Broken record

Otago Polytechnic student-made saw stools can be safely used to support a working platform.

Our carpentry students build saw stools by hand and by machine as a learning exercise, and these are sold to cover the cost of materials. Timber saw stools are sometimes used to support planks for people to stand on while working. The required safety standard is that working platforms have to be able to carry a load of at least 240kg, but no one had tested the load-carrying performance of a saw stool.

Graham Burgess, Learning Leader for our Dunedin Carpentry team, worked out the specifications for a frame that would enable saw stools to be load-tested using our Dennison universal testing machine.  The steel frame was designed and fabricated by our Engineering Trades team including Tyler Benington and John Stocks. 

One of our Engineering Technologies students, Xiu Zhen (Gemma) Huang, then used this frame to test 30 saw stools, both handmade and machine made. Pressure was applied to the centre of each stool until it cracked, at which point Gemma recorded the pressure level. Gemma's work was supervised by Engineering Technology lecturers Tony Green and Robert Cooke, and supported by a Timber Design Association research scholarship.

The saw stools all withstood pressure equivalent to more than one tonne of weight, and some up to nearly three tonnes, so they easily satisfy the safety standard for load-carrying to support a working platform. Gemma produced a user guide to help people identify whether the results apply to their own saw stools.

November 2020