So this will be my first Instructable (but I have viewed so very many), so please be gentle.

First I have to admit that this is not my original idea. It come from The Samurai Carpenter. He does beautiful work. But this has been so very helpful to me, that I just had to share the idea.

Step 1: Collecting Materials

Materials

1 piece of Acrylic (mine is 300 x 300 x 10mm)

Screws to replace the once removed from base plate (more on this soon)

1 Plunge Router

Tools

Pencils and Pens

Rulers and Squares

Drill and bits

Counter sink

Step 2: Setting Out

I am a draftsman by trade, so I like to mark everything out ahead of time so that I know what the finished product is going to look like when I am finished. Also it helps to get things exactly where you want them and figure if there is going to be anything that clashes, or isn't going to work for some unforeseen reason.

This being a router, it won't matter too much if some measurements are a little off, since the bits are round, you can always get a nice offset measurement. We'll get to this later (second time I've said that...)

1. I ordered my acrylic cut to order, so it is 300mm square by 10mm thick. The thickness is to give it the required strength and rigidity. Now just because I ordered to be square doesn't mean it will be. Squareness is not critical for this project, but it makes things like finding the center easier.

2. Find the center of the acrylic. Drafting 101 here. Since my piece is square, I can draw lines connecting opposite corners. I have left the protective paper on the surface for now, so that I can mark out directly onto the paper.

3. I have also created a 10mm offset from all the edges on all sides. This will be where we will drill all the Speed Holes, so that we can work faster (learned this from Homer Simpson).

4. Remove the base plate from your Router. These are usually a plastic of some type, held on with a number of screws. Center the base plate onto your acrylic using the cross marks we made in 2. You may need to do a bit of math here to get the base plate centered, as each one will be slightly different.

5. Once you have the base plate centered, mark the positions of the screw holes onto your acrylic.

Step 3: Drilling (so Much Drilling)

OK, now we are going to be doing lots of drilling and countersinking.

There are some things to take into consideration here.

Remember the Speed Holes a la Homer. These Speed Holes are not just a silly joke. These holes are going to be used to attach timber offcuts to the base of the acrylic to create a fence for your router. So you need to consider what size screw you are likely to use to fasten these offcuts. I am usually renovating one room or another in our house, so I always have a selection of plasterboard wall screws handy, so I will size my Speed Holes for these screws. 3 or 4mm ought to do it (remember, you can always make a hole larger, making it smaller is harder).

In order to get all the counter sinking to the same depth, I used a drill press, but you could do this with a depth gauge on a hand drill, or if you have a highly calibrated eye-o-meter, use that.

1. Drill and Countersink all you Speed Holes.

2. Turn over the acrylic, then Drill and Countersink all the holes for the base plate connection. I ended up drilling these 0.5mm larger than the bolts, to allow a little play when attaching the base plate to the router.

3. Drill a hole in the center of the acrylic. The size of this hole will be determined by the size of the bit that you intend to use. I am going to be using some pretty big bits, and I have some Forstner bits that I like to use, so I went with the big one, 50mm dia I think.

Note: This turned out to be a dumb idea. The acrylic bit into the drill to much. Just drill a bunch of small holes and then cut through with a file.

4. I gave the center hole a sand with some 220 grit to get rid of the scratches created by the Forstner bit, then hit it with some 1000 grit wet and dry to really smooth it out.

5. Now you can attach the base plate to the router. You will need some screws that are (approx.) 10mm longer than the originals. I started with some that were 20mm long and then cut and filed them to make a good tight fit.

Step 4: How to Use

So now you have yourself a big piece of plastic attached to the bottom of your router, yea.

But how is is supposed to work...

Firstly, the extra large surface of the acrylic, means that when you are removing larger areas, you have more surface (than the original base) to rest on.

And by attaching a timber fence to the acrylic base using screws through the Speed Holes, you are able to quickly and easily create an offset for you router. Attach a single screw first to an offcut for a fence, then measure your offset from the edge of the bit, and secure the fence with a second screw. Then route away.

You can add more than one fence, to create through holes for a Mortise and Tenon joint, and create the Tenon by 'fencing' three sides of the acrylic base.

I'm sure there are lots more ways to make use of this handy mod, and I will defiantly be trying to find new ones myself. Let me know if you come up with anything cool