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im#2
10-13-2015, 06:19 PM
Need to pick some brains, today early I tried to drill out a broken off bolt in a 400 gallon propane tank. Said bolt is one of four holding the gage in the tank
and also squeezing a flat gasket beneath same gage thus preventing leeks. I took everything I had along as it was about 40 miles out. tried left hand drill out carbide bit first with no luck, then tried my set of 1/4 inch carbide burrs which barely touched it. after abut an hour we had a dimple almost 1/8 inch deep to show for our efforts. I have never had this happen before in a life time of broken off bolts in various items.
Obviously an EDM would work but might remove me AND the tank from our place on this earth so--- are we agreed this IS one hard bolt!

boslab
10-13-2015, 06:27 PM
I know where this is going, unfortunate but all the solutions are going to include the risk of blowing the **** out of yourself, scrap the tank, it may be safer, I'd rather sit on top of a 1000lb satan bomb from WW2 and drill holes in it than do the same to a propane tank myself!.
If you do diamond drill I'd suggest flood cooling but sign your will before you get your hands wet,
http://youtu.be/Lr15rPHEmeQ
Mark

Left Handed Spud Wrench
10-13-2015, 06:52 PM
Any chance of filling the tank full of water or inert gas or something before breaking out the big guns?

Fasttrack
10-13-2015, 06:59 PM
400 gallon tank? I say scrap the tank. A new tank can't be that expensive compared to your time and materials to drive out there twice and risk life/limb getting a broken bolt out. Last time I checked, you could find a 500 gallon tank for about $800. Even less if this is a 420 lb tank, not 400 gallon.

im#2
10-13-2015, 09:50 PM
I have withdrawn from that project for lack of performance. Please notice we do use a expanding rubber plug to seal the hole while doing this and the tank is at zero pressure. We evac the liquid and release/let off the residue vapor, its takes several days to get ready.
I was just wondering if there was anything I hadn't heard of that is better than the solid carbide burrs as the diamond coated Dremel bits just didn't see very little material removed.
I use a cordless dewalt drill which is pretty well sealed and that combined with the plugged/ no pressure tank

rdfeil
10-14-2015, 12:10 AM
Not to be snarkey BUT.... a 0 pressure tank is a tank full of vapor of some concentration. Get the right fuel to air mix and a spark and BOOM BOOM...

Now enough for the harping. If you encounter this again I would recomend purging the tank with either CO2 or Nitrogen to remove the fuel/air... Lots of purge and keep it purging while you work. A $800 tank is not worth Dead or injured. As for the origional question, I would think the carbide burrs would have worked quite well.

R

Left Handed Spud Wrench
10-14-2015, 12:48 AM
Not to be snarkey BUT.... a 0 pressure tank is a tank full of vapor of some concentration. Get the right fuel to air mix and a spark and BOOM BOOM...

Now enough for the harping. If you encounter this again I would recomend purging the tank with either CO2 or Nitrogen to remove the fuel/air... Lots of purge and keep it purging while you work. A $800 tank is not worth Dead or injured. As for the origional question, I would think the carbide burrs would have worked quite well.

R

Quoted word for word because this is very very critical. Purge the tank and fill it with water. If you can't fill it with water have a tank of inert gas on constant flow. There is no such thing as too careful when welding, grinding, cutting or drilling fuel tanks.

GKman
10-14-2015, 05:45 AM
I don't suppose there is any way to fabricate a clamping system that would make the current bolt unnecessary. The problem I have with trying to plunge with burrs is the zero velocity they have in the center just rubs preventing the remainder from cutting.

Don Young
10-14-2015, 10:11 PM
It is not very fast but a small brass tube from a modelmakers supply and abrasive paste will cut hard parts pretty easily.


I don't suppose there is any way to fabricate a clamping system that would make the current bolt unnecessary. The problem I have with trying to plunge with burrs is the zero velocity they have in the center just rubs preventing the remainder from cutting.

wierdscience
10-14-2015, 11:53 PM
It might be a self tapping screw of the thread forming variety.That would explain the hardness,could also be work hardened from all the unproductive drilling.

I use an induction heater for things like this that are difficult to get to or might go boom with open flame-
https://www.youtube.com/watch?v=_YO_snrzYrs

Another possibility would be a mag base drill and carbide end mill.

Euph0ny
10-15-2015, 05:42 AM
I use an induction heater for things like this that are difficult to get to or might go boom with open flame-
https://www.youtube.com/watch?v=_YO_snrzYrs

Very interesting. I can somehow see the makings of one of those in spare parts for induction kitchen hobs...

boslab
10-15-2015, 11:09 AM
Now that thing is cool(sad pun), wish you could solder copper pipes with one, perhaps you can?
Anyway, until the light sabre is invented, I want one, don't know why but I do!
Mark

philbur
10-15-2015, 12:18 PM
I think you are missing a billion dollar opportunity here, if carbide and diamond wont touch it then you have a fortune staring you in the face, either that or you're not trying hard enough!


Phil:)

tc429
10-17-2015, 07:09 PM
mag base drill press with a vee bottom, or simply ratchet strap a plate to the tank for a mag base...carbide drill would walk right thru it I would think

oxford
10-17-2015, 08:59 PM
Another possibility would be a mag base drill and carbide end mill.

This is what I would go with as well. My opinion is the cordless drill doesn't spin fast enough for the carbide burrs to be effective, but also mentioned before plunging with them isn't the most effective either.

Toolguy
10-17-2015, 09:29 PM
A carbide spade drill dry with no lube will walk right through it.

_Paul_
10-18-2015, 11:50 AM
The humble masonry drill is normally carbide tipped, you can use a diamond wheel to alter its profile to cut metal.

Paul

PStechPaul
10-18-2015, 01:33 PM
FWIW, I have heard that one should not use diamond tools on ferrous materials (carbon steel) because the carbon in the diamond reacts with that in the steel. That might just be for grinding, but it may be worth considering if you have problems.

http://www.toolingu.com/class-250210-grinding-wheel-materials-210.html

http://www.practicalmachinist.com/vb/abrasive-machining/surface-grinding-hardened-tool-steel-diamond-wheel-170891/