What purpose of screw in Forstner Drill Bit shank

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Dominik Pierog

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Hello.
I cleaning my old forstner drills and one have this little screw in shank.
I unscrew it and there was only piece of grease inside. This is a blind threaded hole.
screw.JPG
 

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Might be for adding an extension shank but I suspect it is a remnant of the manufacturing process.
 
This screw have diameter like 2-3mm and proper extension looks that
3019.jpg



Rorschach":3u3c8nze said:
Might be for adding an extension shank but I suspect it is a remnant of the manufacturing process.

If its remnant of the manufacturing process why they bother to put screw inside?

Maybe drawbar?
 
If it was originally made with a Morse Taper then a drawbar makes sense. If it was always a parallel shank then I don't see a purpose in a draw bar. Does it look like it might have been modified? The screw in it might just be to keep the threads clean until needed.

Pete
 
It's for setting the length in a drilling machine, you adjust the set screw which then bottoms out on the chuck/collet , then you can remove and replace in machine without resetting depth stops etc. Hinge boring machine.
 

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