This is the permanent jig I knocked up today for measuring blade alignment. It's pretty much a rip off of the TS Aligner Jnr, just without the fine engineering.

$10 worth of aluminum (100x115x6mm base, 100x25x25x6mm right angle, 200x32x6mm cross bar), $2.50 for a bit of 3/16" key steel, $12 worth of bearings and a ghastly $19 for a 2.5mm tap for just one hole Plus a few sundry bolts and washers I had around the place.

The three bearing "mitre bar" works with the two outer ones riding the right hand side of the mitre slot, with the inner one being able to be slid to the left side and when done up properly gives ZERO play in the slot.

The cross bar has a little room to slide for the difference between measuring vertical and 45 degree and the slot is slightly wider than the 1/4" bolt so it can be pressed down flush with the table (seeing as I'm a dodgy engineer ). It also defaults the dial indicator at about 5mm to cater for a table that's insanely out of whack.

I had a little trouble with the bearings as they are 5mm thick with an inner hole of 7mm. The single set of 7mm bolts I could find in three shops had heads that were going to push the limit of depth already without taking into account the washer I needed to space the bearing from the base so it could spin freely. So I ended up doing a little hack with 1/4" countersunk bolts figuring that the angle on the head would secure the bearing nicely and give me plenty of room underneath. Worked a treat.

Lastly was an extension arm for the dial indicator so I can measure as close to the arbor as possible when the throat plate is taken out. The indicator's original head can be unscrewed and fitted into the arm which in turn screws onto the indicator's needle.

To completely finish the job I just need to tidy up a couple of bolts and maybe put a butterly nut on for the movable bearing and hack up a kind of butterfly bolt for the cross bar. It needs to be sanded down a little more to remove some burrs that are scratching the table, a little tidy up around the edges, and put a bit of thread locker on the stationary bolts, but in general I'm pretty happy with how it's turned out.