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Thread: Drill and Tap suggestions

  1. #1
    Join Date
    Mar 2003
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    Arizona
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    Default Drill and Tap suggestions

    I want to drill and tap a symmetrical pattern (like a grid) of 1/2" x 13 TPI holes in one of my 4'-0" x 4'-0" x 1/2" thick fab-tables. Using them for my mill hold down clamps. I've drilled and tapped before so that's not the issue in the slightest. I'm trying to figure out the best way to accomplish it. I was thinking of renting a magnetic drill press. Never used one and I haven't called to see what the rental price might be yet. Naturally I'd like to accomplish this without renting anythings. Just thought someone might have an idea. Never hurts to ask ya know.

    -SD:

  2. #2
    Join Date
    Sep 2015
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    NW Illinois
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    If the fab tables are already built the mag base drill is likely the only practical way to do it.

  3. #3
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    Mar 2003
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    Arizona
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    Default

    Quote Originally Posted by Illinoyance View Post
    If the fab tables are already built the mag base drill is likely the only practical way to do it.
    Thanks, the fab-table is already built. I only need to do one.

  4. #4
    Join Date
    Jun 2011
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    Northeast, PA
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    Mag drill would be easier but you might get away with a small benchtop drill press if you swing the head away from the base. C clamp it down at the edge and then use the drilled and tapped holes as you go for hold down clamps.

  5. #5
    Join Date
    Aug 2014
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    San Jose, CA:Vancouver, WA
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    We bought a mag drill just to drill ~40 1" holes in 1" steel. Worth the investment (~$1500) to do the job. You find more uses for it.

    Layout the hole pattern and use a center finder to locate each hole carefully and you will be happy with the results.

    Mike

  6. #6
    Join Date
    Sep 2015
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    NW Illinois
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    For one table top just rent a mag drill. If equipped with a chuck you can tap with it also.

  7. #7
    Join Date
    Feb 2015
    Location
    SW VA
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    Yes get a mag drill. I did part of my table with 1/2" holes. Only I didn't tap them. I just use a nut from underneath to hold the clamps.

  8. #8
    Join Date
    Jan 2003
    Location
    On the Oil Coast,USA
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    19,632

    Default

    If you rent a mag drill,make sure it's reversible,not all of them are.

    Expanding on Ncjeeper's comment,you could drill the holes 17/32" for clearance and then tack weld on some 1/2-13 square nuts from the bottom for threads.That would save a lot of tapping.

    I use that method alot at work,McMaster carries the nuts,I use a flathead Allen capscrew to hold them for tacking.The 82* head holds the nut centered in the hole for alignment.One advantage is down the road,if a hread gets damaged or wears out,it's just a matter of knocking the old nut off and welding on a new one.

    https://www.mcmaster.com/90043a055

    Forgot to mention,the reason for using square nuts,is you can weld two opposite corners and not distort the threads.
    Last edited by wierdscience; 06-30-2019 at 12:35 AM.
    I just need one more tool,just one!

  9. #9
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    Mar 2003
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    Arizona
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    Default

    Thanks guys, great idea on the nuts. Glad I asked.

  10. #10
    Join Date
    Apr 2017
    Location
    Kelowna BC
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    Just dril,them to tap size then you can still use 3/8 or 7/16 bolts. Then tap them as you feel like it or its really needed. Meanwhile you have a functioning table.

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