Diamond Coated Finger Bit 1-3/8" for Enlarging Tile Holes Review
A 1-3/8-inch diamond finger bit that enlarges, shapes and polishes holes in porcelain, marble, granite and stone.
| Diameter | 1-3/8 inch (35mm) |
|---|---|
| Work length | 50mm |
| Total length | 65mm |
| Coating | Diamond |
| Mount | 5/8-11 thread |
| Adapter | 3/8-inch hex included |
| Best for | Refining and enlarging holes in stone and tile |
Product Overview
This diamond-coated finger bit enlarges, shapes and rounds existing holes in porcelain, ceramic, marble, granite and stone. It suits tilers and stone workers refining cutouts for taps and fittings. The bit measures 1-3/8 inches across, with a 50mm work length and 65mm total length.
Diamond coating drives smooth, efficient milling wet or dry. It threads onto 5/8-11 angle grinders, and an included adapter lets it run on most electric drills.
Score Breakdown
This verdict is based on the manufacturer's stated specifications, the current Amazon listing and its product images, the confirmed materials and design, real buyer ratings, and our research into the product category. Scores are consistent editorial judgments, not laboratory measurements, and we did not receive a paid sample.
Key Features
Advanced coating for efficient milling and longer working life.
Enlarges, rounds and smooths existing holes to clean openings.
Runs in both modes to suit stone and tile jobs.
Mounts directly on standard angle grinders.
5/8-11 to 3/8-inch hex lets it run on most drills.
Design and Build Quality
The bit carries an advanced diamond coating over its 1-3/8-inch (35mm) diameter. The maker cites a 50mm work length and a 65mm total length, sized for milling and enlarging existing holes.
It is built for shaping holes on porcelain, hard ceramic, marble, granite and other natural stones. The coating supports both dry and wet applications for flexible use.
A 5/8-11 thread mounts the bit on standard angle grinders. An included 5/8-11 to 3/8-inch hex shank adapter also lets it run on most electric drills.
Performance in Everyday Use
The finger shape excels at refinement. It enlarges, rounds and smooths existing holes to clean, even openings across several sizes, which helps when fitting tap bodies or pipe.
Dual mounting adds value. Use it on an angle grinder for control and speed, or fit the adapter and run it from a drill. Wet use helps cut heat and dust on dense stone.
Honest limits apply. The maker recommends using it only to enlarge, shape or round predrilled holes, not to start fresh ones. Optimal RPM sits between 6000 and 11000, so tool speed matters for durability.
How It Performs: The Evidence
| Decision factor | What we found | Evidence and measurement | Score | Why it matters |
|---|---|---|---|---|
| Diamond coating | Advanced coating for efficie | Maker stated | 8.6 | Advanced coating for eff |
| Hole-shaping design | Enlarges, rounds and smooths | Maker stated | 8.6 | Enlarges, rounds and smo |
| Wet or dry use | Runs in both modes to suit s | Maker stated | 8.6 | Runs in both modes to su |
| 5/8-11 grinder thread | Mounts directly on standard | Maker stated | 8.6 | Mounts directly on stand |
| Included drill adapter | 5/8-11 to 3/8-inch hex lets | Maker stated | 8.6 | 5/8-11 to 3/8-inch hex l |
Who Should Buy It
- Enlarging tap cutouts
- Shaping porcelain holes
- Rounding stone openings
- Marble and granite work
- Grinder or drill use
- Drilling a hole from scratch
- Only for predrilled holes
- Best within 6000 to 11000 RPM
- Single 35mm diameter
- Specs are maker-stated, not tested
Full Specifications
How It Compares
| Feature | Generic | Typical budget | Premium option |
|---|---|---|---|
| Diameter | 1-3/8 inch (35mm) | Basic | Better |
| Work length | 50mm | Basic | Better |
| Total length | 65mm | Basic | Better |
| Coating | Diamond | Basic | Better |
Alternatives Worth a Look
This diamond finger bit is a focused finishing tool, and it does that job neatly. Enlarging, shaping and rounding existing holes in porcelain, marble and granite is exactly where it shines, and the diamond coating works wet or dry for cleaner cuts on dense stone. The dual mounting stands out: thread it onto a 5/8-11 grinder or fit the included adapter for a drill. Two points keep expectations honest. It is meant to refine predrilled holes, not start them, and it performs best between 6000 and 11000 RPM. All specs are maker-stated rather than tested here. For tilers and stone workers refining cutouts for taps and fittings, it fills a real gap in the kit.
Frequently Asked Questions
What does a diamond finger bit do
It enlarges, shapes and rounds existing holes in hard surfaces. Rather than starting a hole, it refines one you already drilled, smoothing and widening it to fit a tap, pipe or fitting. The diamond coating mills porcelain, marble, granite and stone to a clean, even opening in different sizes.
Can I use it on an angle grinder or a drill
Both. The bit has a 5/8-11 thread that mounts directly on standard angle grinders. The listing also includes a 5/8-11 to 3/8-inch hex shank adapter, so it fits most electric drills too. That dual mounting lets you pick the tool that gives you the best control for the job.
What materials can it shape
The maker lists porcelain, hard ceramic, marble, granite and other natural stones. It handles both dry and wet applications. Wet use is helpful on dense stone, cutting heat and dust. For best results and durability, keep the tool within the recommended speed range while milling.
What speed should I run it at
The maker recommends an RPM between 6000 and 11000 for optimal performance. Staying inside that range protects the diamond coating and gives cleaner milling. Running too fast can shorten the life of the bit, so check your grinder or drill speed before you start shaping a hole.
Can it drill a new hole from scratch
No. The maker specifically recommends using it only to enlarge, shape or round predrilled holes. It is a finishing and milling tool, not a starter bit. Drill your initial hole with an appropriate core or masonry bit first, then use this finger bit to refine and widen it.
This review is based on the maker's stated features and the product listing. Dimensions, coating, mounting and RPM guidance are reported as stated, not independently lab-tested. Any rating is an editorial score and does not represent a customer star-rating.