Lightweight Welding/Cutting Kit

[Graham Fredeen]

Sorry for not getting back sooner, been kept really busy and havent had the time.

As far as burn/flash back, it can be caused by a number of things, some of which can be hard to pinpoint. What is is is combustion which occurs behind the cutting/welding tip, on the inside of the torch. If the torch head has discolored due to heat that far down, that is something serious and very dangerous. Firstly, and this goes for anyone and everone who works with a torch, dont pick it up unless it has flashback arrestors. If you are getting flash back down the torch while its running and you dont have flash back arrestors you run the risk of having that ignition travel back down the torch and through your hoses and that means bad things for you and anyone else who might be around. Anyway, burn back, or pre ignition or what ever name you like to call it by, can occur if you overheat the torch tip while working (getting it too close to your work allowing the radiating heat to heat the tip up), however this will only cause the burnback when you overheat the tip. If it starts up that way and keeps at it, it is definately something else. You can also over heat the torch tip by running the torch at incorrect pressures for the specific tip you are using. Every tip is designed to operate at a certain working pressure, too much or too little and the torch tip can overheat. A simple fix is a tip psi chart or memorizing the psi's. Always make sure when you start the torch up to add acetylene until the point where the flame begins to feather and it stops producing the soot, this is when the torch tip will function at its best. If you have ever worked with a huge rose bud and not given it enough acetylene you will notice that it will pop, indicating burnback. This is because as the acetylene is consumed outside the tip, where it is supposed to be, there must be sufficient acetylene behind it to keep up with the rate of burn or to "force" the flame out of the tip if you will, if there is not enough, the flame will burn at a rate greater than the acetylene comming out of the tip and therefore the flame will burn down inside the tip and burn the oxygen and acetylene that is comming into the mixing chamber, this greater volume of acetylene and oxygen will produce an "explosion" inside the torch, making the poping sound. This rapid combustion consumes all the fuel inside the mixing chamber and the flame is forced back outside the tip, and more oxygen and acetylene fill the mixing chamber, and the flame is alowed to burn outside the tip until it has consumed enough acetylene to overcome its entrance rate and the cycle repeats. Any drop in acetylene and oxygen pressures can cause this to occur. Some of the guys at the shop I used to work at used to grab the hoses when some one was working and put a quick kink in them and make the torch pop to startle the guy using it. So, since it sounds like your burnback is occuring constantly, that means that something is interrupting the gas flow somewhere along the line. A dirty tip will cause that, a loose tip that leaks will cause it, something that has gotten inside the torch body could cause it, manufacturing defects could cause it, bad valves, o-rings, something in the hoses, and all the way back to the regulators even. First thing I would do is try to narrow down where the problem is comming from. First, replace the o-rings since you said they had been ruined. Start up the torch with the cutting head on, if it pops, shut it down. Pull off the cutting head and put on a welding tip, see if it pops then. If it doesn't, its something wrong with the cutting head, if it does, the problem lies elsewhere. If you suspect the cutting head, make sure the cutting tip is clean, make sure that the cutting tip is sealed correctly and tightly against the head. You might even try different cutting tips to see if it is just a bad tip. Make sure you are running the correct pressures. Check the torch body, cutting heads, valves and anything you can see for any defects or damages. Dropping the cutting cutting head can bend tubing and damage seating that can cause your problem. Something I forgot to ask, has the torch done this from day one, or did it start sometime after, like after doing heavy cutting, or dropping the torch, etc? If you overheated it, or put some physical strain or shock to the torch (drop it, drop something on it, etc), you could have caused some serious damage to the guts of the torch and that could be the source of the problem. If it did it from day one, then its either a bad tip, bad cutting head, bad torch, or something to do with the hoses and regulators. Just start working your way down the line trying to narrow down the source and elimanating the others as you go. Also, clean the torch up, take all the heat oxidization off the outside and clean out the inside of the torch body and cutting head, tips, etc. And check the entire setup for leaks using soapy watter at all of the fittings. Start with the clean torch every time as a good basis for your testing, that way you can make sure that what you change afterwards was or was not the problem.

Thats your best bet for fixing the issue. Unfortunately, due to the nature of the problem it is difficult to pinpoint an exact cause without going through and trying to narrow things down. And unfortunately if the problem is comming from manufacturing defects or damage, or if the torch has been overheated to a sever extent due to the problem (which it might have been from your description), you may not be able to "find" the source of the issue, and won't be able to fix the torch and will end up having to replace it anyway. Hopefully this will be of some help, and hopefully I did not write and ramble too much , there are just too many variables to put into a short post .

Anyway, good luck and I hope you can come to a conclusion about the problem, keep us posted.

[NateDJ]

Wow, I really appreciate the time and effort put into solving problems in this site! Not just mine but those of others as well because I learn a LOT form them.

I apologize for hijacking the thread but hopefully this will also help some others down the road as well.

The problem started when I was cutting apart some steal which kept running back together after the cut. At first I suspected I had the pressure set too low and the gas was just not forcing the metal out of the cut. I turned it up a bit and then found if I held the tip quite close (~1/16'')to the work it would do a much better job. So it sounds like a combination of the 2, too close and incorrect pressure.
I tried a welding tip this weekend and it did not pop so I think the damage is limited to the cutting head or tips.

I will clean the thing up as best as I can and see if I can get it to quit, if so then where would I find a pressure setting chart and about how far should I hold the tip from the work? At what thickness of metal should I move to a larger tip? I currently have a #1 and a #3 tip for the cutting head.

Thanks again for the help!

[Graham Fredeen]

Found a couple of tip charts on a site

Hooper Welding Supply - Tip Charts

It has material thickness recomendations and psi for the range of tips, both welding and cutting. The thickness recomendations aren't set in stone, you can get some tips to do a bit more or less than what is recomended, but that gives a good guidline. Like if you don't have a number #2, you can probably turn a #1 up enough or a #3 down enough to get the job done, but a #1 isnt going to be able to cut up to what a #3 will.

Correct pressure is definately key when cutting, too much or too little and you can get that extra slag that flows back in and seals your cut back up. Additionally proper cutting technique will help as well. When you are cutting, angle the torch slightly into the cut, this allows the preheat flames to provide more heat in front of the cut and will help you keep your cut continuous. Additionally the angle helps to blow the slag out and away from the cut areas towards the colder steel. The cut you just made is hot, and the material in front of the cut is comparitivly not, the hot slag is attracted to the heat and will want to bond with the heat. Cutting with the torch straight down will allow some of the slag to flow back into the heat instead of being blown away. Travel speed is also something that can effect your cut, too slow of a travel speed can cause the slag to build up, too fast and you will loose your cut. A lot of travel speed comes with experience, just knowing how a cut is progressing and what the slag is doing and adjusting to accordance. Also, overheating the material before making the cut can create excess slag as you are allowing the oxidization process to effect more than just your cut area, this will also give uglier cuts with a wider kerf. You should only have to heat the material to about a cherry red at the cut's start and the following oxidization reaction will maintain itself with the heat generated from the process and a little help from the preheat flames.

Whenever cutting or welding, you want to keep the preheat flames, or the cone on the welding tip up above the surface of the metal. The exact distance varies slightly depending on what you are doing, closer for a bit more heat, further away for a bit less, but keep the tip of the cone above the surface of the steel. That flame is also more oxidizing and has more "force" beind it, so if welding, you'll get a lot of undercut and porosity and blow out if you are running the cone in the puddle. Not to mention overheating the tip.

Usually with an overheated tip, if you let it cool off and clean it up it should work just fine, so long as you didn't overheat to the point of drastic failure and disfigurement. Cutting tips aren't as big of a deal to replace as the whole cutting head, so hopfully thats where the problem lies.

And no worries about the advice, always glad to be of help. We all are a pretty tight community and good folks (or at least that's what Id like to think ), and thats what good folks do, try to help when we can or find out where you can get some help. And thats why the forum is here.

Graham

[Sade McCraw]

I suppose if you only wanted to heat treat you might be able to get by, but I think I'd have to agree with everyone else, In the long run u'd be a lot better off with a descent O/A rig.

[NateDJ]

Thanks for the help, the tip chart comes from a supplier that is just a few blocks from where I work and has been bookmarked and sent to the printer! Looks like I still need a lot of practice, I have been angling the tip into the cut but I likely have been going way too slow and keeping the tip too close. Most likely due to cutting WAY too thick material with a small tip. Was trying to cut 2.5'' with a #1 until I switched to a #3 then most likely overworked the #3 by cutting ~60'' of 2.5'' steel only stopping to clean out the tip and change O-Rings.

I suppose if you only wanted to heat treat you might be able to get by, but I think I'd have to agree with everyone else, In the long run u'd be a lot better off with a descent O/A rig.

I would love to be able to drop $300+ on a new torch, believe me I would but my wife would throw a fit! You see... she too was a McCraw so you might be able to understand. She did let me buy a really nice Marquette 300A AC/DC welder because it was on-sale for 1/2 off! (Marquette is made by Lincoln for those who care.) She also tells me she had a relative named Sade but she thought they lived in New Mexico, small world!

[nfinch86]

You would spend a small fortune on oxygen with one of those.
Save up your money for a real oxy/accet set up and then take care of it, it will last you half a life time.

welder19

WELDER 19; i COULD NOT Agree More; BUY the Real Thing: Norm :

Yes I Agree with most on here, Buy the best outfit you can Afford , You will never be sorry!! Norm :

[Finnr]

Pop always said, "Buy the best you can afford and you won't have to replace it every two weeks."
Finnr

[Sade McCraw]

That has my curiosity going NateDJ:o