Milwaukee 5/32" x 6" SDS-PLUS 4-Cutter Rotary Hammer Drill Bit

Milwaukee’s 5/32” x 4” x 6” MX4 4-Cutter SDS-PLUS Rotary Hammer Drill Bit (model 48-20-7308) delivers up to 5x longer life in concrete with rebar — a critical performance gain for commercial contractors drilling anchor holes through reinforced concrete. The solid head carbide construction and 4-cutter geometry prevent lock-up in rebar, while variable flutes deliver up to 20% more holes per battery charge.

This bit matters for Montana contractors installing concrete anchors, drop-ins, and raw plugs in seismically active zones where rebar density runs high. The wear mark indicator shows when the bit no longer meets ANSI B212.15 requirements — essential for code-compliant anchor installations.

Performance in Rebar and Hard Aggregate

The solid head carbide delivers up to 5x longer life in concrete with rebar compared to standard SDS-PLUS bits. That’s not marketing fluff. Rebar guards provide maximum durability in hard aggregate and rebar, addressing the two materials that destroy standard bits fastest.

The 4-cutter design prevents lock-up in rebar, reducing downtime. Standard 2-cutter bits jam when they hit rebar at an angle. The 4-cutter geometry slices through rather than grabbing and stalling. For contractors drilling hundreds of anchor holes through unknown rebar patterns, that difference translates to hours saved per job.

Milwaukee designed their MX4 4-Cutter bits with sharp centering tips for exact spot drilling in concrete and metal decking. The tip starts precisely where you place it — no walking, no pilot holes, no oversized entry wounds that compromise anchor holding power.

Drilling Efficiency and Battery Runtime

Variable flutes remove dust faster, reducing heat and delivering up to 20% more holes per battery charge. Heat kills both batteries and bits. The variable flute design evacuates concrete dust more efficiently than standard spiral flutes, keeping the cutting zone cooler.

Twenty percent more holes per charge matters on remote Montana jobsites where the nearest outlet might be hundreds of feet away. It also matters when you’re 30 feet up setting anchors for seismic bracing — fewer trips down for battery swaps.

Specification	Value	Source
Diameter	5/32 in (0.156 in)	Manufacturer
Usable Length	4 in	Manufacturer
Overall Length	6 in	Manufacturer
Shank Type	SDS-PLUS	Manufacturer
Number of Cutters	4	Manufacturer
Material	Solid head carbide	Manufacturer
Weight	0.11 lb - 1.27 lb (varies by source reporting)	Manufacturer

Safety Compliance and ANSI Standards

The wear mark indicator on each drill bit shows when they no longer meet the ANSI requirement. The bit meets ANSI B212.15 (standard for common concrete anchors). This isn’t optional for commercial work — undersize holes compromise anchor holding power and fail inspection.

Most bits wear gradually, making it hard to judge when they’re out of spec. Milwaukee’s wear mark eliminates guesswork. When the indicator disappears, the bit goes in the scrap bin. No measuring, no judgment calls.

Replace bit when the wear-mark indicator is no longer visible to ensure compliance with anchor specifications. For contractors working on schools, hospitals, or any engineered structure, that visible compliance check prevents callbacks and liability.

Applications and Compatibility

These Milwaukee MX4 4-Cutter Drill Bits are ideal for concrete with rebar and masonry applications. Compatible with all SDS-PLUS rotary hammers, including Milwaukee M12, M18, and MX FUEL cordless systems, as well as other brands’ SDS-PLUS hammers.

The 5/32” diameter fills a specific niche — small-diameter concrete anchors, drop-ins, and raw plugs that don’t need massive holes. Think electrical box mounting, conduit clips, small bracket installations. The kind of repetitive drilling where bit life and battery runtime directly impact labor costs.

German Made: High-quality manufacturing standards. Milwaukee doesn’t specify which German factory, but their carbide bits typically come from facilities that also supply Hilti and Bosch — the companies that invented SDS technology.

Montana Contractor Verdict

Worth it for commercial contractors drilling anchor holes through rebar-reinforced concrete. The 5x longer life in rebar and 20% more holes per battery charge deliver measurable productivity gains. The ANSI wear indicator prevents compliance issues on engineered projects.

Drill bits are generally considered consumables and are not covered for wear and tear from normal use. Covered against manufacturing defects in material and workmanship under Milwaukee’s limited warranty, but don’t expect replacement for normal wear.

For residential contractors drilling the occasional anchor hole in unreinforced concrete, this bit’s capabilities exceed requirements. But for anyone doing commercial work — seismic retrofits, concrete anchor installations, metal deck attachments — the rebar performance and compliance features justify the premium.

Installation and Best Practices

Insert into any standard SDS-PLUS rotary hammer drill until it clicks into place. Apply steady pressure; do not force the bit. Let the tool do the work. Use the sharp centering tip for precise spot drilling without a pilot hole.

The 4-cutter design requires less feed pressure than 2-cutter bits — the additional cutting edges do more work per rotation. Forcing it defeats the efficiency gains and accelerates wear on both bit and hammer.

Frequently Asked Questions

What size anchors work with a 5/32” drill bit?

The 5/32” (0.156”) diameter works for small concrete anchors requiring pilot holes in that range. Always follow anchor manufacturer specifications for hole diameter.

How do I know when to replace this bit?

The wear mark indicator shows when the bit no longer meets ANSI requirements. When you can’t see the indicator mark, replace the bit to maintain anchor compliance.

Does the 4-cutter design work in standard hammers?

The bit is compatible with all SDS-PLUS rotary hammers. The 4-cutter design provides benefits regardless of hammer brand.

What’s the actual cutting length?

The usable length is 4 inches, with 6 inches overall length. That 4-inch working depth handles most anchor installations.

Why does the weight specification vary?

Weight ranges from 0.11 lb to 1.27 lb according to different source reporting. The discrepancy likely reflects whether packaging is included.