Hey Sputnik Jig Owners

[Clockwork]

I just got a used Sputnik and am really excited but have a few questions. It doesn't look like one can fine-tune the BB shell center (side to side). It came with a spacer for 68 and 73mm shells which will be fine for lugless shells, but centering a lugged shell seems like it won't work. Am I missing something?

Thanks, Joel

[ToddFarr]

Joel,
Sorry to thread jack, I'm just curious because I'm still learning about what's important in a jig. Are you saying you need the adjustment because the lugged shell can be slightly oversized to begin with? So when you build a lugged frame are you measuring the width and then dividing that by 2 to find your center?
Thanks
-Todd.

[Clockwork]

Joel,
Sorry to thread jack, I'm just curious because I'm still learning about what's important in a jig. Are you saying you need the adjustment because the lugged shell can be slightly oversized to begin with? So when you build a lugged frame are you measuring the width and then dividing that by 2 to find your center?
Thanks
-Todd.

The problem I see is that all BB shells are different widths, so if you're indexing off the right side, the center will be in a different place every time. This isn't such a big deal if you BB shell center is defined, but lugged BB shells have a defined center.

I've already got an idea for a simple part I can make and I have enough metal to do it so I'll start tonight and take pics.

-Joel

[Eric Estlund]

In practice it hasn't been an issue for me.

[Andrew R Stewart]

Not an answer to your question but some jigs allow the BB shell to be located along a shaft, not determined by the shell's edge but with cones held with set screws or split collars.

In looking at the jig in photos it seems that it would be easy to replace the BB post with a shaft and cones. Or you could face the business side of the shell to the correct dimension before building. Andy.

[prolix21]

Or you could face the business side of the shell to the correct dimension before building.

Any concerns about possible heat distortion during the building process if you face it first?

[dbohemian]

The problem I see is that all BB shells are different widths, so if you're indexing off the right side, the center will be in a different place every time. This isn't such a big deal if you BB shell center is defined, but lugged BB shells have a defined center.

I've already got an idea for a simple part I can make and I have enough metal to do it so I'll start tonight and take pics.

-Joel

I am with Eric on this. Non issue. If you BB shell is very wide than you can chuck it up in your lathe with and internally expanding collet and face down the edge facing the fixture. I blue print all my BB's anyways and leave just a bit for final facing.

Seems complicated to try and modify the fixture as opposed to just making your shells correct and honestly has a 10th of a mil ever made a big difference anyhow?

[Clockwork]

I'm going to give this a shot. The adjuster has a nice slip-fit over the post so the set-screw shouldn't through things off too much.

[Eric Estlund]

I like that the inside face of my fixture and the inside face of my jig are a) the same side of the shell, and b) fixed locations.

Still, neat mod if it works for you.

[steve garro]

I like that the inside face of my fixture and the inside face of my jig are a) the same side of the shell, and b) fixed locations.

Still, neat mod if it works for you.

I like the shifter thumb bolt!
- Garro.

[JFW]

I had the same issue on my Journeyman with a shell or two, and made a solution similar to yours. On the old Master/Supermaster (and perhaps also on the newer incarnations of the Journeyman) there's an adjustable collar (graduated?) quite similar to the one on the Hydra.

T

[e-RICHIE]

...there's an adjustable collar (graduated?) quite similar to the one on the Hydra.

I prefer the internals of the Hydra rather than any exterior lock-downs on the bb faces atmo. The frame piece floats on the collar (your word) when the threads skim the part's O.D. That way, the shell is center by the tubes holding the ports in plane. I pin that joint and then transfer the main triangle to my alignment table where I tack the joint after I ensure that all is where I want it to be. No sense tacking in the fixture and then having to adjust (the tacks) on a table. When my main triangle is in the fixture, the shell faces are never part of the equation.

[e-RICHIE]

I prefer the internals of the Hydra rather than any exterior lock-downs on the bb faces atmo. The frame piece floats on the collar (your word) when the threads skim the part's O.D. That way, the shell is center by the tubes holding the ports in plane. I pin that joint and then transfer the main triangle to my alignment table where I tack the joint after I ensure that all is where I want it to be. No sense tacking in the fixture and then having to adjust (the tacks) on a table. When my main triangle is in the fixture, the shell faces are never part of the equation.

I just loaded this to Flickr. It's the current frame on its way to being shown who's boss. The internal thingy floats on a shaft that is part of the fixture's back plate, and it's an interference fit. I keep it well lubed and remove/replace it often during the set-ups. I've never used the plates that come with the unit and are made to clamp the faces. That method never seemed logical to me, especially when the process includes an alignment table check as part of the sequence.

[EricKeller]

my worldview was shattered a couple years ago when I found out that the minor diameter of BB shells varies quite a bit. I found this out when the beautifully machined bb post I made wouldn't fit into the bb shell I wanted to use even though it fit into the one I had sitting by my lathe. I haven't really been able to pull myself together enough to figure out how this should inform frame jig design; I'm a failure.