Chop Source Budget(?) Frame Jig
 

I finished my first lugged frame recently and did the alignment with no jig. I used "C" clamps and boards, old hubs, etc. It was a bit awkward and I will probably build only a handful of frames in the future, but really need more precision. I am looking at Chop Source (https://www.chopsource.com/bicycle-frame-jigs.html) who makes a kit that you provide the square tubing for, and clamp on their fixtures. The basic kit is $370. It looks like it would make a very solid jig. I was wondering what the communities impressions are and if anyone has had experience with these.

Thanks in advance,


https://cimg7.ibsrv.net/gimg/bikefor...97101760e0.jpg

I'd not yet seen this jig kit. Looks to be pretty cool for the cost. I do question the need for the rotation about the long axis. I see the need for this feature more to make in jig brazing access easier. Since I just tack in the jig and complete the brazing of the joints out of the jig this mobility is less a need for me. And I certainly don't expect any jig to hold alignment. Keel jigs tend to have pretty good access anyways.

The headtube rod is a bit short and I like a removable rear axle, one that can keep with the frame when removing the frame from the jig. But the cost is hard to question.

I've said this before- I'd suggest a flat surface before an frame jig as the first "big" purchase. The surface plate will better help at building a straight frame and serve for many other fixturing needs (like forks or stems). Andy

Added- I should have looked at their website before posting here. I see more options then I thought before. What I didn't expect but now makes sense is the raw square tubing is not included. I figure the tubing will cost $100-300 depending.

I agree with Andy's assessment of the fixture. I think I would get annoyed that it can't rotate the other way. And it needs to be further off the ground. Although that latter point is up to the builder.

Since I tack in the fixture, I want to be able to take the frame out without too much effort. This thing seems like it's going to be a lot of work to get the frame out of.

I think for a hobbyist doing a couple of frames a year this could be a solution. If I didn't have my Bringheli I'd be thinking about something like this. I'm happy to see that the cones they sell would fit my jig and would allow me to build with big headtubes. I may have to get a set of those.

Good pun! Having had a day for this to be in the backround I now think had it been available way back when I would be very tempted to get it. But I suspect that after a while I would have grown frustrated by it's limitations and quirks. Andy

It sounds like with the few frames I expect to ever build, this might be an acceptable option. I probably could not justify a fixture like Henry James use to sell, or perhaps the Bringheli mentioned above. A plate style fixture would be great, and I would try to build one if I had a machining equipment and skills. I have some square tubing laying around and could save a bit there, and just buy the hardware. I appreciate everyones input.

G. Gearloose

My suggestion is to be very patient when removing a tacked frame and you should be fine.

I also suggest trying to verify that it defines a plane, that seems like it could be an issue

It also might be a problem that the top of the HT is free to float around. But overall it looks like a good design. And it can always be modified a bit if necessary.

I think there are two ways to make a jig. Properly square and high precision so it just plain works, or sketchy and baroque but with everything adjustable so that you can check things with a laser and tweak them. This looks like it might be a bit between the two designs.

I will plan on some extra tacking this frame before I take it out of the jig. I will report back in a couple months.

Very few fixtures hold the top tube nowadays. I keep thinking about adding something to mine to make sure it doesn't fall, but the miters hold it fairly well most of the time.

Although I have yet to build a filleted frame in my fixture. Last one I built was a long time ago and I didn't use a fixture at all, so it's doable.

I have a couple of big spring clips like this:

https://uk.farnell.com/duratool/d023...0mm/dp/2444536

And I just clip one on underneath the TT. I usually only need one at the HT end. Small magnets (which can be retrieved from old hard disks) hold things well but mess with the TIG arc. But might be good if you're tacking with brass and gas.

I go with two tacks at the DT to HT, two at TT to HT and two at TT to ST. The BB shell is already fully welded to the ST at this point for me and the CS are also already fully attached. I don't need the jig to do the SS. Just sort of balance them there and sometimes use a bit of masking tape.

Then I take it out very carefully and add a couple more tacks to each junction on the welding table before going any further.

I also use spring clamps and/or magnets to hold the top tube in place. Magnets work fine for TIG(except for causing some arc wander), but the heat from a torch will de-magnetize them.