Bridge I-Beam cutting.

[fried1765]

I am in the beginning stages of building a 12x24' bridge across a gully. I have 6 8" 20' I-beams I need to make 24' long.

That means I need to cut another one into 4' sections.

I don't have a torch, bandsaw, plasma cutter or anything fancy. I do have 4-1/2" grinders and chop saws and a couple hundred HF 1/16" abrasive discs for the handhelds.

My question is, would it maybe better to use 4-1/2" abrasives or get diamond discs. I am sure diamonds discs would last longer, but how much longer. If a lot better then I will run down to Home Depot Monday and get a couple or a few. They are about $13 each. I am sure they would be safer from the shattering aspect.

View attachment 579391.

Any other ideas about cutting other than the ones mentioned would be helpful. I need the cuts to be fairly straight because I need to butt weld them. I will weld a plate on the sides of the joints also.

According to tractordata.com your JD 3720 weighs as much as 3570 lbs,... without a loader.
If you are going to take your tractor (with loader?) across this bridge I would suggest that you forget about splicing 4 more feet on 8" web beams that are already 20' long.
Lengthening the approach segment, as suggested above, is the better idea.

 

[Gary Fowler]

In my opinion, it is going to be really hard to cut the inside web next to the top and bottom flanges of the I-beam using a 4.5" cut off wheel. Even using HF wheels, the cost to cut 4 of those will likely exceed what a welding shop would charge to cut them. They could also bevel the edges in prep to do the buttweld to the other beam. This would be a timesaver also.

The other option which would be my choice is to buy yourself a cutting torch, rent a couple of bottles for the project. The cost might be comparable to paying someone to make the cuts. A good Victor torch can be bought for around $200 or less and you would have it for later projects if needed OR you could sell it and get most of your money back when finished.

Personally I cant imagine anyone with a welding machine that doesn't own some sort of cutting equipment besides a grinder, either a plasma rig or oxy-acetylene torch or even a band saw. I prefer the oxy rig since you can also weld with it.

 

[PILOON]

"Personally I cant imagine anyone with a welding machine that doesn't own some sort of cutting equipment besides a grinder, either a plasma rig or oxy-acetylene torch or even a band saw. I prefer the oxy rig since you can also weld with it."

Well I'm such a guy.
I own 2 stick welders and a wire machine plus have 2 torch sets and a portable set as well.
However the high cost of renting tanks with annual fees simply makes no sense to me.

With the advent of good grinders and abundance of reasonably priced cutting disks my OA kits are gathering dust.

I also own a small 'posta pack' OA kit but the Ox valves usually are so jammed tight that I never can close them consequently they are a 'one time' usage.
(dang 1/4" shut off valve stems seem to have been closed with a pneumatic hammer at the filling stations)

OK, granted I rarely work with metals over 1/8 or 5/32" thick so cut off disks serve me just fine.

Around here each tank is $100 annual rental plus the gas content. Bit pricy for the few times absolutely needed.
Shucks I have opened 250 gal reservoirs (for sheet metal stock) with a handful of 5" disks.
Using a guide of sorts I can cut nice straight lines as well.

Plus I have a 12" chop saw for all my angle and flats 'cut to length' needs.

I really only need the O/A for body work which I rarely do anymore.

 

[Big Barn]

"Personally I cant imagine anyone with a welding machine that doesn't own some sort of cutting equipment besides a grinder, either a plasma rig or oxy-acetylene torch or even a band saw. I prefer the oxy rig since you can also weld with it."

Well I'm such a guy.
I own 2 stick welders and a wire machine plus have 2 torch sets and a portable set as well.
However the high cost of renting tanks with annual fees simply makes no sense to me.

With the advent of good grinders and abundance of reasonably priced cutting disks my OA kits are gathering dust.

I also own a small 'posta pack' OA kit but the Ox valves usually are so jammed tight that I never can close them consequently they are a 'one time' usage.
(dang 1/4" shut off valve stems seem to have been closed with a pneumatic hammer at the filling stations)

OK, granted I rarely work with metals over 1/8 or 5/32" thick so cut off disks serve me just fine.

Around here each tank is $100 annual rental plus the gas content. Bit pricy for the few times absolutely needed.
Shucks I have opened 250 gal reservoirs (for sheet metal stock) with a handful of 5" disks.
Using a guide of sorts I can cut nice straight lines as well.

Plus I have a 12" chop saw for all my angle and flats 'cut to length' needs.

I really only need the O/A for body work which I rarely do anymore.

Piloon:



RIP. Air Liquide oxygen and acetylene rental tanks. 1965-2018.

I just turned in my tanks at the end of October after renting for 53 years. I pursued different options over the years but the gas companies have got it engineered to rape you no matter what you do. I too was paying $100 per tank per year rental the last few years.

I will never give up oxyacetylene usage and I refuse to purchase tanks from them. I had to get creative....

 

[ovrszd]

Terry I bought two sets of tanks at farm sales over the years. First pair included a worn out Victor torch and hoses. Paid $150 in 1985. Second pair were just bottles paid $250 in 2000. Airgas is my supplier and I simply exchange bottles. No fees. I'm very fortunate.

 

[Oldpath05]

Years ago they use to make cutting rods to use with a stick welder, that's how I started cutting steel, when I ran out of cutting rods I used 5/32 6011. It was a little ruff but a lot faster.

 

[Big Barn]

Regarding abrasive cut off wheels. I use 4 1/2” and 7” zip cut wheels every day. Almost exclusively for making a small precise cut or removing a welding tack I screwed up on (lots of those )

These cuts are mostly well under a minute in duration. In my opinion any cut jobs involving longer lengths of time will certainly increase the chance of even a moment of carelessness which could end drastically. A good example would be where Gary mentioned not having enough clearance for the grinder in the web of the I beam. Good chance of getting the disc bound up in that corner while changing direction. JMO

 

[Big Barn]

Terry I bought two sets of tanks at farm sales over the years. First pair included a worn out Victor torch and hoses. Paid $150 in 1985. Second pair were just bottles paid $250 in 2000. Airgas is my supplier and I simply exchange bottles. No fees. I'm very fortunate.

I’m doing similar, Richard.

 

[Big Barn]

Years ago they use to make cutting rods to use with a stick welder, that's how I started cutting steel, when I ran out of cutting rods I used 5/32 6011. It was a little ruff but a lot faster.

BTDT , Oldpath. 6011 also

 

[Deere Dude]

OP here. I used to burn through heavy steel with 1/4" welding rods with the welder maxed out. It was a messy job. I will have to figure out what a zip cutter is, never heard of that.

I got all kinds of good advice so far and all is well received, even to make the bridge not as long. If I made a ramp and jump the last couple feet wouldn't work because I can't build up enough speed.

Either way, I took a beam out today and was able to cut through using a 4-1/2 cheapo discs. I was able to gut through to the webs from the outside with a fresh disc.

Now to cut 6 of them total without any mishap. I got goggles and earmuffs but thought about a face shield maybe. Those discs kind of explode on me so I will get some metal diamond cutters for sure even if I will be done with these cuts.