Tag Archives: drilling

Drill bits for bamboo, part 2

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drill bits for bamboo, forstner bit, triple cutterOn a recent trip to Japan I purchased a few more tools for working bamboo. Visiting yet another large home improvement store on the outskirts of Tokyo, the Star-M triple cutter was spotted. Not by me though: one of my kind and generous Tokyo hosts drew my attention to it. (Thanks Koh). I was too focused on locating more spurred drill bits to even notice the picture of a clean hole in bamboo on the packet.

drill bits for bamboo, forstner bitsWith a little online research it was identified, in English, as the Star-M triple cutter. It is listed in the special use category of the Star-M catalogue.  The drill bit is made in the style of a Forstner bit rather than the more common auger bit.

As a Forstner bit, the triple cutter requires more pressure than an auger bit, so it’s better suited to a drill press than a portable drill. In the absence of a drill press, I did, however, manage to drill a very neat, clean 10 mm hole in a section of dry bamboo using my portable drill without too much trouble. The small diameter probably helped here. And a measure of patience. I had to stop from time to time to clear the shavings from the hole that started to smoulder slightly. Overall though, I’m very pleased with the end result.

Although I couldn’t see any from Star-M, there are some with similar tips to the triple cutter. If you have your own drill press you probably already have a selection of Forstner bits. Do you have recommendations on the best Forstner bits for bamboo? Please leave a comment.

drill bits for bamboo, Star-M, forstner bitsThe Star-M catalogue makes for fascinating browsing (if you like drill bits). It also offers some tips on sharpening the bits. On the Star-M website you will also find this:

“The skilled workers grind the spur and cutting lip by hand one by one and confirm the sharpness”

Confidence inspiring.

Drill bits for bamboo

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Spur and screw point

Spur and screw point

Drilling holes in bamboo is not like drilling holes in wood. With the right drill bit a clean hole can be drilled. A drill bit with a spur, or wing, pre-cuts the bamboo, while the screw point keeps the drill bit where it is needed instead of sliding around on the smooth surface.

Messy exit wound

Messy exit wound

However, drilling right through a round piece of bamboo results in an messy, splintered exit wound where the smooth outer surface outer coating is cracked and split – no matter what drill bit is used. This is a problem discussed at length in a thread on Bamboo Forums if you’re interested in following the discourse.

Star-M packet

Bamboo is NOT kind to drill bits. Of the 2 drill bits I purchased – 4 & 6mm – the 6mm bit turned out to be one I used most, so it rapidly became blunt. The silica outer coating of bamboo blunts drill bits and knifes much faster than wood does.

At my request, some drill bits just arrived from Japan (Thanks Chris!) – I couldn’t find anything similar to replace the 6mm Star-M drill bit I purchased in a VERY large home improvement store on the outskirts of Tokyo this time last year. You can read about the Star-M drill bits in English here.

6mm peg, straight through

6mm bamboo peg, straight through

The freshly arrived drill bits were of two lengths – 16 cm, and the more standard 9cm. Left to my own devices, it would not have occurred to me to buy a 16cm long drill bit, but the long one was instantly handy for drilling straight through the rather scrappy and dry large bamboo that supports the seasonal shade cloth for the vege garden. Straight through. No more need to guess where that hole on the other side of the bamboo should be. (Thanks, Chris).

Have you got a friend in Japan who can dash off to the local hardware to pick up some drill bits for you? (Thanks again, Chris).