So I'll start this new arrangement of forums with a simple question that I might already know the answer for. I'm mid process of a couple of filleted frames (photos at https://www.flickr.com/photos/731955...57658194060433) and have the same occurrence as with previous filleted frames. After the main frame has been filleted and I replace it into my jig for continuing with the rear triangle I find that the frame doesn't fit exactly. There is a slight shrinking between the head tube ends and the seat tube. the result is that I need to slightly shift the jig's reach to have the ST and BB shell seat as well as the HT ends seat fully on their contact points. My process has a small extension of the HT past the ultimate top and bottom of the finished HT length that gets cut off before reaming and facing the HT.
So what's going on?
My take is that the HT goes through a bowing due to the heat being added far more on the back side of the HT (where the TT and DT fillets are). As I have some HT extending above and below the virtual ends of the HT there is more length for any heat distortion to be "seen" by the jig's original settings. As mentioned my solution is to move the HT support (I use a HJ universal jig) back a touch to have the HT ends seat on their cones then jiggle the tube supports a touch to recontact the TT and DT. I use the BB and ST as my base line, in a manor od speaking.
Is this a acceptable way to deal with the after fillet changes?
Many thanks, Andy.
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