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20th April 2016

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Techniques: Using a Dynabolt to Remove a Blind Bush

Philip Packham shows us how to use an anchor bolt designed for construction to remove a worn bush from a blind hole. Norton Commando kickstart shaft, anyone?

A Dynabolt is an example of an anchor bot that uses a wedging effect to expand itself to grip the inside of a hole. Typically used in building construction and civil engineering, RealClassic reader Philip Packham has recently used one to extract the bush from the blind hole in the kickstart shaft on his Norton Commando. Here's how he did it.

Using a Dynabolt to Remove a Blind Bush

A typical Dynabolt is shown above. Tightening the hex-head at the top pulls the conical wedge at the bottom against the inside of the split sides of the sleeve, forcing them outwards. If the right diameter Dynabolt is inserted into a bush in a blind hole, it will grip the bush with tremendous force.

Using a Dynabolt to Remove a Blind Bush

Here's the kickstart shaft held in a vice, with an old socket spacing the Dynabolt and allowing the bolt room to pull the bush clear of the shaft.

Using a Dynabolt to Remove a Blind Bush
Dynabolts on Now...

An old mainshaft bearing was needed to give space for the final removal. Philip was a bit worried he'd break something but then it started to move.

Using a Dynabolt to Remove a Blind Bush

Above is the removed bush, with the expanded section of the Dynabolt on the right.

And below is the new bush, ready to be pressed into place.

Using a Dynabolt to Remove a Blind Bush

Dynabolts are available in a variety of diameters from your local hardware shop, eBay (see advert above) or Amazon.

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