Chemical vs mechanical anchors: how hole cleaning differs

Both need a clean hole, for different reasons. A chemical anchor holds because resin bonds to the hole wall, so dust on the wall weakens the bond, and its data sheet is usually strict about the cleaning method. A mechanical anchor holds in the hole itself, and dust left in the bottom can stop it reaching full embedment. The mechanical anchor data sheets we link name a vacuum as one way to remove the debris after brushing. The chemical ones specify blowing or compressed air, or a dustless or hollow bit drilling system.

How a chemical anchor holds

A chemical, or adhesive, anchor is a threaded stud set in injected resin. The resin fills the gap between the stud and the hole wall and bonds to the wall. That bond is the anchor. If drilling dust is left on the wall, the resin bonds to the dust instead of the concrete, and the anchor may not hold the way its data sheet says it should.

Chemical studs also go in a hole larger than the stud. Ramset [4] and Hilti [5] both give a 10 mm hole for an M8 stud, 12 mm for M10 and 14 mm for M12. Confirm against your product's data sheet.

What the chemical anchor data sheets say

• Ramset chemical anchoring: blow twice, brush twice, blow twice, brush twice, blow twice. A dustless drilling system is listed as an alternative.
• Hilti HIT-HY 200: a hammer drilled hole is to be cleaned with compressed air unless a hollow dust removal drill bit was used.

The two differ from each other, so read the one for the product in your hand. A vacuum nozzle does not replace compressed air cleaning or a hollow bit where the data sheet specifies them. What it can do is pull the bulk of the dust out first, into the vacuum drum rather than the air.

How a mechanical anchor holds

Mechanical anchors hold in the hole itself. A stud anchor such as the TruBolt and a sleeve anchor such as the DynaBolt Plus expand against the wall. A screw-in anchor such as the AnkaScrew cuts its own thread into the hole. None of them needs a bond, but they all need to go in to the depth the data sheet gives. Dust left in the bottom can stop them short of full embedment.

Screw-in anchors normally go in a hole the same size as the anchor. An 8 mm AnkaScrew goes in an 8 mm hole, as does a TruBolt M8 and a DynaBolt Plus M6.

What the mechanical anchor data sheets say

• Ramset TruBolt: clean the hole thoroughly with a hole brush, then remove debris with a hand pump, compressed air or a vacuum.
• Ramset AnkaScrew: brush thoroughly, then remove debris by vacuum, hand pump or compressed air.
• Ramset DynaBolt Plus: brush the hole, then remove debris by vacuum, hand pump or compressed air.

Here a vacuum is a named option. Brush first, then vacuum the loosened dust out with a nozzle sized to the hole.

Side by side

Which kit suits which job

We put the kits together around the anchors. The chemical anchor kit has the 10, 12 and 14 mm nozzles for M8, M10 and M12 studs. The mechanical anchor kit has 8, 10 and 12 mm for the common TruBolt, AnkaScrew and DynaBolt Plus sizes. The dust extractor set has 8, 12 and 14 mm for a mix of both. Each kit is $24.99 with free standard post in Australia.

• Milwaukee M18: chemical anchor kit, mechanical anchor kit
• DeWalt 35mm: chemical anchor kit, mechanical anchor kit
• Bosch GAS 35: chemical anchor kit, mechanical anchor kit
• Ryobi RVC: chemical anchor kit, mechanical anchor kit

Not sure which vacuum fitment you need? Check the compatibility page. For the full cleaning pattern, see the hole cleaning guide, and for quick answers the help centre.