Trenching...and then not :/

I needed to cut several meters of T-slot for the new bench, so I cobbled up a trenching jig for my router. I like fe$tool, and accept that I'll pay many money for a lot of their tools, but their trenching jig is a staggering $350! For a chunk of acrylic with a few knobs. Crazy.

I didn't have ideal raw materials, and didn't want to venture out into virus-laden world, so made do with stuff lying around. Laminated two 5ml pieces of acrylic, stole some clamp hardware from some china tools, and hacked up a couple of mounting bolts to fit the router base.

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I was very pleased with the result - made a few errors: the knobs foul against the dust port on narrow stock (need to lengthen the base), and dust collection is terrible. But it tracked square and straight, and I happily cut around 5 linear meters of slot.

And I finally got to use the Axminster T-slot cutter that I've had lying around for 18 months, waiting for me to get to this stage.

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And just when I was smiling hugely, this happened: with about 3 meters of slot to go...

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Pretty frustrating. Replacement bit would need to come from the UK as I don't know of an equivalent available locally. I usually would't buy the same tool if it failed like this one did, but there don't seem to be alternatives. As the pieces end up as a 4m long run of slot, I need it all to be the same or the clamps will foul.

Bit is out of warranty - even if this sort of thing was covered. It was something I bought a long time back knowing I'd need it for this. Gave it a quick try when it arrived, then stuck it in a box until required. Pretty disappointing. I'd thought of using the dado blade to cut an initial slot, and then use the bit for the final shape - wish I'd gone with that plan now - it'd probably have lasted long enough to finish the job.

That really gives you the poos eh. With the benifit of hindsight a smaller straight cutting bit to remove the bulk of the material first followed by the T cutter.

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Originally Posted by rod1949

That really gives you the poos eh. With the benifit of hindsight a smaller straight cutting bit to remove the bulk of the material first followed by the T cutter.

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Yep, that's a huge ask of a router bit of unknown pedigree. Even with a known high quality bit a first pass with a smaller diameter straight bit is the way to go. If you want to buy quality bits without paying an extraordinary price look for the Arden brand, great quality at a fair price.

They never used to be common in Aus but have made it over. HERE is a 7/16” one on Amazon

Well, lesson learned.

The base of the track clamps is a shade under 12mm, so I think the 7/16ths bit will be too tight. Looks like Arden do one that will work. The Axminster bit cuts a 13mm slot.

My dado blade is accurate/adjustable to 1/10th of a mm, so I got it dialled in and cut the remaining channels, and then routed some wider sections to insert the clamps. These should allow me to get the replacement t-slot cutter in and finish the job. At least I can get on with the rest of the build.

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Originally Posted by rod1949

That really gives you the poos eh. With the benifit of hindsight a smaller straight cutting bit to remove the bulk of the material first followed by the T cutter.

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That's how the manufacturers all tell you to do it as well.

Dimar tools make several, here’s a photo of the page in their catalogue. Ph: 0295218881