Making a hole for a router base in a table

[Brian Kent]

I have been sitting on this step of making my router table for several days - making a hole for the router plate. Don't worry, I haven't been sitting on the router. That might have unintended side effects.

Question #1 - Where the heck do I insert the collars in the router base / sub-base? I bought the reconditioned Porter Cable 892 on Amazon, and the clear plastic base has a 2-1/2" hole, not the 1-3/8" hole that I thought it was supposed to have.

Question #2 - Can I make a router plate hole this way without using a template collar:

The router table is an ash stand and a torsion box covered by a 3/4" piece of MDF, covered by a 1/2" piece of phenolic covered baltic birch. The torsion box already has a space built in for the router. It does not need to be cut.

I butt four pieces of plywood up against the router plate on the MDF. The MDF hole has to be smaller than the router plate to give it something to rest on. So I mark the places, move in the plywood 1/2", and rout a hole inside with a template bit (witha bearing on the top of the bit.)

Then I glue on the top layer of the table, and match the original MDF hole using an edge-trimming bit (bearing on the bottom of the bit.)

I set the plate in place over this hole, butt and clamp the plywood, remove the plate and rout the inside 3/8" down into the table top. This is the depth of the router plate. Since my template bit is 1-1/4 inches of cutting depth, I have glued up 1-1/8" of plywood so the bearing will have something to ride on at this shallow depth.

Final step is to touch up the corners with a chisel since the corners of the plate are almost square and my template bit has a 1/4" radius. My router plate has magnets and adjustment screws.

Do I have the right idea or do I have any fatal flaws ("fatal" meaning another $7 for MDF or $31 for phenolic baltic birch?)

[glenn bradley]

Shopnotes #89 has a great set of instructions for doing this. I couldn't find it online. It's part of their tablesaw workcenter article.

They basically frame the plate in position on the table top as you describe. Then without moving the frame, use a dado cleanout bit to route what will become the rabbet shelf.

Remove the frame and drill four holes at the corners where the opening will terminate. Use a jigsaw to connect the outer edges of the holes and you're done.

Believe me the description here makes much more sense when you see the pics but it is one of the cleanest and most foolproof methods I've seen.

[Bert Johansen]

Or you can simply make a template instead of the aforementioned frame technique. I made mine from hardboard. Easier to clamp a single template, I think, and it might be a bit more accurate since you can tweak the template to get it just right. Note that the depth of the routed part is also a critical aspect of this job. I suggest you do a test rout on some scrap to get the depth just right. Most plates have screws to allow you to raise the corners for a correct depth, so you can rout a bit deeper than the final depth, then compensate with the screws.

[Brian Kent]

Bert, how would you make the template?

My original plan was to make the template using collar bushings, but when I tried I found out that my PC892 came with the wrong size opening in the base (2-1/2").

[James Carmichael]

If it's like my old PC 7593 there may be a bushing adaptor that has to be attached.

[Bert Johansen]

Brian, I just traced the outline of the plate on a piece of quarter-inch hardboard, drilled a hole inside and then used a jig saw to cut short of the line. I used a rasp to bring it to final size.

[David DeCristoforo]

"...my PC892 came with the wrong size opening..."

You can pick up a "stock" PC base plate for a few bucks just about anywhere that sells tools.

[Cary Swoveland]

If I understand correctly, the bottom of your router base will be 1-1/4" below the top of the table. For at least some routers, that will cause a problem.

You want to be able to raise the collet to a point just below the top of the table (or higher). If you cannot raise the collet that high, you will not be able to properly seat some router bits.

For the router I use, the distance from the bottom of the base to the top of the table should not be more than about 3/4".

You may want to consider mounting the router base to the 1/2" ply (and cutting a hole in the 3/4" MDF that is larger than the diameter of the router base). If you don't think 1/2" is thick enough to provide sufficient rigidity, use 3/4" ply (e.g., by laminating a piece of 1/4" ply to the bottom of the 1/2" ply).

You could get around this problem by using a "collet extender", but that would place additional stress on your router's bearings.

Cary

[Brian Kent]

The router will be attached to a 3/8" baseplate, so the bottom of the router will be just 3/8" from the surface. The hole I am working on is the one that is about 9" x 12" to hold the baseplate.

I just stopped by Rockler on an early lunch break and got the stock PC baseplate for $9.99. It has a 1-1/8" made for collets or collar bushings or whatever those brass rings are called.

If it is better to use those, I can do the two step process - make a template around the baseplate, then use the template to make an outer 3/8" deep platform and an inner hole. The math seems like it should be easy enough.

[Brian Kent]

My attempt to cut a template hole last night in layer #1 - the MDF - was pretty scarey. It is obvious to me that I do not have practice yet to do this right.

I will wait on cutting the template hole in the phenolic bb until I have more experience at hand-held router set-up and control.

For today I'll mount the router directly into the top layer of the table. The base will be 1/2" from the surface. I'll drill holes for the screws and the above-table adjustment, then raise my bits throught the table to create the hole. For now I do not have any especially wide bits.

The other problem I discovered is that the 1/2" phenolic bb plywood sold at woodcraft is not 1/2" thick. I am used to this with plywood in general, but was caught off guard since it is sold alongside with 1/2" Incra miter tracks and t-tracks. The phenolic bb is 15/32", which means I have to lower the tracks 1/32" or raise the surface around them. That is what I am planning on doing.

I'll dry fit everything and screw in the tracks. Then I can cut 1/32" strips of wood on the table saw and glue them to the 1st layer. When it's dry, I'll use contact glue to lay in the phenolic bb panels.

[joe greiner]

I'd suggest using the thinnest material suitable for the router plate, so as to minimize the depth penalty for your router bits. Not sure what the material is called, but a stout floor mat for office chairs is about 1/4" thick and tough as. To reduce flexing, make the hole in the table top just large enough to admit the router's handles along the diagonals of the hole. You might experiment with some sort of combination movement to reduce the opening requirements even further than direct placement.

The 2-1/2" hole is consistent with bushing sets made by Milescraft ("Turnlock"). They come with a dummy insert and an alignment tool to enhance centering. For this to be effective, the router should be loosely attached to the plate, and tightened after alignment has been achieved. The standard Porter-Cable bushings take a 1-5/16" hole. The Milescraft set has an auxiliary bushing with this internal diameter. I have no financial interest in this company; just a satisfied customer.

Joe