I'm after, (if one exists) a tool which is capable of coring into 3 layers of railway sleepers (approx 450mm in length) to retrieve a 25mm diameter (approx) sample of the timber for a visual inspection of its condition.
you need to use an auger. they come in a multitude of lengths but i am not sure if you will find one quite that long. you will certainly be able to get a 25mm however. have a look online or go to your nearest decent tool shop. you may also find one in a timber or builders merchant.
Really an auger will only drill a hole and not retrieve a solid core sample of wood intact, only chips will be extracted.
There are circular saws available which will extract solid samples although as far as I am aware these will only give short lenghts, the length of the cutter.
They are core cutters intended for cutting metal, wood and plastics and are available in different diameters but usually come in kit form (hole saw kits); the one I have has 16, 20, 25, 32, 38 and 51mm cutters and two arbors to accommodate the different sizes.
Farnell Electronic Components and RS sell these
I use similar ones to cut through brick and use an extension shaft to go through cavity walls.
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