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Author Topic: Where to get 3/4" hole punches...  (Read 773 times)
KG4NEL
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Posts: 443




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« on: March 05, 2003, 04:29:14 PM »

Hi -

I finally got some time, and installed my IC-706 in my van, and hooked up a temporary antenna to it. Now I'm started work on getting the permanent antennas in place. I've decided on a roof-mounted 2 meter antenna, and a ball-mounted whip for HF. However, I can't seem to find a 3/4" hole punch for the NMO mount anywhere...

I went to both Lowe's and Home Depot...found Greenlee punches that made 7/8" and 1.115" holes (for conduit, I guess). How do the guys at say, Motorola, install NMO mounts? Where can I find the right tool for the job?

Thanks for any help,

Jim
KG4NEL
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K5LXP
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« Reply #1 on: March 05, 2003, 05:54:07 PM »

A punch would certainly make a clean 3/4" hole, but it would be expensive and require access to both sides of the panel to punch the hole.  The best way is to use a hole saw.  3/4" is a standard size.  If you plan to do a lot of antenna installations, or don't mind investing in a tool you will keep a long time, go to a 2-way radio shop and buy the hole saw made specifically for this purpose.  The advantage of the specialty tool is it has a collar that prevents the hole saw from punching through after the hole is made, potentially damaging whatever is underneath.  If you use a standard hole saw, take it slow and easy when it gets close to going through so you can pull back.  If you do it right and pick the right spot you can drill the hole from the outside, snake the coax in and pull it through in a matter of a minute or so without having to remove any interior panels.

Mark K5LXP
Albuquerque, NM
k5lxp@arrl.net
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K0BG
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« Reply #2 on: March 05, 2003, 06:15:08 PM »

A 3/4" punch is typically an electronic item rather than an electrical one. However, my local Home Depot does stock 3/4 hole punches more commonly referred to as chassis punches.

You didn't say how you were going to mount the whip, but if you use a ballmount you'll need a 1-1/8" punch as well.

Alan, KØBG
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WB2WIK
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« Reply #3 on: March 06, 2003, 06:50:16 PM »

Greelee makes chassis punches in small increments beginning with 1/2", and the 3/4" is a popular one.  I have two of them, since I do install so many NMOs.  And if you're installing an NMO, you definitely need access to both sides of the sheet metal!

I don't like hole saws, but I especially recommend against using one if you're sawing "blind" and have no access to the other side of the panel -- don't know what you're going to hit, or damage.

Grainger stocks the Greelee punches, and my local Grainger has all of them.

WB2WIK/6
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AB0RE
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Posts: 293




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« Reply #4 on: March 08, 2003, 02:36:39 PM »

I picked my 3/4" hole punch up from Grainger:
http://www.grainger.com/Grainger/productdetail.jsp?xi=xi&ItemId=1611580430

The hole punch produces *much* nicer results than using a hole saw.  The only disadvantage is that, as others are saying, you need access to both sides of the metal.  This can be a pain if you are installing it in the roof.  The above-listed punch requires a pilot hole (for the punch's shaft) that is a bit larger than a 3/8" hole (it can be made with a 3/8" drill bit if you swirl the drill around a bit).

One last word of advise... if you are punching through thicker metal, I obtained better results by putting the "nut" part of the punch on the outer-facing part of the metal - the "nut" side of the punch produces a near-perfect rounded off edge - looks very nice from the outside of the vehicle.

73,
Dan
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RAD1OMAN
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« Reply #5 on: March 09, 2003, 03:41:27 PM »

A punch would be nice, but I happen to use a Klein steped drill bit. Looks like a cone, steps in size, one version is .25 to .75 inch. You can find these at your favorite Home Depot or Lowe's stores.
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N2MDB
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« Reply #6 on: March 09, 2003, 06:25:36 PM »

To WB2WIK... There are NMO mounts that do not need access to both sides of the metal (I have installed them)...as long as they are of the 3/4" variety.

And to the rest of the thread, I like my Antenna Specialists 3/4" hole saw.

Matt N2MDB

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K3YD
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Posts: 55




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« Reply #7 on: March 10, 2003, 07:27:42 PM »

I have found that most "real" electrical supply houses (the place where electrical contractors shop)carry 3/4" Greelee punches.  They aren't a high volume item so HD and Lowe's don't usually stock them.  
Downside of the supply houses is they work contractors' hours (i.e. 6:30 AM to 4 PM M-F) but the inventory they carry makes a trip worthwhile.  I'm lucky, I live about 3 miles from a good one and can stop in on my way to work.

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