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Cutting Ceramic Insulators




 
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Author Topic: Cutting Ceramic Insulators  (Read 17008 times)
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k4kyv
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Don
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« on: June 20, 2011, 01:03:51 AM »

I needed a set of ceramic stand-off insulators for stringing a run of open wire feedline onto a series of poles from the shack to the base of the tower.  Electric fence insulators are not satisfactory because the nail or screw that passes through the insulator to affix it to the pole would be a source of possible RF break down.  I vainly searched for new or used ceramic stand-off insulators online and elsewhere, but could not find anything usable.  Then it occurred to me that I had five 6" ceramic open wire spreaders, each 3/4" in diameter. Something I have had kicking around for decades, not much good unless I could find more of the same to make enough for a project.  Besides, they would be too heavy for anything but an extremely heavy duty 6" spaced OWL.  

These would serve perfectly if only I could find some way to cut each insulator exactly in two. Then each half-insulator could be mounted vertically into a metal cross-arm, by drilling out holes slightly larger in diameter than the insulators, and setting the insulators in place with epoxy.

I have never had much luck cutting porcelain ceramic using the score-and-snap method; usually end up cracking the piece in every direction but the one desired. Then, I investigated saws used for cutting ceramic bathroom tile. At the local Lowe's I was able to purchase a 7" diamond cutting blade for about $30, to fit in my Skillsaw. I built a wooden bracket to hold the skillsaw in a vertical position, tied off the safety shield and taped the trigger into the "on" position. In this configuration, the saw is turned on and off by plugging in and unplugging the power cord.

The blade, a DeWalt DW4760, is designed for wet cutting, so I used a garden hose with a "high pressure" nozzle attachment, but with the water just barely turned on. This produced a nice steady smooth 1/4" diameter slow stream which was easily directed onto the cut by tying the hosepipe to a handrail with a piece of wire and carefully adjusting its position.

Each insulator was manually held up to the cutting edge of the blade in the bracket and gently rotated until it fell in two. The cuts were clean, and the blade seemed to pass through the ceramic like a knife through butter, velvet smoothly. As shown in the photo, a shallow ring was cut round the circumference at the base of each insulator, about 1/4" from the cut end, to allow for a better grip with the epoxy filler. The epoxy filler at each insulator will be sealed over with a small ring of roofing tar to protect the epoxy (JB Weld) from the weather and solar UV.

Be prepared to get wet during this operation; I got soaked! Probably not a good wintertime project. And of course, eye protection is absolutely a must.

The cross-arms will be made from 1 1/4" X 1 1/4" solid aluminium stock ordered from McMaster Carr, and mounted on the poles using angle brackets and U-bolts.


* saw bracket2.JPG (1147.67 KB, 2576x1716 - viewed 731 times.)

* process closeup.JPG (1155.08 KB, 2576x1716 - viewed 804 times.)

* finished insulators.JPG (1146.44 KB, 2576x1716 - viewed 817 times.)
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Don, K4KYV                                       AMI#5
Licensed since 1959 and not happy to be back on AM...    Never got off AM in the first place.

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Ed/KB1HYS
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« Reply #1 on: June 20, 2011, 06:14:03 AM »

Ingenuity at it's finest!  Nice job Don.
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73 de Ed/KB1HYS
Happiness is Hot Tubes, Cold 807's, and warm room filling AM Sound.
 "I've spent three quarters of my life trying to figure out how to do a $50 job for $.50, the rest I spent trying to come up with the $0.50" - D. Gingery
W2PFY
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« Reply #2 on: June 20, 2011, 10:32:03 AM »

Quote
The cross-arms will be made from 1 1/4" X 1 1/4" solid aluminium stock ordered from McMaster Carr, and mounted on the poles using angle brackets and U-bolts.

 Great finding Don! I hope you will post the end result.
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The secrecy of my job prevents me from knowing what I am doing.
KL7OF
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« Reply #3 on: June 20, 2011, 03:00:51 PM »

Diamonds are a hams best friend
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kb4qaa
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« Reply #4 on: June 20, 2011, 03:31:36 PM »

A low cost method is to purchase a 'ceramic cutting blade (rod)" which fits into a standard hacksaw frame.

I've used them for cutting ceramic tile with surprisingly good results.  Once you break through the thin glaze it is like cutting chalk.
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