On 11/10/22 02:48, John Dammeyer wrote:
From: gene heskett [mailto:ghesk...@shentel.net]
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.
Hi Gene,
I'm mostly using the TTS holders and some of my more expensive tooling is still
R8 so I'm not converting over completely.
I'm thinking that your approach with 4 set screws to hold the tap might work
well with TTS holders. A custom holder with a hole for the tap shank and 4 set
screws keeps the tap from turning.
Now we're back to the original question I posed. If this TTS holder with a 3/4" shank
into the custom R8 holder with say 20 ft-lbs torque on the drawbar won't turn then it's fine
for tapping up to the tap size. Since the TTS come with at least 1/2" holes it makes for
a reasonably large tap. Up to 7/8" shank which is once again listed as the limit for R8.
And it makes the tap holders a lot less expensive than using ER20 collets which are
only good up to a certain size. Purchase a TTS for 1/4" shaft, mount in a
lathe collet and bore to the size of the target tap. Drill the 4 holes and tap
them. Now it's a TTS Tap holder.
And I'm having a hard time visualizing that, can you scribble up
something and put it on your web site?
If one wanted to modify the spindle it would be possible to put a pin hole just
outside the diameter of the TTS tool. Then modify the TTS tap holder to have a
flange like the pin on your holder that goes into the collet.
In fact, modify all the TTS holders to have the flange and it's possible to
prevent all TTS tools from spinning in the R8 holders. Not only that but the
M66 command can put the pin in the same place so installing TTS indexed tools
becomes trivial.
The word flange is confusing me unless its used to establish a constant
length to put in the tool table as TLO. And that would still be subject
to error from inconsistent tightening of the drawbar.
My next mechanical thing on the go704 will be stripping a 1/4 ratcheting
screwdriver motor out, and rigging it on old 3d printer screws to
reengage/disengage from the drawbar, It has the torque I think, to break
the drawbar or strip its threads in left to hammer the bar for more than
1 or 2 seconds. Then rig M6 to run it for tool changing, possibly from
mid gcode file. I use the drywall screw driver to do that now but need
more hands, one to run the driver, one to hold the spindle still, and
one to catch the tool when it comes free. By my count that's three
hands. :o) Needs more thought...
John
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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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