A couple more things:
If you elect to go with 45% silver it pays to check very carefully that you are getting exactly that. The lower alloys will not do the job. Commonly you’ll see way more 34%, 15% and 5% silver rods and someone may say, “oh you can use 34% - it’s only 2/3 the price”.
The 34% is not for high strength applications in steel; it does work for certain applications with specific steels but I almost guarantee that a mower handle won’t be made from that steel type. 15% and 5% are for brazing copper pipe not joining steel.
Also, you’re going to need to get the heat into your assembly uniformly. Then once you get a bit of a glow in the material just touch off your rod on it. The right temperature is when the rod melts on contact with the heated metal and flows smoothly.
It will be possible to get your parts too hot for the Silver brazing. They need to just be slightly above melting temperature for your rod. If it’s too hot the flux will be driven out and molten rod material will run through the joint. I heat the components to what I think is right and test touch, then heat some more, test touch again until I get a nice flow.
If you can do a bit of practice on some similar material before then you’ll get a feel for it. I wouldn’t recommend trying this for the first time on something you care about.
