Message	Date	From	Subject
4031	2010-01-19 07:39:33	Tim	Better PCB box lids and Sheet metal redux
I got some good tips here a while back about bending sheet metal to make useful boxes. With very careful measuring I did several good ones. But yesterday as I was putting stuff together - using a mix of soldered PC board enclosures and sheet aluminum - it became clear to me that without careful measuring (I was too excited about getting the mini-R2 back on the air to slow down!) the sheet metal stuff usually does not turn out with good results unless I am painstakingly careful to get all the measurements just perfect. Things have to be very carefully measured to make all the seams meet up tightly, to better than a 1/16", with sheet metal. I did discover a useful and quick way to make a good "lid" for a box made out of 5 sides of PCB. The "lid" is a piece of PCB slightly larger than the hole to be covered. I took some thin brass strip about 1/4" wide and without a ruler just bent it by hand to fit inside the rectangular hole box. Then I transferred it to the PCB lid and soldered one corner of the brass lip to the lid. By going back and forth a couple of times as I soldered my way around the lip I managed to get a good match between the lip and the box such that it fit snugly inside the hole. What's remarkable, is how easy this was to get a nice seam without going to the painstaking-measurement-and-sheet-metal-box-bending routine. Right now it's purely friction fit but I would guess a couple of sheet metal screws could hold it to the box quite securely and with a decent shield. Tim N3QE

I got some good tips here a while back about bending sheet metal to make useful boxes. With very careful measuring I did several good ones.

But yesterday as I was putting stuff together - using a mix of soldered PC board enclosures and sheet aluminum - it became clear to me that without careful measuring (I was too excited about getting the mini-R2 back on the air to slow down!) the sheet metal stuff usually does not turn out with good results unless I am painstakingly careful to get all the measurements just perfect. Things have to be very carefully measured to make all the seams meet up tightly, to better than a 1/16", with sheet metal.

I did discover a useful and quick way to make a good "lid" for a box made out of 5 sides of PCB. The "lid" is a piece of PCB slightly larger than the hole to be covered. I took some thin brass strip about 1/4" wide and without a ruler just bent it by hand to fit inside the rectangular hole box. Then I transferred it to the PCB lid and soldered one corner of the brass lip to the lid. By going back and forth a couple of times as I soldered my way around the lip I managed to get a good match between the lip and the box such that it fit snugly inside the hole.

What's remarkable, is how easy this was to get a nice seam without going to the painstaking-measurement-and-sheet-metal-box-bending routine. Right now it's purely friction fit but I would guess a couple of sheet metal screws could hold it to the box quite securely and with a decent shield.

Tim N3QE