Heavy-Duty Shield Anchor

Heavy duty shield anchors: how they work

Mungo's HL is a torque-controlled expansion anchor: in Mungo's words, expansion is achieved by applying torque. As you tighten the nut or screw, the steel sleeve (the shield) expands against the sides of the hole. That is different from a hammer-set anchor, where a cone is hammered into the anchor body, and from a chemical anchor, which bonds to the base material with resin.

HL anchors come in three head styles. HL-B has a threaded bolt with a nut, so the fixture goes on over the bolt. HL-S has a hex head screw. HL-SK has a countersunk head for a countersunk fixture hole. Hobson lists the zinc plated anchors in carbon steel and the HL-B also in 316 (A4) stainless.

Heavy duty anchor sizes

Lengths are shown as Mungo labels them: 10 x 100/30 is a size 10 anchor 100mm long with a second figure of 30. The documents Hobson publishes for this page do not explain the size number or the second figure, and give no drill size for each size, so we make no claim from them: match the anchor you are replacing or the one the designer specifies. Select a row to open that anchor in the selector.

Edge distance, spacing, slab thickness and loads

Every load an anchor can carry depends on how far it sits from an edge, how close it is to the next anchor, how thick the concrete is and how deep it is set. For the HL range, none of those figures is in the documents Hobson publishes for this page, and neither are loads, installation torques or an ETA, seismic or fire approval. Mungo's fastening dictionary gives only the general rules: set the anchor to the recommended torque, never set it shallower than the minimum setting depth (plaster, flagstones and insulation do not count), consider the minimum edge distance to avoid failure of the base material, and space anchors in a group 3 times the setting depth apart to reach their full load.

So for anything structural or safety-critical, such as machinery, racking, steel base plates, handrails or anything that holds people or loads, use the anchor and values an engineer or designer specifies. If the job needs published approvals, Clawbolt PRO wedge anchors and the ETA-listed chemical anchors have them; see the links on this page.

Installing a heavy duty anchor

1. Get the drill size, hole depth, installation torque, edge distance, spacing and minimum concrete thickness for the exact HL size from the designer's specification.
2. Mark the holes, keeping to those edge distances and spacings.
3. Drill the hole to the diameter and depth in that specification (Mungo lists SDS hammer drilling for concrete and natural stone), and clean the dust out.
4. Set the anchor through the fixture, then tighten the nut or screw to the recommended torque with a torque wrench.

Zinc plated or 316 stainless?

Mungo's dictionary says zinc coated anchors (5 micron zinc) are for fixtures indoors, except wet rooms, and that outdoor work, wet rooms, humid industrial areas and sites close to the sea need A4 stainless (316). Hobson's finish guide likewise rates zinc plated for indoor and non-corrosive conditions only. On this page, that means the zinc plated HL anchors for dry indoor work and the 316 HL-B M12 x 131 for outside (finish only: the load data still has to come from the data sheet or designer).

Heavy duty anchors in Adelaide

Allmat supplies heavy duty anchors, wedge and sleeve anchors, chemical anchors and SDS drill bits to builders, steel fixers, installers and trade across Adelaide and South Australia. Add them to a quote with the rest of your list, and we will price the lot.

Questions