Star'55,
I don't think this method of fitting and tacking up is nearly as reliable as following every seam in sequence with tightly spaced tacks? IF the edges are dead-on accurate, and most NC but parts are, then tacking from one end of any seam to its other end will rely on the accuracy of the seams/parts' edges for the shape and fit of the parts.
For example; If you have a bottom seam with curvature and tacked that seam every 12-16" 'just to get it fit' (so to speak) I think you'd risk having open seam stretches where the material will not be edge to edge- as shown in the plans and designated in the cut files? If you have exact cuts- then best practice, IMO, is to start at one end, and fit edge-to-edge precisely and tack every few inches precisely and the ends of the material will come to a single meeting point- and you'd tack back from that end by and inch or so.
starbright55 wrote: Wed Dec 18, 2024 6:04 pm
Once I'm happy with the fit up, I will add more tacks to fill in the inbetweens
Many parts intersect in weld seams at an angle to each parts' plane. That means the line of intersection, in 3D, would be best served to line up the cut edges as perfectly as possible and tack in short increments (2-4" max) and not 'go-back' to try to add tacks "inbetweens". Edge-to- edge fit contributes to the cleanest and most uniform weld seams. That method also means the two adjacent parts are fit to a 'knife edge' and therefore any curves are fit to the slightest variation possible- unlike tacking at longer intervals where the 'inbetweens' added later don't allow as perfect an opportunity to get the edges as well aligned for tacking.
Tig Beads:
Your TIG beads look good, now to work on getting back into the bead or 're-starts' which is where most of us have the least consistency but results in the best looking final beads; once mastered.
Re Tack Up:
One method that seams to work pretty well for tacking up tanks, consoles, helm/dash board assemblies involves using the
https://www.midlandtool.com/itemdetail/PGA20 (example) long reach or "deep reach" style of Vise-grip (tm) or equivalent brand. I keep a dozen pc.s about 1/2" long/width of 2" x 2" x 1/8" angle that I hold each side with a long reach clamp. Once located inside the seam to be tacked, I clamp the 90 degree plane and move along the seam every few inches to tack. This seams to work pretty well.
If I can't get a clamp on the back up angle- I just tack one leg of the short pc of angle to the first side- while the surface of the other leg is held to the plane the adjoining face will need to form. Once tacked, the inside tacks that remain, often don't even need clean up- they're not going to be seen but of course, you can dress them off if you prefer.
This method works for everything but the 'top' or final side where you can't get inside to clamp the angle back-up's. You can tack in permanent line up parts but not always the best practice inside a tank. In those cases I put a pc of banding material; thin steel strap over any adjoining corner at 45 deg. This will support the final side and hold it the banding material thickness above the edge of the tank, console or other assembly; while you line it up to tack. Then pull the banding material and tap the tacks slightly tighter- if you plan to keyhole the weld (tank tops) then leave the gap you plan to pull along with the weld. If you're going to MIG the edges, and router them for finish, then tap the gap tight to the inner edge of the sides of the assembly.
By following the parts' edges closely and using a sharpened standard screw driver blade to pry open the joint when too tight for a tack... you can pretty smoothly tack up almost all assemblies where they're joined in an outside corner (shown in lots of photos) and keep great control of the seams' fit until its ready to weld.
Just a few more remarks about how to tack up and hopefully justifying my reasoning of why to tack closely as your progress along any seam.
Cheers,
Kevin Morin
Kenai, AK
