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I need to tack a zinc plated bolt to a steel plate... should I just grind off the zinc plating where the tacks will be? Also will the heat greatly affect the strength of the bolt? (Should I do 1 tack and let it cool before the next tack??)
The bolt is a 1" x 3" bolt so it will take a lot of heat to get it hot.
I also will be doing the same to a 1.5" bolt on the next project......
If you are tack welding a 1" gr8 bolt to a plate, I doubt you need to be concerned with the strength of the bolt dropping. Is the plate intended to tranafer load from the bolt? Is grade 8 specified for some reason?Quote:
Originally Posted by ShaneJackson
You can grind the zinc or just weld it as is. The zinc could add a very small amount of porosity to the welds, but it is minimal. Grinding won't hurt anything.
The proof load for a 1-8 gr8 bolt is over 72,000 lbs.
For a 1.5-6 grade 8 is is over 168,000 lbs.
The tacks are to keep it from spinning or falling out. The plate will be welded to a pipe. The bolt head will be inside the pipe never to be seen again....
Your "tacks" will have to resist about 900 ft-lbs tightening torque if assembled dry.
Assuming a standard 1-1/2" head on the bolt, your welds will be at 3/4" radius (conservative), which makes ~ 14,500 lbs shear requirement in the sum of your welds to prevent torque out.
This all assumes that a Gr8 fastener was required and will be properly tensioned (thus the 900 ft-lb reference)
To go another step, assuming you are using 70ksi filler, and using a 50% knockdown for shear (again, probably conservative), you have 35,000lb/in² shear strength in the material.
14,500lb / 35,000lb/in² = .414 in² weld throat area requirement.
If you have a .25" weld throat, .414in²/.25in = 1.65in total weld length...probably a bit more than just a few tacks.
This is weld throat, not weld leg length and alll of this may be incorrect as I didn't check the math.
How thick is the plate? Why tack vs weld it in?
.250 plate. When I say tack I do not mean small tacks. I mean .5in long beads on each of the sides.
The "job" did not specify grade 8. I just went with grade 8 for the higher strength.
I'd buzz the coating off, flatten the markings, chamfer the edges and burn it in, opposite sides sequentially.