Hammer-In / Nail Anchor

Nail in anchors and knock in anchors

A nail in anchor, also called a knock in or hammer in anchor, goes through the part being fixed into a drilled hole and is set with a hammer: driving the pin down the body expands it against the wall of the hole. There is nothing to screw, so it is quick for repetitive fixing, and Hobson notes the nail-in anchor becomes tamper resistant once installed. Hobson lists its nail-in anchors for signage, pipe and conduit saddles, shelf brackets and switch boxes, for electricians and plumbers.

This page covers five kinds:

• •Nail-in anchors with a zinc alloy or nylon body, mushroom or round head. The nylon body insulates between the pin and the work surface, and comes with a steel or 304 stainless pin.
• •H-IT mushroom and countersunk anchors: all-steel hammer set anchors for concrete, solid brick or stone and core filled block, which Hobson lists as suitable for tamper proof applications. Mechanical galvanised AISI 1040 carbon steel, or 316 stainless in the mushroom head.
• •H-IT tie wire anchors: a hammer set anchor with a hole for tie wire (6.0mm in the 5mm anchor, 7.3mm in the 6.5mm). Hobson's sheet marks them for internal use only.
• •H-IT splice wedge anchors: all-metal, pre-assembled hammer set anchors for light duty fixing to concrete, which Hobson lists for hangers for ceilings, cable trays and pipes, and for plasterboard tracks and battens. The H-IT PRO version has a European Technical Assessment, ETA 19/0351.
• •Mungo hammer screws: the MNA is a nylon plug with its screw already fitted, driven home with a hammer, with a PZ2, PZ3 or T25 head. MNA-G has a large collar, MNA-S a countersunk collar and MNA-Z a cylindrical collar; the MNAR-S has an A2 (304) stainless screw. Hobson also lists the Mungo MEN express nail (6mm) and the MSN steel nail (listed as 12 x 30), with no further data for either.

Which hammer in anchor to use

Hobson publishes no structural rating for any anchor on this page, and the H-IT PRO assessment covers non-structural use only. For anything holding people, a balustrade, a handrail, a heavy load overhead or a structural member, use the anchor the engineer or designer specifies, such as a rated screw bolt, sleeve anchor or chemical anchor.

• •Conduit clips, pipe saddles, switch boxes and signs on brick or concrete: zinc or nylon nail-in anchors, or MNA hammer screws.
• •A fixing that is hard to undo: the H-IT mushroom or countersunk anchors, which Hobson lists as suitable for tamper proof applications.
• •Thicker parts: the longest MNA-S and MNA-Z hammer screws fix through up to 100mm (8mm) or 110mm (10mm MNA-S), and the H-IT countersunk anchors through up to 65mm. Hobson publishes no loads for these, so they are not for structural fixing, and battens that carry ceilings, linings or cladding need the anchor the designer specifies.
• •Suspended ceilings, cable trays and services hung under a concrete slab: use the anchor the ceiling or services designer specifies. Of the anchors on this page, only the H-IT PRO splice wedge is assessed for this (redundant non-structural systems, in dry internal conditions, designed by an engineer).
• •Fixings in the weather, wet areas or near the sea: the 316 H-IT mushroom anchor. Hobson gives installation data for the 5 and 6.5mm sizes but none for the 10 x 75, so the data on this page does not cover that one. See the finish section below.

H-IT anchor drill size, embedment and fixture thickness

Hobson's H-IT data sheets give the installation data below. The drill is the same diameter as the anchor, 5.0 or 6.5mm. Maximum fixture is the thickest part the anchor can fix through while still reaching its minimum embedment. Select a row to open that anchor in the selector.

The H-IT tie wire anchors use a 5.0mm drill with 20mm minimum embedment (5mm anchor, 34mm long, 10.3mm head width) or a 6.5mm drill with 25mm embedment (6.5mm anchor, 30mm long, 13.5mm head width).

Hobson's H-IT sheets also print tension and shear figures by concrete strength, but do not say whether they are working or ultimate loads, so we do not publish them.

Nail in anchor hole size and working loads

Hobson publishes installation data and working loads for the zinc alloy mushroom nail-in anchors only. These working loads are for 32MPa concrete. The sheet gives no edge distance, spacing or member thickness, so do not apply the figures near an edge, between closely spaced anchors or in thin concrete without the designer's check.

Hobson's nylon nail-in sheets list sizes, uses and base materials (concrete, brick and stone) but publish no hole size, embedment or loads. Check the pack or ask us before you drill.

Splice wedge anchors: H-IT mini and H-IT PRO

The H-IT splice wedge mini uses a 6mm drill and a 7mm hole in the fixture, and has a 15mm head. Hobson's sheet gives the data below for 32MPa concrete. The characteristic tensile strength is the 5% fractile (95% probability of being exceeded, at 90% confidence) and the permissible working load, in tension only, applies a safety factor of 2.5 to it. Hobson gives no shear figure. Hobson tested with a fixture at least 13mm thick to make room for the pull-out plate, and gives no minimum member thickness.

H-IT PRO splice wedge: what the ETA covers

The H-IT PRO splice wedge (6 x 40) is covered by European Technical Assessment ETA 19/0351 and labelled ETAG 001 Part 6, with fire resistance assessed in the ETA (Hobson's label says "fire rated"). Hobson lists it for multiple use in non-structural applications in cracked and non-cracked concrete, overhead fixing, suspended ceilings, wire hangers, substructures and ventilation, and as conforming to AS 5216:2018. From the ETA:

• •Drill 6mm in rotary hammer mode, at least 40mm deep, for an effective embedment of at least 32mm. Clearance hole in the fixture 7mm; fixture 0 to 5mm thick for the 6 x 40.
• •Minimum concrete member thickness 80mm, minimum spacing 200mm, minimum edge distance 150mm.
• •Normal weight concrete C20/25 to C50/60, cracked or uncracked, for redundant non-structural systems under static or quasi-static loads, in dry internal conditions only.
• •Characteristic resistance in any load direction 3.0kN (design method C to EN 1992-4, installation safety factor 1.2). These are characteristic values for the designer, not working loads.
• •Characteristic resistance under fire exposure 0.41kN at R30, 0.30kN at R60, 0.19kN at R90 and 0.14kN at R120, at 200mm spacing and 150mm edge distance (300mm if fire attack is from more than one side). Reaction to fire class A1.
• •It is set when it will drive no further and no more than 2.5mm of shank stands proud, and may only be set once. Anchorages are designed under the responsibility of an engineer experienced in anchorages and concrete.
• •Also for the designer, from the ETA: installation by appropriately qualified personnel under the supervision of the person responsible for technical matters on site; under fire exposure, it must be ensured that local spalling of the concrete cover does not occur, and the ETA recommends a partial safety factor γM,fi of 1.0 in the absence of other national regulations; for shear with a lever arm (such as a stand-off fixing), the characteristic bending moment M0Rk,s is 3.68Nm with a partial safety factor γMs of 1.25.

Edge distance, spacing and concrete thickness

Every hammer set anchor needs room around it: too close to an edge or to the next anchor and the concrete can break out. These are the minimums Hobson publishes; closer than this, or in a thinner member than the ETA allows, the published data does not apply.

Hobson publishes no edge distance, spacing or member thickness for the zinc or nylon nail-in anchors, the 316 H-IT 10 x 75, or the Mungo MNA, MEN and MSN fixings in the documents we have. That does not mean they are unaffected by edges: ask the designer, or ask us, before fixing near an edge or close together.

Every nail in anchor and hammer screw we carry

Mungo hammer screws are sold as diameter x length / usable length in mm. Mungo's dictionary calls the usable length tfix: the thickness of fixture the plug fixes through. A 6 x 40/10 is a 6mm plug, 40mm long, for a fixture up to 10mm thick. Hobson publishes no drill size, hole depth or loads for the MNA, MEN or MSN in the documents we have; check the pack or ask us.

Select a row to open that type and size in the selector, then pick the length.

Zinc, galvanised or stainless: indoors and outdoors

Hobson's coatings chart rates zinc plating (5μm) as low corrosion resistance, for indoor and non-corrosive environments, and its corrosion guide for metal connectors calls for stainless steel (304 or 316) or hot dip galvanising wherever a fixing is exposed to weather and rain, such as decks, pergolas and open sub-floors. Mungo's dictionary says zinc coated steel anchors are for indoor fixings, not wet rooms, and that external use, wet rooms, humid industrial areas and locations close to the sea need A4 (316) stainless.

The H-IT data sheets give the mechanical galvanised coating as 4.0μm minimum on the mushroom anchor and 5.0μm on the countersunk anchor, about the same as zinc plating, so treat those like zinc: dry, indoor work. For fixings exposed to the weather, use the 316 stainless H-IT mushroom anchor. The MNAR-S has an A2 (304) screw: Hobson's connector guide accepts 304 for exposed work in most zones, but it is not the A4 grade Mungo calls for outside, and within 2m of a pool edge Hobson's guide lists 316 only.

The H-IT PRO assessment covers dry internal conditions only, and Hobson marks the H-IT tie wire anchor for internal use only. Even 316 is not made to sit in seawater: the stainless steel article Hobson publishes says it stays bright where it is washed by rain or maintained, and can visibly corrode where salt spray builds up.

How to fit a nail in anchor

1. Where the part needs a larger hole, drill it first: 6mm (5mm zinc nail-in) or 7.5mm (6.5mm zinc nail-in), and 7mm for the splice wedges. Then hold the part in place and drill through it into the concrete or masonry at the anchor diameter: 5.0 or 6.5mm for H-IT and zinc nail-in anchors, 6mm for splice wedges (rotary hammer drilling for the H-IT PRO, per its ETA).
2. Drill to the hole depth for that anchor. Splice wedge mini: 50mm for the 6 x 35 and 80mm for the 6 x 65 (Hobson sheet 1901221DS). H-IT PRO: at least 40mm (ETA 19/0351). H-IT and zinc nail-in anchors: Hobson's sheets give a minimum embedment but no hole depth, so drill deep enough to take the whole length of anchor below the part (anchor length less the part thickness), and check that length is at least the minimum embedment in the tables above. Hobson publishes no hole depth for the Mungo fixings or the 316 H-IT 10 x 75; check the pack or ask us.
3. Push the anchor through the part into the hole until the head sits on the part.
4. Hammer the pin or shank home. Hobson describes the pin sliding down the stem and expanding the anchor against the wall of the hole. The H-IT PRO is set when it will drive no further and no more than 2.5mm of shank stands proud, and may only be set once.
5. Check the part is held tight.

Nail in anchors in Adelaide

Allmat supplies nail in anchors, splice wedge anchors, hammer screws and masonry drill bits to electricians, plumbers, ceiling fixers, builders 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