On 11/10/22 00:49, John Dammeyer wrote:
From: gene heskett [mailto:ghesk...@shentel.net]
On 11/9/22 19:59, John Dammeyer wrote:
I've been perusing through my Machinist Handbook (24th Edition) and googling
with no real success.
I think it was on this forum that the discussion came up on the holding power
of R8 collets and how they
were essentially only useful for light machining.
IDK John, but that was the driving force for me to mount all my taps
small enough my spindle could turn them, in a 7/8" brass hat with a grub
screw on all 4 faces of the tap shank, running in a 7/8" r8 collet with
a notch cut in the face to engage a 4mm cap screw in the outer face of
the brass hat, thereby keying the tap to the spindle. Since the go704's
reworked spindle driver limits it to about 2 hp and low gear is about 4x
too fast, I'm stuck pecking the tap about 1/4 turn per peck for holes
above 8mm. It does get the job done, but I hear Jons pwm-servo current
limiting at about 18 amps, the motor iron quietly chirps...
Hi Gene,
I like your solution. Very innovative. I went the route of ER20 collets that
are square in the bottom to keep the tap from turning. But they don't hold all
taps because not all taps are consistent in shaft diameter so I really like
your idea.
Thank you.
John
I often think outside the conventional box. I had a problem and that to
me, was the obvious solution. However, TBT it was someone else's idea at
the time.
It works well John, on the go704. I'd like to come up with a qcth holder
for them on the Sheldon as it has the torque to drive much bigger taps
but haven't quite figured out how to make such a critter, plus the
sheldon has no gibs to constrain the carriage from being lifted clear of
the ways when huge gobs of the torque reaction comes into play. I'd need
to hang another 30 lbs on the back end of the crossfeed to contain that
for say a 3" tap. That in any event even though I have the tap that big,
is a g76 job. But at a 3" size, I'd be longer shaping the boring tool
that doing it, my CBN wheels are quite fine, 2500 grit but fine is also
slow, fragile and expensive.
Don't waste your time and money on diamond for shaping HSS tools, the
HSS steel will just burn up the diamond.
Something it had sorta had in the carriage locking clamps when it
followed me home in a u-haul van but poor operation history wore them
plumb out and since the wear wasn't correctable with what I had on hand
at the time, I left them out, so the carriage, all 25-30 some lbs of it,
is just sitting on the ways. For normal use, it doesn't care, but the
torque on the toolpost from tapping a bigger hole is considerable. That
and G76 has some handy surprises in some of its options. Straight
cylindrical tapping isn't all it can do. Boring tapping at under 7/16
gets very picky, internal tools are too big. Piece of cake for square
threads on a P17 rifle barrel though, once the tool was shaped.
Take care and stay well, John.
Cheers, Gene Heskett.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/>
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