How cut precision holes through steel floor?

[TheHubbardBus]

Not much on metalworking experience, so if I'm asking stupid questions please forgive.

I'm going to have to cut a few holes in the metal floor (IC 3800). Two ~4.5" diameter rectangular holes for the intake air / exhaust of tankless water heater, One 2.5" round hole for the heater's pressure relief, Two or Three holes for 1/2" ID black pipe (propane), and two relatively large round holes for the kitchen sink & shower drains.

All I've got is a jigsaw w/ metal blades, & hole-saws for my drill. Are either up to the tasks at hand? If not, what will I need to do these jobs?

Note: The holes will go not be going through any seams or intermediate ribs. Just through the steel sheet.

 

[PNW_Steve]

Your jigsaw and metal blades should be able to get the job done.

I would use an angle grinder and cutoff wheel myself.

 

[Drew Bru]

Not much on metalworking experience, so if I'm asking stupid questions please forgive.

I'm going to have to cut a few holes in the metal floor (IC 3800). Two ~4.5" diameter rectangular holes for the intake air / exhaust of tankless water heater, One 2.5" round hole for the heater's pressure relief, Two or Three holes for 1/2" ID black pipe (propane), and two relatively large round holes for the kitchen sink & shower drains.

All I've got is a jigsaw w/ metal blades, & hole-saws for my drill. Are either up to the tasks at hand? If not, what will I need to do these jobs?

Note: The holes will go not be going through any seams or intermediate ribs. Just through the steel sheet.

I used a bi-metal hole saw and it cut through without any problems. I was also was able to cut through with a metal cutting blade on my jigsaw, again with no problems. The hardest part for me is knowing where, in relation to the frame or any obstructions, the hole actually is under the bus. For this I sometimes ran a 3" self-tapping screw. The was particularly helpful when I was running the black pipe for the propane.

 

[o1marc]

You'll need a holesaw kit. Used in your drill. Shop around, you may find a kit with the sizes you need that isn't too expensive. You can buy them singularly also.

https://www.ebay.com/itm/Milwaukee-...082355&hash=item4658b11478:g:ZekAAOSwLztbY3SJ

 

[TheHubbardBus]

Sweet guys. Thanks so much! You saved me before I invested in an OA torch (lol).

 

[family wagon]

By "precision" do you mean roundness, or position/placement? If the placement is critical, make your best guess as to where the center belongs and drill a small pilot hole. Check both sides to confirm its position, adjust as needed, and then pull out the hole saw. So long as the pilot is off by no more than the radius of the final hole it doesn't matter if the pilot is dead on. It'll get cut away anyway.

 

[joeblack5]

If you are using the hole saw then go low speed and use some cutting fluid or cooling liquid. Otherwise you risk burning up the saw.

Good luck. J

 

[Ronnie-SKO]

Once you find the center of your hole drill with a 1/4" bit first. If you drill with the pilot bit that is in the hole saw it might go through suddenly then the hole saw itself will hit hard and twist the drill out of your hand. So I find it better the pre drill the pilot hole when working in metal.

 

[TheHubbardBus]

Thanks for the additional responses. They'll prove very useful. As for my definition of precision, I meant both roundness & precision in size of the resulting holes, as well as location. So this all helps a lot.[URL="http://www.skoolie.net/forums/f13/removing-seats-with-cutting-torch-29178.html"][/URL]

 

[PNW_Steve]

If you are using the hole saw then go low speed and use some cutting fluid or cooling liquid. Otherwise you risk burning up the saw.

Good luck. J

I found a water based cutting and drilling lubricant at Napa. It works great and is easier to clean up.

 

[TheHubbardBus]

I found a water based cutting and drilling lubricant at Napa. It works great and is easier to clean up.

Is this it, Steve?

https://www.napaonline.com/en/p/WLD7651526

 

[BlackJohn]

You might want to also look into Greenlee punches. Sized from 1/2"up to?
Rentals have them if you don't care to buy the set.
Just determine where the exact centre of your hole is to be, pilot hole that point and then increase the size for the bolt for the cutters.

Snaps a precise, neat hole that can then be filed for burrs if any.


For hole saws be careful. You'll do better with a 1/2" drill but they can grab and break wrists or shins if you force them too much.
Good luck.


John

 

[wrenchtech]

You mentioned that your last resort would be an oxy-acetylene torch.Most people these days bypass that kind of set up in favor of a plasma cutter/torch. At one time such equipment was beyond the reach of the average home shop user. Thanks to our friends in China’s manufacturing sector virtually anyone can afford one. I picked up a small plasma outfit for $160 on eBay. It’s not perfect and it doesn’t cut quite as thick as they claim, but it makes quick work of metal up to a quarter inch! All without the need to invest $500 or more and oxygen and acetylene tanks, and then to keep refilling them. You will however need a small compressor to provide a supply of clean dry compressed air to make it work properly. Dry air is crucial to the proper functioning of a plasma torch. Most folks at this level of the marketplace are using compressors that are basically spitting water into their plasma process. With the usual result being that the user ends up cursing the Chinese manufacturer.

I still keep an oxygen acetylene outfit because I like to be able to heat stubborn fasteners. Here in the rust belt, any fasteners it would normally snap off and require extraction of the remaining part can be rescued with the application of just a little bit of heat. It also comes in quite handy for making nice tight radius bends in 3/8” steel rod that I like to use for making exhaust hangers.

 

[wrenchtech]

And let’s not forget step drills. This is a tool no home shop enthusiast can afford to be without. If you watch the Make it Extreme video series on YouTube, and I recommend that you do, you will see that that guy uses step drills for almost everything.

https://www.harborfreight.com/search?q=step%20drill%20bit

 

[Drew Bru]

And let’s not forget step drills. This is a tool no home shop enthusiast can afford to be without. If you watch the Make it Extreme video series on YouTube, and I recommend that you do, you will see that that guy uses step drills for almost everything.

https://www.harborfreight.com/search?q=step drill bit

Good point, I've got a couple step drills in my toolbox. HF often has them on sale, I think I got a set of 2 bits for like 12 bucks.

 

[PNW_Steve]

Is this it, Steve?

https://www.napaonline.com/en/p/WLD7651526

That the stuff.

 

[o1marc]

Step drills are great, unless you want 2.5"-4.5" holes like the OP needs.

 

[wrenchtech]

Step drills are great, unless you want 2.5"-4.5" holes like the OP needs.

He did also mention smaller holes for 1/2” black pipe. I figure if he’s running drain lines for a sink there might also be water lines of diameters that will be in the range of the step drill.

 

[wrenchtech]

And someone should mention that drilling holes as large as 3 inches to 4 1/2 inches with a holesaw into steel is likely be beyond the capacity of a handheld drill or the person holding it. I recently under took a project which required me to drill a 4 inch hole in three eights inch steel plate. I had the luxury of using a 1 hp drill press. Even that was very borderline. The belts were slipping and smoking and I really had to baby it along. I don’t think I’d do it again. Saber saw with a metal cutting blade doesn’t always work either, especially when there is not enough room to allow you to work the saw around the diameter, which is why I mentioned the inexpensive new plasma cutters that are in the marketplace.

 

[PNW_Steve]

And someone should mention that drilling holes as large as 3 inches to 4 1/2 inches with a holesaw into steel is likely be beyond the capacity of a handheld drill or the person holding it. I recently under took a project which required me to drill a 4 inch hole in three eights inch steel plate. I had the luxury of using a 1 hp drill press. Even that was very borderline. The belts were slipping and smoking and I really had to baby it along. I don’t think I’d do it again. Saber saw with a metal cutting blade doesn’t always work either, especially when there is not enough room to allow you to work the saw around the diameter, which is why I mentioned the inexpensive new plasma cutters that are in the marketplace.

I had to cut a 4" round hole in 1/4" steel plate. I bought a 1/2" drill from Harbor Freight. That was 20+ years ago and the darn thing still works.

A word of caution: As Wrenchtech mentioned, a big drill and a 4" hole saw will try to tear your arm off if you get too aggressive. I sprained my wrist cutting that hole.