joining plastic drive belts

I use an orange polyurethane belt (no hole) which you join with heat. A soldering iron works fine for heating, and the resulting join is amazingly strong.

Catches are that the belt has to be hot, but not too hot (bubbling is not good). The joint has to be made instantly and held until the joint has cooled (1 minute plus). The joint will also fail if there is any dirt in it.

Dave

x wrote:

I'm not familiar with welding hollow belting, but solid round urethane belting can be heat welded with the proper tools. The setup I've used was a jig/fixture to hold the ends aligned properly, with one jaw that would slide. Then the hot heating iron (with a flat plate end) was placed between the ends. The ends were brought together, with the hot surface between them, and when the ends showed that they're melting, the hot tip is slid out, as the ends are pressed together.

When the belting cools, the excess material at the bond was trimmed away, and the belt was ready for service.

The solid belting length was purposely made for a tight fit, in that the belt length needed to be sized smaller than a V-belt. The extra tension of the urethane belt would prevent slipping of the drive pulleys.

I would expect it to be difficult to weld hollow belting (if it's even intended to be welded), as pressing the melted ends together would likely cause wall shifting or collapse, creating an uneven or not uniform weld. I think it could be easier if the center was filled with the same compound, maybe some scraps cut to fill the void. Overall, it's probably best to join the ends with the method that's recommended by the manufacturer.

WB ..............

x wrote:

I don't think they hollow ones are meant to joined by welding. There is a short brass joiner with a couple of barbs on each end of it ( like a hose fitting) that are pushed into the ends. The solid urethane belts can be welded by placing a strip of clean sheet metal in a vice. Heat the end of the metal with a torch , then push the two ends against the hot metal strip. When they melt,slide them together so they slip off the metal strip and onto each other. Hold them firmly in position till they cool , then trim off the flash. There are special tools for this job,including a Teflon coated heating iron and a jig which holds the ends firmly aligned and at the correct pressure. They are well with the cost if you are doing a lot of these joins,but are too expensive for "a one off job"

I've had good luck with a heat gun. As someone else mentioned, the end has to get hot, but not too hot. When the cut end gets glossy and swells very slightly seems to be about the right time to make the join. A small v-block may be helpul in getting the ends properly aligned. I've found a Scotch-brite wheel to be the best thing for trimming the flash from the joint.

Among the real belt welders I've used, the best was one that used a small radiant heating element to heat the belt ends. It was easier to use and seemed to do a better job than the soldering iron with teflon paddle type.

The belting you have should weld just fine, I've welded all sorts of urethane this way. If you want really nice welded round belts at reasonable price (though there is a minumum), these folks do an excellent job...

thanks everyone! i'll try again.

(it's complicated by having to join 'in situ' to avoid dismantling lathe headstock....i've been practicing on a short offcut)

regards

(it's complicated by having to join 'in situ' to avoid dismantling lathe headstock....I've been practicing on a short offcut)

You may want to make a bracket to hold each end, something simple from two pairs of vicegrips and a bit of fencing wire should do, and do the same while practicing on your offcuts.

Hope this helps, Peter

Second that - I was struggling to get a good joint, using "hot knife" method, until someone showed me the heatgun way.