It is currently Wed Nov 22, 2017 12:44 pm Advanced search

O/A cutting problems

Metal cutting - oxyfuel cutting, plasma cutting, machining, grinding, and other preparatory work.

O/A cutting problems

Postby mjr6550 » Fri Aug 11, 2017 1:00 pm

I know that this subject has been covered before, but I could still use some advice. I have a rusty I-beam that I want to make into a large cross. Along with that I want to "write" some words and dates in the web. I would like to leave the rust on the I-beam unless that is not practical.

I tried cutting and "writing" and had trouble getting clean cuts. I tried 00 and a 000 tips using about 5 psi/15-20 psi. The cuts want to melt back together. I tried not to wait too long before hitting the O2. Since I could not see the metal turn red I hit the O2 and when it did not cut heated just a little more. Also, I had the O2 control on the handle full open and controlled the O2 at the torch end.

I attached photos of front and back.

Thanks.
Attachments
20170729_105620 (1024x576).jpg
20170729_105620 (1024x576).jpg (60.25 KiB) Viewed 347 times
20170729_105614 (1024x576).jpg
20170729_105614 (1024x576).jpg (59.81 KiB) Viewed 347 times
20170729_105600 (576x1024).jpg
20170729_105600 (576x1024).jpg (61.74 KiB) Viewed 347 times
mjr6550
New Member
 
Posts: 4
Joined: Sun Dec 08, 2013 5:31 pm

Re: O/A cutting problems

Postby Arclight Ironworks » Fri Aug 11, 2017 4:39 pm

Torch manufacturer? Base metal thickness? Experience level in operating an O/F torch?

We run Smith/Miller OxyAcet and OxyPro torches. Medium Duty rigs. In our OxyAcet rig with an MC12 tip in "00" for cutting 3/8" steel, we run 10psi for the fuel and 20psi for the O2. Yields a kerf width of 50thou.

You need to achieve a neutral flame while dialing in your torch, and be sure to preheat your base metal before injecting the oxygen. The base metal will approach a near-puddle and begin to sparkle. Then it's time for the oxygen boost.

As with anything, you need to test and learn what works for your tactics amd your torch. There are always minor variables and details that are required for success. Cuttting clean letters in i-beams is not a "light off the torch and produce perfect results" the first time.
Purpose, then passion; practitionership and practicality. Patience. Obsession and hard work. That's the discipline.
User avatar
Arclight Ironworks
Active Member
 
Posts: 37
Joined: Tue Apr 11, 2017 10:31 pm

Re: O/A cutting problems

Postby noddybrian » Sat Aug 12, 2017 3:30 am

I would say that trying to cut steel that rusty with O/A is something you would only do when cutting scrap to a size so it fits in a skip or trailer - the torch cuts by oxidizing the steel - rust is iron oxide & has already got to a point it won't react much more with O2 if it's thick so it won't cut - my suggestion would be roughly mark out the cuts & letters - carefully clean about 1/2" width where the cuts will go with a grinder on BOTH sides then re-mark accurately & cut as carefully as your experience allows with as previously mentioned a neutral flame - that way you get a fair cut & the overall effect is still the original weathered surface - the small area ground will quickly blend in as the HAZ from the cut oxidizes quickly.
noddybrian
Weldmonger
 
Posts: 1170
Joined: Thu Jan 24, 2013 12:13 pm

Re: O/A cutting problems

Postby Lightning » Sun Aug 13, 2017 6:33 am

I don't know how thick your steel is, but I would go up a size or two on your cutting tip, and I would up the oxygen pressure some, even higher than the recommendation from the cutting tip manufacturer. When I was having similar problems, that's what solved it for me.
Lightning
Active Member
 
Posts: 32
Joined: Wed Aug 24, 2016 9:55 pm

Re: O/A cutting problems

Postby Poland308 » Sun Aug 13, 2017 8:31 am

I run a real small cutting head like that on my work truck setup. I run 30-40 on the oxygen and about 7-10 on the acetylene.
I have more questions than answers

Josh
Poland308
Weldmonger
 
Posts: 2278
Joined: Thu Sep 10, 2015 8:45 pm
Location: Iowa

Re: O/A cutting problems

Postby mjr6550 » Sun Aug 13, 2017 1:56 pm

Thanks for the replies.

My experience is pretty much what you see in the photos-very little.

The torch body is a Victor 100FC. I don't recall the number of the cutting attachment. It is a Victor clone. The cutting tips I was using were 00-3-101 and 000-3-101. I looked at the 00 tip that came with the torch (I bought the torch used). The center hole and perimeter holes connect, at least at the face of the tip. The other tips I bought (Victor clones) do not look the same.
Because of that I decided to try a 0 tip using about 7.5/35. I cleaned the steel a bit also. The cuts are a bit better. I made a pretty clean cut through a flange that varies from about 1/4" to 3/8" thick and pretty clean cuts through the web, that is slightly less than 1/4". I also went away from the cleaned steel and it cut just about the same. When I was cutting a curved line I probably went a little fast or moved the torch away from the line. You can see where I messed up the line getting back on track. I also cut a round hole to see how that worked. That seemed to go fine.

Here are a few more photos. Feel free to be critical. I appreciate the feedback.
Attachments
P8139736 (1024x683).jpg
The new cut us the vertical one at the upper right
P8139736 (1024x683).jpg (64.43 KiB) Viewed 272 times
P8139741 (1024x683).jpg
Back side of fourth photo
P8139741 (1024x683).jpg (68.93 KiB) Viewed 272 times
P8139735 (1024x683).jpg
P8139735 (1024x683).jpg (50.17 KiB) Viewed 272 times
P8139740 (1024x683).jpg
The wavy line next to the 2 is the new cut-note where I went off course-the jagged edged hole is of course the one I cut
P8139740 (1024x683).jpg (74.51 KiB) Viewed 272 times
P8139737 (1024x683).jpg
back side of first photo
P8139737 (1024x683).jpg (66.14 KiB) Viewed 272 times
P8139734 (1024x683).jpg
Cut through flange
P8139734 (1024x683).jpg (73.22 KiB) Viewed 272 times
mjr6550
New Member
 
Posts: 4
Joined: Sun Dec 08, 2013 5:31 pm

Re: O/A cutting problems

Postby Poland308 » Sun Aug 13, 2017 7:40 pm

Angle of the torch head is also important when cutting.
I have more questions than answers

Josh
Poland308
Weldmonger
 
Posts: 2278
Joined: Thu Sep 10, 2015 8:45 pm
Location: Iowa

Re: O/A cutting problems

Postby Otto Nobedder » Mon Aug 14, 2017 6:13 pm

You can also rapidly rust bare metal from cleaning by hitting it with a 50-50 mix of white vinegar and household bleach. Just keep the surface wet until you get the patina you're after, the lightly rinse it with water.

Steve S
User avatar
Otto Nobedder
Weldmonger
 
Posts: 8404
Joined: Thu Jan 06, 2011 11:40 pm
Location: Near New Orleans


Return to Metal Cutting