How to Tie an Underwriters Knot

Underwriters Knot

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Post subject: Underwriters Knot

Posted: Dec Sun 26, 2004 5:57 am

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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1400
Location: Illinois

I have this notion that before the advent of strain reliefs, an underwriters knot was used on radio line cords. I had to refresh my recollection of how to tie one, and found this through Google: <A HREF="http://www.homestore.com/HomeGarden/HomeImprovement/HowTos/HowTos/CRHO_ReplacingLightSocketandSwich.asp?poe=homestore" TARGET=_blank>http://www.homestore.com/HomeGarden/HomeImprovement/HowTos/HowTos/CRHO_ReplacingLightSocketandSwich.asp?poe=homestore</A> Now, in the various old radios that I come across, most have had their original line cords replaced sometime before. But, in any case, I don't recollect encountering any with an underwriters knot.Can anybody shed any light on this? Should I be using an underwriters knot intead of a simple overhand knot?------------------ ********** Doug Criner <A HREF="http://www.enginova.com" TARGET=_blank>http://www.enginova.com</A>

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Alan Douglas	Post subject: Underwriters Knot Posted: Dec Sun 26, 2004 6:30 am
Joined: Jan Thu 01, 1970 1:00 am Posts: 25381 Location: Pocasset, Cape Cod, MA	I've never seen one in a radio. The Underwriters knot is for plugs, where space is tight, and the wires need to exit the knot in opposite directions.<P>------------------<BR>
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dcriner

Post subject: Underwriters Knot

Posted: Dec Sun 26, 2004 6:55 am

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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1400
Location: Illinois

Hmmm.Alan, with a regular zip cord going into a radio, the two lines do go in different directions after they get into the radio.What, then, is the preferred approach for anchoring the line cord inside an old radio? Just an overhand knot? A modern strain relief seems kind of out of place and they evidently weren't used with most pre-war radios.Also, the hole in the chassis used for the power cord is frequently protected with a bushing, which would prevent inserting a modern strain relief. If there is no bushing, I guess you could drill out the hole, or make a new one of the right size for a strain relief.If I encounter a power cord hole without a smooth bushing, I just wrap a little electrical tape around the cord as it enters the hole, for protection, and call it "good." I'm probably violating somebody's rule when I do this.------------------ ********** Doug Criner <A HREF="http://www.enginova.com" TARGET=_blank>http://www.enginova.com</A>

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trainman	Post subject: Underwriters Knot Posted: Dec Sun 26, 2004 7:28 am
Joined: Jan Thu 01, 1970 1:00 am Posts: 2165 Location: Waukegan, IL	I never can tie an underwriters knot. The only radios I put a power cord with out a molded plug on are the 30's woods that had cloth covered cord( and I fake a UL knot for the attached plug). Everything else gets a cord with a molded plug. I just use a new rubber grommet at the chassis hole ant tie the corf with a simple knot.<P>------------------<BR>Tony
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easyrider8	Post subject: Underwriters Knot Posted: Dec Sun 26, 2004 11:33 pm
Joined: Jan Thu 01, 1970 1:00 am Posts: 10748 Location: Mpls, Minnesota	The Underwriters Knot was commonly used in many appliances including radios, lamps, and plugs. It is a very good knot as it will not slip and is simple to tie.<P>Dave<P>------------------<BR>Intelligence is the ability to use your knowledge
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Jim Koehler	Post subject: Underwriters Knot Posted: Dec Mon 27, 2004 5:47 pm
Joined: Jan Thu 01, 1970 1:00 am Posts: 3785 Location: Freeport, LI, New York 11520	Hi Doug...<BR>Ditto on what Alan says about the Underwriter's know being used in the early plugs. Usually, it's the overhand variety that's used in the chassis.On other chassis's,you may also find a strain-relief that's similar to a cable clamp assy. The thru-hull bushing that was used in the chassis's usually shrinks with age and ends up falling out of the chassis hole. Two things you can do here...either glue the bushing back into the hole, or use a grommet to replace the bushing. The problem with the modern strain relief bushing is that a "D" hole is needed for the bushing to work properly...and unless you have the punch to create that hole, or you're willing to sit at the bench filing away at the original hole, it's a lot more expedient to just "tie the knot" and be done with it.<P>(BTW...you have a great website! I must've spent an hour reading the articles)<P>...Jim <P>------------------<BR>
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Chuck Schwark

Post subject: Underwriters Knot

Posted: Dec Mon 27, 2004 6:17 pm

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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3465
Location: Evanston, IL

When I re-cord a set with repro cloth cord, vintage bakelite plug and cardboard insulator, I always tie an Underwriter's Knot in the plug, as I was taught many moons ago - Industrial Ed class ("shop").------------------ Chuck Schwark The Philco Repair Bench at <A HREF="http://www.philcorepairbench.com" TARGET=_blank>http://www.philcorepairbench.com</A>

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Smokenradios	Post subject: Underwriters Knot Posted: Dec Tue 28, 2004 3:33 am
Joined: Jan Thu 01, 1970 1:00 am Posts: 871 Location: Wa	Here another one with arrows to show direction of tie<P> <IMG SRC="http://images.lowes.com/general/l/lamp_kit_knot.jpg"> <P>------------------<BR>The light of one candle can extinguish all the power of darkness (evil)
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TDRyan	Post subject: Underwriters Knot Posted: Dec Tue 28, 2004 3:35 am
Joined: Jan Thu 01, 1970 1:00 am Posts: 293 Location: Holland, MI	What the...I see the code and not the image! EDIT: n/m, there it is.<P>------------------<BR>
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Smokenradios	Post subject: Underwriters Knot Posted: Dec Tue 28, 2004 3:37 am
Joined: Jan Thu 01, 1970 1:00 am Posts: 871 Location: Wa	I just edited it you should see it if you refresh the page<P>------------------<BR>The light of one candle can extinguish all the power of darkness (evil)
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jgrady	Post subject: Underwriters Knot Posted: Dec Tue 28, 2004 11:36 pm
Joined: Jan Thu 01, 1970 1:00 am Posts: 1475 Location: ayer ,ma usa	Bringing up the ole electrician stuff, UL knots make for a great short circuit/explosion, in old cord hung light fixtures and probably in radios.The rubber dries out...look again at knot to see what happens next. UL is very often "full of it", You don't want to ask me how I know. At one time Boston "required" UL Bx cable because it "would turn a nail"It turns out more fires are now started by 1910-1930 BX cable than anything else...the rubber crumbles right where wires leave the metal sleeve, usually at an overheated ceiling "pan" fixture, which was cobbled over a former chain hung light mount(no box).A short to shield will pull maybe less than the 15,20 or 30 amps fuse, shield back to ground at panel acts like excellent steel toaster element(it even burns off the UL label that says "do not remove") 30A fuses that fit 15 A wires were also UL approved. Cure for early BX problem was "UL" approved "redhead" fiber bushing, aka "antishort"(2nd try and counting); Then aluminum armor bonding strip (3rd try). Latest try is Aluminum BX, which cold flows and gets loose in ground clamp a day after you tighten it(4th try) Fifth try is MC cable, which is BX aluminum armored with a full size copper green wire. (aluminum won't turn a nail....). UL can't yet diss BX in favor of MC because it was "approved" method in past. (never, ever admit you screwed up..there are lawyers out there.....)This is called progress..Ever notice knob and tube , or even the first non grounded Romex installs do not have these problems? Knob and tube will work with red hot wires and no insulation, as wires never touch anything except porcelain, except where they go into outlet box, which requires added flexible tube protection("LOOM"); yet "experts" say "get that out of here" mainly so they can charge you to replace it. It is all soldered connections ,too, and no "loop thru" wiring at outlets, and resulting loose series connections/arcing. (cure for that is "arc fault interrupter" at 30$ each, now required in bedroom circuits) Anyway, a black tiny tie wrap holding zip cord together right after entering chassis is safer in the long run, as is added sleeving like "Varglass" sometimes seen on line cords,or both ...or 1/4 shrink tube..which looks a lot better than a soon to be sticky tape ball. FYI, John<P>------------------<BR>
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blareout	Post subject: Posted: Jan Tue 12, 2010 9:56 pm
Joined: Jan Tue 12, 2010 9:48 pm Posts: 1	It appears that JGRADY has taken Mrs O'leary's cow to the barn without kicking over a lamp. Good job Grady. I don't agree with many,but you are one of few.
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airgrabber	Post subject: Posted: Jan Tue 12, 2010 10:24 pm
Joined: Aug Mon 25, 2008 4:10 pm Posts: 235	ummm...this topic is almost six years old
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Dave Doughty	Post subject: Posted: Jan Wed 13, 2010 12:20 am
Joined: Jan Thu 01, 1970 1:00 am Posts: 18867 Location: Utica, NY 13502 (USA)	airgrabber wrote: ummm...this topic is almost six years old Grady's commentary is as good today as it was 6 years ago. I doubt the method of tying an Underwriter's Knot has changed much since then either. Dave
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glasdave

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Posted: Jan Wed 13, 2010 3:37 am

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Joined: Feb Tue 24, 2009 8:20 am
Posts: 10179
Location: Aurora Colorado

Yes sir.

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jkaetzjr	Post subject: Posted: Jan Wed 13, 2010 4:35 am
Joined: Jan Tue 16, 2007 11:48 pm Posts: 6679 Location: Hueytown, AL	A 4" tie wrap two turns around the cord and cinched up makes a pretty good stopper.
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