A little more clarification may be needed here. First which Shopsmith Jig Saw are we talking about? The first was made for the Shopsmith Model 10E and 10ER. It is different from the one made beginning in 1954. Below is a Model A-34 Jig Saw made for the Model 10's.
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The one pictured above is the later version and differs from the first version in the Lower Frame casting.
The Jig Saw pictured below is the Model 610 and later changed the model's name to 505644.
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In both cases I believe you are referring to the Upper Chuck. That is where the blade is clamped into and is part of the Spring Cylinder Assembly. Below is the Upper Chuck /Spring Cylinder Assembly from the Model A-34 Jig Saw on the left. On the right is the Lower Chuck. Sorry I don't have a picture of the Upper Chuck/Spring Cylinder Assembly for the Model 610/505633 Jig Saw.
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Parts for either of the Shopsmith Jig Saw, like the Jig Saws themselves, have been discontinued. Shopsmith may have very few parts left for the Model 610/505644. You may have to contact Customer Service. The used market is the only source for most parts.
Parts are not interchangeable between the Model A-34 Jig Saw made for the Model 10's and the Model 610/505644 made primarily for the Mark series tools.
If you can post pictures of what you have and a close up of the part area you are referring to that would be helpful.
