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935 spindle nose piece removal

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petertha

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#1
On the PM website is a nice PDF guide for 935 mill with pictorial instructions to adjust the depth of the collet locating screw. That part of the procedure is straightforward. But before that, the disassembly sequence begins by removing a set screw on the quill housing & then unscrewing the nose piece with 2 pin spanner wrench on the underside.

But my question is - what exactly is this set screw engaging? It almost appears to be lining up with the threads on the nose piece itself which would seem like a dubious way to secure it (potentially marring threads just by tightening)? Or am I misinterpreting the dimensions & it lands at some safe part of the nose piece?
 

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Stonebriar

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#2
The set screw sets the depth of the pin for the collet holder.
 

petertha

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#3
Nope, maybe this will clarify. Red arrow = locking set screw I'm asking about. Looks like it intersects threads on nose piece? Green arrow = where the pair of set screws go you are referring to. Inner one is dog point that engages tool holder slot. Outer one locks that in position jam nut style.
 

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davidpbest

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#4
I took off the nose ring that holds the bottom quill bearing in place on my PM935 tonight and inspected with a scope. As best I can tell, those set screws (red arrow) bind against the threads on the nose ring keeping it from unwinding during normal use. I added a brass ball to compress against the nose ring threads so the set screws would not chowder up those threads.
 

petertha

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#5
Thanks David. So you would concur that the 'anti-slip-rotation' set screw is conventional steel (as opposed to some soft alloy) and it would land about here, directly on the threads?
 

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davidpbest

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#6
Yes. I'll also add that the tighter you run that set screw against the nose ring, the more the quill return spring system will hang up and not return. I have no idea why this is the case, but it is. I have my set screw (with brass ball under it) tightened to 1nm. At 3nm the quill will not return fully.
 

ddickey

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#7
Interesting. I noticed after I got my quill back from PM the spindle doesn't return properly.
 

petertha

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#8
Here is actual nose cap removal for completeness. I figured it might be worth making an inexpensive pin spanner with wood scrap on hand thinking if I lucked out it didn’t cost me anything. If it broke, well, then I knew what I was up against. It has 2 lamination's of 3/8” ply on the head. Pins are 3/16” drill rod pressed in. I left the head as a round donut for strength in case I measured wrong or if it took a few tries & ripped the pins out I could drill more holes. Turns out it fits pretty well as shown. The proper tool would be something like 1/8" steel plate.
 

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