[Amps] Want to use a knob with a 3/8" opening on a 1/4" shaft.

[HAROLD B MANDEL]

Usually, the lathe's tailstock has a collet and matching chuck. That's
where the drill bit goes.

The work piece gets clamped in the jaws of the headstock and it turns
the work while the drill remains stationary.

Having the tailstock in a perfect line with the center of the headstock
is the first achievement in setting up your lathe to drill true.

Cenrtering the work in the headstock chuck jaws is easy with an accurate
self-centering 3-jaw chuck, but odd shaped pieces need to be clamped
in 4-jaw independent chucks and this is where the rubber meets the 
road. You will need a magnetic dial indicator to find the drilling center
to make sure your work truly turns around its drilling center and  not
in an oval or circle.

Tiny pieces need to go as close to the jaw faces to achieve good
centering
accuracy, and stepping more sizes in drills means better accuracy.

Hal
W4HBM

Oh, yeah, don't leave the chuck key in the headstock!




On Fri, 23 Dec 2005 08:00:27 -0800 Bill Turner <dezrat1242 at ispwest.com>
writes:
> 
> ORIGINAL MESSAGE:
> 
> At 03:03 AM 12/23/2005, W0UN -- John Brosnahan wrote:
> <snip>
> >finding some 3/8 brass rod and drilling a 1/4 inch hole in it -- 
> plus
> >clearance holes
> >for the set screws.  Easier on a lathe, but with care a drill 
> press
> >will do it.
> <snip>
> 
> 
> 
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> This brings up a question for you machinists out there.
> 
> I once watched a program on the Discovery Channel which showed how 
> rifle barrels are made. It said in order to drill a perfectly 
> centered hole in a rod, you clamp the drill bit stationary and 
> rotate 
> the rod as if it were the drill bit. Done this way, the rod will 
> automatically center itself around the drill bit.
> 
> Is this true or just an old (machinist's) wives's tale?
> 
> 73, Bill W6WRT
> 
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> 
> 


Harold Mandel
Superintendent of Construction
Baran Telecom Inc.
606 - 205 - 0172
hmandel at barantelecom.com