Re: grommet strips

Mike Czuhajewski

Somewhere I saw an article on how to make a air wound coil by using these strips on a piece of PVC......
This has been covered a few times over the years in the QRP press and elsewhere. One I know about for sure is the Fall (October) 2011 issue of the QRP Quarterly, where it was part of my column. That was based on the web page of Phil Salas, AD5X. You can find his article here:

Not sure about either of these, but I think he also wrote about this in QRPp quite some tiame ago, as well as QST. The idea has been around for quite some time. (I think one of the St. Louis QRP folks also wrote about it, maybe Dave Gauding.)

As for the grommet strips, here is some info on that from my 2011 column. (This is my commentary)--

"The grommet strips are also known as caterpillar strips, or edge trim. They are available from McMaster Carr (, a well known industrial supply house. They have no minimum order and I've made many small orders from home. Their stock number for this particular nylon edge trim is 85085K8. It's sold in packages of 25 foot long pieces for about $12, enough to make a number of coils.

"This particular strip gives a coil of 8 turns per inch due to the spacing between the teeth. McMaster has several different versions available. KC6ZZT asked how to determine how many teeth per inch there are since the product descriptions don't give that; he was wondering if it would be possible to get one that would give him 6 turns per inch instead of 8.

"N3OX pointed out that the number of teeth per inch is not part of the specification and really isn't an important parameter, considering the use of this product. It's purpose in life is to fit over the edge of a panel or sheet of metal to provide protection against sharp edges. The important dimensions are the gap between the two rows of teeth (how thick a panel it will fit) and the length of the teeth.

"KC6ZZT later called McMaster; someone went into the warehouse and checked, and told him that all of the nylon strips of this type in the catalog are 8 teeth per inch.

"They also told him that they get them from Thomas & Betts, their part numbers GSNY-052-9-C, GSNY-085-9-C, GSNY-128-9-C, and GSNY-192-9-C. (You can find them on their web page,, by entering GSNY into the search block.) Thomas & Betts sells them in packages of 100 (and McMaster by packages of 25)."


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