DIY mitre join on an IKEA Pragel bench-top

A reader requested I give details on how I did the DIY mitre join on my IKEA Pragel benchtop:

Warning: this was tricky, do at your own risk. Ask for clarification if you need it, I wrote it quickly and from years-old memory, but if enough people want it I can add more info. If it’s difficult, or you ruin your benchtop, don’t blame me for trying to help you.

1. Carefully mark a 1cm x 1cm square for the diagonal cut (pencil on masking tape)
2.  Cut the “male” piece, to the correct length (keeping an 1cm for the join!) with a $50 Ozito circular saw (upside down for a neater cut as saw cuts from the bottom, masking tape along cut on the top (now the bottom – where saw enters). |‾‾‾‾‾‾‾|
3. Draw a pencil line joining corners of the 1cm square and cut it with a hand saw (new blade is best).  |/‾‾‾‾‾‾‾|
4. For female piece, cut the 1cm square diagonal first very carefully with hand saw.  _/_______|
5. On the bit to be removed, go 5cm along from that cut (in step 4) and carefully cut 1cm in. _/_|______|
6. Circular-saw the 1cm thin cut-out piece from the edge to that cut (in step 5). (Actually I used a router, but the cheap circular saw cut cleaner and straighter). _/_|‾‾‾‾‾
7. Use the handsaw again for the last 5cm from the step 5 cut to the step 4 diagonal cut. _/‾‾‾‾‾‾‾
8. Hopefully (!) they fit together nicely now.
9. Get 2 benchtop joining bolts from the kitchen section at Bunnings (you must see that 5$ bunnings flatpax DVD that shows how these work to understand the next steps).
10. Mark 4 holes on the bottom, 2 each on each bench piece, about 8cm from the join edges (not sure it’s 8, check this with the bolts, circle edge should end up 1-2cm from join edge) and about 30% of the way along the edge so they are evenly spaced from each other and the edges.
11. Use the biggest wood spade from Bunnings (32? 35?) to drill wide holes – only 1-2cm or so deep – for the “C” part of the benchtop fasteners.
12. Drill/saw/route a hole for the bolt part of the bolts, from those holes to the join edges, so the bolts will work as you’ve seen in the video
13. In the video, they say biscuit join for strength; I didn’t actually need to, just carefully matched heights of benchtop pieces and supported both from below near join
14. Put it all in place for a “dry run” (semi-tight bolts but no glue) to see if any adjustment needed.
15. Glue a line of glue (good wood glue or MRMDF glue – I used araldite but wouldn’t recommend, it dried super fast in my hot kitchen window sun, and I almost couldn’t tighten bolts in time!) along the middle of the join, and a small line of silicon along near the top of the join.
16. Put together in place in kitchen, make sure it’s all perfectly level and tighten the bolts.
17. Some silicon should squeeze out the top. Make sure the whole join is covered by silicon so no moisture gets in the top.
18. Spray some spray’n’wipe over the silicone so it doesn’t stick to the benchtop itself (just the join) when you wipe the silicon off
19. Wipe the excess silicon off with your finger (pausing to wipe finger with something as needed). Check glue bottle for drying times.

Note: don’t forget to waterproof the underside of Pragel benchtops if near wet (sink, dishwasher, oven or cooktop) as said in Pragel’s instructions.