Question about oxy-fuel in moderately heavy plate

[Steel Burner]

Hi there,

I've got a question about oxy-fuel (specifically acetylene) cutting circular shapes on reasonably heavy plate (1.5" - 2.5"). I've noticed that when cutting profiles out of this size of plate, the cuts are great when moving in a straight line, but as soon as the torch gets a little ways into curve, the cut will start to flare out a bit at the bottom half of the plate, or the cut will become convex. It seems to me that the travel speed is too high, but the quality of the straight cuts prior to the curve are great. Any input on this would be very much appreciated. For 1.5" plate I use a #2 tip, oxy psi is about 33, fuel gas psi is at about 5. A lot of the pieces we make are quick attach ears for heavy equipment out of QT-100 plate, being that this stuff is so expensive I would like to be able to improve cut quality without practicing if you know what I mean.

edit: the cut will become concave, not convex.

[damage inc]

1.5 - 2" is moderately light plate compared to what I've seen/cut, although most of my cuts are out of A-36/HR/1045/4140/514 material. In my experience, with light plate oxy fuel cutting (1-2") a concave cut edge, or bevel is caused by 4 things.

1. Your torch is too high from the plate: Ideal torch height is around half inch MAX.
2. You are cutting too fast: Using propylene and a #2 tip, I cut 1.5 around 11.25 - 12.5 ipm, depending on how I adjusted my torch temp.
3. You are burning too hot: adjust your torch to lowish volume, and fairly cool. Like the torch sounds like it is kind of breathing on you (volume), and blue inner cones are around .25" long.
4. Your tip is dirty/getting dirty: Run a cleaning cycle on your plate before you cut. high preheat torch setting (very hot) run torch over cut area around 60-130 ipm, but cool your torch down before you cut!!! also, after you pierce, clean your tip and scrape the pierce hole to clean it up.

You're using a #3 for the 2-2.5" correct?

I don't know if this all is too basic or what? Sorry if I offend, I don't know anyone's experience burning here, just found the site...

[WSS]

Here is a good read....

WSS

[m230042]

acetylene has a very close thermal coupeling height so the .5 inch cut height is out. way too high. you are at a disadvantage with a 6 hole cutting tip as the pre heat is not liniar around the tip. Proplene has like 32 slots in it's tip so it's directional preformance is better.

To test this put a sharpie mark on the tip and the torch. Make cut, rotate tip 90 degrees re test.

some machines have a minimum corner speed setting. this is mainly usesed for THC on plasmas but can cause trouble.


Marv

[NoLimit]

Sounds to me you are running to fast...