Originally Posted by
Kuromori
It's also good reason to dish out a few extra bucks on 631 (or 853 etc) tubes, expert or not, when making big fillets. It's not just that the steel is stronger against breakage, but that the steel is also harder and a bit more abrasion resistant post-brazing. I'd also steer away from the fancy grinding belts.
Huh, hadn't thought about that, but it makes sense.
I made some lugless Aermet 100 Alloy frames (precursor similar to 953), and that stuff was noticeably hard to scratch.
Made a bunch of 853 frames too, but they were lugged, so I never had the experience of cleaning up fillets on 853.
Yes the added hardness is working in your favor when it comes to not digging trenches around the fillets, but it's still not an excuse to use a dynafile on thin tubing. IMHO. I dynafiled miles of fillets (maybe literally?) when I was making tandems all the time, but I stopped when tube walls got thinner (and coincidentally my fillets got smoother, less need for power tools). I'm not saying you can't use that tool, if you're very good and careful. I'm just saying a lot of guys think they're good enough but they're not.
Dynafile owners probably know this already, but they make a contact arm that is all unsupported belt (#11219). And 1/8" wide belts exist, much less likely to dig in the edge than 1/4" belts. But I
still recommend people avoid them for very thin tubing. Even if you're trying to feed your kids -- make shortcuts somewhere else!
Mark B