holding zero clearance insert rings

[MikeThePom]

Hey guys (and gals),
I have been revisiting my TR001 based router table I built many moons ago and replaced the 6mm acrylic top I made way back when with a 10mm aluminium plate. I first though about buying one from local suppliers but the store with blue background and white lettering nearby didn't have any and couldn't tell me when they would come back in stock. So I went to Action Aluminium, a very friendly place in Green's road in Dandy who are always ok with me rummaging through their off cuts and paying scrap prices, however this time I bought a 10mm plate about 300 square and set about drilling the center hole (which I made about 10mm larger in diameter than the hole in the router base so that it would act as a support for the zero clearance rings) and the router mounting holes. I even allowed for the 'cock eyed' pattern so that the handles were parallel to the sides. I then added some 8mm threaded holes for a starter pin. I then used some 15mm cutting board and made a whole load of zero clearance insert rings and will, when needed make the hole bigger of different bits.

For the majority of tasks the insert ring has been fine however, I want to add a template bushing to an aluminium insert ring and worry that it might come loose. I could use some M3 screws to hold it down but I thought about the way that taper lock bushings hold pulleys on and wondered whether I could drill 4 holes around the circumference of the aluminium insert ring, thread them and use some grub screws to hold it in place.

What do you reckon, Would it work?

[Bohdan]

That would work but it would be unique to that particular insert ring. To use a different ring you would need a different set of tapped holes.

When drilling and tapping the holes make sure that you have the ring clamped down in its final position. Two holes should be more than enough.

[MikeThePom]

That would work but it would be unique to that particular insert ring. To use a different ring you would need a different set of tapped holes.

When drilling and tapping the holes make sure that you have the ring clamped down in its final position. Two holes should be more than enough.

Thanks for the reply. I had thought about 3 holes @120 degrees apart so making half holes would be possible using the milling machine and an endmill so it is possible to add it to the plastic ones already made if they start to move in use.

Regards

[malb]

I would prefer 3 holes to two to minimise chances of the insert rising on one side and throwing things out with setups etc. Also don't make the holes 120 deg apart, make a pair about 110 degrees apart and place the third opposite. That way there is a single position where all three holes, the table and the insert all line up, rather than three positions where they may be close but not spot on.

If you have access to machining facilities as suggested, maybe set it up to use screws with oversize cheese heads recessed into the table and insert in a counterbore, but with the threaded hole in the table, with the oversize head contacting the top face of the counter bore.