Rotary Tool Bits Explained: A Beginner’s Guide to Cutting, Sanding & Polishing
- Nest Alpha
- 2 minutes ago
- 4 min read
You finally bought a rotary tool. You opened the hard plastic case, excited to start your first project, and were immediately greeted by a chaotic jumble of metal tips, sandpaper barrels, and weird-looking orange stones.
It looks less like a tool kit and more like a dentist’s nightmare.
A rotary tool is the "Swiss Army Knife" of the DIY world, but it is useless if you don't know which bit does what. Use a wood bit on ceramic tile? You’ll ruin the project. Use a wire brush at max speed? You might send metal bristles flying across the room.
If you are looking to upgrade your actual tool, check out our hands-on review of the Best Cordless Rotary Tools, but if you just need to understand the accessories, read on.
This is your ultimate rotary tool bits guide to cutting, grinding, and polishing like a pro.
The Color Code: How to Read Dremel Bits
While there are many brands of bits (Dremel, Wen, generic), Dremel set the industry standard for color-coding. If you look at the packaging or the chart that came with your kit, you will see a color square next to the accessory.
Here is the cheat sheet:
Red: Cutting (Metal, plastic, wood)
Green: Grinding & Sharpening (Stone, glass, ceramic)
Orange: Grinding & Sharpening (Metal, rust)
Purple: Sanding (Wood, fiberglass)
Yellow: Cleaning & Polishing (Jewelry, silver, brass)
Teal/Blue: Carving & Engraving (Detail work)
Cutting Bits: The "Tiny Records" (Red)
These bits look like miniature vinyl records. They are designed to slice through material.
Look: Dark grey/black discs with a mesh pattern.
Best For: Cutting stripped screws, rusted bolts, sheet metal, and hard plastic.
Pro Tip: These are tough but can still shatter. Always keep the tool straight; if you tilt it while cutting, the disc will snap. Always wear eye protection. See OSHA Portable Power Tools Guide.
2. Thin Cut-Off Wheels
Look: Very thin, reddish-brown fragile discs.
Best For: Extremely fine cuts in wood or soft plastic.
Warning: These are extremely brittle. We recommend sticking to the fiberglass-reinforced version for most home repairs.
Sanding & Grinding: Smoothing Rough Edges
Once you make a cut, the edge will be sharp and jagged. This is where the sanding and grinding family comes in.
1. Sanding Drums (Purple)
Look: Little brown barrels of sandpaper that slide onto a rubber cylinder.
Best For: Shaping wood, removing heavy rust from garden tools, or smoothing down fiberglass.
Note: These are aggressive! Don't hold them in one spot too long, or you will gouge a divot into your wood.
2. Grinding Stones (Orange & Green)
Aluminum Oxide (Orange): Shaped like cones or cylinders. Use these on metals (sharpening lawn mower blades, axes, or screwdrivers).
Silicon Carbide (Green): Use these on hard, non-metallic materials like glass, ceramic tile, or stone.
Polishing: Making Metal Shine (Yellow)
Want to restore old jewelry, clean up a tarnished brass doorknob, or make a chrome faucet sparkle?
1. Felt Polishing Wheels
Look: Soft, white compressed cotton pads.
How to use: You must use them with Polishing Compound (that little tub of red or white paste in your kit). Spin the felt wheel into the paste first, then touch it to the metal. If you run it dry, you will burn the felt.
2. Wire Brushes
Look: Tiny brushes made of steel or brass bristles.
Best For: Cleaning electrical contacts, removing light rust, or cleaning up golf clubs.
Safety Rule: Keep the RPMs low (under 15,000). If you spin these too fast, the wires can fly off like little needles.
Carving & Engraving: The Fun Stuff (Teal/Blue)
This is where the artistry happens.
1. High-Speed Cutters
Look: Drill bits with unique heads (balls, cones, cylinders).
Best For: Carving out soft wood (like making a sign), shaping plastic, or hollowing out pumpkins.
2. Diamond Engraving Points
Look: Rough-textured, sparkly metal needles.
Best For: Etching your name into tools, engraving glass jars, or doing detail work on ceramic tiles.
The "Mandrel" Mystery Solved
Beginners often get confused because many bits (like the cut-off wheels and felt pads) have a hole in the middle but no stick attached.
You need a Mandrel.
A mandrel is simply the metal shank (shaft) that goes into the tool and holds the accessory.
Screw Mandrel (402): Has a tiny screw on top. You unscrew it, put the cut-off wheel or polishing felt on, and screw it back tightly.
Drum Mandrel: A rubber cylinder. You slide the sandpaper band over it, then tighten the screw on top to expand the rubber, holding the sandpaper in place.
Which Kit Should You Buy?
You don't need to buy every single bit in the hardware store aisle. Buying them individually is expensive ($5-$8 per pack).
For 95% of homeowners and DIYers, we recommend buying one comprehensive "All-Purpose" kit to start.
Our Top Pick: Dremel 710-08 All-Purpose Accessory Kit (160 Piece)
This kit is the "Goldilocks" set. It includes the mandatory EZ Lock mandrel (which makes changing cutting wheels much faster), plenty of sanding drums, and the polishing compound you need.
Whether you are fixing a leaky faucet or carving a wooden spoon, having the right bit turns a frustrating struggle into a satisfying project.
FAQs
Q: Do Dremel bits fit other brands?
A: Yes. The industry standard shank size is 1/8 inch. Dremel bits will fit perfectly in Milwaukee, Ryobi, Wen, and Black+Decker rotary tools.
Q: What speed should I use for polishing?
A: Always use low speed (5,000 - 10,000 RPM) for polishing. If you go too fast, the polishing compound will fling off, and you risk burning the material.
Q: Can I cut glass with a rotary tool? A: Yes, but you cannot use the standard red cutting discs. You must use a Diamond Wheel. Keep the glass wet with a little water to prevent it from cracking due to heat.
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