Joining two desktops - options

Question

I have an office-style desk, with a 25mm thick wooden top. I know it is fake-wood because there's edge trim around the lot. But its not enough surface area, so I wish to abut a "return" in such a way there is nothing to interfere with my legs/knees, so standing a 4 legged table to the side is not going to work for me.

I have a suitable small top, and purchased two kit legs for the outer end. That's all good. My question is how do I join them, for support and no exposed lip?

The new top appears to have thin strips of real wood as a veneer, but the core remains fake wood. There is a "wood-like grain" laminate on both faces.

The original desk has a top that can slide to the right by 100mm for access to a cable trough on the rear - so that grey metal bar has about 6mm of clearance to the underside of the top, and the top can be exposed to work on it.

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Options for butt-joining the tops - The two tops should be co-planar and have no lip. A small recess is acceptable, from the corner chamfer. I suspect the rubbery trim would peel off acceptably well, but the wood veneer won't.

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1. 
   Pocket screws - use some long wood screws at a slight angle, up from below so they terminate inside the original top.

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2. 
   Some kind of metal plate below both pieces, screwed upward. Often called a "mending plate" or similar.

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3. 
   Benchtop joiner kit- uses two circular recesses excavated into the underside of the top, and is then tightened.

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4. To make removal easier, would two L brackets mounted back to back with a bolt through them be an option? Downside, nothing here holds the top of the edge closed.

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5. Other methods I haven't thought of ?

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Your thoughts ?

Answer 1

I recently added a desk extension so I had the same problem, I needed the two surfaces to be flush and stable. The solution I came up with was to use a dowel jig to drill dowel holes at the same depth below the level of the top surface, then used dowels to join the surfaces, which worked very well and I'm pleased with the result.

Once you have the two surfaces doweled together a couple of mending plates will keep them pulled into each other.

Answer 2

I would bolt a piece of angle iron to the existing metal frame. Set one face flat against the metal frame and the other flush with the bottom of the current top, and extending out far enough to support the new top. Put a few screws into the new top to secure it in place.

Answer 3

For closure - here's what I ended up doing. It's not perfect, I know what to do better next time.

0. I bought a starter kit for dowelling, consisting of a drill, some transfer markers, and a bunch of precut dowels.
   This cost around $23 NZ, and didn't have a guide block which was another $66, so I skipped that as a luxury.
   

1. Stripped the plastic edging from the left desk so it was flush. This showed an inner core of chipboard. There's a layer of yellowish adhesive still here, which was removed using a chisel. Presumably that was wood glue or PVA.
   
   

2. I then drilled a 10mm hole near each end, and fitted two of the alignment transfer stud pin things. Then I pressed the new table against the old, and tapped it with a rubber hammer to make a dent. This worked well, but neither piece of wood was straight, so there's a subtle offset. This wasn't helped by having a slightly radiused corner on the new table, which fooled my fingers.
   Also notice that the chipboard drills poorly. The larger flakes of wood push the drill bit about and off-center, and also give an oversized hole.
   

3. I then drilled to the same depth on the other side. The second table had a real wood veneer which I chose to leave in place. In hindsight this was a bad choice.
   This top was made from Customwood and drilled nicely. However the dust had a weird habit of packing up in one flute but not the other.
   

4. With two end dowels in place dry, I added 4 more spaced across the gap of ~500mm. Once all holes were drilled, I used a rasp to tooth the smooth veneer side, and fitted half the dowels to each side using PVA wood glue in the hole. Dowels mostly pushed in without issue. Glue was spread out on the mating surfaces too.
   Then I pushed the two tabletops together. Friction meant I needed the rubber hammer to tap it all home, and then clamped the whole thing with a sash clamp.

5. FINAL RESULT Not sure how well this shows it, but there was a minor step (more of a curve really) left. I tried clamping this at glueup time, but it was too late, the offset came from the dowel holes.
   
   

All up, I'm satisfied with the result. I had mending plates ready to fit, but the current result is solid-feeling with just wood and glue. Time will tell; I'll try to give an update in 12 months, or sooner if it breaks/needs work.