HELP - How do you make a smooth cut with a torch? - tRustyK5 where are you?

[DPI]

Just like the subject says.

I finally got a torch set up using Propylene as the fuel. I am curious on how to make a smooth cut. I have cut some metal this weekend for my new between the frame rails winch mount. The plate I was using was 3/8" and 5/8" plate.
I am using a #1 propylene tip that is rated @ 3/4" - 1" thick plate. The problem isn't the actual cutting, I made some good looking free handed cuts and some good "guided" straight cuts.

The 3/8" and the 5/8" plate cut good except there were jagged edges. There was also something weird. There was a grove down the center of the 5/8" plate. This groove ran along the length of the plate and was about 1/32"-1/16" deep.

What is causing the groove? And how can I keep from making the jagged edge?

 

[DPI]

Somebody has got to know why this is happening.

 

[yellowK20]

Practice ,and lots of it is the only way to make good clean cuts you'll have to play with the torch to get it just right sorry that's the only thing I can really say to do once you figure out your cutting rig a little better and get some practice you should be good to go

 

[tRustyK5]

Re: HELP - How do you make a smooth cut with a torch?

Use a smaller tip and understand that cutting smooth, straight, and free of slag is a very tedious art form.

I have spent countless hours cutting miles of plate freehand, with a cutting bar (or guide), a track cutter, and a manual profile cutter for patterns. It's not an easy skill to master and the devil is in the details as is usual.

For freehand there isn't much I can tell you that'll help except to experiment with different heat settings, and tip sizes. You will get a feel for it with enough practice. Until then the grinder is your friend.

If you're stuck with only the large tip at your disposal turn the fuel and oxygen down so the torch is barely running. Set it so when you hit the oxygen bar the flame goes fuzzy...then while holding the bar down adjust the O2 until it just sharpens up.

The gouge you're referring to is from too much heat which is melting the edges of the 'kerf' as you cut.

If you're cutting thinner plate like 1/4" or 3/16" angle the torch in the direction of the cut. 30 degrees or so if the tip is quite large which it sounds like it is.

Plan your cuts, mark it well with soapstone and make all your movements as smooth as possible. I usually make a dry run over the line slowly to see whether or not I'm gonna be jamming an elbow into my ribs or anything...

Get comfortable and use an elbow as a pivot. Trying to maintain a steady torch without a 'rest' or 'support' from an elbow is very difficult.

The thinner the material the less O2 you should be running. How much less is determined by the tip size. Generally up to 1/2" plate I do not run more than 40 psi O2. With a smaller tip you'll get a much cleaner cut at 30 psi, with sharper edges at the cut.

Get some quality tip cleaners and make sure the tip is clean. A quick check is to fire it up and hit the O2 bar once it's set. There should be a sharply defined stream of O2 visible in the center of the flame. A clean tip will have an O2 stream several inches long and not veering off in any direction.

Rene

 

[tRustyK5]

[ QUOTE ]
tRustyK5 where are you?

[/ QUOTE ]

I was replying in detail...have patience young man!/forums/images/graemlins/grin.gif

Rene

 

[DPI]

Re: HELP - How do you make a smooth cut with a torch?

As usual, thanks for the tech help! That is some very solid sounding advice I am going to try.

One more question - How far from the metal should the tip be using the propylene?

I guess my next stop will be to pick up some smaller tips.

Thanks again - <font color="red"> oh Great welding &amp; cutting dude! </font>

 

[tRustyK5]

Re: HELP - How do you make a smooth cut with a torch?

I usually try to keep the tip of the torch about 1/4"-3/8" away from the material I'm cutting. Any closer and you'll usually put the torch out.

One thing that will mess up your tip is piercing a plate. An example would be cutting an oval hole for a hawse fairlead in a piece of plate. On thinner material it's not to hard to pierce the plate, but you always run the risk of blowing molten steel back at the tip and yourself as you do it. I prefer to drill a small hole where I want to begin my cut. 3/16" is pretty easy to drill through most anything quickly. Now you have a sharp edge of the drilled hole to begin your cut with. Less heat and easier on the tip.

I honestly think good cutting is harder to achieve than good welding. Both require lots of practice, but cutting is an art.

Are you using M.A.P.P?

Rene

 

[DPI]

Re: HELP - How do you make a smooth cut with a torch?

I am using a mixed gas called Propylene. It's suppose to have the same saftey charateristics as propane, but has a higher nuetral flame temp...

Here is some information about the fuel gas...

Thanks again for the help!

 

[tRustyK5]

Re: HELP - How do you make a smooth cut with a torch?

It sounds similar to MAPP. MAPP uses a regular torch tip unlike Propane and propane blends which use a different type of tip.

I've cut with Propane and it's not bad, a hair slower on the pre-heat but overall a good alternative fuel. What I do like is that Propane is easy to handle safely around home.

We use acetylene at work, which is fine but handling and stuff is a little more finicky. You must pay attention to the fuel level in the bottle so you don't inadvertantly draw the acetone crap out of the bottom...plus if the flow exceeds 1/7th the pressure in the cylinder it may spontaneously ignite./forums/images/graemlins/eek.gif As a general rule of thumb once the main regulator says 50 psi left I swap bottles. At 50 psi I can safely run 7 psi line pressure...but it's becoming a fine line.

Rene