Help. How do you avoid undercut.

   / Help. How do you avoid undercut. #1  

4570Man

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I'm using a miller stick welder with 7018 rods. I can't run anywhere close to the amperage most guys say to run without getting severe undercut. My Grandpa had a buddy who was a certified welder, but sadly he passed away a few years ago. He could run 150 amps on drive shaft tubing, but I can't go over 80 amps. On 3/8 inch steel I have to run about 110 amps. Any help would be much appreciated.
 
   / Help. How do you avoid undercut. #2  
Can you post some pictures of where your having problems? You don't give enough info to be able to give an answer. Is the welder DC or just AC, what were you welding, etc.
 
   / Help. How do you avoid undercut.
  • Thread Starter
#3  
I would be glad to post pictures, but I won't be able to get back in the shop until the first of October. It was my Grandpas welder and I don't know if it is AC or DC.
 
   / Help. How do you avoid undercut. #4  
First thing that comes to my mind when dealing with undercut, is rod angle. For a guy who doesn't weld much I'd say check the arc length.
 
   / Help. How do you avoid undercut. #5  
You are not saying what size electrode you are using. 150 amps sounds a little like you are using 5/32 electrode. On DC reverse polarity I usually run 3/32 rod on around 85 amps. 1/8 rod at around 120 amps, flat. Vertical will be less. 1/8 rod vertical around 105 amps. welders will vary on heat. I used a gas drive Hobart once that I had to turn way down because it just ran so hot.
A starting point for amperage for a rod would be 20 to 30 amps for each 32nd of electrode size. Then adjust accordingly.
 
   / Help. How do you avoid undercut. #6  
Nevermind what the dial says.

If it' too HOT, turn it DOWN.
If it's too COLD, turn it UP.

If you can't tell if it's too hot or cold, you need motr practice.

One of my old welding text books had an exercise of changing the current by a small amounts untill you couldn't weld, to see how it effected the bead.
 
   / Help. How do you avoid undercut. #7  
if you are doing any sort of weave I would try pausing on the edges for a split second. if you are just dragging the rod I would try a slower travel speed.
 
   / Help. How do you avoid undercut.
  • Thread Starter
#8  
I think the rod is 1/8 inch, but I need to measure it to be sure. I can't run 150 amps. 115 is about as hot as I can do.
 
   / Help. How do you avoid undercut. #9  
There's just so many things that might be causing the undercut. It could be a combination of things as well. Rod angle, travel speed, arc length, amperage, etc.
 
   / Help. How do you avoid undercut. #10  
That amp setting on the welder is just a guideline. My old ac/dc tombstone would run 1/8 7018 all day long at 90 amps, One click on the knob would turn the rod red as I welded. My lincoln 250amp stick tig machine I havent found that sweet spot yet.
 
 
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