Straightening tonkin cane

[EricW]

Does anybody on here have any experience or wisdom to impart with regard to straightening the large diameter butt section of a cane pole. I am restoring one at the moment and it is not as straight as I would like. I could live with it if it is too difficult a job. I suspect it would not be as easy as straightening a split cane section with a heat gun, or is it? Any advice gratefully received.

[Catfish.017]

Eric, I've used heat on sections up to three quarters of an inch but nothing bigger. I would think it would be OK on larger diameters with care? Does the section you are working with have a general curve or is it kinked at a node?

[Old Man River]

I straighten poles up to about an inch and a quarter using a heat gun, it works pretty well, if you are careful, I have never tried straightenng anything larger.

If you search on Youtube you will see poles of up to about 4 inches dia being straightened using heat , so you should not have any problems.


David

[Watermole+]

Taking out the node offsets and curves between them is quite straightforward on large diameter bamboo but you will need to pierce the internal node dams first, otherwise they will split or go bang!

I presume that you are making a net handle? In which case, you will need a metal rod long enough to reach two or three nodes (work from both ends). I made a special drill for that purpose by fixing a small drill into a piece of metal tubing about two feet long or so, gripped in a drill chuck.
Failing that, use a metal rod as a punch and tap it through. As long as there is a small hole in each node for expanding gases to escape through, that's good enough.
You will also need a somewhere to hold the cane. A vice with a couple of wooden blocks with matching "half rounds" cut in each one, to act as 'soft' jaws, so that the vice will not crack the cane is ideal but always hold it as gentle as possible to avoid cracking as it expands.

A good heat source is essential. A really hot heat gun might do it, but I prefer a blowlamp which spreads a good heat over about three / four inches and doesn't concentrate it too locally, otherwise you will scorch the cane before it gets hot enough.

Thick gloves are also an absolute must. Bamboo can hold its heat for a long time! Scaffold Rigger's gloves should be OK but be careful.

Always start from the middle and move outwards, NEVER from one end to the other. Apply the heat to the relevant node, turning the cane so that it all heats up evenly.
If you can get it hot enough, bamboo will suddenly go very 'plastic' and bend easily. Hold in position until it has cooled a little so that it will not bend further. When you have straightened that particular part, move outward to the next, working as quickly as possible. Get the sections straight on each side of the nodes first; you can come back afterwards and straighten any curving in the actual section.

As you near each end, hot resin moisture will start steaming, then ooze from the bamboo wall. Be very careful as this can cause a nasty burn to the arms.

After you have straightened your cane pole, you can dress up any bad nodes will a coarse file and finish with sandpaper, always working along the grain and without twizzling it around in the hand. All scratches will show up!

If you want to scorch a pattern, do it at this stage with a butane lamp or similar-but do not concentrate the heat too long in one area.
Should any splits show up, you can run down a generous amount of resin wood glue inside and when dry, use proprietary filler on the outside.

Rub down well before applying finish and fix fittings. If you are fitting a pice of brass studding or a ferrule, make sure that it is well reinforced at that point. A piece of wooden dowelling is ideal, but do be sure to make it a slack fit and glue in with Araldite or a good wood glue. Gorilla glue is very strong but it expands as it dries and may split open the cane.

Polish with oil or varnish as desired..

Job done!

Regards from wm+

[EricW]

Thank you all for your helpful response. This is actually the butt of a roach pole rather than a net handle but it is all still relavent. Upon closer inspection, this section has several kinks in it between nodes and it looks as though it has born previous attempts at straightening. Rather than iron out all the kinks, I settled for getting it to turn fairly true between centres. I supported it at each end with the bow uppermost, and by applying heat with a hot air gun to the centre of the bow and applying downward pressure managed to even things out. FYI this pole was 40mm (1.5"+) in diameter and it took no more than 5 min to achieve an acceptable result, so thanks once again.