Thread: Frame Table
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Old 04-18-10, 01:48 PM
  #8  
Doug Fattic 
framebuilder
 
Join Date: Dec 2009
Location: Niles, Michigan
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I'll mention several different ideas that fall under the category of checking alignment. First off if I could have only one decent main tool to make frames it would be a full sized metal alignment table. I would get this before some kind of fixture. It can even become a fixture by placing blocks on it made by Alex Meade. Instead of doing a drawing on paper, it can be done right on the table. A 2' X 3' works if the post is in the southeast corner. However I much prefer something closer to 3' X 4' because that allows space for the rear triangle. I use it for all sorts of purposes like getting bridging straight, brazing lever bosses exactly on the side, making sure seat stay cap flutes are not twisted, binder bolts are square in all dimensions to the seat tube, etc. If I see those parts off, I assume the builder is careless with the rest of the frame as well.

However I understand that some don't have the money or space for a full sized beast for hobby building so something smaller is appropriate. Besides the channel and mill bed already mentioned, one idea used often in England in the classic days (I visited lots of builders in the UK in the 70's before, during and after my apprenticeship) is a long piece of heavy angle iron. It isn't ground flat. At one end is a way to fasten down the bb shell similar to what any alignment system has. On the other end is an adjustable screw with the point rounded down. The concept is that the frame can be rotated around the bb and the bolt pointer can be pre-adjusted so that it just touches the seat tube and down tube if they are in alignment. Bend them straight as necessary. The bolt has to be set by an already straight frame. It is possible to sight along the lines of the seat tube and compare that to the head tube line to see if the head tube is twisted.

One big concern about a full sized table is the weight. Some don't know how long they will be at one place or work in a tough-to-get-at-space. Moving around a heavy table isn't an option. A steel or granite table weighs at least 700lbs. I experimented with getting a cast aluminum table that is 32" X 48" from the Wolverine Bronze Co. It is cast with webbing underneath and they grind the top flat (as well as the pads on the bottom) and bore a hole for the post. On the pads in each corner on the underside are tapped holes to accept legs that just bolt on (that have some length adjustment at the bottom). I paid just over $1000 for the table and another $400 for the legs. My post cost me (which I also sell) another $300. Aluminum is softer than cast iron and requires some care but mine has held up will under normal student use. However at 170lbs, it can be moved by a couple of people or just a carrying cart of some kind. (I also have other cast iron tables.)

A tool everyone should have is a straight edge with an fine thread adjustable screw. I use mine for making sure the rear dropouts are equal distant from the frame centerline. I place it against the head tube and seat tube and adjust the screw so it just touches the inside face of the DO. Then I do the same on the other side to see if the other dropout face is the same distance away from the centerline as well. It could also be used as your front triangle alignment tool by placing it against the face of the bb shell and setting the screw on the DT and ST near the BB and seeing if the tubes remain the same distance from the screw at their other ends. Mine is made out of some kind of aluminum channel and the smallest profile (1" X 1/2"?) from 80/20 should work.

Last edited by Doug Fattic; 04-18-10 at 01:53 PM.
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