How did you mitre the ends of the top and down tube?
I filed it until I was satisfied with the angles. Using the existing mitres as guides for the filing. It took a couple of day getting it right. Checking the toptube, seattube and new heatube constantly with Clinometer app on my iPhone.
I am currently working on a jig, but this can be done with files, a hacksaw, a vise, frameblocks and a brazing kit.
I filed it until I was satisfied with the angles. Using the existing mitres as guides for the filing. It took a couple of day getting it right. Checking the toptube, seattube and new heatube constantly with Clinometer app on my iPhone.
I am currently working on a jig, but this can be done with files, a hacksaw, a vise, frameblocks and a brazing kit.