Painted Oval Mirror and wood movement

PointFive · 11-28-2008, 10:14 AM

Hi,
I have been asked to make an oval mirror frame for a medicine cabinet in the powder room. The existing cabinet mirror frame is plastic, so I have a free template to follow with the router bearing.

My question has to do with wood movement. We live in an area of extremes of humidity in winter vs summer. I purchased and watched a video with Rick and Bob making an oval mirror using four pieces of wood, joined at the corners (biscuit joint). Then I saw another technique that was used with maybe 8 segments joined together. I plan to use poplar because it takes paint well and the finished frame will be painted ( not 1/4" glue and 1/2" paint, unfortunately ).

Is there a "best way" (segments) or (4 larger pieces) and what method of joining will make the best final product? I even thought of using dowels from the outside of the joints, since it will be painted, but on second thought the dowels will make the wood movement noticeable when the wood expands and contracts.

**bobj3** · 11-28-2008, 10:54 AM

HI PointFive

I would suggest using spline joints

see below

======

Quote:

Originally Posted by PointFive

Hi,
I have been asked to make an oval mirror frame for a medicine cabinet in the powder room. The existing cabinet mirror frame is plastic, so I have a free template to follow with the router bearing.

My question has to do with wood movement. We live in an area of extremes of humidity in winter vs summer. I purchased and watched a video with Rick and Bob making an oval mirror using four pieces of wood, joined at the corners (biscuit joint). Then I saw another technique that was used with maybe 8 segments joined together. I plan to use poplar because it takes paint well and the finished frame will be painted ( not 1/4" glue and 1/2" paint, unfortunately ).

Is there a "best way" (segments) or (4 larger pieces) and what method of joining will make the best final product? I even thought of using dowels from the outside of the joints, since it will be painted, but on second thought the dowels will make the wood movement noticeable when the wood expands and contracts.

PointFive · 11-28-2008, 12:17 PM

Bob: Thank you for your response. I had not thought about splines. In your illustration, the term "one way blocks" is used. What does that mean?

Also, you suggest in this illustration the use of 6 segments. However, the segments cross the interface of the four pieces of wood. Is this on purpose to achieve a certain orientation of the grain or just a drawing convenience?

Thank you,

Paul

**bobj3** · 11-28-2008, 01:19 PM

HI Paul

Blocks = just rip some stock (4 blocks) and then join the sticks with splines,then set you template on top of the blocks and use a pattern bit to cut the frame out...

6 segments = this one is a bit harder,,,rip the stock so the grain is running like in the illustration and then ruff cut it with the band saw then put your template in place and use the trim bit to clean it up and to put the fine edge on it..

====

Quote:

Originally Posted by PointFive

Bob: Thank you for your response. I had not thought about splines. In your illustration, the term "one way blocks" is used. What does that mean?

Also, you suggest in this illustration the use of 6 segments. However, the segments cross the interface of the four pieces of wood. Is this on purpose to achieve a certain orientation of the grain or just a drawing convenience?

Thank you,

Paul

PointFive · 11-28-2008, 06:11 PM

Bob:

If you were trying to avoid problems with wood grain caused joint blowout / splitting etc., would you choose,

4 blocks

6 segments?

Thanks for all of your help,

Paul

**bobj3** · 11-28-2008, 06:36 PM

Hi Paul

I would suggest using the 4 blocks,,,once the splines are in place you will cut right across them and should help with the blow out.
I would also suggest using a skew angle bit, it will cut and not chop the wood out..

Shear Angle Flush Trim Bits
http://www.mlcswoodworking.com/shops..._bottom_anchor

Because you are going to paint it you can glue on some 1/8" birch plywood to the back side this will help support the joints..

but do glue it in place b/4 you route it...then just round it over and it will almost disappear ...

=======

Quote:

Originally Posted by PointFive

Bob:

If you were trying to avoid problems with wood grain caused joint blowout / splitting etc., would you choose,

4 blocks

6 segments?

Thanks for all of your help,

Paul

**harrysin** · 11-29-2008, 01:00 AM

As you intend to paint the finished frame, I would, without doubt rout the whole thing from a sheet of MDF. The fact that you have the template makes this a very simple job. Draw around the frame, inside and out, cut away the waste using whatever means you have, a jig saw is ideal, some waste must be left. Attach the template to the MDF using pins or carpet tape and with a straight bearing cutter clean-up inside and outside. You now have a nice clean frame which just needs some edge treatment using whatever cutter/s you have.

Now don't let anyone tell you that MDF wouldn't survive in such an environment, about eight years ago I made a large bathroom cabinet, about 3ft. wide, I sealed it, under coated it followed by several sprayed coats of high gloss lacquer. It is still as good as the day I made it.

**bobj3** · 11-29-2008, 07:38 AM

HI Harry

I know you are not to far from the water, but you only get 2" rain a year. :
Plus it's so hot and dry you can grow banana's in your back yard..

========

Quote:

Originally Posted by harrysin

As you intend to paint the finished frame, I would, without doubt rout the whole thing from a sheet of MDF. The fact that you have the template makes this a very simple job. Draw around the frame, inside and out, cut away the waste using whatever means you have, a jig saw is ideal, some waste must be left. Attach the template to the MDF using pins or carpet tape and with a straight bearing cutter clean-up inside and outside. You now have a nice clean frame which just needs some edge treatment using whatever cutter/s you have.

Now don't let anyone tell you that MDF wouldn't survive in such an environment, about eight years ago I made a large bathroom cabinet, about 3ft. wide, I sealed it, under coated it followed by several sprayed coats of high gloss lacquer. It is still as good as the day I made it.

**harrysin** · 12-01-2008, 11:05 PM

Quote:

Originally Posted by bobj3

HI Harry

I know you are not to far from the water, but you only get 2" rain a year. :
Plus it's so hot and dry you can grow banana's in your back yard..

========

You have a good memory Bj, regarding the bananas, however the rest of your "facts" are a bit off the mark. Our average rainfall is 34" per year and it isn't unusual for humidity to be around 70-75%

**bobj3** · 12-02-2008, 08:59 AM

Hi Harry

I knew you would see that

. but only 2" hits the ground. water always runs down hill and because you are down under I didn't think most of it hit the ground.

I have not been down under but what I see most of it is dry most of the year...I know you have a rainy seasons but most of it falls off b/4 it can sink in..

LOL LOL have a good one MATE

=======

Quote:

Originally Posted by harrysin

You have a good memory Bj, regarding the bananas, however the rest of your "facts" are a bit off the mark. Our average rainfall is 34" per year and it isn't unusual for humidity to be around 70-75%

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Username		Remember Me?
Password