O/A Cutting Help

[Hilbilly]

I'm a newbie at this and I'm looking for some help. I've been cutting some gusset plates out of 3/8" x 3" flat bar. First I cut the bar into 8" lengths with my abrasive saw and then I cut the 8" lengths on a diagonal using O/A.

The issue I am having is that one side of the diagonal cut is nice and square to the face but the other side of the same cut is on an angle. Sometimes the angle is pronounced. What am I doing wrong?

 

[IslandTractor]

Photos??

Have you tried altering speed that you move the torch?

 

[Baby Grand]

So a cross section of the kerf would show a kink in it, like this?



Could be caused by a material defect in the steel strap, like a delamination.

 

[Shield Arc]

One thing you may be doing wrong is pressing the oxygen lever to far down. You'll want to adjust your torch where you have a neutral flame. Then press the oxygen lever down slow. When the cutting cone extends out as far as it's going to go, and the flame sounds like a small jet engine. You have found the sweet spot for that cutting tip. Then it's all about preheat, and travel speed.

First picture is a neutral flame.
Second picture is a cutting cone.

 

[blueriver]

Yep that "sweet spot" .. Flame, preheat and travel speed .. Obviously thicker material requires more flame .. Proper flame that is .. The angle for the preheat and the travel speed.. Just like welding machines .. Practice

 

[Gary Fowler]

Sounds like a dirty cutting tip. That is the case in 99% of the times when cut is not clean. A clean tip produces a lot less slag on the backside also.
For up to 3/8" plate, an 0 tip would be the size to use. It requires less gas to operate and will cut 3/8" plate easily with about 35-40 psi on the oxygen and 5 psi on the acetylene.

Get your tip cleaners out and clean the tip till you get a long feather like in the ShieldArc photos and hear it sounding like it is sizzling.

 

[Hilbilly]

Sorry guys but no pics. I already ground the pieces and some are welded in place. The cut is not bent in the middle. It is weird. One side of the same cut is square to the face and the opposite side is at about a 75 deg angle.

I am using the 0 tip as that is what my Victor booklet states to use and this is a new tip. Maybe only used it for 15 minutes but I will clean it.

After looking at those pics of SA's I think this may be the issue. I'm still not sure what the neutral flame is supposed to look like (even with the pic staring me in the face) but I know for sure my cutting flame does not look like SA's pic. I've been adjusting the cutting flame to get suck that orange flame back to the tip of the blue flames. I've had that jet engine but thought that was wrong. Know I know better and will try again. Thanks for that SA.

For preheat, should I preheat the whole cut area or are we just talking about the start of the cut, to get that puddle started?

 

[Shield Arc]

When cleaning the tip, make sure you turn the oxygen on just a little bit.

Once you have a clean tip, light the torch, and adjust until you get a neutral flame. Then slowly press on the oxygen lever. Watch the cutting cone in the center of the flame. When that cone gets as long as possible. Remember how far down you pressed the lever. Because that is the sweet spot!

I only preheat the plate on the bottom, if the plate is really thick.

 

[IslandTractor]

I only preheat the plate on the bottom, if the plate is really thick.

Caution: Be aware that when Shield Arc says "really thick", that he built bridges and similar structures for a living. I doubt he would consider 3/8" steel plate "really thick".

 

[Shield Arc]

Isn't 3/8" thick metal considered sheet metal?