screw Is Still Usable
Before reinserting a self-tapping screw, inspect both the screw and the hole. On the screw itself, look for:
- Rounded thread crests. The sharp edges of the threads should still be well-defined. If they look rounded or flattened, the screw has lost its ability to grip.
- Flattened or bent threads. Any deflection or flattening means the screw was stressed beyond its design limits, often from cross-threading or overtightening.
- Corrosion or coating damage. Many self-tapping screws have a zinc or other protective coating. If that coating is scraped off or the screw shows rust, it will corrode faster on reinsertion and weaken the joint over time.
- Grooves or gashes on the shank. Deep marks from removal or material transfer from the workpiece can change the screw’s profile enough to reduce holding power.
For the hole, run your finger around the opening and look inside if possible. If the edges are crumbled, cracked (in plastic), or visibly wider than the original pilot hole, the material is compromised regardless of the screw’s condition.
Practical Tips for Successful Reuse
If you’re reinstalling a self-tapping screw and want the best possible hold, a few simple steps make a real difference. First, drive the screw back into the exact same hole at the same angle. The existing threads in the material are cut to match the screw’s pitch and orientation. Going in crooked creates a cross-threaded mess that strips out fast.
Second, don’t overtighten. The original insertion created peak clamping force. On reinsertion, you have less margin before the hole strips. Tighten until the screw is snug and the joint feels solid, then stop. If you’re using a power driver, drop the torque setting a notch from what you used the first time.
Third, consider going up one screw size if the hole feels loose. A slightly larger diameter screw will engage fresh material around the edges of the old hole. This is common practice in woodworking and sheet metal repair, and it works just as well with self-tapping screws in other materials.
Finally, if the joint is structural or safety-critical, use a new screw. The cost of a replacement is trivial compared to the cost of a failed connection. Self-tapping screws are inexpensive precisely because they’re designed as single-use fasteners in most engineering applications. Reuse is fine for non-critical assemblies like access panels, covers, brackets, and light-duty fixtures where a small loss of holding power won’t matter.