Cutting Hard Line

Want to know how something works? Harness the power of the Brainiacs!
Post Reply
W9PXZ
Posts: 84
Joined: Mon Dec 03, 2007 2:21 pm
Location: Boiling Spring Lakes, NC

Cutting Hard Line

Post by W9PXZ » Tue Jul 16, 2019 8:01 pm

I've been away from the board for a long time, but I'm back with a new job and a new location.

I have a project next month installing a new GatesAir FAX40 transmitter. I have spent the last 14 years taking care of nothing but small class A's and this is my first big boy TX that I have had the opportunity to install. On the Class A's, I would just use the pipe cutter method on the 1 5/8" to cut the line taking care to go slow so as not to flare the cut inward, but on the 3" line, finding a cutter that will do an adequate job is tougher.

I think back to my days at WLAC in the late 90's when we rebuilt the entire TX plant except for the towers and Mike Gideon's tool of choice for cutting line was the portable bench style band saw. (I wonder where Mike is today? Does anyone know?) My Regional DOE here prefers the cutoff saw with the abrasive blade. I have also seen saw blades for non-ferrous metals that are made for a miter saw. Trouble is, I don't have access to any of these tools. If I need to spend the money, which should I spend it on and why? Keep in mind that I generally have to buy my own tools.

I am thinking the band saw is the likely direction I'll go, but want to hear the arguments for the methods and why. This FAX40 install will likely be the first of 3 if our capex allocations are favorable. I have a 30+ year old Continental on the cluster's top biller and a Continental 6C that almost no tube you can get these days will make it get to full power. But this year it is a Continental 5C that uses the infamous YC130 that gets retired to backup status. Can I hear the Hallelujah!!
Mike Dinger
Wilmington, NC

DaveSt
Posts: 49
Joined: Mon Jul 23, 2018 2:21 pm
Location: UK

Re: Cutting Hard Line

Post by DaveSt » Tue Jul 16, 2019 11:24 pm

I have seen all sorts of tools used and I have come to the conclusion that so long as you get the end square and clean and clear out the dust it does not matter how you do it. A band saw sounds reasonable to me. I hope the install goes well, the FAX is a good transmitter in my experience.

User avatar
jthorusen
Posts: 49
Joined: Sun Sep 02, 2018 4:35 am
Contact:

Re: Cutting Hard Line

Post by jthorusen » Wed Jul 17, 2019 12:16 am

I used to use a tubing cutter for 3 1/8 on TV channel 2 (54-60 MHz). I also used a deburring tool to take the inward sharp edge off. I never had any difficulties at that frequency. As I recall, we ran about 15 KW peak sync. I can't remember whether or not I ever cut any hard line for the FM station (93.1 MHz).... but I don't think anything special was used there either. If I recall correctly, one of the hard line manufacturers (Andrew?) recommended a wooden mitre box and a hack saw. :)

I would agree with Dave... as long as you have a clean square cut and don't get any metallic debris loose in the line, you should be fine.

Regards,
James K. (Jim) Thorusen
KB6GM
Central Coast Electronics
www.centcoast.com
NW Oregon Consulting Bdcst Eng.

User avatar
davek
Posts: 187
Joined: Sun Aug 02, 2009 7:28 pm
Location: Sydney, Australia

Re: Cutting Hard Line

Post by davek » Wed Jul 17, 2019 5:20 am

I've had excellent results using a drop-saw with a non-ferrous metal cutting blade. Often the cut is so clean the end doesn't even need de-burring.

Another advantage is being able to shave small amounts off the end, which you can't do with a pipe-cutting tool. This method was especially useful when I was cutting rigid line to length-match some transmission feeders for UHF (where every millimeter counts).

The saw blade does throw off a lot of chips so it is a little messy, but the results and ease of cutting are well worth the clean up.

radio_guru
Posts: 127
Joined: Sat Oct 02, 2010 11:23 pm
Location: Illinoid

Re: Cutting Hard Line

Post by radio_guru » Wed Jul 17, 2019 6:17 am

I am user of the Ridgid tubing cutters along with a good sharp deburring tool.

While the roller tubing cutters do require a certain amount of deburring to get rid of the slight inward material deformation at the cut, a light touch will minimize that circular deformation, the amount of deburring necessary, and subsequent (minimal) debris to be fished/cleaned out. With that, you are assured of a true and clean 90 deg. cut. And besides, you don't a ragged edge sliding into the flange or surrounding a bullet. Those create hot sports and impedance bumps. Neither of which are good long term...even with filing the end.

I have tried band saws with jigs and have experienced mixed results as well a deformed inners and outers. The least of which is lots of scattered debris/material from the cut. And they too need some measure of deburring too. I've not tried abrasive cutters. But The result would be the same: lots of debris to clean out and debur/treat the cut end to assure a smooth and even contact surface.

Good luck...plumbing with rigid line is very precise, challenging, and unforgiving. Particularly with flanges. But in the end, a very satisfying installation. After my first install with 3" 30 years ago, I quickly developed an appreciation for my brother-in-law's pipe fitter skills.

RG...

W9PXZ
Posts: 84
Joined: Mon Dec 03, 2007 2:21 pm
Location: Boiling Spring Lakes, NC

Re: Cutting Hard Line

Post by W9PXZ » Wed Jul 17, 2019 8:08 pm

Thanks, guys.

I didn't mind the tubing cutters on 1 5/8". Just keep a light touch so as not to flare the cut inward as stated. I was not aware they made them big enough to do 3", so I have some shopping to do. If I can find one that is reasonably priced, that would change my mind on the band saw. I'd rather have something that I can toss in the toolbox rather a couple hundred dollar power tool that I have to lug around and store for those jobs that only come along once in a while. A lot less mess than the others too.
Mike Dinger
Wilmington, NC

radio_guru
Posts: 127
Joined: Sat Oct 02, 2010 11:23 pm
Location: Illinoid

Re: Cutting Hard Line

Post by radio_guru » Thu Jul 18, 2019 5:42 am

3" can be cut by their #153 tubing cutter with the same copper/aluminum cutting wheel used on the smaller cutters. You will go through cutting wheels much faster on the 3" to be certain. So buy them in bulk.

And given the newer versions of the 153 have only two rollers, a light touch and many more rotations is necessary so as to not deform the circularity of the line being cut.

Also, deburring tools can be found at Grainger. Deburring is an absolute necessity if using a cutting wheel to cut any rigid line be it copper or aluminum. I keep a deburring tool with each cutter I own as a kit.

RG

User avatar
kkiddkkidd
Posts: 842
Joined: Mon Dec 03, 2007 11:13 am
Location: Lawrenceburg, TN

Re: Cutting Hard Line

Post by kkiddkkidd » Thu Jul 18, 2019 7:10 am

I use a tubing cutter or bandsaw on 1-5/8in and typically use a band saw on 3in. I have a large tubing cutter that will just barely fit over 3in but I have had all kinds of issues with it causing more inward dinging than a bandsaw or even a plain old hack saw.

I hadn't thought about the chop saw but that would certainly make nice square cuts quickly.
--
Kevin C. Kidd CSRE/AMD
WD4RAT
AM Ground Systems Company
http://www.amgroundsystems.com
KK Broadcast Engineering
http://www.kkbc.com

User avatar
Dale H. Cook
Posts: 901
Joined: Thu Dec 20, 2007 9:08 am
Location: Roanoke/Lynchburg, VA
Contact:

Re: Cutting Hard Line

Post by Dale H. Cook » Thu Jul 18, 2019 9:16 am

W9PXZ wrote:
Wed Jul 17, 2019 8:08 pm
I was not aware they made them big enough to do 3"
A friend who is engineering director of a statewide system of NPR stations has a Rigid that will do 6" hardline (that is what their flagship station uses to feed a 5 bay).
Dale H. Cook, Contract Engineer, Roanoke/Lynchburg, VA
http://plymouthcolony.net/starcityeng/index.html

radio_guru
Posts: 127
Joined: Sat Oct 02, 2010 11:23 pm
Location: Illinoid

Re: Cutting Hard Line

Post by radio_guru » Thu Jul 18, 2019 10:09 am

It's most likely a cast pipe cutter using the copper/aluminum cutting wheel. Heavy....and a bit of a bear to use.

RG

ncradioeng
Posts: 65
Joined: Wed Nov 18, 2015 3:58 pm

Re: Cutting Hard Line

Post by ncradioeng » Thu Jul 18, 2019 11:33 am

I've used a hose clamp as a cutting guide and a fine-tooth hacksaw. Takes a little time, but if you're only doing a couple of cuts, it works OK.

Ray
Posts: 68
Joined: Sat Mar 22, 2014 10:04 am

Re: Cutting Hard Line

Post by Ray » Fri Jul 19, 2019 6:03 am

I also use a hacksaw, but I put the Heliax in a mitre box when I cut so that I can get a square cut. This works up to 1 5/8 diam.

User avatar
AMFMSW
Posts: 3
Joined: Mon Aug 05, 2019 12:53 pm
Location: DFW

Re: Cutting Hard Line

Post by AMFMSW » Tue Aug 06, 2019 10:24 am

The last hardline install I had we used a chop saw with a fine tooth blade on both 1-5/8 and 7/8 line. Make sure you have shooters' muffs or other suitable hearing protection! A little deburring with a file and some plumbers cloth and all was well.

Josh
Transplanted radio engineer in Texas.

Post Reply