GRAHAM’S GUIDE TO BONSAI POWER CARVING TOOLS

INTRODUCTION
CHOOSING POWER TOOLS
CHOOSING CUTTERS – SHAFT DIAMETERS
CHOOSING CUTTERS
BLOCK CARVING TOOLS FOR SMALL SHAFT MACHINES
BLOCK CARVING TOOLS FOR LARGE SHAFT MACHINES
ABRASIVE CUTTING AND FINISHING TOOLS
TUNGSTEN CARBIDE OR HIGH SPEED STEEL ?
CLEANING CARVING TOOLS
SO WHAT’S IN YOUR TOOLS BOX?
SAFETY PRECAUTIONS

 

INTRODUCTION
The choice of wood carving tools available today is vast. Before spending money it is important to ascertain which tools are right for the job you need to do. There are some unique facets to carving bonsai that are not of concern to conventional wood carvers and these largely dictate how we work. Therefore not all wood carving tools are suitable for use in bonsai carving work. Consider that often the wood we are carving can still be green and alive. Also we have to carve types of wood not well suited to regular wood carving, like pine and larch that are soft resinous woods. Sometimes the wood can be degraded by decay and fungal activity; we also have to deal with stripping bark, either alive or dead. So, I would like to differentiate the types of carving tools into two main groups……

ABRASIVE ACTION TOOLS.
I.e. Structured tooth tools, flap wheels, rasps and wire brushes.
These are great tools for finishing work, smoothing, graining and texturing.

CHIP CARVING TOOLS.
I.e. Tools with a small number of large cutting ‘teeth’ Weasels, Terrier and Samurai type tools and fast cut burrs.
These tools remove lots of wood quickly and are used for shaping and hollowing in many forms.
 

CHOOSING POWER TOOLS
Because we are considering power carving we are going to need a machine to ‘power’ the cutters we choose. Our choice of machine is largely dependent on the size of work to be completed. For instance it would be possible to create a huge hollow in a massive trunked bonsai with a small hobby machine using a micro burr but you might be very old before the work is complete!

It is important to bear in mind the running speeds of our tools. Most chip cutting tools have an optimal running speed of between 10-18,000 RPM. So things like electric drills are woefully inadequate. Smaller cutters and abrasives will on average run better at 15-25,000 RPM. Tiny abrasives like diamond points are best at 30-45,000 RPM. Always follow the guidance supplied with the cutting bit you are using.

Power carving machines can be divided into two main categories for our purposes.
Larger machines will run cutters having a ¼” shaft to mount them.
Smaller machines will run cutters having a 1/8” shaft to mount them into the business end.
Obviously this is not an absolute distinction but it serves our purpose. For instance a machine that can handle a ¼” shaft bit can be adapted easily to run a 1/8” shaft bit. However a small machine like a Dremel or hobby tool does not have the capacity or the power to run the large cutters.
A flexible shaft machine like the Foredom SR is capable of handling tools with shaft sizes from 3\32” to ¼”. However due to the considerable cost of this excellent unit I assume that by the time you are considering buying one you will be well versed in the subject.

If you are new to bonsai carving work I would recommend starting out with a small machine like our “Hobby Tool” or something like a Dremel. With the right attachments this will allow you to complete some fair sized projects on small to medium sized bonsai. You will have the chance to gain experience with power carving and the benefits it can bring to your bonsai without spending a fortune. Also consider that your money will not be wasted because, even if you choose to move to a larger machine in the future, your small machine will still be needed for detailing and finishing once the large unit has done it’s work. A flexible shaft can also be purchased to add to these smaller machines. Once you gain confidence with using this attachment I wager it will become a permanent fixture of your bonsai workshop.

Small machines do have their limitations in terms of the size of cutters they can run and also their ‘duty cycle’ i.e. how long they can run without a cooling off period. For large projects on big bonsai trees you are going to have to invest in a powerful machine designed for the job. Something like the Makita GD0600 or Metabo G700 may seem expensive but consider that these are full cycle industrial machines designed to run day in day out for years with very little maintenance. The Makita is a lighter weight machine with less power that does not have the benefit of adjustable speed, which precludes it running wire brushes and abrasive flap wheels. However it is a perennial favourite with bonsai carving experts across the world. The machines relatively light weight; slim design and operating speed make it our most popular “entry level” power tool. By comparison the Metabo is a big heavy brute but its variable speed control makes it more versatile. I would guess you are only ever going to need to buy the Metabo once and by the time it’s worn out you will be too old to care ;-))

So as a rule of thumb, large machines for large work and the small machines for small projects, detailing and finishing work.

 

CHOOSING CUTTERS – SHAFT DIAMETERS
Our choice of cutting bits is dictated firstly by what power tool we have and for all practical purposes can be divided into categories based on shaft size. The shaft is the part of the cutting bit that actually mounts into the power tool. It is very important to make sure the bit is well secured into the machine for safety. Cutting bits move at very high velocity and can come out of a machine at high speed, obviously if this happens the risk of personal injury can be severe and the results very serious indeed. Also if a bit is not mounted properly in the machine it can vibrate badly, this can cause damage to the machine, the cutter and the work. Collets are rarely cheap but using the wrong one could end with a visit to the hospital so don’t try to ‘make do’. Buy the right part for the tool you are using, keep them clean, lightly greased and replace if broken. BE SMART!

Cutters usually mount in high-speed power tools by virtue of a collet. This is a small precision part with a bore that should exactly match the shaft of the cutter being used. With the shaft of the tool inserted into the collet it will clamp itself tight onto the bit when the securing nut is tightened. Most small power tools use a collet of 1/8” or 3.2mm. This is a safe and strong enough shaft to run smaller chip cutting bits and abrasives. There is also a 3/32” 2.35mm commonly available but this is really only suited to small abrasives and micro cutters. Most small machines are supplied with collets of these sizes. Larger power tools generally come with a 6mm collet. This will mount European tools with a 6mm shaft, however it is NOT suitable for securing ¼” tools. It is a common miss-conception that ¼” and 6mm tools are interchangeable. However ¼” is in fact 6.35mm and a 6mm collet will not accommodate that extra fraction of a millimetre. It may be possible to force the larger shaft a little way into the collet but this can damage the collet and is VERY DANGEROUS. Conversely it is possible to mount a 6mm bit into a ¼” collet and generally the collet will take up the slack when tightened. However the cutter will have excessive run out (will not run true) and this WILL cause damage to the bearings in your machine in time.

 

CHOOSING CUTTERS
If you are carving a project from scratch (as opposed to refining existing work) you will need to begin with what I like to call block carving, or roughing out. This involves creating a rough shape and opening up hollows. This work requires chip-carving tools, which remove bark and wood quickly without clogging.
 

BLOCK CARVING TOOLS FOR SMALL SHAFT MACHINES
WEASEL 100 OR 101A - Cuts fast and clean and removes wood faster than any other tool suited to small power units. Cuts out hollows and allows external shaping with ease.

WEASEL 100 or 101B - Removes wood quickly but allows for a higher level of detail, graining and layering. Can be used to make ‘cracks’ and splits in wood.

WEASEL 100 or 101C - Removes wood as fast as A if drawn sideways. Its unique structure allows it to make three parallel grooves in one pass that gives a nice grain appearance to external surfaces.

CARBIDE DETAIL CUTTER – Removes material both from the front and sides. Allows the removal of lots of wood with the accuracy of a pen. A great cutter for use after roughing out with the Weasels. available in larger and smaller sizes.

 

BLOCK CARVING TOOLS FOR LARGE SHAFT MACHINES

THE TERRIER – An all new cutter specifically designed by us for bonsai carving work. Three replaceable cutting inserts on the small versatile head simply vaporise wood without effort. You can create shapes curves, sweeps and hollows almost effortlessly as wood vanishes in front of the tool. A very refined and easygoing tool without any hint of aggression in it’s cutting performance. The long shaft makes this one of the most versatile power carving tools in the world. Guaranteed to be a revelation this new tool will become the standard by which all others are judged. Available from March 2008.

WEASEL 102 OR 103A - Cuts fast and clean. Cuts out hollows and allows external shaping with ease. A very robust cutting edge makes this an ideal tool to use where contaminated wood is being carved, for instance where there may be traces of sand or stones trapped within the wood (roots).

WEASEL 102 OR 103B – Removes wood quickly but allows for a higher level of detail, graining and layering. Can be used to make ‘cracks’ and splits in wood.

WEASEL 102B - Removes wood as fast as A if drawn sideways. Its unique structure allows it to make three parallel grooves in one pass that gives a nice grain appearance to external surfaces.

4” END MILL – Incredibly fast removal of any wood hard or soft. A little aggressive when new but this tool goes where others cannot.

FAST CUT BURRS – Various patterns of these cutters are on offer from bull nose, ball shapes and cones. A very efficient tools for carving harder types of wood. Very refined and smooth cutting action.

TORNADO CHAINSAW DISK – Probably the best tool made for carving soft resinous woods like pine and larch. A very smooth cutting action.

PROTEUS - a nice new tool that bridges the gap between chip cutting bits and abrasives. The end of the tool consists of two teeth that open up hollows very quickly. The side of the tool is a very coarse rasp that allows it to move sideways through wood in a very controlled manner.

 

ABRASIVE CUTTING AND FINISHING TOOLS
Once you have completed block carving work it’s time to create some detail and texture before burnishing the final result.
My own personal preference is to go from chip cutting bits to rasps and burrs to wire brushes and sanding flaps. These are available in large and small shaft versions. 

TERMITE BURRS – A variety of shapes and sizes. An aggressive abrasive action makes these tools ideal for sculpting and shaping after block carving work is complete.

MICRO BURRS – Fine cutting/abrasive action for surface detailing on a very small scale.

SANDING DRUMS AND FLAPS – Before using these I tend to run over the work with a small gas torch to dry the surface of the wood and remove wood fibres. Good tools for smoothing and taking out cutting tool marks.

ROTARY WIRE BRUSHES – Available with mild or aggressive action depending upon the length and thickness of the wire incorporated. Use at a fairly slow speed with the grain.

 

TUNGSTEN CARBIDE OR HIGH SPEED STEEL ?
Over the years I have used hundreds of different tools for bonsai power carving work. I categorically recommend using only tungsten carbide tools. They cost a lot more than their steel equivalents but will last indefinitely if used with care and consideration. High-speed steel will quickly lose its edge, especially where it becomes very hot in use. Because of the intricate nature of the tools sharpening is rarely successful. Blunt tools tend to need more applied pressure to cut and that’s when accidents happen. My advice is only to buy and use tungsten carbide tools for bonsai carving work.

 

CLEANING CARVING TOOLS
Bonsai carving work creates some unique problems for power carvers. One of these is the tendency for cutting bits to clog or ‘load up’ due to their working temperature and the often sappy or resinous nature of green wood. Keeping tools clean means they cut more easily without you having to apply excess pressure, this helps avoid accidents and breakages. Clean tools also run cooler which extends their life and reduces the load on your power unit.
Because tools have intricate cutting edges we cannot recommend using any type of abrasive cleaners such as wire brushes. It is certainly NOT a good idea to burn deposits from the tools. Our detergent TOOL CLEANER is a highly efficient solution that will remove the most stubborn deposits. Simply pour a little cleaner into a tiny container and soak tools overnight. Contamination can simply be wiped away with an adsorbent cloth and your tools will be as good as new.

SO WHAT’S IN YOUR TOOLS BOX?
My own collection of tools is a rag tag assortment of bits collected over a number of years.
For power I use one of our Hobby Tools with a flexible shaft permanently attached and an old Makita 906. I also use a Metabo G700

Bits for the small machine include…
Weasel 100A 101B and 101C,
Carbide Detail cutter in 2 sizes.
Termite Burrs in 2 patterns,
Pinnacle, small wire brushes, sanding drum kit and sanding flap wheels.

For the larger machines I have…
Tungsten Tornado (no longer available – replaced by The Terrier)
Tempest (no longer available)
Weasel 102B and 103 A & B
4” end mill & Proteus
¼” round burr and bull nose
Rotary wire brushes.

 

SAFETY PRECAUTIONS
Never take risks with any form of power tools.
Ensure cutting bits are mounted safely in your machine.
Never use a broken or ill-fitting collet.
Always wear eye or full-face protection.
Take precautions against breathing dust.
Never exceed manufacturers recommended operating speed with any cutting bits.
Do not use excess force to drive a cutter.
Ensure power tools and cutters are well maintained and store safely when not in use.
Keep power tools and cutting bits away from children.
Always be mindful of bystanders when using power tools.

Graham Potter.
© Kaizen Bonsai Ltd 02/2008