Frame Alignment and Fixturing Table - AlexAndChristine's Photos- powered by SmugMug

Using a Bridgeport 9x36 milling table, bits of 80/20, and homemade parts to construct a bicycle frame tacking fixture and alignment jig.

The milling table was Brandon Ives idea and it seems like it'll be a good solution. I bought this one used for $40 (the freight cost 3x that). It's flat and the t-slots are very helpful for fixturing items in place.

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AlexAndChristine > The table and items that I've built so far sitting on top of it. None of the items are complete except for the bottom bracket post on the far right.

The stand for the table was the stock stand for my tablesaw. I reconfigured it to match the table dimensions. The casters suck (and will be replaced), but otherwise the stand works well.

AlexAndChristine > Close up of some of the items. From left to right:
* Start of an alignment block. The dummy axle is 135mm.
* A piece of 80/20 (1020 extrusion) with a seatpost centering cone mounted on it. You'll see how this fits together once I get the rest of my 80/20 bits.
* Another cone, this will end up being used for the headtube.
* Dummy headsets. A 7/8" steel bar fits inside to be used for alignment purposes.
* Bottom bracket post for frame alignment. The same two handles can be used in the post or nut.

AlexAndChristine > Bottom bracket alignment post in action.

There is more to this than you'd think. The bottom is 2" in diameter and about 3.5" tall. It has 1/2"-13tpi threaded holes coaxially on both ends and 1/2"-13tpi threaded holes through the center of the other axis for handles. The bottom hole connects with a short piece of all-thread to a T-Nut in the table.

There is a bushing that you can't see that locates the bottom of the BB.

There is a brass bushing and washer that locates the top.

The top nut is made like the bottom, it is just about an inch tall.

AlexAndChristine > Dummy headsets for head tube alignment. They are setup to fit in 29.8mm head tubes (for 1" steerers) when flipped one way, or 33.8mm head tubes (for 1 1/8" steerers) when flipped the other. Alistair got the design from Martin Tweedy.

They are easy to make, drilling the 7/8" hole on the lathe takes the most time.

AlexAndChristine > This is an alignment cone which can slide on 80/20. I like the idea of the seat tube cone that is in this 80/20 frame jig[1], but I didn't like that it couldn't be adjusted for height. My cone will mount to the block, which then mounts to a piece of vertical 80/20 extrusion.

I made this mounting block, but I decided to just buy 80/20 "manifold" blocks for the rest of them. They are $11 each which seems like a lot for $1.50 worth of aluminum, but it saves me about 45 minutes of work per block and I need 4 of them total (two for the head tube, one for the seat tube, one for the bottom bracket).

[1] http://www.instructables.com/id/SPHE0MXF1JZQZZZ/

AlexAndChristine > Component parts for my frame alignment block. I'm copying the design from this one that Jamie Swan built for John Clay:
http://www.flickr.com/photos/21624415@N04/2511994501/in/set-72157603540228783/

The dummy axle has a groove in the exact center for alignment purposes. The 90 degree V isn't perfectly centered, I'll have to do a little cleanup work to get everything just right. It is important that the dummy axle and the V have the same centerline.

AlexAndChristine > Frame Alignment and Fixturing Table photo

AlexAndChristine > Milling the alignment block. I used a 45/45/90 triangle and a square to get the block at exactly 45 degrees from the milling table. It is supported on parallel bars and clamped into place (my vise won't open wide enough for this large of a block). I used a hack saw to rough cut the V (about 1/4" away from the reference lines) and then milled it clean. It took a fair amount of time because the block is 1.5" thick and my end mills only have 1" of cutting height.

The table and items that I've built so far sitting on top of it. None of the items are complete except for the bottom bracket post on the far right.

The stand for the table was the stock stand for my tablesaw. I reconfigured it to match the table dimensions. The casters suck (and will be replaced), but otherwise the stand works well.