Learning to Cut with Oxy-Acetylene

[ToolCrazyDude]

Hi Everyone,

I'm starting to get involved in welding and fabrication. Right now it's a hobby to make things I need, but I'd like to work on getting better and maybe make some money someday. I've done a few cutting projects with an oxy-acetylene torch that got the job done, but I'm sure I can get better.

Attached is a photo of a project I'm working on for a spare tire mount for my boat trailer. The two pieces of metal will basically be squeezed together on either side of the trailer frame with bolts, then I'll weld some square tubing and plate on to hold the tire.

I've noticed as I cut I normally have to take it pretty slow and there is a bit of molten metal buildup. Is that normal? Let me know how I can improve on the cutting side of things as far as settings on the torch, speed etc. based on the picture of the cut. Thanks!

 

[royce]

In your shoes, I would look up the chart for the torch you are using.
It will tell you what size tip you should be using, gauge settings and travel speed.
Those parameters will get you on the right track and from there it just takes a bit of practice.

Royce

 

[Downwindtracker 2]

Cutting is a serious skill. Even when I was doing it regularly, my cuts were sadly much like yours. The guys who were good, it was like it was sheared with as much slag as a sheared cut. First off use the correct size tip with the factory pressures for that tip. Different tips mix differently and as such have different pressures. Tips need to be clean , any turbulence will mess up your cut. You should have a long oxygen stream. A guy joked about my tip, "you could do brain surgery with this". He might have been able to, my cuts weren't that good. When you get a melt, raise up and use your oxygen stream. Your edge and your blown metal will tell you. Basically you want to go as quickly as you can. Otherwise you melt as much as cut. Use an edge quide. On the LAs I used, a 2" angle iron allowed me to ride the head. If I couldn't find that size, anything I could bump up against.

 

[cvairwerks]

A good primer on OA cutting:

 

[dr_clyde]

Proper tip size and pressures are probably the most critical things to get right. Travel speed and stability are second.

Nothing beats practice though.

When I was in welding school we had to prep all our test plates with oxy-acetylene, and cut our coupons for bending with the torch. We had to scarf off the backing straps, and do all the prep for the bend test.

If you boned the cutting, you failed the test.

You learned pressures and travel speeds pretty quick.

 

[sberry]

Cutting is a serious skill. Even when I was doing it regularly, my cuts were sadly much like yours. The guys who were good, it was like it was sheared with as much slag as a sheared cut. First off use the correct size tip with the factory pressures for that tip. Different tips mix differently and as such have different pressures. Tips need to be clean , any turbulence will mess up your cut. You should have a long oxygen stream. A guy joked about my tip, "you could do brain surgery with this". He might have been able to, my cuts weren't that good. When you get a melt, raise up and use your oxygen stream. Your edge and your blown metal will tell you. Basically you want to go as quickly as you can. Otherwise you melt as much as cut. Use an edge quide. On the LAs I used, a 2" angle iron allowed me to ride the head. If I couldn't find that size, anything I could bump up against.

Some of this is good and hard to explain. Getting a clean long stream with just enough to burn thru.

 

[joe49]

So you want to improve your torch cutting skills?
1] Acquire a tip chart for your torch.

2] USE IT. Tip size to thickness. Pressures as given. Travel speed as given.

3] New or clean tip. CLEAN TIP. CLEAN TIP. CLEAN TIP... Face of tip and cut
hole are most important.

4] Lighting torch gas on flame Ac only flame is not in contact with tip, close
valve till flame just touches tip, then open it a little. O2 on till preheat
flame cones are just defined.

5] When torch is clean and correctly adjusted and lit, it will make a ripping
sound with cut air on.

6] Start cut at edge by holding preheat cones 1/16'' above corner steel. Bring steel
just past red heat. Apply cut air smoothly, and begin to travel.

7] Clean steel will allow max travel speed, rust and **** will slow you down
and if real bad will not allow good cuts.

8] Float preheat cones 1/16'' to 1/8'', tip should be leaned just slightly back
from direction of travel.

9] Travel speed is correct when the cut is making a consistent sputtering
sound.

10] CORRECT ADJUSTMENTS, CLEAN TIP, AND CONSISTENT SPUTTERING
SOUND.

11] MOST IMPORTANT IS TO ALWAYS CONSTANTLY CLEAN THE TIP.

 

[Downwindtracker 2]

Cleaning Tips

I copied this from another millwright. He kept his tips in little boxes with cotton batting. You can laugh , but his cuts were clean, square, no drag marks, and no slag to speak of. Like a machine cut. The company torches would have tips that served double duty, the other being a hammer. If you wanted to save yourself extra work with the grinder, you kept your own tips, or repaired the company ones. Everybody here used LA torches.

I would file the end square, with a 6" flat smooth, then use the tip cleaner rods to clean the holes , up as deep as they would go. I then used the tip cleaner file to remove the burrs on the edges of the holes.

 

[joe49]

I re-purpose my old Tillman tig gloves into 5 tip cases.

 

[royce]

This might go against the grain, but I only clean my tips when the cut shows that it needs it.

Also, I don't clean the preheat holes unless one is producing a funky cone.

Be gentle when running the cleaner in and out, it only takes a couple strokes.

I figure that cleaning is also wallowing out the oxy hole and unnecessarily wearing the tip out, when not needed.

Not all tips cut as good as others, so if you find a good one, take good care of it.

One last thing that some will see as poor practice but works fine, is keeping a piece of scrap wood close by to rub the lit torch on and let it backfire a bit to clean the tip.

Royce

 

[joe49]

Agree, but for waiting till cut deteriorates, that is why tips are consumables.

 

[ToolCrazyDude]

Thanks for all the replies! Sounds like I need to get some new tips and charts. Any suggestions for tip kits or suppliers and chart types? I just bought a welder and could add these supplies to my list.

 

[sberry]

A tip CAN last a long time. On occasion they get damaged and cant be fixxed. I had one a while back, could feel the difference with cleaners. Got some kind of scale in the Lance hole and wouldn't smooth out, cut filled with slag no matter what. I should have tossed it in the scrap but someday generations from now someone will find it in the woods.

 

[Downwindtracker 2]

Wander into your local welding supplier and ask them. Around here, it's mostly Liquid Air. When the company moved on to HD combinations, I got the old medium duty units, welding/brazing tips and a couple of rosebuds, as well as the cutting heads. At the distributor, now called Air Liquide', with some talking I got a pamphlet chart, with some more talking and some new tips $$ in sizes I didn't have, I got an old product book. Gold !!

For the brand you are using, you should be able to get the chart on line.

If you buying , the LWS should be able to supply you with good used equipment. Some brands even though the product # is the same are now sourced in China. The guy at the LWS told the story about supplying a local fab shop, the first batch was fine, but the next one was Chinese, and he had some unhappy weldors .

 

[hefnerconstructionlc]

Check out Wayne's fix it shop on YouTube. Between him and Jody at welding tips and tricks. You will learn more in one hour then days reading and playing with it.

 

[JJohns3WG]

One thing that has helped me over the years I always go through the cutting motion as a dry run. Make sure you can have a fluid motion throughout the length of the cut, If you need to stop and reposition yourself you will be better off than trying to to force movements in a odd position just to keep the cut going. You can tell alot about how the cut is going by the slag, It should be coming off the bottom of the metal in a spray pattern. If its dripping big globs your traveling to slow and if its bubbling back up on the top your not cutting all the way through- to fast or not hot enough.

 

[ToolCrazyDude]

Hi Guys,

I know this is an older post, but i wanted to let you guys know I took your advice to heart. I got a handful of new tips in different sizes and with some practice, I'm making good cuts in 3/8" plate. I may not be the best with a torch, but I'm proud of that progress!

 

[The Cobbler]

nice, thanks for the update !

 

[Downwindtracker 2]

I'm glad I could help.

On one job, I worked as a fitter mostly. My weldor came up to me and asked where the pretty girl was. "What pretty girl ?" " The one you waved at when you were cutting this."

 

[royce]

Right on Toolcrazydude,
It is always nice, when progress is made.

Royce

 

[jhn9840]

Practice makes perfect

jhn9840
John

 

[sberry]

I have burned 1000s of feet and doing common work it doesn't matter much, it looks good but if I wanna be fussy can tell that I don't do it regular any more. It still looks good,, not great.

 

[lis2323]

Nice work Toolcrazy! If you are like me, once you get it dialed in you will find having the control addictive.

 

[BD1]

If you're making straight cuts clamp a straight edge guide down as a guide.
Use flat washers, like 3/8", to place under your straight edge. Positioning the tip lock nut so the flat follows angle maybe best.



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[lis2323]

If you're making straight cuts clamp a straight edge guide down as a guide.
Use flat washers, like 3/8", to place under your straight edge. Positioning the tip lock nut so the flat follows angle maybe best.



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Bob did you break the Welding Web again?

 

[BD1]

Yes sorry. Posted naked pictures of my welding machines .
Remember last time it took forever to return and hasn't been the same since.


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[lis2323]

Yes sorry. Posted naked pictures of my welding machines .
Remember last time it took forever to return and hasn't been the same since.


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Oh good I thought it was just me. Thought I’d have to create a new profile and username[emoji3]

 

[BD1]

I got a message from member asking about it.
Hmm, I bet it was that political thread. Weldingweb executives going to be impeached [emoji23]. Might be up after trial depending results.


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[Ohmthis]

Yes sorry. Posted naked pictures of my welding machines .
Remember last time it took forever to return and hasn't been the same since.


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I used to frequent that site tons before the mishap. Now, maybe every other month. I miss it!

 

[ToolCrazyDude]

So funny all the familiar names here. I'm weldcrazydude on the other forum. These cuts are plates for the casters of the welding table I'm making.