When using a router table, you want the throat — the opening the bit pokes through — to be the smallest diameter possible that still allows the router bit to turn freely. If the opening is too large, small pieces can dip or even fall into the throat. Some throat plates twist and lock into place, and others are held in place by screws, but by far the coolest way to hold a router throat plate is with magnets.
INCRA’s MagnaLOCK laser cut steel rings are held in place with four rare earth magnets; just drop the right-sized ring in place and you’re ready to route. The donut-shaped magnets are held in place with counter-sunk screws and sit on top of O-rings. This setup presumably allows you to adjust the height of the rings so that they’re flush to the table surface.
Many of INCRA’s router plates, lifts, and table packages use the MagnaLOCK system. The only downside that I can see is since the plates are made of steel rather than aluminum, brass, or plastic, you might chip the router bit if you make a mistake. It’s a small concern, but I’m sure if you take care to keep the bit below the table when you change inserts and keep your table tuned so the router is centered, you shouldn’t have a problem.
INCRA sells MagnaLOCK rings with 3/8″, 5/8″, 7/8″, 1″, 1-3/8″, 1-5/8″, 1-7/8″, 2-1/8″, 2-5/8″, 3-3/8″ or 3-5/8″ diameter openings. They even sell a ring that accepts Porter Cable-style guide bushings.
Individual rings cost $10 a piece or you can buy a set of eight rings: 3/8″, 5/8″, 7/8″, 1-3/8″, 1-5/8″, 1-7/8″, 2-5/8″ and 3-3/8″ for $60. All MagnaLOCK router plates, lifts, and table packages also come with the 1″, 2-1/8″ and 3-5/8″ rings. The cheapest solution way to get into MagnaLOCK is INCRA’s router plate at $100.