reddog3

Uhh- yeah but Andy. You, Eric, and I are all old enough to have learned that lesson- either the hard way or the easy way.

Live Wire 

...and I can't believe two people have posted saying they are willing to buy a frame jig built by someone that's never built a frame!
Is this the thinking that gets all those Kickstarter projects funded?

To the OP, you've got a great start, but once you begin building on your jig, I'll bet you find more than a few things you'd like to change on it.

unterhausen

One thing I wish I had done better when I made my jig was machine in some marks for some critical dimensions. For example, I put a slot that allows you to measure from the center of the bb post in both the vertical and horizontal directions. However, I should have repeated these at intervals, particularly the horizontal position of the center of the bb shell. It's one thing to hold a batch of tubes together, but what you want is to hold a batch of tubes in particular places. That means that measurements are key. It's very easy to make mistakes in measuring

It's also nice to be able to proof the fixture by putting it on a table. The king of this method is the Sputnik, the downside is that there is a huge flat plate in your way when actually using the fixture. One thing I noticed with mine is that I have to be careful to make sure everything is tight and the moving parts are flat relative to each other.

I think it's a pretty sensible design, unlike the kickstarter designs. And only twice as much The kickstarter design I'm familiar with is good for people that want to say they build frames but never will.

Andrew R Stewart 

I'll plug Doug Fattic's sizing fixture (or whatever he calls it). It does not have any inherent flatness. It sits on a flat surface to achieve the planerity (if that's a word).

To further focus on this idea. I make little brazing holding fixtures as i need them. One of the design goals i strive for is NOT having to make them with precise machining or surfaces.

I find the efforts spent on one's jig being precise is lost when you braze with poor or uneven heat control. All a "straight" jig will do is reduce the amount of cold setting after tacking and before fully brazing.

To the OP's jig- one element I picked up on is the rear axle that looks to have no ability to fit drop outs of different thicknesses. Andy.

unterhausen

Andy,
Doug's whatchamacallit does sit really flat on a flat surface. He doesn't try to make it hold the rear triangle in place. I think if a fixture rigidly holds a frame out of alignment it's probably even worse than poor heat control. Most people just tack in their fixture nowadays.

I made sure my fixture could use Anvil dummy axles. I have considered trying to get Paragon to sell me the ones that they make, but they probably wouldn't. They are very accurate, particularly if you use their dropouts, which are also more accurate than most.

Mark Kelly 

Planarity. With two As.