Drop-In Anchor
Anchors · female anchor · drop in anchor · flush anchor
Definition: A drop-in anchor is a female expansion anchor hammered flush into a drilled hole, leaving a flush surface that receives a bolt — ideal where the anchor must not protrude.
Anatomy
■ Body■ Internal thread
Governing standards: ICC-ES AC193
Common Sizes
| Inch | Metric | Head width | Head height |
|---|---|---|---|
| 1/4-20 | M6 | 3/8 drill | 1-1/8 embed |
| 3/8-16 | M10 | 1/2 drill | 1-1/2 embed |
| 1/2-13 | M12 | 5/8 drill | 2 embed |
Representative sizes. Full dimensional data lives in the standards listed below.
Grades & Strength
| Grade | Material | Tensile (psi) | Marking |
|---|---|---|---|
| Zinc | zinc-plated steel | — | Indoor |
| Stainless | 304 stainless | — | Outdoor |
Materials
- Zinc-plated steel
- Stainless steel 304
Pros & Cons
Pros
- Sits flush — nothing to trip on
- Strong pull-out once set
- Bolt removable without losing the anchor
Cons
- Concrete only
- Needs a special setting tool
- Hard to remove if abandoned
Typical Uses
- Flush-mounted machine attachments
- Formwork and precast
- Handrails where no stud protrudes
- Concrete slab fixtures
Alternatives & Related
- Wedge Anchor — Stud-style anchor for maximum strength
- Sleeve Anchor — Works in brick and block too
Where to Buy
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FAQ
How do you install a drop-in anchor?
Drill to size, clean the hole, insert the anchor flush, and drive the internal plug with the setting tool to expand it. Thread the bolt in afterward.
Drop-in vs wedge anchor?
A drop-in anchor is female and flush, so the bolt can be removed and replaced; a wedge anchor is a permanent protruding stud. Both suit solid concrete.