Drilling steel.

tuolumne · Jan 28, 2008

I need to create four 1-1/4" diameter holes in a scrap propane tank. The walls appear to be about 3/8" thick. What are my options? I have no tool suited to the job unless a holesaw would work with cutting oil.

shvl73 · Jan 28, 2008

A bi-metal hole saw should work fine with slow speed and oil. Do a search on propane tanks, I've no experience in drilling one and there was alot of discussion on how to do it and if it was even safe to do at all.

CATMAN · Jan 28, 2008

For safety; Is there any way you could fill it with water first, so you displace any possible residual, explosive gas BEFORE drilling. I met a guy who had a portable air tank (old,rusty) blow up between his legs while filling. Almost killed him. I have never personnally drilled this type of tank before, but I think a hole saw will work.

ultrarunner · Jan 28, 2008

For what it's worth, I seen people fill the tank with water.

In the machine shop, we would purge tanks with Nitrogen prior to welding,

tuolumne · Jan 28, 2008

ultrarunner said:
For what it's worth, I seen people fill the tank with water.

In the machine shop, we would purge tanks with Nitrogen prior to welding,

I'll try the holesaw then...these tanks have been sitting outdoors for several years. The 6 holes in the top (1" to 1-1/2" have been open, as well as the 3/4" drain hole in the bottom. Is residual gas an issue? I will be welding a bushing around the holes to accept threaded pipe. I can partially fill with water, but two of the holes would be near the bottom, so I cannot fill very deep.

Edit: These are 500 gallon tanks, so not very maneuverable!

NFA Fun · Jan 28, 2008

Look at renting a "mag drill" basically a small drill press with a strong electromagnetic base. Using a hole saw in a hand drill...you will be there forever. Not to mention risking damage to the hole saw.

Is torching an option as long as you are welding an insert?

CATMAN · Jan 28, 2008

I used to read a lot of Smokey Yunick stuff (highly regarded professional mechanic/inventor). He tells of a test with a old,empty 55 gallon gasoline barrel, that has set outside open (2 holes) for 3-5 years(if memory is correct) and he put a spark plug down into it with a long spark cable attached and iqnited it with a magneto. It BLEW up. This was to show the power of vapor. I always think of vapor when it comes to these kinds of projects. I have heard of people who pump tractor or automobile exhaust into gas tanks before they weld on them to try and remove any vapors and oxygen out of that internal space/cavity.

rich_ncal · Jan 28, 2008

A couple of years ago, I met someone that made and sold yard art out of discarded propane tanks, mostly the smaller 5 or 10 gallon types.

He had a special process for cleaning the tanks. I think he also partially filled the tanks with water while working on them.

He said even if the tank was empty for some time there was still propane that was embedded in the metal that came back out to the surface.

I don't know if this is true, but be careful.

Casco1 · Jan 28, 2008

CATMAN said:
For safety; Is there any way you could fill it with water first, so you displace any possible residual, explosive gas BEFORE drilling. I met a guy who had a portable air tank (old,rusty) blow up between his legs while filling. Almost killed him. I have never personally drilled this type of tank before, but I think a hole saw will work.

Being the last person to talk safety to anyone, I would like tell a story. Friend replacing gas tank on old mahogany boat. he removed the tank brought it home. We needed to remove filler assembly which was soldered on the steel tank. The first think that I thought of was the danger of explosion so we filled the tank with water thinking we could still get enough heat to soften the connection.

Flaw in our plan: Not realizing tank was baffled and the water just pressurized remaining fumes in the compartment we were working on. In short BOOM!!!!!
the explosion knocked us both on our butts 6 to 7 feet away, temporary hearing loss ( several minutes ) What saved us was the tank was made from heavy enough steel it blew a seam rather than split into pieces ( shrapnel ).

Good Luck. but be very very careful.