Rabbet for a mirror - how to enlargen?

[Prashun Patel]

I'm making a mirror frame that requires a 7/16" deep rabbet along the inside perimeter to accomodate the mirror. The frame is made and rabbeted, and the mirror's made. Unfortunately, I somehow made the frame a shade too small, and now I need to expand the rabbet by about 1/16+". My router bit (with the smallest bearing) only cuts to a 7/16" max wide rabbet.

Is there a way to expand the rabbet uniformly?

I don't have a rabbeting block plane unfortunately...

[Lee Schierer]

You can use a router with either a rabbeting bit or with a straight bit and edge guide to enlarge your rabbet. The rabbeting bit will leave rounded corners which you will have to open with a chisel. The edge guide won't let you cut as close in the corners so you will have more chisel work to do.

[Joe Scharle]

You may have a smaller bearing on some of your other bits?

[Prashun Patel]

Thanks guys. I've already swapped out for the smallest poss bearing on my rabbet bit.

The problem with a straight bit is that there's not enough room to support the guide and the base of the router without a lot of auxiliary support which'll be a bear to jig up.

Can I MAKE my own bearing out of some small washers - or even just the machine screw itself without the bearing? I'd hate to muck up the frame at this point - racing to Xmas!

[Lee Schierer]

Thanks guys. I've already swapped out for the smallest poss bearing on my rabbet bit.

The problem with a straight bit is that there's not enough room to support the guide and the base of the router without a lot of auxiliary support which'll be a bear to jig up.

Can I MAKE my own bearing out of some small washers - or even just the machine screw itself without the bearing? I'd hate to muck up the frame at this point - racing to Xmas!

Some of the old style pilot bits had just steel shafts that were part of the bit and spinning at the same speed as the bit. They would cause burn marks if you hesitated at all when you were moving them along the edge and some would even burn while moving.

You can also make a template that will do just a corner and part of each side. Use double sided tape or small screws to attach it to the back of the frame. Move the template from corner to corner to get all four corners done. Then you can use a template guide bushing and a straight bit to do the cuts.

[David DeCristoforo]

"...I've already swapped out for the smallest poss bearing on my rabbet bit..."

In that case, you need a bigger rabbeting bit, preferably one that comes with several different size bearings like this:

http://www.rockler.com/product.cfm?page=2116

[Prashun Patel]

Aw Dave!
My bits have a habbit of multiplying like...er...rabbets....already.

[Jay Jeffery]

I've used my rabbeting bit without a bearing when I needed a deeper rabbet in picture frames. It works, but it can leave slight grooves in soft wood since the bearing shaft has a sharp edge at the end of it.

You may be able to purchase a rabbeting bit of a larger diameter, but if the holiday clock is ticking, you might do well to at least try using the bit you have without a bearing. You will still of course have to hit the corners with a chisel.

[David DeCristoforo]

"My bits have a habbit of multiplying like...er...rabbets..."

http://www.daviddecristoforo.com/Misc/rofl.gif

[Karl Brogger]

Drop it in on the tablesaw. (Assuming you have straight edges to work with.)

edit- or just cut down the mirror. Kinda sucks if you have bevel'd edges, but not impossible, it is only a 1/8" too big.

[Josiah Bartlett]

You can avoid burn marks on the frame by clamping a straight edge just below it for the bit to ride on, or cover it with masking tape. Alternately, use a router guide, or if it is straight you could kiss it with a saw blade on the table saw.

[george wilson]

You could buy one of those inexpensive new 1/4" shoulder planes from Lee Valley. What? $26.00? Probably another router bit would cost about as much. Lay it down and plane the rabbet wider,finishing up near the corners with a chisel. I wouldn't risk cutting down a mirror so little. Take off 1/16" per side?

[Colin Helms]

Do you have a router table? Provided your frame is straight, adjust the fence to cut the amount you need to remove. Remember you will have to run the wood left to right, and please use caution while doing this (cutting in the blind) and also install stops so you don't go too far. You will have to chisel out the corners.

Good luck,
Colin

[Karl Brogger]

Take off 1/16" per side?

Belt sander. Your right, cutting it would end poorly.

[glenn bradley]

Doesn't sound like you have a combination of parts to make this happen but this might give you an idea: http://www.sawmillcreek.org/showthread.php?t=116755

[Prashun Patel]

Glen-
That's a great idea. I was going to do something like that but I didn't want to make the opening larger - just the rabbet.

I removed the bearing and it worked fine. There are some minor burn marks in the corners - where I hesitated, but I can deal with them later.

Thanks.