Concrete grinders for epoxy prep: types, brands and what fits the job

For epoxy prep you need a diamond grinder that leaves the profile the coating’s data sheet asks for, connected to a dust extractor. Four kinds do the work: hand-held grinders for edges, single-disc and dual-disc walk-behinds, and planetary grinders with three or more heads. For a garage, a 22-inch dual-disc walk-behind, which does about 400–500 sq ft an hour and costs $8,488 new, plus a 7-inch hand grinder for the edges does the job. Planetary grinders, at about $15,700–17,800 new, pay off on large commercial floors.

This guide compares the types, explains what separates them, matches them to jobs, and lists the brands you’ll run into. It’s part of the epoxy flooring equipment list; for renting, see the concrete grinder rental guide.

The types compared

Hand-held grinders

A 5- or 7-inch angle grinder with a diamond cup wheel and a dust shroud does the edge grinding: along walls, around posts, inside corners and on steps. It’s slow on open floor and hard to keep even, so it’s the companion to a walk-behind, not a replacement. Small walk-behind edgers exist too; EDCO’s 7-inch TMC-7E lists at $4,950.

Single-disc walk-behinds

One 10-inch head, suited to areas under about 1,500 sq ft. It strips mastic, thinset, paint and resin buildup, takes off thin urethane and epoxy coats, and smooths trowel marks and high spots. Its selling point for garage work is power: it plugs into a dedicated household outlet. Home Depot’s tool rental carries an EDCO 10-inch grinder.

Dual-disc walk-behinds

Two counter-rotating heads side by side, about 22 inches wide, doubling the single-disc’s output to about 400–500 sq ft an hour at a 1/32-inch depth. EDCO’s 2EC-NG comes with 80 lb of added weight, six 30-grit, medium-bond Double Dyma-Dots, and a vacuum port for 2- or 3-inch hose. It’s also what rental yards stock: the standard rental dual-disc is a 1.5-hp, 115-volt EDCO 2EC, renting for about $90–142 a day.

Planetary grinders

Three or more discs spin while the head they’re mounted on turns the other way. Husqvarna’s PG 5 has three grinding discs and a 4 kW motor and handles everything from coating removal to grinding and polishing concrete or stone; its chassis separates from the grinding head for transport. Planetary machines are heavier, need 200–240-volt power, and cost about $15,700–17,800 new for the 20-inch class, against about $350–425 a day to rent at specialty shops.

Alternatives: shot blasters and scarifiers

A shot blaster throws steel shot at the slab and recovers it, leaving a rougher, more uniform profile: anything from CSP 2 to CSP 9. An 8-inch walk-behind shot blaster is rated up to 350 sq ft an hour on 110 volts. Scarifiers cut the surface with rotating cutters and leave an aggressive profile that suits only thicker coatings. Neither is a first purchase for a garage business.

What separates one grinder from another

• Production rate. Going from a 10-inch single-disc to a 22-inch dual-disc doubles the output (200–250 sq ft an hour to 400–500). On a 2,000 sq ft shop floor, one pass takes 2,000 ÷ 500 to 2,000 ÷ 400 = 4–5 hours with the dual-disc against 2,000 ÷ 250 to 2,000 ÷ 200 = 8–10 hours with the single-disc.
• Weight on the heads. Diamonds cut with pressure. Walk-behinds carry bolted-on weight (80 lb on EDCO’s dual-disc; a weight tray on its single-disc); planetary machines carry their own mass (403 lb for the PG 5).
• Profile and finish. All of these can create a concrete surface profile suited to coatings with coarse metal-bond diamonds; planetary machines are also used for polishing. Grinding is a good option for thinner coatings; thicker systems may need a shot blaster.
• Power. 115 volts for single-disc and 1.5-hp dual-disc machines; 230 volts for the 3-hp dual-disc, heavy-duty and planetary machines.
• Dust port and shroud. EDCO’s Multi-Vac port takes a 2- or 3-inch hose; the PG 5 uses a floating steel shroud that follows the floor surface. Under OSHA’s silica standard, a floor grinder has to run with water or with the dust collection system its maker recommends; see dust extractors and OSHA’s silica rules.
• Tooling system. Tooling isn’t universal. Trapezoid tooling fits EDCO Magna-Trap and Lavina grinders; Husqvarna’s Redi Lock system takes rectangular tooling. The diamond tooling guide covers bonds and grits.

Matching the grinder to the extractor

OSHA’s silica rules treat the grinder and its dust collector as a pair, so choose them together:

• Walk-behinds. Use the dust collection system the grinder’s maker recommends, at its recommended airflow or more, with a 99%-efficient filter and a filter-cleaning mechanism. EDCO, for example, pairs its dual-disc with its 200-cfm VAC-200.
• Hand grinders. The collector needs at least 25 cfm per inch of wheel: 5 × 25 = 125 cfm for a 5-inch wheel, 7 × 25 = 175 cfm for a 7-inch. A compact 120-volt extractor rated at 124 cfm is short on paper for either.
• Planetary machines. Same rule, bigger numbers. The PG 5’s matching extractor is Husqvarna’s 224-cfm DE 130 H, and a pre-separator adds a first filter stage where there’s a lot of dust.

Rent or buy the extractor with the grinder, not after it. Dust extractors and OSHA’s silica rules covers the filter and airflow requirements in full.

What fits the job

The 1–2 hours per pass for a 400–800 sq ft garage is 400 ÷ 500 = 0.8 hours to 800 ÷ 400 = 2 hours at the dual-disc’s rated output, before edges, tooling changes and cleanup.

Brands you’ll see

Examples, not rankings or endorsements:

• EDCO (Frederick, Maryland): the Magna-Trap single-disc, dual-disc, heavy-duty and turbo grinders, the TMC-7 edger, and matching VAC-series vacuums. Its dual-disc is common in rental fleets.
• Husqvarna: planetary grinders including the PG 5; its catalog also includes HTC-branded grinders and Blastrac-branded shot blasters.
• Lavina (Superabrasive): planetary grinders, including 20-inch models that need 200–240-volt, 30-amp power.
• Diamatic: planetary grinders such as the BMG-555, rented by specialty supply houses.
• Blastrac: walk-behind shot blasters and dust collectors.

Rent or buy

Rent while you learn which jobs you’ll get; buy when you’re grinding most weeks. At $90–142 a day, an $8,488 dual-disc equals about 60–94 rental days (8,488 ÷ 142 = 59.8; 8,488 ÷ 90 = 94.3). The rent vs buy guide builds the full break-even, and the rent-vs-buy calculator runs it with your numbers.