Build Bonsai Benches Print E-mail

By Terry Davis

If I remember correctly, the concept for these benches came from Ann Erb.  Although the individual parts are weak, the method of construction results in a very strong bench, the strength coming from the compression by the threaded rods.  You can use thicker rods, but these are quite sufficient and about a buck cheaper each than 3/8” rods.  I suspect larger holes may weaken the bench, too.  They meet the following qualifications for bonsai benches:

1) Inexpensive.
2) Strong.
3) Portable.
4) Weather-resistant.
5) Open structure doesn’t collect water and debris, has good air circulation.  They collect less water than 2x4’s, which therefore deteriorate more rapidly. Air circulation helps keep the trees healthy.

I had initially been getting aluminum benches made by a local garden supplies vender.  They were $70 apiece, but all of a sudden they were $300 apiece (i.e., they didn’t want to do them).  The materials listed are for two 12” wide, 8’ benches, although I have made some much wider.  It is most efficient to build them in pairs, as you will be using a little less than 3 ca. 13” lengths of the threaded rods (you will cut them to size as you after you assemble them), which amounts to 1 1/2 3’ rod per bench.   Other than the unique equipment listed, a portable drill, hack-saw, 3/8” wrench, and skill saw are helpful.  Only the hack-saw is indispensable:  as far as the portable drill, how have lived without one all these years?  I use a table saw to cut the spacers, but it is not necessary.  I didn’t individually price the deck screws, as they are sold by the pound and I always have some on hand, anyway.  You want weather-proof screws.

If you don’t use the wood right away, strap it together so it doesn’t warp as it dries out.

Spacer blocks: Cut two of the pieces (I choose two that do warp) into 3 1/2” long spacer blocks.  You will need 66 for two benches.  I use the most warped pieces for this, or any that have large knot-holes that I missed when choosing lumber.  Leave a little over 2’ on two strips to make end caps.

Build a jig to drill the spacer blocks from one of the 2x4’s:  screw two blocks on with a channel in which a third block easily fits.  If you don’t use a jig, they may spin when drilling and you could break a finger.

Using the jig, drill the blocks in the center. A wood bit is best for this, because they have a sharp point and are easier to center, they make a cleaner cut than the standard twist bit, and the blocks ride up with a twist bit and get out of control (they can really break your fingers).  The bit specified is a little over-size: you will need a little extra size to make them easier to assemble.

Drilling the stringers:  Cut three holes in each of 24 strips: 1 in the center, two 1’ 10” from the ends.  The positions don’t have to be dead accurate, but they need to be the same in each stringer.  The strips are not uniform in length, so I use the first one I bore as a jig for the rest of each bench (make sure you don’t turn any end-for end, as they may not go together properly).  After drilling the first stringer, align the second strip at one end, and clamp them:  alternatively, after I drill the first hole, I drop a 3/8” bolt through the holes to keep the holes in alignment.  Use the same piece as the jig each time for one bench, so you don’t get alignment drift.

Assembly:  thread a rod with a washer and nut through each hole of a stringer and slide a spacer block on top.  Make sure both go all the way down.  I keep the rod end flush with the nuts.  Repeat until you have 12 stringers, with no spacer block after the last one.  Slip a washer over the rods and spin a nut down it:  you are spinning it down quite a length, so I move it faster by dragging my hand and arm past it.  Tighten the nuts on the long ends first, making sure the spacer blocks are aligned with the stringers.  Then tighten the short ends.  Next, cut off the excess rod with a hack-saw.  I generally dress the cut ends with a file so there aren’t any jagged gotchas waiting for me or my pants legs.

Dressing and capping the ends:  Next I clamp two pieces of 2x4 about 8” back from the ends to bring the ends into alignment (they are all a little warped).  I slip spacer blocks between the stringers to make sure the spacing is correct (or pieces trimmed from another bench).  I then use a saw to dress the ends so they are even: as I said, the stringers aren’t really uniform in length, by as much as an inch.  While still clamped, I screw a piece of 1x2 to the end to keep them in alignment, using deck screws.  You will need to pre-drill the screw holes, as the 1x2’s split easily.  I put two screws in the ends pieces, one screw in each of the rest.   I stagger those in an up and down pattern so I don’t split the end caps.  Then I cut the end cap flush.  If you don’t end-cap, the ends warp and become a problem.

Mounting: I mount the benches on stacks of cinder blocks, which I get from a local cement products company (cheaper than the hardware store).  Be advised that, up here among God’s Frozen People, these may frost heave each winter and need re-setting.  I have had some of these for 10 years with no sign of deterioration.  I generally make a pair each year, so the War department doesn’t get upset about the cost, which is about $67 a pair.

Materials Price # Total

threaded rod, 5/16th 2.62, 3 total - $7.86
3/8x1 1/2” fender washers 0.24 ea, 12 total - $2.88
5/16” hex nuts 2.46/25, 12 total - $1.18
1 1/2 or 2” deck screws 6.11/lb, 46 total-  
8'x1"x2" pressure treated firring strips,1.97 ea, 28 total - $55.16 
Total Price: $67.08

Capital Equipment

3/8” wood bit   
2 16" 2x4's   
2 C-clamps

Bonsai Bench Assembly

 

 

 

 

 

Bonsai Shelf Overview by Terry Davis