In article ,
"DoN. Nichols" wrote:
On 2008-05-02, Joseph Gwinn wrote:
In article ,
"DoN. Nichols" wrote:
On 2008-05-02, Joseph Gwinn wrote:
In article ,
"DoN. Nichols" wrote:
[ ... ]
As am I. I've got the 5418 (similar bed profile, but manual
change belts), and have very little chatter.
[ ... ]
You know -- there is one other possibility which occurs to me.
I presume that your lathe, like mine, has the hollow level adjusting
screws in the feet of the bed through which pass the bolts to lock it
down to the stand. If you have something like the near side bolt loose
and the level adjusting screw a little clear of the stand, the bed would
wind up under torque, which could give you similar behavior.
Do you mean the bolts between cabinet and the floor, or that hold the
headstock to the bed? I assume you mean between headstock and bed.
I see that you figured out what I was talking about from
examining the manual for the 5418. Since I don't have the manual for
yours, I had not realized how different they were.
Ahh. Yes. It will take a while, but I may scan my manual, which does
not appear to be copyrighted.
Hmm ... beware that you can't e-mail it to me. There is a limit
of 30K total size on incoming e-mail, to keep virus infections out of a
couple of small mailing lists which I host. No problem with my systems,
of course -- but I first turned on the limit when I got over 300 copies
of a new spam on the first day, and 200 more on the next day. I forget
what it was, but it was spreading like wildfire, and it took a long time
to clean out my mailbox enough so that I could read valid e-mail.
OK. I'll probably post it to the metalworking archive.
[ ... bed twist ... ]
O.K. As long as you are that close, it would not really matter.
Where it would matter is turning some distance from the headstock, or
running something like a 1" drill bit in the tailstock -- especially
with a long workpiece extension from the chuck.
While using the 1" drill, the bed will most certainly wind up a bit. I
guess that what would resist permanent twist would be the leveling, with
the lathe resting on a concrete floor, as it now does.
Better with the near foot on the tailstock end and the back foot
on the headstock end bolted down, even if the other two are not. That
should resist the twist introduced by the drilling.
Well, if I do bolt it down, I'll probably do all four feet. But I'm
reluctant to bolt it down, because I may move it. Nor is a basement
slab all that thick and rigid, compared to the floor in an industrial
plant.
[ ... ]
O.K. Quite different. The 5418 is supposed to have the cabinet
bolted firmly to the floor (I don't), and the bed leveled relative to
the stand and chip tray.
The 5914 manual also speaks of bolting to the floor, but few people
actually do this I suspect.
Indeed -- unless forced by OSHA inspectors. :-) Now, if I were
doing lots of faceplate work, I would bolt it down just to be sure that
the lathe does not start walking around the shop with a bit of imbalance
on the faceplate. :-)
I'm still looking for a faceplate. One can buy a new faceplate plus L00
back from Bison for about $300, but the need is not immediate, and so
I've been watching eBay.
In looking at the 5418 manual, I see that it was also sold without
cabinet stand, for mounting on an owner-provided bench. Thus, the
adjusters had to be between cast iron stuff and the base (bench or
cabinet).
I looked the the 5418 manual. Now I understand. The designs of 5914
and 5418 are very different in this area. But there is no harm in
making sure that all those bolts are nice and tight, especially those
holding headstock to bed.
Agreed. Check the tailstock end too -- because that is what
would flex when the torque is transmitted from the spindle to the
carriage. It would wind up the bed (a little, at least).
The tailstock now clamps pretty firmly to the bed. This is one of the
first things I cleaned and adjusted, mainly because it was easy and
could be done without the manual.
It was not the tailstock to the bed that I was thinking of. I
was assuming that it would be well clamped, and for turning it would not
make a difference anyway. But bed feet to stand and/or stand to floor
are where the wind-up could be controlled.
Ahh. Now it makes sense.
BTW For parting there used to be a gooseneck parting tool. It went
in a lantern style toolpost, came out, turned up, formed an
Omega shaped arch, back down to where the parting tool is
actually clamped. The result is that excessive cutting forces
tends to move the tool away from the workpiece, thus eliminating
chatter. But your machine *should* be rigid enough to not need
this, especially with an Aloris style quick-change toolpost, and
the T-profile parting blades.
I vaguely knew (from reading old books) that there was such a tool, and
that it involved a gooseneck, but I had the "picture" upsidedown in my
mind, and couldn't see how it would work. I just googled it, and found
a book from 1910 that explained the principle as applied to use in a
planer. They did understand the self-feeding effect, saying that the
gooseneck would eliminate gouging the work, but a sufficiently rigid
machine didn't need gooseneck tools.
Yep.
http://books.google.com/books?id=Skd...lpg=RA8-PA36&d
q=gooseneck+tool+lathe&source=web&ots=edrQWKc6hu&s ig=QsKeq0Vn7zebOdjC5ydY
KtuqnkA&hl=en#PRA8-PA35,M1
Hmm ... I don't think that I'm going to bother cut-and-pasting
all three chunks of that URL. I know the tool anyway, and see them
occasionally on eBay auctions.
In the original posting, you should be able to just click on the URL,
even though it appears wrapped, because I provided start and end
delimiters ( ... ). In quoted postings, this won't work, and editing
is required.
It occurs to me that a negative rake cutting tool could be set up to
develop enough outward force to at least partially counteract the
tendency to self-feed.
Right.
Perhaps this is why one commonly stated cause of
chattering is too-sharp tools. When one carefully blunts such a tool,
one puts a little bit of very negative rake right at the cutting edge.
How much backlash is there in your cross-feed leadscrew? The
self-feed can take the slack out of a worn leadscrew/nut pair. And you
want the cross-slide gibs to have a bit of drag, too.
I have the gibs adjusted so there is much drag, but the cross-slide
backlash is about 0.020", and the compound slide backlash is about
0.006".
The compound slide backlash was ~0.055" when I got the lathe, and so I
replaced the screw and its bronze nut. What a difference it made. I
have no idea why it was so worn compared to the cross-slide; perhaps
someone replaced the cross-slide screw and nut.
The cross-slide wasn't too bad (after being cleaned and adjusted), so I
left it alone. At least for now.
[ ... ]
Hmm ... another thing to check. While you have chatter, see
whether there is any relative motion between the headstock and the bed.
If it is not clamped down firmly enough, or if there are chips trapped
between the headstock and the bed, that could introduce enough give to
create problems.
Hmm. Offhand, I don't see any safe way to do this, as my hand would
need to be very close to the spinning chuck, or to various gears and the
like.
There is space where the outer ways stick out from under the
headstock (which is clamped to the inner ways) and you should be able to
check back along the near side far enough to be clear of the chuck.
Ahh. I see what you mean. One can get at the back of the lathe safely
enough. The problem is that I cannot then reach the handwheels to
advance the toolbit into the work. I'll have to cogitate on this.
I think I'll just torque all the clamp bolts, to see if any are loose.
O.K. That will deal with loose bolts, though not with chips.
I doubt that the headstock was ever unbolted, at least not by the people
who caused all the ignorance-induced problems. Taking the headstock off
would have frightened them, at least one fondly hopes that it would. In
any event, chips can only get in there is the headstock is unbolted.
Well ... you have the lathe in your basement I believe? Some
people disassemble the lathe to several heavy components and take each
down separately. If you didn't, perhaps someone else did previously.
It's possible, but I'm pretty sure that I am the first HSM owner of this
lathe, so this is probably its first basement gig. And my basement has
level entry, so no disassembly was needed.
The headstock is located on the bed ways by careful fitting of headstock
bottom to ways, plus a pair of steel dowel pins to prevent sliding.
O.K. Mine has one taper pin, not two dowel pins.
What I called dowels are in fact #6 taper pins, and they fix the
headstock to the bed way, preventing motion along the bed way.
There are in addition four pointed bolts that attach the bed to the cast
iron pedestal foot. I thing these studs are pointed for ease of manual
assembly in the factory.
Unlike the 5418 manual, in the 5914 manual, there is no
procedure for adjusting how the cast iron stuff rests upon the sheet
metal stuff.
O.K. This assumes that the sheet metal stuff is rigidly bolted
to the floor, I guess.
That would make sense. In the 5914, these adjustments have moved to the
cabinet-floor feet.
O.K. This produces fewer paths for swarf to get down into the
drawers and the motor/pulley assembly in the pedestals.
Yes. Not that the defense is perfect. I have pulled swarf out of just
about everywhere.
Joe Gwinn