Thread: What am I doing wrong

Generally, popping means your gas flow is too low. Open the torch valves more (but not till the flame detaches from the tip!), and if this makes the cut messier, switch to a smaller cutting tip.

Pic 003 suggests that you need more oxygen as it's not that clean a cut...but could also be too slow a cutting speed.

And I thought a no. 15 tip was for thick plate????

remove the nozzle and clean the seat make sure it is not even slightly nicked, also clean the cutting end, make sure holes are not blocked use a tip cleaner, make sure nozzle is tight, make sure tip is not too close to work, you may also have to adjust pressure

Did you pre heat the plate at all.

Looks like the flame was on the oxidising side, not enough acetylene, burning on the cold side. What angle was the torch at? Parallel to the plate or hand end raised about 150mm (6") off the plate, this preheats the plate also when cutting.
Kryn

Thanks for Your replies.
Master Splinter -I think a 15 is for 1" to 3".
China -The flame looks good but will Check and clean as suggested.
Inner cone was just clear of plate.
Pipeclay -I ran the torch along and back which wouldn't be much preheat.
KBs PensNmore -Fairly close to parallel.
Will have another go on Saturday
John.

The plate looks nowhere like an inch thick. Try the next nozzle size down.

Heat the initial starting point of the cut to cherry red with a little molten pool just starting to form - you don't need to heat any more of the plate than that.

If you've got it well adjusted and you've had a lot of practice, you can actually be a fancy-pants and shut off the acetylene once you've started cutting and just let the oxygen/iron reaction provide the heat (some 3-4,000 degrees).

Is the plate as rough as it looks in this picture?
https://www.woodworkforums.com/attach...ng-oxy-006.jpg
If your guide wheels are riding up in down over that it wont help.
Though the plate looks ok in the other pictures.

Originally Posted by Master Splinter

If you've got it well adjusted and you've had a lot of practice, you can actually be a fancy-pants and shut off the acetylene once you've started cutting and just let the oxygen/iron reaction provide the heat (some 3-4,000 degrees).

I used to do this just for fun. I've always wondered why cutting robots dont(acetylene isnt cheap) or at least none that I have seen, any ideas?

Stuart

Originally Posted by Stustoys

I used to do this just for fun. I've always wondered why cutting robots dont(acetylene isnt cheap) or at least none that I have seen, any ideas?
Stuart

/sarcasm
Because the old timers who knew how to set up the robots to do this had heaps of amassed annual leave/sick leave so it looks better on the company books to get rid of these 'liabilities' at the next down-sizing opportunity.

The pimply $12-an-hour teenagers who replaced them gained all their metalworking knowledge from watching 'American Chopper' on TV and the higher gas cost is simply billed to the customer anyway, while the business pockets the savings in labour cost.
/end sarcasm

Other than that, I dunno!

When you start the cut, is your torch angled instead of being parrallel to the cut. I have an old CIG welding booklet from the 80's. Taught myself to weld and cut with oxy, all from this book. Book suggests to angle the torch after you heat the start of the cut.

Hi Blokes,
Had a mate call in today,he has a lot more experience than me.
He cleaned and checked everything,played with the pressures a bit
and had similar results (but not as bad). He gave up on the guide bar
and followed a series of centre punch marks. He is also more even in
his travel than me. Also helped by not dragging the wheel along the
guide bar.He kept the tip at 90 degrees to the plate and didn't preheat.
Plate is 26 mm thick and has a smooth surface when cleaned up with a
josco wheel. Our conclusion is that the regulators are fluctuating.
We also tried LPG with a 12 tip but the tip wasn't big enough so we
went back to acetylene.
John

With a #15 Nozzle the plate should cut like buttter.

To me it appears a cold cut. I would start by checking the the seat is tight and that the nozzle cutting aperture is clean..

Make sure the Oxy feed knob is advanced all of its rotation,if its not you starve the flame of oxygen during the cut.

Light the acetylene and advance the acetylene knob until the flame becomes bright and starts to lift off the nozzle face. At that point adjust the flame back until the acetylene flame just sits on the seat.
Then bring in the oxy, adjusting until the points on the six needle like flames are softly rounded.

Depress the cutting nozzle and adjust the cut flame until the long flame jet stream is the longest it can be. At this point you are ready to cut.

Move the flame up and down the cut line to preheat the plate for a few moments ,say 30 or 40 secs.

When you begin the cut, preheat until ignition temperature and fully depress the cut lever. Keep it fully depressed as you cut.

Unless there is faulty equipment, you should have a much better cut.

Grahame

Graham has given you a perfect guideline to cutting your plate,all i would add is that the scale on that plate looks odd to me,either very thick or not mild steel or down grade or something like that.is it popping of the plate in 5mm or so sized flakes?Maybe try a little cut over an area you have ground clean of scale and see if its any cleaner?? cheers danny

Have been cutting today and have cut 25 to 30 ft.
Have done all of the things Grahame recommended.
I had not been turning the taps on far enough.
Danny got it right, I ground the scale off until I had
bright steel and that fixed the problem.
When I bought this plate about 5 years ago it had
a rusty brown colour to it but no deep or flaky rust.
Since then it has been outside covering some potholes
in our concreted yard. In that time it would have had
thousands of trucks drive over it. When I picked it up
it didn't look any different even on the underside.
I guess it had some sort of treatment in it's past life.
Thanks for your help,
John.

Silly question - but do you know if it's actually steel and not one of the bissloy steels? At work the bis has a similar type of "scale" and I've been told it needs to be cut with plasma - not oxy

The fact your guy could centre punch it probably measn it's steell - but just to be sure....