Post by grumpy on Feb 24, 2008 9:16:26 GMT 10
Tacking and assembly of to be welded components.
Those of you new to welding will need to develop this skill,so hopefully these few lines will equip you with most of what you need to know.Hopefully if I miss anything our other experienced members can add in what I may miss.
Firstly tacking should not be attempted until the deposit of sound material is mastered by the beginner.Poor quality tacking is worse than none at all,as it needs grinding out.
Tacking described
Tacking describes a small temporary or sometimes permanent deposit of weld used to position the work before the full welded bead is applied. The tack is meant as a semi rigid fixing which allows some limited manipulation or adjustment of the adjacent welded components.
Why tacking is needed
When a tack is applied the surfaces may not be square to each other or flush in the case of butt welded components. If the tack is of sufficient size and strength, work may be levered of tapped with a hammer( not beaten to a mangled pulp) to desired alignment.
How big to tack
Sizing of tacks is of course relative to the the thickness volume and overall dimensions of parts being joined. A general starting point for most work is a round the cross sectional size of a pencil.Vary this up and down relative to work dimension.
How,where and why
Tacks placed in diagonal opposition to each other will build in enough initial strength to resist the massive distortion force of a full weld bead.This is why full welding is not done on a job until completion of assembly tacking and alignment.Tacks should be firstly diagonal and then at either end of what is being welded and in the same plane to allow a hinging movement if necessary to gain alignmemt or square. If you are smart you should try to place tacks in such as position for easy removal ( by angle grinder) if they do not give the result desired.
Welding amps and electrode
A tack should be carried out at substantially higher set welding amperage than normal set amps for any given electrode size. This allows a deeper penetration and also the deposit is flatter allowing over welding of the tack bead at later stages.
Further information
Some very good information on avoiding distortion is available through the Lincoln website link as follows www.lincolnelectric.com/knowledge/articles/content/distortion.asp
Cheers
Grumpy
Those of you new to welding will need to develop this skill,so hopefully these few lines will equip you with most of what you need to know.Hopefully if I miss anything our other experienced members can add in what I may miss.
Firstly tacking should not be attempted until the deposit of sound material is mastered by the beginner.Poor quality tacking is worse than none at all,as it needs grinding out.
Tacking described
Tacking describes a small temporary or sometimes permanent deposit of weld used to position the work before the full welded bead is applied. The tack is meant as a semi rigid fixing which allows some limited manipulation or adjustment of the adjacent welded components.
Why tacking is needed
When a tack is applied the surfaces may not be square to each other or flush in the case of butt welded components. If the tack is of sufficient size and strength, work may be levered of tapped with a hammer( not beaten to a mangled pulp) to desired alignment.
How big to tack
Sizing of tacks is of course relative to the the thickness volume and overall dimensions of parts being joined. A general starting point for most work is a round the cross sectional size of a pencil.Vary this up and down relative to work dimension.
How,where and why
Tacks placed in diagonal opposition to each other will build in enough initial strength to resist the massive distortion force of a full weld bead.This is why full welding is not done on a job until completion of assembly tacking and alignment.Tacks should be firstly diagonal and then at either end of what is being welded and in the same plane to allow a hinging movement if necessary to gain alignmemt or square. If you are smart you should try to place tacks in such as position for easy removal ( by angle grinder) if they do not give the result desired.
Welding amps and electrode
A tack should be carried out at substantially higher set welding amperage than normal set amps for any given electrode size. This allows a deeper penetration and also the deposit is flatter allowing over welding of the tack bead at later stages.
Further information
Some very good information on avoiding distortion is available through the Lincoln website link as follows www.lincolnelectric.com/knowledge/articles/content/distortion.asp
Cheers
Grumpy