by Frank Tabor
machine burning a large number of parts from thin material
up to a quarter inch in thickness it is often advisable to "stack-burn" the job.
You old-timers out there know what I'm talking about.
You stack up several layers of steel and burn through all of them.
This saves time and gives a neater burn, eliminating the "slobbers" that form under the kerf when only one plate is burned at a time.
Stack burning does have its problems.
Microscopic air spaces between the layers of plate will insulate your torch heat,
causing a loss of your kerf in the center of the stack, and making a big mess out of the whole job.
To prevent this, we clamp the plates together as tightly as possible and run weld beads across the edge to hold them.
However, that insulating air between the surfaces can be used to advantage on some applications.
I will explain one instance where it comes in handy after I go over another point in the process of acetylene burning.
In another article, I explained the wick of the initial penetration of a thick plate when burning a hole in same.
By doing it this way. you will never ruin a torch tip, and, for those of you who may have missed it, here it is again:
Hold your torch in cutting position until the plate is hot.
Then, barely press the oxygen lever, at the same time, slowly moving your torch tip.
As you continue moving. increase the oxygen pressure.
I always jam one finger between lever and torch barrel to help a gradual increase in the oxygen flow.
You old boys know how fast that oxygen tripper can go down.
Once you've tripped it. As you travel, the slag will boil out onto the plate surface behind the tip, and you'll only go a short distance further before your cut is though the material.
The principles and observation of the above two procedures are responsible for pulling me through a difficult repair situation.
That and a little plain luck.
Two loggers came into our shop one morning and borrowed a cubing torch.
Three hours later, they brought the torch back with a ruined tip, and a request for assistance to solve their problem.
As usual I turned out to be the goat. so I jumped into the repair truck and followed the loggers out to their repair operation.
At the scene, when they told me to claw my way under a huge crawler tractor, I had a hunch I was in for a challenge.
On the frame of this particular cat, was a huge cross member that was bolted between the tracks with six 3/4" cap screws on each side.
Typical rough logging usage over the years had finally taken its, toll by shearing off all of these bolts, leaving broken-off studs in the tapped holes.
To further complicate the repair, the loggers lad burned up our torch tip trying to burn out the broken ends.
Being loggers and not welders. they failed miserably and only added to the complications.
What's that, Bunky? You say they should have welded nuts to the studs and screwed 'em out of there?
Well, maybe yes and maybe no.
That works sometimes when accessibility to a job is good but, here we were, in close confinement, working in a prone position, and they had the studs recessed in their holes by the failed burning attempt.
One look told me that it was either burn out those studs or take apart the whole damn cat, haul it to town and drill them out.
You burners know what happens when you try lo burn in a hole.
The torch gets overheated and suddenly starts a fast rat-a-tat-tat that would put Al Capone's mob to shame.
It was probably this factor that contributed to the loggers flunking out on their burning try.
So. the first thing I did was lo get a can of water to dunk the torch in when it sounded off.
It took several water dunkings of the torch per stud until I got them to a burning heat.
Then, by using the penetration method described herein, I blew out all twelve broken-off bolt ends.
The "air insulation" factor worked to my advantage by letting the stud fragments burn out without doing serious damage to the threaded holes.
A couple got hot enough to slightly nick the threads.
I was able to chase the remaining residue with a 3/4 inch NC tap I had brought along.
I saved those guys several thousand dollars in repairs and down time.
Luckily they were both busy chewing tobacco, or that might of been the closest I ever came to being kissed by a lumberjack.
* Originally published in Northwest Metalworker