Article 15 – ‘Making bonsai clamps’

How to make adjustable clamps

The tools required for making clamps are:

  • a vice, hammer, centre punch, 8mm tap and holder, drill, 2.5mm, 5mm and 6.5 drill bits,

  • gas burner, heavy duty pliers or grips, a file, insulation tape and shrink wrap

The components needed to make the clamps are:

  • 1. 2 lengths of 4mm threaded bar approximately 130mm

  • 2. 1 length of 8mm threaded bar approximately 110mm

  • 3. 1 8mm threaded locking nut

  • 4. 1 length of 4mm threaded bar approximately 80mm

  • 5. 1 length of flat bar 120mm x 4mm x 25mm

  • 6. 1 piece of aluminum 30mm x 20mm x 5mm (The pressure plate)

  • 7. 2 washers 5mm holes

  • 8. 2 standard nuts 4mm (Do not use nylon locking nuts)

  • 9. 2 4mm wing or butterfly nuts

The blue shrink wrap is used to cover the threaded 4mm hook sections to protect the tree’s bark and your fingers when winding the clamps. See the illustration below.


Making the clamps

Cut the threaded bars to length and file down the burred ends

Measure 15mm in from each end of the holding bar (no. 5) and the centre line, use the punch on the marks to make an indentation for the drill bit to locate

Drill 3 holes where marked using the 2.5mm drill bit – this is your pilot hole. If you dispense with a pilot hole, the drill bit can wander and the holes will be out of alignment.

A bench drill is recommended, but if this is not available a battery/electric hand drill can be used. Making sure the drill is perpendicular, enlarge all 3 holes using the 5mm bit then enlarge the centre hole with the 6.5mm – file off any rough edges

Insert the 8mm bar into the locking nut (no. 3) till the end is just below the surface. Make a mark 5mm in from the end and carefully drill a hole (2.5mm drill bit) then enlarge using the 5mm. Insert the small 4mm bar (no. 4) and wrap insulation tape around the exposed ends just enough to stop it from falling out

Make a mark on the centre of the pressure plate, (no. 6) drill a pilot hole and enlarge with the 5mm and then 6.5mm. Make sure the hole is straight if the hole is on the skew the plate will not be able distribute pressure evenly

Put the holding bar (no. 5) in the vice and use the 8mm tap to cut a thread in the centre hole. Repeat the process on the pressure plate. File down any rough edges, insert the 8mm centre bar and screw on the pressure plate. Check to see that all is correctly aligned

Place the 2 x 4mm bars in the vice at the same height you need at least 70mm protruding upwards. Heat the bars till red hot and bend with the pliers or grips to get the first curve. When satisfied with the shape, spray with water to cool down

Repeat the process to form the rest of the hook shape making sure not to disturb the first bend. This is achieved by distributing the heat gradually. It takes a few minutes to do this operation and if both bars are at the correct temperature bending them is relatively easy and a uniformed shape is achieved.

When cold tightly wrap insulation tape around the threaded hook ends about 3 turns, this will bed into the threads making a smooth surface – use shrink wrap over the top as shown in the illustration.

Finally attach a piece of foam to the pressure plate as this will protect the trunk or branch. Assemble all the parts together to make the clamp as show in the next illustration.

Questions on tools and materials

The tools needed are normally found in most DIY work boxes or tool kits. Perhaps the vice, which is necessary for this work may not be common, but these are not expensive and can be purchased for €25,00 upwards depending on size and manufacturer. You will always find use for a vice.

All the materials or components to make the clamp can be found at most hardware, supermarket stores or electrical suppliers.

The threaded bars are approximately 1metre in length hence there is sufficient to make several clamps. For the centre bar, an old warning triangle surplus to requirements was used, these are usually found in the boot/trunk of a car, which when cut was sufficient for 6 clamps. Alternatively flat aluminum bar can be found at most hardware stores.

The pressure plate was cut from an aluminum satellite antenna mount. And being circular concave on the inner radius allowed a branch or trunk to fit snugly into the curve. (Shown below)


Of course not every one has a spare satellite antenna mount available, so what to use instead. A piece of metal plate the same as the centre bar could be used, but it would have to be heated and shaped to make it concave – then drilled and tapped. Other materials can be used, but should be strong enough and able to take enough threading – at least ¾ of those found on its corresponding nut. This is important because (a) the pressure plate has to be stable when mounted and the bar should not protrude through the plate as this will mark the branch or trunk – it must be flush. (b) Bending branches or trunks puts a lot of pressure on a clamp so they have to able to withstand this.

This site is trying to make life easier for the bonsai enthusiast rather than complicate matters therefore, an alternative in making the pressure plate could be the following.

Take a piece of wood approximately 20mm thick x 20mm wide x 30mm long, mark the centre and drill a pilot hole. Gradually enlarge the hole to 10mm, but only go enough to set the nut below the surface. On the opposite side use a round file, to cut a groove down the length forming a concave radius. Be sure to follow the grain as this will retain wood’s strength, clean out the hole and check the alignment. On the reverse side (10mm hole) take an 8mm nut affixed to a spare length of bar, heat it red hot and gently push it into the hole. As it burns its way in, the hole will take on the nut’s shape. Make sure you have water to spray on the wood so it does not catch fire. Repeat the process until the nut is parallel to the wood’s surface. Check the plate and bar alignment then apply a small amount of epoxy resin to secure the nut in place. This wooden pressure plate needs to be painted to protect it from moisture if left to the elements, finally glue a piece of foam to the inner radius, see illustration below.


This is just an example, one way to solve the problem and obviously there are many others. If you have any suggestions I will be glad to hear them. Until next time when we discuss how to make a lighting stand from a coat rack. BW. N.

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