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-   -   Disc brake jig (https://www.bikeforums.net/framebuilders/1123719-disc-brake-jig.html)

calstar 10-01-17 11:36 AM

Disc brake jig
 
I just saw a pic(don't remember where) of a disc tab ready for brazing that was fixed in place using a hub with a disc mounted. The mechanical disc brake to be used was secured/clamped to the disc using the brake's clamping cable, then the disc tab was directly mounted to the brake body and positioned for brazing(and/or final fitting then brazing) to the fork(or rear stay). I tried to explain this as best I could, hope it makes sense without a pic. Any down side to this method?

thanks, Brian

dsaul 10-02-17 04:13 AM

Damage to the brake caliper from the torch. Its probably mostly cosmetic, but the heat will discolor the anodizing on the caliper and brake mount adapter.

If you're going to be mounting disc tabs more than once, just buy the proper fixture from Anvil or Incepi.

unterhausen 10-03-17 08:49 PM

the nice thing about a disc fixture is that you can use it to fit the tab to the frame. I have the Anvil Post Punk, and use it like that every time.

duanedr 10-06-17 12:21 AM

I bought a used 'dummy' hub, disc and caliper/lever for this purpose and used it successfully twice and unsuccessfully once. I build for myself so, it's not a huge deal to make a custom machined caliper adapter. I tried to make my own Post Punk-like thing but the tolerances have to be very tight to match the spec and well, i'm also a newbie machinist so...I bought an Anvil Post Punk a few weeks back. It's wonderful to hold.

I think that hub/disc/caliper approach is appealing for newbies. It's intuitive and re-assuring where things are and what will work or not work. The downside is that it's not as accurate/precise or reliable - just waving the torch past the disc warps it enough to make the placement potentially out of spec...

unterhausen 10-07-17 10:25 AM

the Post Punk is really nice, and you can just use adapters to go to ISO. In fact, I have yet to use it on a post mount. Back when you had to buy front and rear ISO fixtures, that was a lot more money. I was trying to figure out how to use it with direct mount for forks, but it seems somewhat pointless, unfortunately. The adapter for direct mount rear is somewhat ungainly. Haven't seen direct mount fittings for forks that I like anyway.

calstar 10-08-17 09:17 PM

I searched around and found several references to the method I first posted about, works ok but as you(those above) point out a proper fixture is better/faster/more accurate. Rather not spend the $$, probably copy one of the diy versions found on the web.

thanks for the input,

Brian


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