# Joining O'ring cord



## picclock (Apr 20, 2011)

My attempts to join O'ring cord have always been hit and miss affairs. even with trying to just get square cuts on the ends. I've tried various methods, even drilling a hole in some plate the same size as the cord, poking it through and cutting it off with fairly poor results. As for getting the ends to line up perfectly I find it impossible. 

I have made some that work but I'm really looking to up my game on this. 

Does anyone here do this on a regular basis, and have they any insider tips ?

Best Regards

picclock


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## doc1955 (Apr 20, 2011)

We do this where I have my real job. We created a little jig for cutting and gueing it isn't much just a plate with a slot cut in it for the o ring to fit snug not tight and a cross slot for the exacto knive to cut it the to line them up use the same jig and put the o ring ends together in the slot and glue them. The plate we used for the jig is teflon.


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## Swede (Apr 20, 2011)

That's a good idea. You could make a "universal" plate by taking a teflon block and milling 2 or 3 "V" grooves into it. Select the groove closest to the size of the O-ring material.

If one did a lot of one particular size, like 1/8", using a ball end mill in that size to create grooves on two plates, you could make a sandwich of the plates.

For me, the problem has been the glue. The joint always seems to be a little weak.


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## Omnimill (Apr 20, 2011)

http://docs-europe.electrocomponents.com/webdocs/0859/0900766b80859bd3.pdf

May help?

Vic.


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## picclock (Apr 20, 2011)

Thanks for the good ideas. I've got some polypropylene and nylon I can try this out on. 4mm is the current requirement and I have a ball end mill which should do this. It will be interesting to see how straight a cut the end is. I would think that the top of the rubber would compress but whether this will cause a significant error I will find out.

I've tried various adhesives for joining the nitrile and have come to the conclusion that most forms of cyanoacrylate seem to work about the same. Honestly could not tell the difference between Zap and Locktite 8020 ?? (brainfade again). 

Thanks for the info

picclock


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## jct842 (Apr 20, 2011)

Almost 40 years ago the shop I worked at bought a kit to be used for making new belts for cassette recorders. they used what appeared to be long o rings of various lengths. the kit came with a jig, several rolls of round rubber and tubes of super glue. you cut the rubber diagonally making both cuts a the same time so that the ends would match. I don't ever remember where a customer brought the recorder back where the glue had let loose.  john


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## MachineTom (Apr 20, 2011)

JCT already said it, the trick is the shallow angle cut. 35 years ago our shop did alot of hydraulic cylinders and sometime we just needed to make one. The plastic jig had two holes like an O/U shotgun and a slot for a razor blade, shallow angle maybe 10° from axis, after cutting glue on one piece and lay it in a vee groove to join. As I recall the jig was set that you leave the stock exactly 1 inch longer than needed, after cutting it was the right lenght.


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## Captain Jerry (Apr 20, 2011)

I have never made an 0-ring from cord stock but that is not going to keep me from offering a suggestion. I have had some experience cutting rubber products and one of the factors that affects an accurate cut is compression and stretch. Compression can be reduced by using a VERRY sharp edge with a slicing motion. The slicing motion can produce drag and stretch unless the cut is lubricated. The best lubrication for steel on rubber is water, plain water, no oil, no soap. Just a drop of plain water and a slicing, not chopping, cut using a clamp as mentioned above will produce the best cut.

An angled cut gives more surface area for adhesive but I would be afraid of introducing twist in the assembly.


Jerry


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## slkride (Apr 20, 2011)

In my past life as a Diesel Mech I needed to make O rings now & then. We used a kit from Loctite it had a simple jig with it. just a piece of plastic with a V in it about 2" long to lay the ends to be stuck together in to keep them in alignment and different size holes in it to stick the cord stock in, with a thin slit in the center to push a razor blade down to do the cutting at a 90deg. dab the adhesive on the end and slide together using the V as a guide. Make sure things are CLEAN Had good using it.


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## Swede (Apr 30, 2011)

One last thought... there is a synthetic material I used to buy from Small Parts that consisted of a green plastic cord stock, came in different diameters, and it was used to make drive belts for small machinery. It was joined thermally. You'd cut the cord, then place both ends simultaneously in an alcohol lamp until the ends melted and blobbed. Then, the ends were immediately joined using a jig. When cooled, the flash or excess was trimmed with a razor blade.

The joint was as strong as the virgin stock.

I wonder if there might be suitable O-ring material that could be joined in this manner?


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## el gringo (Apr 30, 2011)

FYI....don't know how good this is, I'm going to try one. Had good luck with similar in my other life years ago. 

 Metric/American O-Ring Splicing Kit Material: Buna 
Material: Buna 


Model #TP505-3884 
Low Price: $43.98 ea  *$21.99 ea  * 
Availability: Backordered 
  Quantity  
 Master Catalog Page 916 


Ray M


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