I've got the Trend M&T Jig, - and their Guides and their Bits set, played with their instruction. Fit, for some guide/bit combi- inations were off spec, resulting in oveversized tenons on one combination and undersized tenons with another. The cause was a few thousandths off on both the guide and the bit. The other problem was the 1/4" shank router bits with the longer shafts than normal. You need to make shallower passes which takes longer. Try hogging out too much in a pass and you can get a little flexing - and a sloppy joint.
SO - since I'm a fan of loose tenons - it works great cuting mortices for them - one guide to center the bit in the opening, I can use 1/2" shank fluted bits (end mill type bits).
Here's more I put together on this jig
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you have a precision fence for your plunge router, you can make a jig for cutting loose tenons
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