router table insert - newbie questions

[Jacob Reverb]

Hey, all,

Edited to add: I think I already answered these questions in post #4 below (by looking at the OEM router base plate), so I may be OK for now.

I'm making a router table to go on the side of my TS. Have a place rabbeted out to put a 1/4" piece of aluminum into, that I will mount the router to. But I'm new to router tables, and have some dumb questions:

Question: How big of a hole should I bore into the plate for bits to protrude through? (Not using a pre-made plate -- just a piece of 1/4" aluminum, so I need to decide on everything regarding where to drill holes, and how big.) My plan now is to use a hole saw on drill press to make a hole to accommodate the largest bit I will ever likely use, and then make smaller acrylic or lexan inserts to fit into the hole in the aluminum for a zero-clearance type of setup. Don't have panel-raising bits now, but will probably get some at some point. My concern is that if I make the big hole in the aluminum plate too small now, that I'll have trouble making it bigger later on, down the road.

Question: Assuming I make a 3" or so diameter hole in the aluminum plate, and the router is screwed to the aluminum plate, and I use 1/4" thick clear plastic inserts to fill the large hole when using smaller bits, will the clear plastic "ZCI" just sit peacefully in a rabbeted hole – or do I need to fasten the clear plastic "ZCI" firmly to the aluminum plate so that it can't bounce out, or rotate, or otherwise move? The ZCI on my table saw just sits there, and I just push down on one end of it to lever up the other end – in other words, it's "loose" in its rabbeted hole – but I've never had any trouble with it bouncing out or anything. Can the "ZCI" for my router similarly be just set loose into a rabbeted hole, or does it need to be securely held in the hole somehow? I know the MLCS sub-inserts look like they're threaded into the router insert plate...but if I need to somehow secure the clear plastic ZCI inserts in my setup, I'm not sure how to do so.

I considered using a hole saw to make a 3" or 3.5" diameter hole into the aluminum plate, and then welding a piece of 1/8" aluminum to the underside with a smaller hole in it, to make a rabbeted "ledge" for my clear plastic ZCI inserts to rest upon, but I'm afraid of warping the aluminum with the welding. So I'm considering just using epoxy, or possibly very small machine screws, to fasten a piece of plastic or aluminum to the underside of the aluminum plate to create this rabbet or ledge for the ZCI inserts to rest upon. Does anyone see any possible problems doing it this way? The aluminum plate will bear the weight of the router (Freud FT3000), so all the glued-on (or screwed-on) piece will do is hold up the clear plastic ZCI inserts, so I'm thinking it doesn't need to be terribly strong/secure.

But again, I may be way off base, since I've never used a router table (other than a router clamped upside-down into a WorkMate), so I probably know just enough to be dangerous, and need all the help and advice I can get here. Thanks in advance for any clues.

J

ETA: I probably won't ever add a router lift, as I'm not sure I'll need it -- my Freud FT3000 lets you adjust depth of cut and lock the spindle from above the table – so I don't think that's a consideration at this point.

[Jim Morgan]

I don't know what the base of your router looks like, but it either needs to have a large enough opening to accommodate the plastic or aluminum piece that you attach to the underside of your plate or you will have to extend that under piece so the router contacts it all around.

For the last router table I made, I used 3/8" phenolic for the base and routed a rabbet in the 3.5" cutout. I then carefully routed some lexan inserts (use plastic that doesn't shatter!) so that they would snap into the opening. Because the fit was so snug, I did not need to fasten the ZCIs. A loose insert could easily float up into the router bit with unhappy results. So it depends on how accurately you can work. As always, YMMV.

[Wayne Jolly]

Personally, I think you are ok with the size of the hole being a little larger that the largest bit you will EVER use. As for the inserts, I have not looked at many lately, but all I have seen have some way to fix the inserts in place. I assume there is a good reason for it, even it is is just to keep lawyers unemployed. But if you wanted to proceed, could you machine a 1/8 x 1/8 or so rabbet around the perimeter of the opening, and then maybe then match your inserts to that? OR . . . You mentioned adding another aluminum ring to the bottom with a slightly smaller hole. What about JB Weld (or other epoxy) a steel ring underneath, and add some small rare earth magnets to the inserts?

[Jacob Reverb]

Thank you for your replies, James and Wayne.

I now realize that the original base plate on my router has the rabbeted rebate to hold a ZCI insert, as well as some brass threaded inserts that appear to be intended to hold a ZCI in place, maybe. It also looks like maybe Freud was trying to give me a hint on the size of hole to drill in the aluminum plate, as the rabbeted-out area is about 3-7/16" diameter.



So maybe the answers to my questions are right there in front of me...?

Again, thank you for your replies.

J

ETA: I guess those threaded brass inserts in the base plate are actually for attaching an adapter ring for template routing...when all else fails, RTFM!