the vast majority of builders dont weld/braze in the jig. Many would consider it bad practice. By brazing in the jig you can build stresses into the frame. Most people, myself included, tack in the jig then remove it...you have to be in control of the welding process so as not to warp the frame, but you dont have the capacity to build in stresses.
This only goes for tig/fillet brazed frames, IDK about lugs.
Ron cooper mainly used lugged. And I think they sort of hold the angles themselves. Just a bit of cold setting afterwards.
I've also seen a clip of seven cycles tigging up titanium frames that move quite a bit when building. They tack them up and change welding directions as it warps, constantly checking on a separate jig.
Hi bed_bug, sorry for he late response. The kit I bought was exactly what @PhilDAS shared, although you get a print of the jig design as well, should you chose that one.
I got the pieces because they seem to be fairly generic, many (most?) of the jigs use something similar.
I've paused for a bit because of life, and also because of the reasons @wildwest and @Biggles567 and @Rik_Van_Looy outline. I'm going to be building with lugs, and from what I am understanding (please correct me if I am wrong), the jig is not supposed to hold the frame in alignment through the brazing process.
This is a fundamental misunderstanding I had made - I have several jig designs on paper where I was looking to make sure the jig was fairly stiff and unlikely to deform.
I now think that the purpose of the jig is to hold the tubes in place accurately, but without any real strength, because that may lead to twisting/misalignment stresses.
For lugged frames, I am wondering whether I am better with a surface plate, a BB post and then to use the aluminium kit I got just to hold the tubes pretty loosely. That way I can check frame alignment with a dial gauge after each braze.
Did I see someone had bodged a 12mm dummy axle on here somewhere?
I need to mount what is left of a crashed Cotic BFE in my frame jig and don’t fancy paying for a 142x12 dummy axle as I’m unlikely to use it again any time soon. The dropouts and stays are all in one piece so I don’t need to do any brazing around it, it’d just be to hold things in alignment.
Ive seen people make them out of threaded rod, could do that depending on how your jig takes the DA
I did this and it worked okay.
I did have to re-do one dropout on the fork as it just had that slight cross thread feel. I hadn't used the biggest diameter tube that would fit in the axle recess shoulder (I don't know what to call that little lip that the hub sits on while you put the axle in). I did again with a bigger tube and all good. I reckon use the biggest tube you can fit in there for the most rigidity/best chance of square.
That looks pretty good. Not terribly worried about rigidity and stuff as it’s just to hold the rear triangle in the jig while I track stuff to it so I think a budge like that will be fine.
I was totally unaware of these ideas2cycles jig parts. I was about to spend a load of time lathing stuff up. That's a bargain for what it is. (I'm a rubbish lathe operator). Just ordering now.
interesting jig from PVD
Bit of a long read, basically he just whacked it on a surface plate. Its cool, probably works nicely. Though im not sure how you're meant to get any tacks on the "table" side of the frame when its in the jig. He mightve mentioned it in the words, i skimmed it only.
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