You asked,
I would not try unless there is a specific reason it needs to come off for the restoration. I haven't needed to do that on any of the 10 Model A-34 Jig Saws I have owned/restored. You should be able to clean it out well enough while those two parts are still together. Unlike the Model 610/505644 Jig Saw there are not any additional parts in there that could need attention. It is simply that casting attached to the cylinder.One question: Should I try and separate the Upper Guide Bearing from the Spring Cylinder for cleaning?
Glad to see you were able to get the Upper Chuck Assembly out of the Spring Cylinder Assembly. It all looks in really good condition even the Leather Seal. From the picture it looks like it is ready to go back together. The only thing I don't see is the lock nut.
The first picture below is the early version of the Model A-34 Jig Saw.
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In the picture above is a bolt on the top of the Upper Arm which is the Belt Cover Bolt and a handy place to store it while using the Jig Saw unless you have a lamp mounted there which is the reason for that threaded hole.
The picture below is the later version of the Model A-34 Jig Saw
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As you can see from looking at the Lower Frame Assembly, it is easy to tell the difference between the two versions.
The link to Marc's Model A-34 Jig Saw has some good information in it. As I told Marc in that thread,
If your Jig Saw is the early version like Marc's, you may want to consider sealing the gear box like Marc did. Only three of the ten Model A-34 Jig Saws I have owned/restored are the early version and all three had saw dust/gunk in the gear box.Your Jig Saw is the early version and something to watch in it is accumulation of saw dust inside the lower frame. In this version of the Jig Saw the lower frame is hollow throughout. Any saw dust entering the frame holes can make its way into the gear box. I currently have one of the early ones I am restoring and found saw dust in the gear box. 2 others I restored of this early version had gunk in there too. The later version of the Jig Saw has a separation which encloses the gear box.