Heat effect on joinery

[John Moorhead]

Folks -

I need to build some lamps, and am wondering if heat from the bulb inside is going to cause trouble. The lamp is a cube of small lap-jointed face frames, mitered together. If I am using kiln dried wood, say 10-12% MC, will I be okay? Using the online moisture calculator (

) shows that the EMC will be approximately 7% with humidity at 50% at 150 degrees. I have no way of knowing just how hot it would be inside the lamp until I build one, but from what I've figured out, UL labs calls for a maximum of 174 degrees for wooden lamps. The rails and stiles of the lamp are less than 1 1/2" wideand the assembled "face frames" are about 8" x10". I will be primarily using vertical grain doug fir, with black walnut.

I am concerned about the corners of the lamp where the face frames are mitered together. Is this an issue? Should I take the wood and dry it some more - perhaps the oven or over the fireplace?

This is an important project that could lead to more work, so I don't want to screw it up any more than I normally might. I'd appreciate any insight y'all might have to offer.

TIA,

John Moorhead

[Andy Dingley]

You need a prototype, even a crude one, so long as it's the same materials and the same joinery.

I'd be concerned about joinery here. Wood movement isn't that much of a problem in such an open structure, unless it starts to strain the joints. The lampshades I've done have used some sort of finger joint with a mechanical interlock, not relying on a glued mitre that might suffer a bending force.

[bridger]

make a prototype. you'll need to do the setups anyway, right? it sounds like the amount of wood in each one is small. kinda arts and crafts, eh? post a pic of the design to ABPW?

set the prototype up and run it for a while and see what it does. let your client know what you are doing and why and what happens.

drying the wood more could help, or hurt. hard telling how the end user is gonna use it from here. will these be wall mounted, like a sconce? having an open top will go a long way towards keeping the innards cool. these are for interior use, right?

miters don't fare well with wide MC swings. any way you can redesign it to eliminate the miters?