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Some thoughts on splitting bamboo

March 2, 2010

Splitting bamboo into workable strips is notoriously difficult initially but becomes almost second nature with experience. Here are some tips on how I approach it.

I start with the culm cut to length (a few inches longer than for the rod sections I will be making). I stand the culm vertically on the floor.

First mark off the intended splits on the base of the culm. To do so wrap a piece of paper around the culm to determine the circumference. Remove the paper and mark off on it the strip divisions with a ruler. Re-wrap the paper onto the culm and transcribe the strip divisions onto the cross-section of the culm. Alternatively you can eyeball the divisions if you have a good eye. I find I can judge relative distances fairly accurately, so often simply eyeball the divisions.

In order to keep the strip edges at the right angle it is important to keep your splitter perpendicular to the enamel of the bamboo i.e. running from the edge through the centre of the culm.

The first split into halves (or thirds)  is easy as the culm is still intact and you can visually line the splitter through its centre and through the middle of the check split.  For further splits, I stand the pieces vertically resting against a bench and draw in my mind an imaginary line through what would have been the centre of the culm. I line the splitter (a wide blade hunting knife or froe) with this imaginary line, rest it on the section and when I am sure all is aligned I then give the splitter a short sharp tap with a hammer to start the split. To ‘run’ the split I twist the knife (hence the need for a wide blade) and then slide it down the split – NEVER FORCE or DRIVE THE KNIFE/SPLITTER down the split. The twisting action is a rotational twist like you use with a screwdriver – i.e. torque. The twist should be just enough to open the split a little further and I then simply move the knife down the split. At the nodes some more force is required in the twist to break through the node. If you overtwist the splitter, the side of the split may move off perpendicular. Use just enough force to open the split and keep the splitter running through the imaginary line passing through the centre of the culm.

Once I have got strips narrow enough that it is possible to bend either either side of the split  away from the splitter as you split, it is then possible to control (‘walk’) the split down the centre.  At this point I mount a splitter (knife or old screwdriver with sharpened side) in a vice and feed the strips into the splitter rather than the splitter into the strips. Instead of twisting the knife I now push and pull the strips laterally against the knife, which is effectively the same thing as twisting the knife. Again NEVER DRIVE or FORCE THE STRIPS into the splitter. Only feed them in as far as the split easily allows before pushing and pulling again to open the split further. Doing this there is no chance of slipping and mashing your hand into the splitter as the force you are applying is at 90 deg to the strip/knife blade – not in the same line.

The big trick for getting even width strips is when the split starts to go off centre, to bend the strip as you work it against the knife. Work gently/slowly i.e. making short further splits until it is back on track. Bend the fat side of the strip away from the split. Bend the whole strip – both behind and ahead of the split – in this direction as you work it against the splitter. Once the split has been walked back into the centre carry on splitting as previously.

Doing the above it is possible to split a larger culm into 32 or even 36 pieces (for use on  lightweight rods as the strips get quite narrow).

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