Quote Originally Posted by Andrew Drummond View Post
Drew,
This may have been addressed elsewhere, or even previously in this thread, but I've missed it if it has. I'm curious about your inspection technique - it seems most builders mount their frame to the table by the BB shell; you use bench centers and the head tube. Can you elaborate? If I may guess, it looks like you put the head tube between centers, insert a dummy axle with a center mark to check the rear end (with a height gauge?) and use an indicator to check the parallelism of the seat tube and the head tube. There's probably more to it, though! I've seen some photos of your inspection table with what looked like a collet chuck and a 5C expanding arbor - do you use that at any point in the inspection process (seems like a good way to get the BB square to the table, without relying on the accuracy of the facing), or is it all based on the head tube? How did you come up with your approach?

And thanks for documenting so much of your work, here and in your Flickr stream - it's nice to see photos of what different builders are doing, but it's even better to get a thorough explanation of why they're doing it the way they are.

Andrew
Andrew,
My process of inspection has evolved over the years and I have been using the system I use now for some time. I use the bench center to mount the head tube parallel to the surface. I trust this datum more than the BB shell since it has less distortion and the distortion that is there is not effecting the measurement as much as 4 tubes connected to a BB shell pulling it in all different directions. I have a post the stops the seat tube at the same centerline as the headtube and has interchangeable blocks depending on the size of the seat tube. This allows a permanent height gauge for the rear axle centerline. I use the dial indicator to check for seat tube twist and also check the face of the BB shell at 4 points (this I am actually making sure the high point is where I would expect it based on the distortion). I use a height gauge to check the inside flat of the drop out face and last I put a wheel check tool in the frame that rotates on bearings. Rotate and check at 3 or 4 spots to make sure it is flat. You can use the wheel check tool to make minor adjustments kind of like a Der. hanger tool.

I had an expanding collet that was used for BB mounting but I needed that chuck for my lathe after selling my South Bend Heavy 10 and took it off the table. I since made a standard BB post that I use to make minor adjustments to the rear end if needed.

I probably missed something but I think you get the idea. I feel my process is very accurate and trust worthy. The biggest thing I like is how repeatable it is. Just about every bike I pull out of the fixture is within .005" of the last bike I pulled. That tells me all is well. If it is way out I figure something is up and first re clamp everything. If still off then I back track. This might happen once a year and usually I scrap the bike.

Thanks for the kind words.

Cheers,
Drew