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Thread: 3" hole Mild Steel 3/8" thick

  1. #1
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    3" hole Mild Steel 3/8" thick

    Friend of mine ask me if I could make a hole in a cast steel column sq and 3/8" thick. I immediately thought of my torch. But he would like to have a clean 3" hole and I do not believe i can do that with oxyacetylene. Would a hole saw and going slow work? He would like a clean cut. Thanks
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    Re: 3" hole Mild Steel 3/8" thick

    A slow hole saw and cutting fluid should get you there. Should be able to get it done in 30 min's max.

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    Re: 3" hole Mild Steel 3/8" thick

    Should work. Take a scrap piece of 3/8 and try it. You'll find out if the result is to his liking.

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    Re: 3" hole Mild Steel 3/8" thick

    A really good bi-metal hole saw will make quick work of that job. I usually cut thick stuff dry with an air jet keeping the kerf clear, cutting oil just gums up the chips and binds things up. Oh, pre drill the pilot hole, you bend fewer pilot bits when it doesn't have to drill through and catch the cutter when it breaks through.

    Before everybody screams about the dry cutting, get a Lenox cutter with highspeed teeth, I have some that have cut hundreds of holes and still cut well. Even up to 5" through 3/4" plate. Air and safety glasses are the key.

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    Re: 3" hole Mild Steel 3/8" thick

    .
    geezer


    Quote Originally Posted by geezer View Post
    . . . if I could make a hole in a cast steel column sq and 3/8" thick -

    . . . thought of my torch . . . he would like to have a clean 3" hole
    and I do not believe i can do that with oxyacetylene . . .

    Would a hole saw and going slow work? . . . clean cut . . .
    What is a 'cast' steel column ?

    Until the introduction of carbide/tipped cutters - I considered hole-saws
    garbage technique for structural applications . . . and still do . . .

    Do you have the power [coolant/lube] to turn 3 inches without burn ?

    You left out 'the last part first' - what 'final operation' drives the hole be
    'clean' and requires tight tolerances . . .

    I have torch-cut holes to be tapped - cutting a 3" close tolerance hole is
    easy with an OA Circle-Burner . . .

    The downside: you have to have Old School skill - with said skills, it can
    be done manually - without a Circle-Burner . . .

    What is going in the hole . . . ?

    hth


    Opus


    .

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    Re: 3" hole Mild Steel 3/8" thick

    They make a torch circle
    attachment for cutting torch.
    I works very good. I just drill 3/16” hole for the attachment and cut the hole.

    Later I used a magnetic pattern torch.
    The best was electric eye pattern torch
    Today they have cnc pattern torch's

    Dave

    Quote Originally Posted by geezer View Post
    Friend of mine ask me if I could make a hole in a cast steel column sq and 3/8" thick. I immediately thought of my torch. But he would like to have a clean 3" hole and I do not believe i can do that with oxyacetylene. Would a hole saw and going slow work? He would like a clean cut. Thanks
    Last edited by smithdoor; 09-09-2020 at 11:07 PM.

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    Re: 3" hole Mild Steel 3/8" thick

    Here are the choices I would suggest:

    Either carbide tipped hole saw (first choice) or

    plasma cutter with a template.

    Circle cutting guide will be awkward for a small diameter such as 3”.

    :

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    Re: 3" hole Mild Steel 3/8" thick

    Quote Originally Posted by 12V71 View Post
    A really good bi-metal hole saw will make quick work of that job. I usually cut thick stuff dry with an air jet keeping the kerf clear, cutting oil just gums up the chips and binds things up. Oh, pre drill the pilot hole, you bend fewer pilot bits when it doesn't have to drill through and catch the cutter when it breaks through.

    Before everybody screams about the dry cutting, get a Lenox cutter with highspeed teeth, I have some that have cut hundreds of holes and still cut well. Even up to 5" through 3/4" plate. Air and safety glasses are the key.
    I do the same with air even with annular cutters.
    :

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    Re: 3" hole Mild Steel 3/8" thick

    Quote Originally Posted by Lis2323 View Post
    I do the same with air even with annular cutters.
    I thought for sure you were going to post up a pic with a couple cold air guns working with the magdrill!!!!

    Name:  coldairgun2.jpg
Views: 420
Size:  304.3 KB

    https://www.vortextube.co.uk/cold-air-guns

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    Re: 3" hole Mild Steel 3/8" thick

    Quote Originally Posted by ronsii View Post
    I thought for sure you were going to post up a pic with a couple cold air guns working with the magdrill!!!!

    Name:  coldairgun2.jpg
Views: 420
Size:  304.3 KB

    https://www.vortextube.co.uk/cold-air-guns
    That’s out of the budget for my farm /retirement/hobby shop
    :

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    Re: 3" hole Mild Steel 3/8" thick

    Quote Originally Posted by Lis2323 View Post
    That’s out of the budget for my farm /retirement/hobby shop
    LOL!!! I remember when I first saw the cold air guns show up in the catalogs!!! I really wanted one but they were pretty expensive... never did get one... now I see they're a lot cheaper!!! must be the patent ran out or something????



    P.s. I think you're taking this whole retirement/downsize thing too far

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    Re: 3" hole Mild Steel 3/8" thick

    Thanks for all the replies, much appreciated. Obviously many of you have experience using hole saws in metal, I just never had a reason.

    Apologize for not listing why a 3inch clean hole. It is more appearance than function.

    So if I have it correctly, purchase a good quality by metal hole saw, hold the rpms down and drill slow and steady, pre drill pilot hole. No air jet so lubricate well and clean hole frequently.

    We will run a test piece.

    thanks for taking the time to reply
    Last edited by geezer; 09-10-2020 at 08:49 AM.
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    Re: 3" hole Mild Steel 3/8" thick

    [QUOTE=Lis2323;8767361]Here are the choices I would suggest:

    Either carbide tipped hole saw (first choice) or

    plasma cutter with a template.

    Circle cutting guide will be awkward for a small diameter such as 3”.

    Thank you very much, I have seen many test pieces you post with your replies. Very thoughtful.

    What type hole saw is that please?????
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    3" hole Mild Steel 3/8" thick

    Not necessarily from this seller, but I bought mine off eBay.




    https://www.ebay.ca/itm/174130409771

    Edit. Just noticed this set doesn’t have a 3” (75mm) cutter)

    You will need to search for the individual one(s) you require.
    Last edited by Lis2323; 09-10-2020 at 09:51 AM.
    :

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    Re: 3" hole Mild Steel 3/8" thick

    A lennox hole saw will cut thru that no problem. As mentioned predrill your center hole. I use cutting oil and lots of it. Probably more for coolant than anything.

  21. #16
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    Re: 3" hole Mild Steel 3/8" thick

    A photo would help and what the hole is used.
    A 3" hole is not hard to do.
    But it is cost if just welding or electrical maybe something else.
    I have used torch for welding to milling machine for ball bearings but I had look at cost.

    Dave

    Quote Originally Posted by geezer View Post
    Friend of mine ask me if I could make a hole in a cast steel column sq and 3/8" thick. I immediately thought of my torch. But he would like to have a clean 3" hole and I do not believe i can do that with oxyacetylene. Would a hole saw and going slow work? He would like a clean cut. Thanks

  22. #17
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    Re: 3" hole Mild Steel 3/8" thick

    Quote Originally Posted by ronsii View Post
    LOL!!! I remember when I first saw the cold air guns show up in the catalogs!!! I really wanted one but they were pretty expensive... never did get one... now I see they're a lot cheaper!!! must be the patent ran out or something????



    P.s. I think you're taking this whole retirement/downsize thing too far
    Vortex cooling has been used for decades. I recall it was used in tanks in WW2 to cool the crew some, so no way there are patents on it anymore. They are quite loud and use a ton of compressed air...
    -Dave
    XMT304 with: 22A Feeder, or HF251 Hi Freq DC TIG air cooled

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    Re: 3" hole Mild Steel 3/8" thick

    Quote Originally Posted by davec View Post
    Vortex cooling has been used for decades. I recall it was used in tanks in WW2 to cool the crew some, so no way there are patents on it anymore. They are quite loud and use a ton of compressed air...
    Yeah they do use a bit of air but I was meaning the miniaturized versions that came out in the 90's - more efficiency, less air... albeit less cooling btu's also not too bad on loudness especially when you have other machines running anyways.

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    Re: 3" hole Mild Steel 3/8" thick

    A circle cutting guide will do a 3" inch hole. A really clean tip is essential and the cut could be cleaned up with a flap disc in a die grinder or hand drill. Cut hole slightly smaller to allow for polishing it. Not too hard to make a simple circle guide. Kind of crude but makes a nice hole in thicker plate.

    Last edited by Welder Dave; 09-15-2020 at 03:34 AM.

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    Re: 3" hole Mild Steel 3/8" thick

    I think it hasn't been mentioned yet but it is recommended to drill one or two holes (say 10mm holes) on the inside of the circumference (just touching the hole saw cut line) to chips to evacuate so the teeth can keep on cutting. Otherwise you will clog the teeth and just creat heat. It prevents you from having to stop, blow chips, drill again, etc.

    If the hole is in the flat, it is pretty much mandatory. For the vertical, maybe not so much.

    Post a few pictures of the results of the operation!

    Mikel

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  28. #21
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    Re: 3" hole Mild Steel 3/8" thick

    Quote Originally Posted by Mikel_24 View Post
    I think it hasn't been mentioned yet but it is recommended to drill one or two holes (say 10mm holes) on the inside of the circumference (just touching the hole saw cut line) to chips to evacuate so the teeth can keep on cutting. Otherwise you will clog the teeth and just creat heat. It prevents you from having to stop, blow chips, drill again, etc.

    If the hole is in the flat, it is pretty much mandatory. For the vertical, maybe not so much.

    Post a few pictures of the results of the operation!

    Mikel
    Another good tip, thank you.

    It will be a day or two until a finished post since this project is at club house by the lake.
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    Re: 3" hole Mild Steel 3/8" thick

    3" TUNGSTEN CARBIDE TIPPED HOLE CUTTER
    BM-THC300_1

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    Write a review
    $109.99

    Dont think my friend will spring for this, we will try carbide tip conventional hole saw first. This is a one time project, if we had a series of these then a more substantial cutter would be justified.
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    Re: 3" hole Mild Steel 3/8" thick

    I worked for an old blacksmith back in the 70's. He used water & dish soap as coolant for drilling. Works pretty good & is easier to clean up afterwards than cutting oil, just blow it off & coat with wd40.

    Just don't let the bit get hot before you start cooling it. Hot bit/saw + water = cold quench.

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  32. #24
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    Re: 3" hole Mild Steel 3/8" thick

    I just use a regular bi metal hole saw in the drill press. I usually use air nozzle to help cool and remove chips. Go slow and wear earplugs
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  34. #25
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    Re: 3" hole Mild Steel 3/8" thick

    for one, Torch and template.

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