How do I router this rabbit?

[Neverending Project]

I want to make the following rabbit cut, so I can fit some interchangeable panels into it. It will look like this:


But I am wondering how I can get the corners as "sharp" as possible. The hole is just a rectangle with the corners chamfered by 1". I figured I would cut the hole first, and then use a rabbit bit on the router to get the step. But when I reach the corners they will be rounded the radius of the router bit, 1/2"...

Does anyone have any ideas how I can make it more angled and not a 1/2" rounded corner? Oh, and I thought of chiseling out the corners after using the router, but it is MDF and I am not sure how well it will take a chisel. Any thoughts?

[sstorkel]

OK, the first thing to realize is that a "rabbit" is a small furry animal that eats carrots and other vegetables. Attacking one with a router is generally frowned upon... A "rabbet" (a.k.a. "rebate") is a groove cut into the edge of a piece of wood.

The second thing to ask yourself is: why do you need sharp corners? As you've already noticed, they add considerable hassle to the construction.

How you cut this will depend on the difference in size between the rabbeted corners and the "sharp" corners that you consider ideal. If the difference in size is small, and you know how to sharpen a chisel, then I'd just chisel away the material left by the router bit. If you don't know how to sharpen a chisel, you'll need to do something else. Probably the best bet would be to make a second pass with the router using a small, straight bit. You'll probably want to build a jig to guide the router. Template collars may be helpful if you decide to go this route.

[javeryh]

If you are patient you can just score the MDF with a razor knife in each corner (use a straightedge).  This is what I did for my joystick mount and it worked fine.  The material will pop out once you get close with the router and make a straight line.  You can probably only cut about 1/16" deep though with the knife so the rest will have to be removed with a chisel but that top edge will be perfect.  Here's how mine came out:



HERE'S the full explanation.

EDIT: I wouldn't recommend using MDF for interchangable panels.  It's a sort of soft material and the constant moving around over time will really mess things up.  Even running the ball bearing of a router bit along the edge will leave an indentation in 2 or 3 passes.  I'd use plywood.

[sstorkel]

EDIT: I wouldn't recommend using MDF for interchangable panels.  It's a sort of soft material and the constant moving around over time will really mess things up.  Even running the ball bearing of a router bit along the edge will leave an indentation in 2 or 3 passes.  I'd use plywood.

I was just about to post the same thing!

In fact, the more I think about it the more I'd be tempted not to use the router at all... Cut out the opening with a jigsaw, then make a frame out of 1x2s and attach it to the plywood with glue and screws. In addition to being stronger, using this method will mean that you don't have to do any routing of the inserts; they can be full-thickness pieces that simply rest on the 1x2 frame. Should be much easier to construct and more durable...

[ChadTower]

He could also make that panel out of two half-thickness pieces and glue them together.  It wouldn't solve his corner issue, of course, but it would get around having to execute some poor fuzzy bunny.

[Neverending Project]

@sstorkel: Thanks for the spelling correction. I thought it didn't look correct, but since I have never seen it written, I went with it. And the only reason I want to keep sharp corners, or relatively sharp, is because I want to keep the look consistent with the edges of the CP, and I don't want to have to round off each of the 8 corners on the 10 panel inserts I have.

@javeryh: I realize now that I shouldn't use MDF, but the box is already cut, as are the panels (pics here). It wouldn't be too much work re-cutting the panels and surface in plywood, but I don't really want to rebuild the box. I suppose I can leave the box in MDF... I'll have to think about it.

I have so little time to work on it that I have a hard time taking two steps back. I just want to move forward.

[Neverending Project]

It wouldn't solve his corner issue, of course, but it would get around having to execute some poor fuzzy bunny.

According to Mr. Merriam and Mr. Webster, the etymology of rabbet is, "Middle English rabet, perhaps from Middle French rabat act of forcing down, from Old French rabattre to force down, fold over, reduce".

So maybe subconsciously I was thinking about beating the rabbit with the router?  (It's a stretch, I know)

[sstorkel]

@javeryh: I realize now that I shouldn't use MDF, but the box is already cut, as are the panels (pics here). It wouldn't be too much work re-cutting the panels and surface in plywood, but I don't really want to rebuild the box. I suppose I can leave the box in MDF... I'll have to think about it.

If the panels are still the same thickness as the top, then the quickest way to finish the project is what I suggested: buy some 1x2s at the local lumber store and attach them to the bottom of the CP (using both glue and screws) to support the inserts. If you want your setup to be in use for a long time, it would be ideal to make the CP top and the inserts out of plywood.

If you don't have the time to redo the top and inserts in plywood, consider making a few extra MDF panels and setting them aside. That way, if one of your inserts does end up getting banged up, you can always drill holes in one of the extra panels and move the controls over. Plus, you could use the extra blank as a template for making plywood inserts... if you ever get around to that.

[nostrebor]

The rabbet solution will work fine, and you really just need to square those corners off with a good sharp chisel after making the cuts. MDF is easy to cut with a sharp chisel. If you dont have a chisel (shame!) you can also clean out the corners with a sharp utility knife and a straight edge. (just like the poster above noted.)

[sstorkel]

The rabbet solution will work fine, and you really just need to square those corners off with a good sharp chisel after making the cuts. MDF is easy to cut with a sharp chisel. If you dont have a chisel (shame!) you can also clean out the corners with a sharp utility knife and a straight edge. (just like the poster above noted.)

This can be done, but really isn't the ideal solution. Here's why:

1) New chisels bought from a store aren't sharp. Most people don't know how to sharpen a chisel to the point where it cuts well. If you buy a high-end chisel, it might be lapped well enough at the factory to cut MDF... but then again it might not. If you buy a cheap chisel from Sears or your local home center, I'd be fairly worried that it won't cut straight.

2) MDF isn't very strong to begin with, so routing away half the thickness to make a "ledge" to support the inserts isn't a great idea. In addition, you'd also have to create rabbets on the back of all the inserts so that they'll sit flush with the top of the control panel. Again, this will make these edges more prone to damage.