Dr.Al
Forum Supporter
- Messages
- 2,064
- Location
- Gloucestershire, UK
I'm in the process of making a simple cuboid frame out of 12 bits of 30 × 30 × 2 mm box section. The plan is to have the top and bottom rectangles made with mitred corners (I've already cut these bits, making sure the lengths are identical where they should be) and then have square-ended uprights joining the two frames together (with some strategically placed vent holes in the uprights to prevent blow back).
This I've done a few times before. What I've never quite managed is to get the frames I've made properly square. In the hope of getting it better this time I thought I'd ask for some advice!
When I've made them in the past, I've made the frames in two parts first (two right-angle joints). I've clamped them firmly and then done the two angled welds (the faces, not the inside or outside corner joint). I did one of the angled welds outside in and one inside out in an attempt to balance the distortion. Most of the reason I've done the frames in two parts is because my bench is never big enough!
This time I thought I'd try something different, so I've clamped the four bits for one frame up like this:
Another view:
As you can see, it's on an MDF sub-bench (always the best material for a welding bench, no?!?) which has the advantage of actually being (just) big enough. I've spaced all the bars off the bench with some aluminium t-slot extrusion to try to keep the heat away from the wood.
Three corners are clamped with (two different size) right-angle clampy things. The other one is bodged with a slightly rusty v-block as I've only got three of the clampy things. Three of the bars are clamped down to the MDF; the other one isn't as I don't have a clamp that will do the job, although I'm considering bodging something with the milling clamp set I've got.
I've spaced the mitres out with a bent bit of 1 mm TIG wire so that there's a chance for adjustment if needed: is this a bad idea?
What should I do to stand the best chance of getting it both flat (without twist) and with right-angles on all the corners after welding? My current plan is:
Any and all advice would be welcome!
This I've done a few times before. What I've never quite managed is to get the frames I've made properly square. In the hope of getting it better this time I thought I'd ask for some advice!
When I've made them in the past, I've made the frames in two parts first (two right-angle joints). I've clamped them firmly and then done the two angled welds (the faces, not the inside or outside corner joint). I did one of the angled welds outside in and one inside out in an attempt to balance the distortion. Most of the reason I've done the frames in two parts is because my bench is never big enough!
This time I thought I'd try something different, so I've clamped the four bits for one frame up like this:
Another view:
As you can see, it's on an MDF sub-bench (always the best material for a welding bench, no?!?) which has the advantage of actually being (just) big enough. I've spaced all the bars off the bench with some aluminium t-slot extrusion to try to keep the heat away from the wood.
Three corners are clamped with (two different size) right-angle clampy things. The other one is bodged with a slightly rusty v-block as I've only got three of the clampy things. Three of the bars are clamped down to the MDF; the other one isn't as I don't have a clamp that will do the job, although I'm considering bodging something with the milling clamp set I've got.
I've spaced the mitres out with a bent bit of 1 mm TIG wire so that there's a chance for adjustment if needed: is this a bad idea?
What should I do to stand the best chance of getting it both flat (without twist) and with right-angles on all the corners after welding? My current plan is:
- Place a tack on the top face near the outside edge of all four corners (red dots in the photo below)
- Place a tack on the top face near the inside edge of all four corners (blue dots in the photo below)
- Unclamp it and see how square and flat it seems; try to adjust with hammer if needed
- Flip the whole thing over and clamp it down again
- Place a tack on the inside edge of all four corners (blue dots, but on the other side)
- Place a tack on the outside edge of all four corners (red dots, but on the other side)
- Unclamp it and see how square it seems; try to adjust with hammer if needed and possible
- TIG weld (with 1.6 mm filler) each joint in turn on the faces, going red to blue on one side and blue to red on the other
- Do the outside corner joints on each corner
- Don't bother with the inside corner joints (gives it all somewhere to vent)
- See how square and flat it seems and try not to cry too loudly if it's all bent and horrible.
Any and all advice would be welcome!