What is the BEST solder to use on a 4-40 rod and clevis? Do I need flux?

Jimbo, silver solder is probably the best. You will need flux, it usually either comes as a "silver solder kit" or you can buy the flux separately. The more silver the better, but they are proud of it. You'll need a small torch.

I use regular acid core solder on them and have never had a failure, just be sure to shine the rod up good first. 60-40 Lead/Tin. A heavy iron or small torch, but I've used a butane lighter and the kitchen stove for speed.

With either kind, be sure to clean the flux off good after you are finished or rust will set in and don't get the rod too hot.

I have started using a lot of carbon fiber pushrods and just JB weld a roughed up piece of 4-40 rod ( I use a pair of diagonal cutters to really score the rod) with threads already on it into the CF tube.

While silver bearing solder is somewhat stronger, I often use plain old rosin core electrical solder with no problems or failures over many years. As mentioned above, cleanliness is of paramont importance; and, yes flux is required for easy success. I shy away from acid core or acid flux due the the requirement for complete neutralization after soldering to preven rust and corrosion--difficult to accomplish. If you use a torch, be carefull, to much heat can be as detrimental as to little.

I agree. I've done a few without flux and it is harder to do. Flux allows for the solder to seep in and melts the solder faster, requiring less heat.

MinnFlyer did an awesome tech article on soldering, do a search for it. It is definately worth the read.

Here it is:

http://www.rcuniverse.com/magazine/a...article_id=172

Thanks y'all, that was a big help !