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Customs how to cut large round holes in body panels?

Discussion in 'The Hokey Ass Message Board' started by oldpl8s, Mar 29, 2016.

  1. oldpl8s
    Joined: Apr 11, 2007
    Posts: 1,412


    I need to cut 2 3/8" holes in my 64 Chevy Fleetside C10 to add backup lights. What is the best way to cut holes of that size? It is already painted so I don't want to use a torch.
  2. dogwalkin
    Joined: Jan 17, 2013
    Posts: 91

    from tn

    volvobrynk likes this.
  3. squirrel
    Joined: Sep 23, 2004
    Posts: 49,774


    Hole saw.
    volvobrynk likes this.
  4. Find an electrician and ask to use his 2" conduit knock-out punch. Actual OD is 2 3/8 and if the punch is sharp, will give a nice clean hole....
    volvobrynk likes this.

  5. All of the above. The knock out won't be as hard on your wrist as the big hole saw. ;)
    volvobrynk likes this.
  6. ...And won't skate around while drilling and leave thin edges.
  7. Tape it up first...
    volvobrynk and falcongeorge like this.
  8. PKap
    Joined: Jan 5, 2011
    Posts: 593

    from Alberta

    If you tape up the whole area, lay a good line to follow, a good quality jig saw with a metal blade will do a nice job, and nicely controllable
    volvobrynk and falcongeorge like this.
  9. Bader2
    Joined: May 19, 2014
    Posts: 1,143


    Yep,electricians greenlee punches.
    Hitchhiker and OLSKOOL32 like this.
  10. tfeverfred
    Joined: Nov 11, 2006
    Posts: 15,792

    Member Emeritus

    Come on, man. This is hot rodding. We like to make it complicated.:confused:
    volvobrynk likes this.
  11. squirrel
    Joined: Sep 23, 2004
    Posts: 49,774


    I might even use snips, after drilling a smaller hole. Depends how ambitious I feel. But when I had to poke a 7/8" hole in the nicely painted dash in my Chevy II yesterday, I just used a hole saw.
  12. mike bowling
    Joined: Jan 1, 2013
    Posts: 3,556

    mike bowling

    Back it up with a piece of 3/4" plywood or a block of 2x6. If you can't clamp it, get someone brave to hold it for you. This gives the pilot bit something solid to go into, and will help prevent the hole saw from "walking".

    Attached Files:

    Speedys Garage likes this.
  13. Jim, smaller hole saws aren't too bad at 'wandering', but the bigger they are, the worse they wander. Even with 'backing' you can still have issues (wait until the pilot bit breaks and you scar the paint around your hole...) And the bigger saws just don't leave a 'clean' hole. As a retired electrician, I used both saws and punches more times than I can possibly count and always preferred to use a KO punch where possible. No sharp hot metal chips, no burned paint at the edge, just a cleaner deal all around. Actually, for holes up to about 1.125", a step bit works better than a hole saw on sheetmetal.
  14. squirrel
    Joined: Sep 23, 2004
    Posts: 49,774


    Which is fine, if you have access to knockout punches, and step bits...the few knockout punches I have are always the wrong size. But they will definitely leave a nice hole!
  15. Can you rent a set? That's what I'd do here in the UK - would cost about $25 for the weekend. Better to spend some money on renting a punch than risk having a big hole saw wobble around and do $$$$ of damage to your paint. Do you have tool hire shops in the US?

    If not, I'd tape up, mark out and then chain drill using a 3/8 drill inside the line. Then join up the dots with a pad saw. File to finish. Job done.
  16. '51 Norm
    Joined: Dec 6, 2010
    Posts: 748

    '51 Norm
    from colorado

    X2 on the knockout cutters. I bought a cheapo harbor fright set and they even work.
  17. rusty rocket
    Joined: Oct 30, 2011
    Posts: 4,336

    rusty rocket

    db9e8730cfddefaf2a50cead11d4df42.jpg Get this guy to help ya.
  18. I would use a fresh 2-1/4" hole saw with band saw stick lube and carefully file to final size. Any small irregularity should be under the gasket for rage light.
  19. deathrowdave
    Joined: May 27, 2014
    Posts: 2,690

    from NKy

    Greenlee punch is 1st choice , 2nd Holesaw low speed
  20. indyjps
    Joined: Feb 21, 2007
    Posts: 4,377


    If you use a hole saw, drill your pilot then remove the bit and either flip it around, or replace it with round bar.

    It helps keep the bit from wollowing out the pilot hole and prevents some of the hole saw walk.
    volvobrynk, H380, pat59 and 3 others like this.
  21. A radio "chassis punch " ( knock-out punch?) is good if it's new or sharp, otherwise drill a small pilot hole (3mm), holesaw on low speed and lube it while you go.
  22. oldolds
    Joined: Oct 18, 2010
    Posts: 3,185


    You can do it the hard way. Tape up the area, draw your line, take a drill with an 1/8" to 1/4" bit. Drill lots of holes just inside that line. Knock out that piece and file it until it is the right size.

    Well somebody and to say it!
  23. 35WINDOW
    Joined: Jul 7, 2005
    Posts: 454


    I was looking for a better way to punch holes/flare them (besides a HoleSaw), and decided to buy a Greenlee punch set (along with some individual ones on Ebay)-while the quality is first rate, I found that the sizes offered did not correlate (at all) with my hole flaring set-obviously, they are made for the Electricians of the World (which I am not), and, I found that there are at least two different designs of the Cutters ( I think the newer ones are ok)-

    What I didn't like was the hole that was left-usually there were "ears" left (which, admittedly could be filed), but I was less than impressed (anybody looking for a nice Greenlee Punch set? :) )-

    I get along pretty well using a Holesaw (like others), but I've always wanted to buy a set of these:
  24. aaggie
    Joined: Nov 21, 2009
    Posts: 2,531


    I have used all of the mentioned tools over the years and they all have good and bad points. Lately I have found the small air saw made for panel cuts works really well. It is basically a cylindrical jig saw.
  25. Yeah, those carbide cutters are the cats meow... But just as expensive as the KO punches if you buy a set, and they do wear out.

    As to Greenlee-type KO sizes, there's 'other' sizes available (non-conduit-sized round, square, rectangular, and 'specialty' types) but they can get pretty pricey. While I got my sets in the course of my work, you can find the cutters/dies at swap meets, yard/garage sales and usually fairly cheap as most people don't know what they are. You can buy new drawbolts. Enerpac also makes KO cutters and sets that are almost identical to the Greenlee sets and the cutter and dies will interchange. There's also offshore-made sets available these days for pretty cheap, if you limit them to no thicker than 14 gage mild steel they'll hold up plenty good enough for 'hobby' use.
  26. Dan Timberlake
    Joined: Apr 28, 2010
    Posts: 1,331

    Dan Timberlake

  27. in sheet metal? the best/fastest way is to make the opening, then use a hole saw a size smaller, file the opening out to the marks. done and no damage to paint.
  28. ididntdoit1960
    Joined: Dec 13, 2011
    Posts: 1,015

    from Western MA

    Having flashbacks of installing a rear antenna in a buddys freshly restored 57 chevy convertible.........he was very careful, cut the hole undersize, was fileing it out when he pulled the "rat tail" file a lttle too far and.......ran it down the know this isn't gonna end well......right? Be Carefull and tape up the panel before starting
  29. blackanblue
    Joined: Feb 20, 2009
    Posts: 408


    X2 on the knockout punch mayby from a rental place.
  30. BigDogSS
    Joined: Jan 8, 2009
    Posts: 912

    from SoCal

    I say you don't need back up lights. Leave it "as is".
    Last edited: Mar 29, 2016
    Mike Miller likes this.

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