Wednesday, April 30, 2014

Step #3: Establishing the first surfaces on the Steady Rest frame halves

Well, Christmas in September arrived! The upper and lower parts for the frame were the first to arrive from Shapeways. As you can see, the finish resembles casting even though there is no casting involved. A big difference is that there is no differential cooling shrinkage and warping happening like you get in traditional casting. This means I didn't have to design an overly thick part to remain material safe and that in turn has huge benefits like:
  1. All critical surfaces are very close to final dimensions and can be brought to final dimension with a file and lapping, or you can machine them as well, your choice. I used both.
  2. I am able to include very accurately located guide holes for drilling out screw and pivot locations without having to blue and scribe or spend hours doing centering and numerical set up on a mill.
The raw bronze-infused stainless steel frame parts

Raw lower frame part showing guide holes on the back

Raw upper frame part
The very first surface to fit are the sides of the two little alignment nibs on the top surface of the lower frame half. This can be done with an edge file (only the edge has teeth), or by milling a very small amount of material off the mating surfaces of the top flat and the sides of the alignment nibs. Be sure to check frequently and take pains to make these surfaces generally perpendicular to the front face of the steady rest (the face without the clamp tightening screws). It's not hyper critical as the true reference surface (the front) will be lapped with both parts held together insuring alignement.
frame mating surface fitting

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