I would not call out a "tack" weld, but would rather specify the proper weld if it is required. Tack welds are usually only temporary work-holding welds, and are usually left up to the welder. If you need to specify them, then I would call them out like a normal weld process- specify the weld type, length and any other pertinent information.
If you are not familiar with weld documentation, you might want to look at the following:
No, stitch welds are intermittent welds, at fixed spaces and weld length.
As the other guys said, "tack weld " is a shop term for temporary welds to hold pieces together before making the primary weld.
Welding nuts over a clearance hole to make cheap tapped holes is good in many applications, but the weld should be defined by type, size, symbol, and whether at 2 points, 3 points or all around.
I'm sure there is a book some where that has a specification and details of this ...probably in some aero-space discipline somewhere. But in my world (oilfields) the contractor are use to the basic term "tack weld" so we just show a fillet weld symbol with the "fish tail" at the end of the welding symbol and plug in "tack weld" behind it. I've been working in this area 20+ yr.s now and nobody ever came back to me and asked what I meant.
I too have used it when I designed welded equipment for Chemical Process industry. But:
1) I didn't use a fillet symbol, just line, arrow, and words tack weld behind the fish tail. (It used to be shown in AWS 2.4 that way, but isn't there anymore.)
2) I only used it when I indeed wanted a temporary weld. If it was to be permanent, I wanted more control than that, so I specified a size.
AWS 3.0 defines tack weld as "A weld made to hold the parts of a weldment in proper alignment until the final welds are made."
Colloquial terms aside, that is it's proper definition.
While I'm sure it's not technically correct, I usually use a fillet weld symbol with "Tack" written in the length/spacing location. If it is necessary, I will put a fillet size, but if it is a nut smaller than 1/2" this usually isn't necessary. I may also include "3 places" either under the word "Tack" or with a fishtail. Again, this probably is ambiguous, but the guys in the shop know what to do.
This reminds me. Just yesterday I heard someone reffering to what is technically stitch welding as tack welding. He was American too, so it's not just a Brit thing. That said, he was an electrical guy turned manager so...
KENAT, probably the least qualified checker you'll ever meet...
