What are Dynabolts or Sleeve Anchors?

What are Dynabolts or Sleeve Anchors?

First off, lets get the names right, sleeve anchors are the description of a type of expansion bolt for masonry and concrete while dynabolts are a brand. Dynabolt is made by Ramset in Australia and the name has taken on every marketeers dream of becoming synonymous with all expanding anchor bolts, much in the same way hoover did for vacuum cleaners.

These excellent anchor bolts are very popular, mostly because they are simple to use and relatively inexpensive, their only downsides are :

they are difficult to get out again if you have to remove them
they are expansion bolts and so may crack weak bricks or concrete, especially near the edges
they shouldn’t be used in hollow brick or block walls (although often are) as they need solid surrounding masonry to tighten properly
they shouldn’t be used for heavy duty or heavy structural applications (although often are) as they are a medium duty anchor only
They get there name from the way they are made, they are based around a centre core bolt, with an expansion cone on the end, surrounded by a full length sleeve. When you tighten the head it pulls the centre bolt up into the sleeve and the cone expands it and provides the grip, the great thing about sleeve anchors is as the sleeve expands it grips up its full length instead of just at the end (as in most concrete anchors) so it spreads the load over a bigger distance making it OK to use in weaker materials such as brick and sandstone (that would shatter with other bolts).

Dynabolts are what’s called through fixings meaning you can position your item where you want it, say a large timber frame, drill through it and into the masonry and then tap in the bolt without moving the frame, it saves you the hassle of positioning, marking the holes, moving the frame while you drill and then trying to line up again on the exact spot to put the bolt in.

They come in standard versions with a nut head and also flush versions (with a bolt head) for fitting in areas where you need a low profile, to avoid trip hazards etc, they are also available in countersunk heads for door and window frames and such, however are often difficult to tighten because of the screwdriver type fitting. Materials are generally mild steel 4.6Gr sometimes up to 6.8Gr but not usually high tensile 8.8Gr, stainless steel is also very popular, finishes are zinc plated for general work and galvanised for external areas where corrosion might be a problem and for treated timbers.


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