In message , Harry
Bloomfield writes
Richard submitted this idea :
I'm (fairly) good at sticking bits of trailer together with my MIG
but have never built anything from scratch.

Friend wants me to build him a light duty security door which will
allow him to prop the main door to an underground building open so as
to allow increased air flow but which exclude unwanted visitors. I
guess that he envisages something like a tennis court gate but with
expanded sheet steel in place of the chain link netting.

So, to the questions. Assuming that I make the frame and door from
RSA steel, how do ensure that everything stays flat and square as I
weld it up? Do I need more/fewer/different braces? How do I attach
hinges and locks? Any pointers to plans/instuctions on the web would
be much appreciated.

Depending upon the accuracy needed, it needs to be laid out on a good
flat surface and either clamped or weighted down so it doesn't move.
Then make several tack welds around the various bits, before
progressing on to the full weld runs.

For largish agricultural doors (2mx5m) I use 50mm x 50mm box section.
For a similar weight, you get much more stiffness.

As others have said, tacking is essential to avoid movement as welds
cool and to allow adjustment on checking for square. I am fortunate in
having large areas of concrete floor to work on. Using stick welding, I
find vertical runs difficult so keep turning the work to provide
horizontal welds.

While we are here, has anyone a sub 99ukp auto darkening welding shield
to recommend?

regards




--
Tim Lamb