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Radio Equipment Installation Forum - Forum for discussing how to install radio communications equipment in Mobile, Base, Command Post, EOC, etc configurations.

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  #21 (permalink)  
Old 05-15-2017, 9:21 AM
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I've never used oil when cutting holes in a vehicle roof. As noted above, I could see it staining the roof liner. However for other cutting purposes, I've used bar soap. It acts as a lubricant as well. (It makes driving wood screws easier too.) If I had my heart set on not cutting dry, I'd go that route. Not saying its necessary though.
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Old 05-15-2017, 9:24 AM
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Originally Posted by prcguy View Post
Not in a sheet metal car roof.

prcguy


Really? I've used them for years with no problems. Many others in here will agree.
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Old 05-15-2017, 9:39 AM
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Another hole saw debate? Might as well throw my 2 pennies in. I've come to the conclusion that there is no ONE particular way that is the RIGHT way. However there are several wrong ways. A grinder, a sawzall, a torch, hammer and punch, tin snips, jig saws and spade bits are the wrong way. But using a proper sized hole saw or hole punch that leaves you satisfied with the end result could be deemed the RIGHT way. It's basically however you feel comfortable doing it.

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Old 05-15-2017, 9:57 AM
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Quote:
Originally Posted by 12dbsinad View Post
Thousands of NMO holes here as well, no oil either as I don't want to be responsible for telling the owner of a brand new 75,000 + vehicle why there is a large oil stain in the headliner. Blades last a long time if you proceed slow and let it do the work.
Two thoughts:

You lose 20-50% of the tool life if you don't use some sort of lubricant/coolant on the cutting surfaces. There are other options besides oil; WD-40 works quite well without requiring so much that it forms puddles.

You should have a basin or tray under the hole to catch metal chips. Oil stains are undesirable, but so is getting a metal sliver embedded in your backside because you sat on a chip from the hole being cut. Steel chips can be very sharp. If your catch tray/basin is sufficient to prevent chips from being scattered through the vehicle interior, then it will catch any lubricant drips as well before they stain anything.
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Old 05-15-2017, 10:51 AM
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Home Depot type 3/4" hole saws work great for drilling NMO holes and you can drill up to maybe a dozen car roofs before needing to replace or sharpen and adjust the teeth. As mentioned by other professional installers, you never want to use any lube on a vehicle roof and there is no need to. The tool has a finite life and replacing it is just a cost of doing business.

For other use as cutting holes in metal projects with a drill press, oil will certainly improve the cut and prolong the life of the tool. Just don't do it on car roofs.

From your description of using a catch basin or tray under a headliner to catch oil and chips, I gather you are just imagining cutting the hole in a vehicle roof and have never actually done what you are describing?
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Originally Posted by jonwienke View Post
Two thoughts:

You lose 20-50% of the tool life if you don't use some sort of lubricant/coolant on the cutting surfaces. There are other options besides oil; WD-40 works quite well without requiring so much that it forms puddles.

You should have a basin or tray under the hole to catch metal chips. Oil stains are undesirable, but so is getting a metal sliver embedded in your backside because you sat on a chip from the hole being cut. Steel chips can be very sharp. If your catch tray/basin is sufficient to prevent chips from being scattered through the vehicle interior, then it will catch any lubricant drips as well before they stain anything.

Last edited by prcguy; 05-15-2017 at 12:28 PM..
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  #26 (permalink)  
Old 05-15-2017, 11:56 AM
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I've used Greenlee hole punches MANY times and never had a problem with sheet metal car roofs. We always had small square blank metal with the 3/8 hole for the stud and it would punch the sheet metal without the draw bend occurring.
Albeit, the hole punch works better with heavier gauge metal, but car roof's sheet metal can be done if you use the square, ( or round ) blanks to act as a thicker gauge.
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  #27 (permalink)  
Old 05-15-2017, 12:19 PM
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To use a hole saw in a car roof, Home Depot type or one made for NMO, you simply peel back a little rubber weather seal around the headliner near a door, cut the hole, install the mount and pull the coax towards you and tuck the coax under molding to the floor and to the radio. A professional radio installer NEVER drops the headliner and rarely completely removes molding to route coax.

The whole process takes maybe 5min including sliding a thin sheet of plastic between the headliner and metal roof on some headliners so you don't snag the headliner. That's 5min for the topside work to get the mount and coax in and maybe 15min total for the antenna install including putting on a connector unless its a particularly difficult vehicle. When I was in the business a long time ago a busy day would be 6 or 7 radio and antenna installs per day.

To use a Greenlee punch you have to do at least the same prep, drill a 1/4" hole, then try and get half the punch between the headliner and roof, which is not easy on many vehicles. If you are in the install business you will be out of business soon wasting time putting antenna mounts in using a Greenlee punch.

I'm not saying a Greenlee punch doesn't make a nice hole or it can't be used, its just not the right tool for the radio installer. Any other actual radio installers want to comment?

Some of the comments remind me of a guy I worked with years ago that did things that I thought were silly. For example, we needed a new office light switch installed in a sheetrock wall where an outlet box was needed and wire run to the switch. Most people would use a coarse sheetrock hand saw and cut the hole out in less than a minute with no problems, no pilot hole needed and little mess.

Instead, my work mate liked to use a dremel moto tool with cutoff wheel for some reason and he picked that tool every time we had to cut a hole in sheetrock. It was very slow, very loud and filled the room with fine white dust, plus it prematurely wore out the Dremel with all the fine grit that got sucked through it. Some people use the right tool for the job and others have made up their minds on something else.
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Originally Posted by KC4RAF View Post
I've used Greenlee hole punches MANY times and never had a problem with sheet metal car roofs. We always had small square blank metal with the 3/8 hole for the stud and it would punch the sheet metal without the draw bend occurring.
Albeit, the hole punch works better with heavier gauge metal, but car roof's sheet metal can be done if you use the square, ( or round ) blanks to act as a thicker gauge.

Last edited by prcguy; 05-15-2017 at 12:37 PM..
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Old 05-15-2017, 1:33 PM
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I've used Greenlee punches, hardware store hole saws (which are actually made for wood), and antenna hole saws. All will work if you're careful, measure at least twice before cutting, and make sure you can get at the underside of where you are cutting. For automotive sheet metal, I've never felt the need to use oil, other applications I have.

The nice thing about the antenna hole saw is that it makes a nice grounding ring around the hole.

The least successful technique, at least for me, was using a "cone cut" drill. It works for some things but has a lot of downside when drilling into a vehicle. Mostly because it's long enough that it might snag the headliner if you're cutting into a roof.
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Old 05-15-2017, 2:50 PM
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Quote:
Originally Posted by prcguy View Post
From your description of using a catch basin or tray under a headliner to catch oil and chips, I gather you are just imagining cutting the hole in a vehicle roof and have never actually done what you are describing?
prcguy
Actually I have. I dropped the headliner partway and put an old cookie sheet on the headliner under the hole site. It worked great to catch the chips and drips. A couple pieces of masking tape held it in place nicely.
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Old 05-15-2017, 3:03 PM
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A round 3/4 inch hole is a round 3/4 inch hole. Doesn't matter how you make it. Some techniques are easier and cleaner than others.
Hole saws designed for NMO mounts have a number of benefits, depth limiting, replaceable blades, etc. They are widely accepted as the "right" tool to use.

I've used both hole saws and chassis punches with good results. I wouldn't fault anyone for using either method.

I'd never use one of the Christmas tree bits myself, too many potential problems, and not the right tool when I have the correct hole saw and chassis punch.
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Old 05-15-2017, 4:59 PM
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Quote:
Originally Posted by prcguy View Post
To use a hole saw in a car roof, Home Depot type or one made for NMO, you simply peel back a little rubber weather seal around the headliner near a door, cut the hole, install the mount and pull the coax towards you and tuck the coax under molding to the floor and to the radio. A professional radio installer NEVER drops the headliner and rarely completely removes molding to route coax.
Wasn't an option in my case. Too many doodads in the headliner and the roof support structure to fish blind, and I had to pull the trim off the pillar to route the coax from the roof down under the dash to the radio.
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Old 05-15-2017, 7:53 PM
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Quote:
Originally Posted by prcguy View Post
A professional radio installer NEVER drops the headliner and rarely completely removes molding to route coax.
I have no doubt this is true. A professional installer who does several of these projects a week gains a lot of experience and self-confidence that they guy who does one project every five years simply doesn't have. Us amateurs can read about the tips and techniques from others, but nothing beats direct experience. Also, a professional installer is probably working on a deadline, so finishing the job expediently makes the boss happy.

I did one install on my personal vehicle where I did not drop the headliner. For as long as I owned that vehicle, I could hear the loose coax slapping against the inside of the roof/headliner whenever the vehicle shook. Took me a long time to tune that out. If I had dropped the headliner, I could have taped or otherwise anchored that coax (not with Ty-Wraps) so it wouldn't flop around.

Note, I'm not disagreeing with the NMO-specific hole saw method. It's the right tool for the job.
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Old 05-15-2017, 8:05 PM
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HA! this is a good one.. "A Professional radio installer never drops the headliner ".. Apparently we can tell who the hacks are in the business. I as a professional installer and emergency vehicle upfitter always does it the CORRECT way as to avoid hidden wire harnesses and air bag components.Catch a harness or break a connector on a air bag system and see what it will cost you...If you dont blow out the SRS computer also...
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Old 05-15-2017, 8:22 PM
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Quote:
Originally Posted by prcguy View Post
Home Depot type 3/4" hole saws work great for drilling NMO holes
Also for beer tappers in stainless steel fridge doors!
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Old 05-15-2017, 9:18 PM
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Some vehicles have more cable path obstacles than others and past experience helps guide you on unfamiliar installs. My 6 year carrier as an installer ended 36 years ago and I don't do many installs these days, so you certainly have more experience on newer vehicles than me.

A hack? Maybe on the one and only screw up I did in about 1,000 installs, but overall I was very well respected in the area. In the end I managed the service shop and trained new installers for several sites. Still, the only headliners I ever removed in my career was to repair other installers mistakes.
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Originally Posted by FFPM571 View Post
HA! this is a good one.. "A Professional radio installer never drops the headliner ".. Apparently we can tell who the hacks are in the business. I as a professional installer and emergency vehicle upfitter always does it the CORRECT way as to avoid hidden wire harnesses and air bag components.Catch a harness or break a connector on a air bag system and see what it will cost you...If you dont blow out the SRS computer also...
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Old 05-15-2017, 9:33 PM
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There's a lot more wiring in the headliner of newer vehicles than the ones you worked on. My Silverado is a 2001 and there's NO WAY one could run the coax without dropping the headliner. Newer vehicles are even worse--more detail lighting, sensors, and other stuff that doesn't like being poked, and can't practically be routed around in situ unless you moonlight as a proctologist.
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Old 05-15-2017, 10:18 PM
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I've done an amount of newer vehicles up to some Toyota's and several big Dodge diesel trucks of last year with air bags, sensors, etc, and still have never had to drop a headliner. My skills might be a little rusty but their not rusted out.

With what I know today I would not want to be in the commercial installation business due to the liability and frankly it doesn't pay enough.
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Originally Posted by jonwienke View Post
There's a lot more wiring in the headliner of newer vehicles than the ones you worked on. My Silverado is a 2001 and there's NO WAY one could run the coax without dropping the headliner. Newer vehicles are even worse--more detail lighting, sensors, and other stuff that doesn't like being poked, and can't practically be routed around in situ unless you moonlight as a proctologist.
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Old 05-16-2017, 6:01 AM
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Quote:
Originally Posted by jonwienke View Post
There's a lot more wiring in the headliner of newer vehicles than the ones you worked on. My Silverado is a 2001 and there's NO WAY one could run the coax without dropping the headliner. Newer vehicles are even worse--more detail lighting, sensors, and other stuff that doesn't like being poked, and can't practically be routed around in situ unless you moonlight as a proctologist.
That's odd. I have an 03 Silverado and installed 4 NMO mounts without dropping the headliner. And they were all installed from the outside top of the roof using a fish tape.

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Old 05-16-2017, 11:33 AM
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Quote:
Originally Posted by K9DAK View Post
Also for beer tappers in stainless steel fridge doors!
Now, that's PROPER use of a hole saw!
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Old 05-16-2017, 12:55 PM
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Speaking of holes ... too paraphrase an old codger.

22 is for phone line
38 for coax
12 gage for most 1/2 pipe and conduit

So what's a NMO - a 10 gage ?
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