SDS Bit Selection for VACDRILL: Diameter, Length and Carbide Geometry (5–40 mm)
The bit is half the system. The wrong carbide, the wrong length, or the wrong shank wastes the accuracy the column was built to give you.
The operating window: 40 mm max, 200 mm long, 145 mm deep
VACDRILL accepts straight-shank SDS bits up to 40 mm diameter and 200 mm overall length, with a maximum usable drilling depth of 145 mm set by the column. That window covers the majority of post-installed anchor holes — M8 through M20 — plus MEP penetrations and dowelling.
Specifying a bit longer than 200 mm does not give more depth; the column bottoms out. Specifying a 45 mm bit does not fit the chuck. Stay inside the published window.
Bit length also affects rigidity. A short, stout bit resists deflection on hard aggregate better than a long, slender one. When the required depth is 80 mm, a 160 mm bit will typically run truer than a 260 mm bit.
Carbide heads: two-cutter vs four-cutter
Two-cutter heads cut aggressively and clear debris well. They suit soft-to-medium concrete and brick where speed matters and aggregate is forgiving.
Four-cutter (cross-head) carbides add secondary cutting edges that reduce jamming when the head strikes hard aggregate or rebar. On dense concrete above C35/45, or where occasional light reinforcement is expected, a four-cutter head materially reduces binding and the shock load transmitted to the anchor pad.
Use 90°-class carbide tolerances for anchor work: under-size holes cause binding and inadequate adhesive annulus; over-size holes reduce mechanical anchor bite. Reputable SDS bits are ground to tight diameter tolerance — avoid no-name bits where diameter is nominal only.
Core bits and diamond crowns
VACDRILL can run small diamond core bits within the diameter window for clean, round openings where a percussive bit would spall — for example MEP sleeves in finished concrete. Use a core bit rated for rotary (non-percussive) drilling and feed slowly.
Percussive core bits (carbide-tipped) are acceptable in brick and soft block but not in dense reinforced concrete, where diamond is the durable choice. A guided column is especially valuable with cores, where side-load ruins the cut.