Trepanning and Parting Off - Loose Gibs Chatter Chips
 

I installed the new gibs in the Clausing 5914 yesterday and today. The
difference is amazing. Worn and misshapen gibs appear to have been a
large part of the problem, and is why tightening the gibs didn't have
quite the expected effect.

Now I can trepan in forward rotation, without the drama, although there
is some squealing. In reverse rotation, turning very slowly (~90 rpm),
there is no problem making a 3/16" wide face groove in 6061 aluminum,
and there is no squealing. I went to 3/8" deep, and could have gone
deeper if the toolbit were better shaped. The chips are about 0.010"
thick by 3/16" wide. This, using a shop-made 1018 steel 0.75" diameter
coaxial boring bar held in a BXA-4D boring bar holder. Back gear is
needed, in both directions.

It's hard to really tell, but my theory is that the too-long 1/4-20 flat
head socket cap screws that protruded and rode on the top of the
cross-slide dovetail prevented the dovetail from fully seating, and
caused the gib to wear oddly, rendering the whole affair a bit springy.
The gib was too worn for this to be corrected without making it too thin
to work.

The compound slide dovetail was also not resting quite right. I did
find a flattened chip firmly stuck to the bottom dovetail, plus some
dings. I carefully scraped and file-dressed all mating surfaces to
eliminate everything sticking up, and then installed the new gib.
Again, the old one was quite worn, and also had been damaged by someone
adjusting the gibs with more muscle than brain, the corners being broken
off. One of the gib screws came to me pre-bent, presumably having been
damaged in this muscle-bound process. Replaced the bent screw.

Cleaned up and with the new gib, the compound now feels much better than
before, and doesn't have nearly as much looseness in the center of the
travel range as before.

It appears that Clausing makes the gibs from far softer cast iron than
that used in the dovetails, as almost all the wear was in the gibs.


For the record, I torqued the bolts holding the headstock to the bed
ways, and found them to be very tight, so motion between headstock and
bed seems unlikely.


More generally, I'm catching up on a whole lot of deferred maintenance.
I'm just now getting to the point that I can make things on the lathe,
versus having to work on the lathe itself.


For the record, I did some measuring of the new gibs. The taper is
exactly 5/32" per foot. The height is different in the two gibs, but
the taper is the same. The height is not critical, so long as it fills
most of the available space. It does not look hard to make new gibs if
one has a surface grinder.

The new gibs are 10-5/8" long, and one cuts them to length. This is
because Clausing cannot know how much the dovetail has worn, and so must
cover a range of possibilities.

Clean dovetail, assemble, insert gib, tap in deeper until it just stops
solidly, mark with scriber, cut the thick end off 1/16" in from the
scribe line, and the thin end 3/8" in from the scribe line. Dress with
a file. Clean, oil, install, and adjust.


Joe Gwinn

Trepanning and Parting Off - Loose Gibs Chatter Chips
 

Joseph Gwinn wrote:

The new gibs are 10-5/8" long, and one cuts them to length. This is
because Clausing cannot know how much the dovetail has worn, and so must
cover a range of possibilities.

How much did Clausing charge you for the gib?

WEs

Trepanning and Parting Off - Loose Gibs Chatter Chips
 

On Sun, 04 May 2008 18:46:54 -0400, Joseph Gwinn
wrote:
snip
Now I can trepan in forward rotation, without the drama, although there
is some squealing
snip
========
Thanks for closing the loop. I often wonder how things turn out.
Sounds like a good job.


Unka' George [George McDuffee]
-------------------------------------------
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).

Trepanning and Parting Off - Loose Gibs Chatter Chips
 

In article ,
Wes wrote:

Joseph Gwinn wrote:

The new gibs are 10-5/8" long, and one cuts them to length. This is
because Clausing cannot know how much the dovetail has worn, and so must
cover a range of possibilities.

How much did Clausing charge you for the gib?

$174.23 each. Clausing has it well-calibrated. It's a lot for that
little piece of cast iron, but it would take me at least that much
trouble to make one, absent the surface grinder.

Joe Gwinn

Trepanning and Parting Off - Loose Gibs Chatter Chips
 

Joseph Gwinn wrote:

How much did Clausing charge you for the gib?

$174.23 each. Clausing has it well-calibrated. It's a lot for that
little piece of cast iron, but it would take me at least that much
trouble to make one, absent the surface grinder.

Damn! The delrin af bushings I bought from them seem like such a deal in
comparison. Hopefully, next weekend I'll get to moglice the pulley shafts if
I don't have to work at work, or work on my moms house.

http://wess.freeshell.org/clausing/A...moglice_on.jpg

I guess I need to rotate it for up to 4 hours. I have two drive sheaves
coupled together using the mandrils I'll be using to turn them down between
a collet and a tailstock center.

I'm glad you are making progress. Having a real working American chunk of
iron at the end, will be sweet for both of us.

Wes

Trepanning and Parting Off - Loose Gibs Chatter Chips
 

Wes wrote:

I guess I need to rotate it for up to 4 hours.

If you use the non-fluid Moglice, it won't run away.
But is that a bearing surface you want to form with Moglice?


Nick
--
The lowcost-DRO:
http://www.yadro.de

Trepanning and Parting Off - Loose Gibs Chatter Chips
 

Joseph Gwinn wrote:

I installed the new gibs in the Clausing 5914 yesterday and today. Â*The
difference is amazing.

They are tapered gibs, right? Then you have to scrape them in. I doubt that
they fit perfectly from the factory either because of a slight difference
in slope or because of wear on the dovetail itself.


Nick
--
The lowcost-DRO:
http://www.yadro.de

Trepanning and Parting Off - Loose Gibs Chatter Chips
 

Nick Mueller wrote:

If you use the non-fluid Moglice, it won't run away.
But is that a bearing surface you want to form with Moglice?

I believe I have Moglice Semi but I was told it will droop if I don't spin
it. The roughed up surfaces will be coated turned to slide in the mating
sheaves bores.

Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller

Trepanning and Parting Off - Loose Gibs Chatter Chips
 

In article ,
Nick Mueller wrote:

Joseph Gwinn wrote:

I installed the new gibs in the Clausing 5914 yesterday and today. Â*The
difference is amazing.

They are tapered gibs, right? Then you have to scrape them in. I doubt that
they fit perfectly from the factory either because of a slight difference
in slope or because of wear on the dovetail itself.

I though of this, but haven't done it. The instructions that came with
the gibs makes no mention of scraping, although it cannot hurt.

The improvement even without scraping is immense. I don't think the
gibs the lathe came with were scraped, but have no way to know if these
are the original gibs.

I'll use the lathe a while, and then take the gibs out and inspect them
under a magnifier for uneven wear. That would be a good time for
testing with hi-spot blue.

Joe Gwinn

Trepanning and Parting Off - Loose Gibs Chatter Chips
 

Wes wrote:

I believe I have Moglice Semi but I was told it will droop if I don't spin
it.

The semi will certainly droop. It is still quite soft even after 8 hours.


The roughed up surfaces will be coated turned to slide in the mating
sheaves bores.

Be sure to first rub in a thin layer and then the rest on top of that.
Calculate at least 50% loss, you won't be able to distribute it evenly and
controlled enough.


Nick
--
The lowcost-DRO:
http://www.yadro.de

Trepanning and Parting Off - Loose Gibs Chatter Chips
 

Joseph Gwinn wrote:

That would be a good time for testing with hi-spot blue.

But you can do that at installing. Blue the mating surface and hammer in the
gib. Pull it out and inspect for spots. You can only cut the gib to length
when it was scraped in, not before. :-)

I recently scraped two "factory worn"*) gibs. Hammered them straight, stress
relieved them, milled in a pocket and cast that out with Moglice. And then
scraped to fit, including stickout of the gib.

*)
The Chinese-Idiot-Clan bent them in the factory to hide the sloppiness.


Nick
--
The lowcost-DRO:
http://www.yadro.de

Trepanning and Parting Off - Loose Gibs Chatter Chips
 

In article ,
Nick Mueller wrote:

Joseph Gwinn wrote:

That would be a good time for testing with hi-spot blue.

But you can do that at installing. Blue the mating surface and hammer in the
gib. Pull it out and inspect for spots. You can only cut the gib to length
when it was scraped in, not before. :-)

Too late, then. Unless the adjustment is slight.

The instructions that came with the gibs were a little vague, saying
only the the gib should be "snug", so I made the first one too loose,
but not terribly so. The second one I did hammer into place.


I recently scraped two "factory worn"*) gibs. Hammered them straight, stress
relieved them, milled in a pocket and cast that out with Moglice. And then
scraped to fit, including stickout of the gib.

*)
The Chinese-Idiot-Clan bent them in the factory to hide the sloppiness.

Cast iron doesn't bend very well. Is the gib cast iron? It should be,
for low wear.

Another excuse to make one's own gibs.

Joe Gwinn

Trepanning and Parting Off - Loose Gibs Chatter Chips
 

Joseph Gwinn wrote:

Cast iron doesn't bend very well. Â*Is the gib cast iron? Â*It should be,
for low wear.

It bends good enough to make bad tapered gibs. :-)


Nick
--
The lowcost-DRO:
http://www.yadro.de

Trepanning and Parting Off - Loose Gibs Chatter Chips
 

Nick Mueller wrote:

he semi will certainly droop. It is still quite soft even after 8 hours.


I was planning on spinning by hand until some one told me the cure time is
long.


The roughed up surfaces will be coated turned to slide in the mating
sheaves bores.

Be sure to first rub in a thin layer and then the rest on top of that.
Calculate at least 50% loss, you won't be able to distribute it evenly and
controlled enough.

Getting a nice forced coat into the roughing sounds like an excellent idea.

Thanks,

Wes

Trepanning and Parting Off - Loose Gibs Chatter Chips
 

Wes wrote:

I was planning on spinning by hand until some one told me the cure time is
long.

Put it in the oven. :-)
I once must have gotten the mixture wrong (not enough hardener) and it still
was soft after two days. As I didn't want to start all over again, I cured
it at 50°C for 4 hours. That fixed the problem. :-)

You'll also need a high resolution scale. Mine has 0,1 g, the 0,5g is
useless. Because I often only needed 20g or so (about 10ccm, IIRC). 1mm of
thickness of the coating is enough and saves some money.


Nick
--
The lowcost-DRO:
http://www.yadro.de