Welding advice please.

[Richard]

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.

TIA

Richard

[Clint Sharp]

In message , Richard writes

It's easier IMHO, you get nice clean corrosion free metal of your choosing and you can set up the MIG on the offcuts so you know exactly how it's going to work.

I'm probably completely wrong and going to be shot down in flames but when I've built frames in the past I've used magnetic squares on corners and put a tack weld on each corner/joint. Once the frame was 'complete' I checked for square , adjusted as necessary and then finished off each joint. Obviously measuring and cutting accurately makes your life *much* easier in that respect.

I made my own hinges with tube and bar but my application probably wasn't the same as yours and I didn't need a lock. ISTR that Machine Mart had a range of metals and bits like hinges etc. for building gates? Might be worth a look.

[Harry Bloomfield]

Richard submitted this idea :

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.

[Tim Lamb]

In message , Harry Bloomfield writes

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

>

[Richard]

I had wondered about making accurate 90 deg corner plates at home and taking those to site to use almost jig-like to ensure accuracy. Might that work?

Richard

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Richard saying something like:

Of course.

[Andy Dingley]

Tack it together carelesssly with _small_ tacks, then bend it very carefully to be as absolutely flat as you can make it.

A concrete driveway is _not_ a trustworthy surface plate, unless you've verified it to be flat first. However the water surface on a flooded driveway is! Probably the simplest method for a single edge is to use a long aluminium brickie's spirit level.

Once you then have it wedged carefully to be level, and weighted down so that it won't warp (much) you can then proceed to do the finish welds. Do these slowly, allowing heat to dissipate between them.

if you have to, weld temporary stays in place and angle-grinder them off afterwards. Don't trust a mag clamp to hold anything accurately in place. Don't trust a cheap mag clamp (or cheap non-Vise Grip vise grips) to even hold.

[Andy Dingley]

SIP, the cheapie one.

[Tim Lamb]

In message , Grimly Curmudgeon writes

Just check the diagonals are equal

regards

[RW]

If you can why not cut the material to the correct lengths and prop it into the door frame with spacers around it on each side, top and bottom. Weld temporary bracing to it and tack the joins so that it can be manhandled to a better place for welding properly. When at a suitable area you can add the internal mesh and weld properly.

The advantage being that if you are near the site you can offer it up to ensure a perfect fit and check where to add the hinges.

[Richard]

Good idea.

[Dave Osborne]

Tim, did you get this sorted? I just found this website. Haven't used 'em yet, but choice of auto-darkening helmets for well under a ton.

Rumble

[Tim Lamb]

My birthday coincides with Christmas.

At those prices, I could get two:-)

Advice was to look for SIP version and elsewhere that battery operation was safer.

thanks