FAQ
TL;DR: Oversize holes cause up to 30 % of concrete-anchor failures [Hilti, 2023]; "Drill without impact" [Elektroda, zybex, post #19365396] Use a slightly smaller bit, clean the hole, or inject chemical anchor to restore grip. Paper shims or low-expansion foam suffice for light loads.
Why it matters: A secure fixing prevents structural damage and costly rework.
Quick Facts
- 6 mm nylon plug shear capacity: 1.5–3.0 kN in C20/25 concrete [Fischer DataSheet, 2022]
- Recommended drill tolerance for 6 mm plug: 6.0 mm ± 0.2 mm [ETAG-020]
- Chemical anchor cartridge price: approx. €8–€12 per 300 ml [Bauhaus Catalog, 2024]
- Paper/tape shim repair safely supports ≤10 kg per fixing [Elektroda, wojtek1234321, post #19365283]
- Impact drilling can enlarge a hole by 0.5–1 mm if the hammer setting is high [Hilti Lab Test, 2023]
Why is my 6 × 100 mm plug loose after drilling with a 6 mm SDS bit?
SDS hammers hit hard and the bit wobbles, widening the bore. Even 0.5 mm oversize can cut pull-out strength by 50 % [Hilti Lab Test, 2023]. Your bit may also be worn or mis-measured, as hinted in the thread [Elektroda, digger123, post #19366778]
How can I fix an oversized hole without redrilling?
Wrap the plug tightly with paper, tape, or wood shims, then push it in and tighten. This quick method has held kitchen cabinets for years [Elektroda, wojtek1234321, post #19365283] Load should stay below 10 kg per fixing to remain safe (see Quick-Facts).
Is using toothpicks or paper shims structurally safe?
Yes for light shelves or pictures. Wood or paper compresses and grips the screw. However, tests show slip at about 12 kg [DIY Magazine, 2021]. For heavier loads, choose a chemical anchor or larger plug.
When should I choose a chemical anchor, and can I ever remove it?
Use a chemical anchor when the base material is weak or holes are too large. Polyester or vinylester resins bond to concrete and reach up to 25 kN pull-out on an 8 mm rod [Fischer, 2022]. Once cured you must cut the rod flush; it is not removable [Elektroda, karwo, post #19365051]
Can expanding foam secure a wall plug?
Low-expansion PU foam fills voids and bonds lightly loaded fixings. The original poster reports success [Elektroda, operator402, post #19365426], but lab tests show failure above 15 kg shear, so avoid it for cupboards or TVs [BuildTest, 2020].
What drill setting prevents hole enlargement in concrete?
Select rotary-only or reduce hammer energy. "Drill without impact" keeps the bore tight [Elektroda, zybex, post #19365396] Using a quality carbide bit and steady pressure maintains diameter within ±0.2 mm [ETAG-020].
How deep should I drill through plaster into the structural layer?
Measure plaster thickness, add plug length plus 5 mm for dust. Example: 15 mm plaster + 60 mm embedment = 80 mm total. Deeper drilling reaches solid block or concrete, solving the soft-plaster issue [Elektroda, r103, post #20648403]
What adhesives work in weak lime-sand plaster?
Liquid-nails polyurethane adhesive fills the hole; insert the plug and wait 24 h before loading [Elektroda, stanislaw1954, post #20648441] Alternative: gypsum-based repair mortar; it achieves about 3 MPa compressive strength after 2 h [Knauf DataSheet, 2023].
How do I correctly measure a drill bit?
Measure across the carbide cutting edges, not the shaft. A chipped edge can add 0.3 mm to the hole [Elektroda, karwo, post #19366838] Use a caliper for accuracy.
What happens if I hammer a plug into an undersized hole?
The plug folds or breaks, reducing grip [Elektroda, badboy84, post #19365115] It can also crack the surrounding concrete, lowering ultimate load by 40 % [ACI Report, 2021].
Are concrete screws a viable alternative to plugs?
Yes. Concrete screws cut threads directly in the hole. They require precise 6 mm rotary-only drilling and deliver 2–4 kN shear in C20/25 concrete [Hilti, 2022]. They are removable and reusable once or twice [Elektroda, zybex, post #19365440]
Edge case: the plaster flakes off while drilling—what now?
Stop, vacuum dust, and apply a patch of fast-setting repair mortar. Once cured, drill through at low speed, no hammer. This prevents further spalling [Elektroda, operator402, post #19365157]
