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Thread: Can I drill a 1 3/4” hole through a manhole cover

  1. #1
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    Can I drill a 1 3/4” hole through a manhole cover

    We have a manhole in our back yard that goes to a rain sewer. I want to back flush the in ground pool ont the sewer. I can lift the cover every time but what I really want is to have a hole with 1 1/4” sch40 pvc through it so I don’t have to mess with it.

    I can drill it fairly easily with a 1/4” twist drill. I got out my Milwaukee hole saw and was a littl surprised that it made some progress before the pilot drill snapped.

    I can rent one of those magnetic drill presses for $55/day but the rental place has no bits.

    suggestions?

  2. #2
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    No clue of the legality of what you are wanting to do. Should be no different than flushing into the driveway or street. I would think with a clean pilot hole and plenty of lubricant it should drill fine. I suspect you wandered off vertical some which caused pilot bit to break. If enough of a grove were cut prior to breaking it I would give it a try without a pilot bit

  3. #3
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    A magnetic drill press can use the holesaw you have. It needs a substantial thickness of metal under the base to grab. Even if it doesn't grab strongly enough to hold it to drill with a lot of force, it should still be stable enough if you feed it slowly, and will be easier than you expect. I bought one for working on a tractor, thinking I'd sell it when I finished that job, but I liked it so much I kept it, and have been glad several times that I did.

    I needed to drill a 3/4" hole through three layers of 1/4" steel to put a lifting ring on the front of a mower. About an inch and a half below that metal was some pretty expensive parts of the steering system. It was easy to control, and cut like butter.

    The mower weighs 1800 pounds, but the marine lifting ring is rated for 5500 pounds. I can pull it straight up in the air, and sit it on the big flat back end to swap blades. Picture was just first test lift.
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  4. #4
    Quote Originally Posted by Roger Feeley View Post
    ... what I really want is to have a hole with 1 1/4” sch40 pvc through it so I don’t have to mess with it.

    ...
    Realizing that you probably don't move the manhole cover everyday, even to back flush, but you may still need to move it. I'd be sure to insert a union in that 1-1/4", so I can disassemble/move the PVC without a sawzall.

    I'll make the leap of faith you have determined who owns the manhole, and the right-of-way its sitting in, and have permission.

    Oh, and +1 on the mag-base drill.

  5. #5
    The way I resolve snapping off pilot bits is to use a piece if 1/4" rod in hole saw in place of bit. Using 1/4" bit, drill a pilot hole first.

  6. #6
    --do you/don't you have a drill press?
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  7. #7
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    Quote Originally Posted by Kev Williams View Post
    --do you/don't you have a drill press?
    I do have a drill press. I just didn’t think about carting the heavy manhole cover to the basement and then somehow supporting it while I drill. Maybe I should give that a try. That and substituting a piece of 1/4” rod for the pilot bit.

  8. #8
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    We have a manhole in our back yard that goes to a rain sewer.
    Is this manhole your property or does it belong to a local entity?

    You may be able to get them to replace the cover with a grate. Maybe don't tell them you want to use it to drain your pool.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  9. #9
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    Quote Originally Posted by Bruce Wrenn View Post
    The way I resolve snapping off pilot bits is to use a piece if 1/4" rod in hole saw in place of bit. Using 1/4" bit, drill a pilot hole first.
    I second this. If a tooth on the hole saw bites in it forces the flute of the pilot bit into the metal in the side of the pilot hole. That'll cause the pilot bit to snap. Switch to a 1/4" rod and it's like magic. Also after starting the actual cut with the hole saw stop and drill a 1/4" hole in the hole saw cut so metal has a place to go as you cut the hole since I wouldn't use oil (environmental reasons). Manhole covers are most likely cast iron of some sort so making a hole shouldn't be hard.

  10. #10
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    What drill were you using to spin the hole saw?

  11. #11
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    Quote Originally Posted by Tom M King View Post
    What drill were you using to spin the hole saw?
    I have a Milwaukee 3107-6 right angle drill with gobs of power. Pre-drilling the pilot hole was easy.

  12. #12
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    That should be no problem. I'd rather use a spade handle, but a right angle will work fine. I had an 18v cordless drill come all to pieces in my hands trying to drill a hole with a holesaw once. I knew I was pushing my luck, but it was the only drill I had in the truck at the time. I thought it might just lock up, and I positioned myself for that possibility, but the handle broke into multiple pieces when it did.

  13. #13
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    I’m thinking that the tooth geometry is the problem. The hole saw I have has teeth that are Hooke to bite into wood. I ordered a carbide saw where the angle of attack is much more vertical.

  14. #14
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    Haven’t heard about the legality of this yet. Is the storm drain the property of the AHJ? If so you likely shouldn’t be tapering with it without at least asking first.

  15. #15
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    I realized that I am approaching this wrong. Instead of cutting a hole through the cast iron, maybe I should replace the cover with a plastic one. This is next to a fence in our back yard. No one will ever want to drive over it so it just has to be able to support a person. The light weight presents a security issue for the children. I would need to screw it in place. Drilling and tapping cast iron is easy.

    https://www.amazon.com/dp/B00JEKKPNY/ref=emc_b_5_t

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