|
Posted by DoN. Nichols on May 4, 2008, 9:43 pm
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>
[ ... ]
>> > 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.
You mean to the dropbox <http://www.metalworking.com>? That
should do -- or perhaps to the archive of manuals which Iggy is building
up.
[ ... bed twist ... ]
>> 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. Mine is not bolted down -- but I don't see the kind of
chatter that you do. Perhaps it is because most of the industrial
service life of the machine was as a turret lathe, where most of the
motion was in the turret ram.
[ ... ]
>> > 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.
O.K. So was I -- until I found one at a flea market/picnic held
by the local metalworking club (which, BTW, is also where the dropbox
is. :-)
> In looking at the 5418 manual, I see that it was also sold without
> cabinet stand, for mounting on an owner-provided bench.
With a somewhat different headstock which allowed the belts to
run back to a rear-mounted motor instead of down into the pedestal.
> Thus, the
> adjusters had to be between cast iron stuff and the base (bench or
> cabinet).
Yes -- but before that, it was common to adjust between the feet
and the cabinet (or table) with stacks of shims.
[ ... ]
>> >> 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.
Good.
[ ... ]
>> ><http://books.google.com/books?id=SkdSAAAAMAAJ&pg=RA8-PA36&lpg=RA8-PA36&d
>> > q=gooseneck+tool+lathe&source=web&ots=edrQWKc6hu&sig=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.
Nope! *I* can't -- because I don't use a GUI-based newsreader.
I can click on the url and get at most a single line of it to paste to
a browser or another window with a command line.
People with GUI-based newsreaders (especially those built into
web browsers) can do so. Frankly, I am glad that I can't, because it
makes it more difficult to accidentally click on a malicious link.
[ ... ]
>> > 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".
O.K.
> 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.
Well ... my cross-slide had 0.070" backlash. But I know why.
The power feed was used for parting off workpieces after the turret does
most of the work of shaping them. So the carriage just sat there, the
compound was untouched, and the cross-slide cycled under power for every
part made.
> The cross-slide wasn't too bad (after being cleaned and adjusted), so I
> left it alone. At least for now.
O.K. But when you are experiencing chatter, you might also try
placing a finger where it can sense motion along the cross slide.
>
>> [ ... ]
>>
>> >> 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.
Isn't there access above the quick-change gearbox? The gearbox
is bolted firmly to the bed, so you could sense motion between the top
of the gearbox and the front of the headstock.
[ ... ]
>> > I doubt that the headstock was ever unbolted, at least not by the people
[ ... ]
>> 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.
O.K. That helps greatly.
>> > 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.
O.K. That is as it should be.
> 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.
Hmm ... I've not checked how my bed feet are attached.
[ ... ]
>> 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.
It does tend to get everywhere.
Enjoy,
DoN.
--
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---
|
|
Posted by Joseph Gwinn on May 5, 2008, 10:02 am
Please log in for more thread options
> >
>
> [ ... ]
>
> >> > 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.
>
> You mean to the dropbox <http://www.metalworking.com>? That
> should do -- or perhaps to the archive of manuals which Iggy is building
> up.
I meant the dropbox, although Iggy would be welcome to a copy as well.
> [ ... bed twist ... ]
>
> >> 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. Mine is not bolted down -- but I don't see the kind of
> chatter that you do. Perhaps it is because most of the industrial
> service life of the machine was as a turret lathe, where most of the
> motion was in the turret ram.
OK.
> >> > 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.
>
> O.K. So was I -- until I found one at a flea market/picnic held
> by the local metalworking club (which, BTW, is also where the dropbox
> is. :-)
It helps to be lucky...
> > In looking at the 5418 manual, I see that it was also sold without
> > cabinet stand, for mounting on an owner-provided bench.
>
> With a somewhat different headstock which allowed the belts to
> run back to a rear-mounted motor instead of down into the pedestal.
>
> > Thus, the
> > adjusters had to be between cast iron stuff and the base (bench or
> > cabinet).
>
> Yes -- but before that, it was common to adjust between the feet
> and the cabinet (or table) with stacks of shims.
Yep. I wanted a lathe with integral cabinet stand, on the theory that
it would all fit together better.
> [ ... ]
>
> >> ><http://books.google.com/books?id=SkdSAAAAMAAJ&pg=RA8-PA36&lpg=RA8-PA36&d
> >> > q=gooseneck+tool+lathe&source=web&ots=edrQWKc6hu&sig=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.
>
> Nope! *I* can't -- because I don't use a GUI-based newsreader.
> I can click on the url and get at most a single line of it to paste to
> a browser or another window with a command line.
>
> People with GUI-based newsreaders (especially those built into
> web browsers) can do so. Frankly, I am glad that I can't, because it
> makes it more difficult to accidentally click on a malicious link.
If you are not on Windows, why would this be a problem?
> [ ... ]
>
> >> > 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".
>
> O.K.
I figured out how better to adjust things, and got this down to ~0.003".
> > 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.
>
> Well ... my cross-slide had 0.070" backlash. But I know why.
> The power feed was used for parting off workpieces after the turret does
> most of the work of shaping them. So the carriage just sat there, the
> compound was untouched, and the cross-slide cycled under power for every
> part made.
>
> > The cross-slide wasn't too bad (after being cleaned and adjusted), so I
> > left it alone. At least for now.
>
> O.K. But when you are experiencing chatter, you might also try
> placing a finger where it can sense motion along the cross slide.
Yep. I tried the same improved adjustment method on the cross slide,
but the backlash remained at ~0.020", so this is probably inherent to
the screw and nut.
Did you ever figure out how much of the 0.070" was the screw versus the
nut? I think I recall you saying that the Acme threads were worn down
to sharp points, which would imply that screw wear was the larger
contributor.
> >> [ ... ]
> >>
> >> >> 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.
>
> Isn't there access above the quick-change gearbox? The gearbox
> is bolted firmly to the bed, so you could sense motion between the top
> of the gearbox and the front of the headstock.
Not without some disassembly.
> >> > 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.
>
> O.K. That is as it should be.
And it turns out that there is only one taper pin, not two, so the two
models are about the same here. I recalled that there were two, but
when I cleaned the dirt off, only one.
> > 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.
>
> Hmm ... I've not checked how my bed feet are attached.
>
> [ ... ]
>
> >> 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.
>
> It does tend to get everywhere.
In the shoes is the worst. And chattering tools generate particularly
annoying swarf - millions of sharp little steel needles. Coolant helps
by wetting the whole mess down, keeping it from blowing around in the
shop.
Joe Gwinn
|
|
Posted by DoN. Nichols on May 6, 2008, 1:30 am
Please log in for more thread options >
[ ... ]
>> > OK. I'll probably post it to the metalworking archive.
>>
>> You mean to the dropbox <http://www.metalworking.com>? That
>> should do -- or perhaps to the archive of manuals which Iggy is building
>> up.
>
> I meant the dropbox, although Iggy would be welcome to a copy as well.
Good.
[ ... ]
>> > 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.
>>
>> O.K. So was I -- until I found one at a flea market/picnic held
>> by the local metalworking club (which, BTW, is also where the dropbox
>> is. :-)
>
> It helps to be lucky...
And to not be in a hurry. :-)
[ ... ]
>> Yes -- but before that, it was common to adjust between the feet
>> and the cabinet (or table) with stacks of shims.
>
> Yep. I wanted a lathe with integral cabinet stand, on the theory that
> it would all fit together better.
And you got that. (And got rid of the chatter problem with the
new gib. Congratulations.
BTW -- the squeal might be because the trepanning tool is not
ground to give proper clearance on the curve of the slot.
[ ... ]
>> Nope! *I* can't -- because I don't use a GUI-based newsreader.
>> I can click on the url and get at most a single line of it to paste to
>> a browser or another window with a command line.
>>
>> People with GUI-based newsreaders (especially those built into
>> web browsers) can do so. Frankly, I am glad that I can't, because it
>> makes it more difficult to accidentally click on a malicious link.
>
> If you are not on Windows, why would this be a problem?
Because I don't depend on them *always* focusing on Windows
systems, just because they are the easiest target. There have been
experimental attacks which used javascript, or java, and I see lots of
information about security holes in the flash plugins (information from
the CERT mailing list). Anything attacking something other than the
basic native machine language can be made to work on other systems.
[ ... ]
>> > 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".
>>
>> O.K.
>
> I figured out how better to adjust things, and got this down to ~0.003".
Good!
[ ... ]
>> O.K. But when you are experiencing chatter, you might also try
>> placing a finger where it can sense motion along the cross slide.
>
> Yep. I tried the same improved adjustment method on the cross slide,
> but the backlash remained at ~0.020", so this is probably inherent to
> the screw and nut.
>
> Did you ever figure out how much of the 0.070" was the screw versus the
> nut? I think I recall you saying that the Acme threads were worn down
> to sharp points, which would imply that screw wear was the larger
> contributor.
It was about half. Cranking the cross-slide out to near falling
out of the nut reduced the backlash to 0.036".
[ ... ]
>> >> 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.
>>
>> Isn't there access above the quick-change gearbox? The gearbox
>> is bolted firmly to the bed, so you could sense motion between the top
>> of the gearbox and the front of the headstock.
>
> Not without some disassembly.
Hmm ... it must be much more enclosed there than the 5418 is.
[ ... ]
>> >> 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.
>>
>> O.K. That is as it should be.
>
> And it turns out that there is only one taper pin, not two, so the two
> models are about the same here. I recalled that there were two, but
> when I cleaned the dirt off, only one.
:-) That dirt does tend to mask details, doesn't it? :-)
[ ... ]
>> >> 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.
>>
>> It does tend to get everywhere.
>
> In the shoes is the worst. And chattering tools generate particularly
> annoying swarf - millions of sharp little steel needles. Coolant helps
> by wetting the whole mess down, keeping it from blowing around in the
> shop.
O.K. I don't have problems with the shoes. I wear
oil-resistant steel toed boots, and the legs of my pants come down below
the top of the boots, so it would have to bounce off the floor and come
up to get in. :-) Given some of the things I have dropped, I am glad to
have those steel-toed boots. :-)
And if you want nasty needles, try a horizontal mill with a
conventional milling cutter on steel. :-) I'll take what comes from my
lahte any day. :-)
Enjoy,
DoN.
--
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---
|
|
Posted by Joseph Gwinn on May 6, 2008, 8:58 am
Please log in for more thread options
> >
>
> [ ... ]
> >> Yes -- but before that, it was common to adjust between the feet
> >> and the cabinet (or table) with stacks of shims.
> >
> > Yep. I wanted a lathe with integral cabinet stand, on the theory that
> > it would all fit together better.
>
> And you got that. (And got rid of the chatter problem with the
> new gib. Congratulations.
Thanks. I've been reflecting on how I came to the conclusion that the
5914 needed new gibs.
The key was the gross tilting of the toolpost, which moved something
like a tenth or even an eighth of an inch, and yet nothing broke (except
for a tool bit now and then).
There is a reason people don't make springs out of cast iron, so the
castings could not be bending enough to explain such large deflections.
So it had to be the joints and/or slideways. The only joints were
firmly bolted (toolpost to slide) or wedged (tool holder to toolpost),
and no relative motion could be felt. And the headstock was firmly
bolted to the bed.
This left the slideways, of which there are three.
The first is between the bed ways and the carriage. This originally had
~0.003" wear-induced clearance, reduced to ~0.001" by removal of one
0.002" brass shim from each of the two rear hold-down plates. The
carriage is about 12" wide along the bed, so this 0.001" could account
for only about 0.001" of the tilt (measured at the end of the 5"
overhang). Only ~0.099" to go.
The second is the cross-slide dovetail (~2" wide), and the third is the
compound dovetail (~1.625" wide). The observed wear (~0.004" in both)
would easily explain the observed deflection, given the leverage from
the overhang plus the 2:1 amplification in each of the 60-degree
dovetails.
And it didn't feel right when I tightened the gibs. The effect on
slideway drag was very gradual as I tightened the gibs; one would expect
the effect on drag to be far more abrupt. This pointed to misshapen
gibs springing under pressure, versus being in pure compression.
> BTW -- the squeal might be because the trepanning tool is not
> ground to give proper clearance on the curve of the slot.
That also happened, when the groove got deeper, until I ground a little
more off the bit.
> [ ... ]
>
> >> Nope! *I* can't -- because I don't use a GUI-based newsreader.
> >> I can click on the url and get at most a single line of it to paste to
> >> a browser or another window with a command line.
> >>
> >> People with GUI-based newsreaders (especially those built into
> >> web browsers) can do so. Frankly, I am glad that I can't, because it
> >> makes it more difficult to accidentally click on a malicious link.
> >
> > If you are not on Windows, why would this be a problem?
>
> Because I don't depend on them *always* focusing on Windows
> systems, just because they are the easiest target. There have been
> experimental attacks which used javascript, or java, and I see lots of
> information about security holes in the flash plugins (information from
> the CERT mailing list). Anything attacking something other than the
> basic native machine language can be made to work on other systems.
It's true that everything has vulnerabilities, but as a matter of actual
(versus theoretical) risk, once you leave Windows things get pretty
quiet, and the expense (dollar cost and time cost and lost opportunity
cost) of security soon outweighs the cost of cleaning up the occasional
problem.
I read in one of the Mac magazines that only 10% or 15% of Mac owners
use any kind of add-on anti-virus product, and the unprotected Mac
owners are none the worse for it, and have been for years.
Unix/Linux users have even less to worry about.
By contrast, an unprotected Windows machine on the web will last a few
days at most, and a dialup machine might manage months before getting
caught.
> [ ... ]
>
> >> > 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".
> >>
> >> O.K.
> >
> > I figured out how better to adjust things, and got this down to ~0.003".
>
> Good!
I should say how I did this. It turned out to be simple. There is a
black steel collar upon which the dial rotates, the collar being fixed
to the screw shaft with a setscrew. Loosen setscrew. Tighten the cone
nut (or nylock nut) until the screw shaft binds, then back off just
enough that the screw shaft turns freely. Tighten setscrew.
Before doing this, it helps to disassemble, clean, and lubricate the
entire dial assembly, so things can turn freely.
> [ ... ]
>
> >> O.K. But when you are experiencing chatter, you might also try
> >> placing a finger where it can sense motion along the cross slide.
> >
> > Yep. I tried the same improved adjustment method on the cross slide,
> > but the backlash remained at ~0.020", so this is probably inherent to
> > the screw and nut.
> >
> > Did you ever figure out how much of the 0.070" was the screw versus the
> > nut? I think I recall you saying that the Acme threads were worn down
> > to sharp points, which would imply that screw wear was the larger
> > contributor.
>
> It was about half. Cranking the cross-slide out to near falling
> out of the nut reduced the backlash to 0.036".
I just tried this same crank-it-out test on the 5914: the backlash is
0.020" throughout the range, which implies that the bronze nut is the
culprit. And implies that the screw is far newer than the bronze T-nut
it now mates with.
Hmm. The nut is far cheaper than the screw, and very easy to install.
Replacing just the nut might be worthwhile.
> [ ... ]
>
> >> >> 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.
> >>
> >> It does tend to get everywhere.
> >
> > In the shoes is the worst. And chattering tools generate particularly
> > annoying swarf - millions of sharp little steel needles. Coolant helps
> > by wetting the whole mess down, keeping it from blowing around in the
> > shop.
>
> O.K. I don't have problems with the shoes. I wear
> oil-resistant steel toed boots, and the legs of my pants come down below
> the top of the boots, so it would have to bounce off the floor and come
> up to get in. :-) Given some of the things I have dropped, I am glad to
> have those steel-toed boots. :-)
>
> And if you want nasty needles, try a horizontal mill with a
> conventional milling cutter on steel. :-) I'll take what comes from my
> lahte any day. :-)
Someday I'll have the room for a horizontal mill. I keep running into
jobs for which it would be perfect. But it sounds like a perfect
application for copious flood cooling, if only to control the swarf.
Joe Gwinn
|
|
Posted by DoN. Nichols on May 6, 2008, 8:55 pm
Please log in for more thread options >
[ ... ]
>> > Yep. I wanted a lathe with integral cabinet stand, on the theory that
>> > it would all fit together better.
>>
>> And you got that. (And got rid of the chatter problem with the
>> new gib. Congratulations.
>
> Thanks. I've been reflecting on how I came to the conclusion that the
> 5914 needed new gibs.
>
> The key was the gross tilting of the toolpost, which moved something
> like a tenth or even an eighth of an inch, and yet nothing broke (except
> for a tool bit now and then).
>
> There is a reason people don't make springs out of cast iron, so the
> castings could not be bending enough to explain such large deflections.
> So it had to be the joints and/or slideways. The only joints were
> firmly bolted (toolpost to slide) or wedged (tool holder to toolpost),
> and no relative motion could be felt. And the headstock was firmly
> bolted to the bed.
>
> This left the slideways, of which there are three.
>
> The first is between the bed ways and the carriage. This originally had
> ~0.003" wear-induced clearance, reduced to ~0.001" by removal of one
> 0.002" brass shim from each of the two rear hold-down plates. The
> carriage is about 12" wide along the bed, so this 0.001" could account
> for only about 0.001" of the tilt (measured at the end of the 5"
> overhang). Only ~0.099" to go.
>
> The second is the cross-slide dovetail (~2" wide), and the third is the
> compound dovetail (~1.625" wide). The observed wear (~0.004" in both)
> would easily explain the observed deflection, given the leverage from
> the overhang plus the 2:1 amplification in each of the 60-degree
> dovetails.
And -- your compound has less adjustment range for the gib
because the dovetail itself is shorter, so the compound would show the
problems sooner, given equal wear.
> And it didn't feel right when I tightened the gibs. The effect on
> slideway drag was very gradual as I tightened the gibs; one would expect
> the effect on drag to be far more abrupt. This pointed to misshapen
> gibs springing under pressure, versus being in pure compression.
Yep! Good diagnostics.
>> BTW -- the squeal might be because the trepanning tool is not
>> ground to give proper clearance on the curve of the slot.
>
> That also happened, when the groove got deeper, until I ground a little
> more off the bit.
O.K.
[ ... ]
>> > If you are not on Windows, why would this be a problem?
>>
>> Because I don't depend on them *always* focusing on Windows
>> systems, just because they are the easiest target. There have been
>> experimental attacks which used javascript, or java, and I see lots of
>> information about security holes in the flash plugins (information from
>> the CERT mailing list). Anything attacking something other than the
>> basic native machine language can be made to work on other systems.
>
> It's true that everything has vulnerabilities, but as a matter of actual
> (versus theoretical) risk, once you leave Windows things get pretty
> quiet, and the expense (dollar cost and time cost and lost opportunity
> cost) of security soon outweighs the cost of cleaning up the occasional
> problem.
>
> I read in one of the Mac magazines that only 10% or 15% of Mac owners
> use any kind of add-on anti-virus product, and the unprotected Mac
> owners are none the worse for it, and have been for years.
>
> Unix/Linux users have even less to worry about.
Yes -- though there is a tradeoff to being a user of the most
numerous unix version -- which I think is now Solaris 10. That makes it
the next likeliest target.
> By contrast, an unprotected Windows machine on the web will last a few
> days at most, and a dialup machine might manage months before getting
> caught.
An unpatched Windows box, from first connection to the net in a
college dorm, has an expected mean-time-to-infection significantly less
than the time needed to download the patches via the net -- even with a
fast pipe. This is why at least some colleges (those who care about
security) will not connect a new box to the net until one of their staff
have come around with a DVD or CD containing all the patches and applied
them. This at least slows down the infection rate somewhat. :-)
>
>> [ ... ]
>>
>> >> > 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".
>> >>
>> >> O.K.
>> >
>> > I figured out how better to adjust things, and got this down to ~0.003".
>>
>> Good!
>
> I should say how I did this. It turned out to be simple. There is a
> black steel collar upon which the dial rotates, the collar being fixed
> to the screw shaft with a setscrew. Loosen setscrew. Tighten the cone
> nut (or nylock nut) until the screw shaft binds, then back off just
> enough that the screw shaft turns freely. Tighten setscrew.
Oh -- the thrust bearing was loose. On the cross-slide of mine,
the handcrank screws onto the leadscrew and then is locked by a cone
nut which goes into a countersink in the crank (IIRC). It is easy to
get this too tight. But it is also easy to tell that this is the source
of the play by feel. You feel a bit of a "thud" as the bearing play is
taken up, while the backlash in the actual leadscrew/net interface is
less sudden. :-)
> Before doing this, it helps to disassemble, clean, and lubricate the
> entire dial assembly, so things can turn freely.
Of course.
[ ... ]
>> > Did you ever figure out how much of the 0.070" was the screw versus the
>> > nut? I think I recall you saying that the Acme threads were worn down
>> > to sharp points, which would imply that screw wear was the larger
>> > contributor.
>>
>> It was about half. Cranking the cross-slide out to near falling
>> out of the nut reduced the backlash to 0.036".
>
> I just tried this same crank-it-out test on the 5914: the backlash is
> 0.020" throughout the range, which implies that the bronze nut is the
> culprit. And implies that the screw is far newer than the bronze T-nut
> it now mates with.
That narrows things down significantly.
> Hmm. The nut is far cheaper than the screw, and very easy to install.
> Replacing just the nut might be worthwhile.
I think so.
[ ... ]
>> > In the shoes is the worst. And chattering tools generate particularly
>> > annoying swarf - millions of sharp little steel needles. Coolant helps
>> > by wetting the whole mess down, keeping it from blowing around in the
>> > shop.
>>
>> O.K. I don't have problems with the shoes. I wear
>> oil-resistant steel toed boots, and the legs of my pants come down below
>> the top of the boots, so it would have to bounce off the floor and come
>> up to get in. :-) Given some of the things I have dropped, I am glad to
>> have those steel-toed boots. :-)
>>
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