From: Robert Bastow <"teenut"@ hotmail.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: Lathe Technique: Conical Facing Problem with Heavy Cuts on a Super
Date: Sat, 29 Jan 2000 19:44:39 GMT

I have a similar Emco Maximat Super II, Nice lathe.

Locking any slide, saddle, table ect., not actually required to move during a
cut, is SOP, be it on a lathe , mill or WHY!

Quite aparte from reducing the tendency to shift under a heavy cut it reduces
chatter.

Research has shown that chatter is a significant factor in rapid WEAR of
slides...the hammering effect breaks down and disintigrates guide surfaces muck
faster than simple sliding abrasion.

I don't allow my slides to chatter under any circumstances, for that reason.  It
is one thing to grit your teeth and push on during a roughing cut...Quite
another, when you realise it is actively reducing the accurate life of your
machine!!

teenut

Robert Swinney wrote:

> Doug,
> Sounds like you figured it out - about locking the saddle.
> Bob Swinney
> Doug White <gwhite@alum.mit.edu> wrote in message
> news:86upp3$661@news-central.tiac.net...
> > I've been puttering with lathes more off than on for almost 40 years as
> > an amateur.  I've worked on a large variety of machines in various
> > student shops, from little Craftmans to huge LeBlonds & Monarchs.  Most
> > of these have been a bit old & battered, and I've mostly worked in brass,
> > plastic & aluminum.  I've always tried to take cuts where the machine
> > wasn't really straining at all, and I've had the time to take it easy.
> >
> > I now have my very own Emco Maier Super 11 lathe, in pristine condition.
> > It's not as sturdy as a LeBlond, but it's certainly as tight & rigid
> > as a South Bend.  It's got a 1 HP motor.  I'm also using 303 stainless
> > for more and more projects, and when I'm confronted with a lot of metal
> > removal, I've been trying to push things a bit harder than I have in the
> > past.  I'm still pretty timid, but I'm getting more aggressive.
> >
> > Last night, I was trying to turn some 2 1/4" 303 SS.  I need to leave a
> > 1/4" long, 1/2" dia. stub sticking out the end, and I was making facing
> > cuts.  I had the machine at 400 rpm, using a very sharp brazed C6 carbide
> > tool (no rake, no chip control), occasinally applying Cool Tool II with
> > an acid brush.  I ran the compound in & out by hand so that I could get a
> > feel for how hard it was cutting, and also to try to compensate for the
> > change in sfpm as the diameter of the cut changes.
> >
> > After taking a couple of fairly light facing cuts, I tried taking off
> > about 0.025".  This worked OK, although it required a bit more force on
> > the Y-axis lead screw than I'm used to.  However, when I backed the tool
> > out, I noticed that what had started out as a 0.025 deep cut had shrunk
> > down to only about 0.010 or less in the center.  I now had a conical face
> > on the piece.  A few more attempts at heavy cuts showed that the cutting
> > forces were slowly pushing the entire saddle back away from the cut.
> >
> > The saddle feed is just a big rack & pinion, and now that I think about
> > it, there really isn't anything other than the mass of the saddle &
> > compound to prevent it from wandering away from a heavy facing cut.  I
> > don't recall how other lathes I've worked on operated in this regard, but
> > I don't recall ever seeing this conical-cutting problem before.
> >
> > Now that you've waded through my long-winded intro, I have a few
> > questions:
> >
> > 1) Is this a common problem?  Is this an issue with the simple rack &
> > pinion feed on the Super 11, or am I being too aggressive?  It may just
> > be that all lathes behave this way, and I've just never pushed one that
> > hard (or noticed the conical effect).
> >
> > 2) The simple (but slightly more tedious) fix is to lock the saddle.
> > There is a clamping bolt on top of the saddle that _should_ prevent it
> > from moving.  I just checked the manual, and that seems to be what they
> > recommend.  This may be standard practice, but I don't recall ever seeing
> > it done, and clamping & unclamping with every cut is definitely going to
> > slow things down.  Is there some trick I'm missing?
> >
> > 3) I've been itching for an excuse to play with carbide inserts.  I
> > suspect that a cutting edge with a better geometry & chip control might
> > help reduce the cutting forces.  I've been trying to find someone who
> > makes negative-rake trigon inserts (so I get 6 edges) with enogh relief
> > at the edge that I get a net positive cutting geometry.  There are a few
> > out there, but they all come with beefier holders than my AXA tool post
> > can handle, and I'd have to cut them down.  Any suggestions?
> >
> > 4) Can anyone give me a feel for just how aggressive one can be with 303
> > on a 1 HP lathe?  I'm not under time pressure, I'm not getting paid by
> > the hour, and I don't want to push my machine anywhere CLOSE to a point
> > that might cause excessive wear or risk damage.  On the otherhand, I
> > don't want to take all day taking 5 thousandths cuts when I can do 50
> > with the right tools & some nerve.  I've also decided that a chip shield
> > may be a good investment.  The smoke from the Cool Tool is foul enough,
> > but the shower of hot chips can be very exciting when one lands on your
> > hand.
> >
> > One of the great things about machining & this news group is that I learn
> > something new on almost every project.  This one looks very promising in
> > that regard.
> >
> > Thanks!
> >
> > Doug White
> >

From: Robert Bastow <"teenut"@ hotmail.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: Lathe Technique: Conical Facing Problem with Heavy Cuts on a Super
Date: Sun, 30 Jan 2000 17:23:40 GMT

Exactly Bob...I forgot to mention that I have modified lever locks on the
saddle, cross slide and top slide of my Super II.  Just a flick of the finger to
lock, unlock.

On heavy cuts I snug up the moving axis too, just enough to give a little drag
and damping.

teenut

Bob Unitt wrote:
>
> In article <86upp3$661@news-central.tiac.net>, Doug White
> <gwhite@alum.mit.edu> writes
> >2) The simple (but slightly more tedious) fix is to lock the saddle.
> >There is a clamping bolt on top of the saddle that _should_ prevent it
> >from moving.
> I had the same problem on my Myford 254. I made a replacement clamping
> bolt with a lever instead of a hex-head. Moving the lever 1/4 turn goes
> from saddle-free to saddle-locked, so I can now lock the saddle for
> every facing cut, without having to waste time looking for the right
> spanner.
>
> --
> Bob Unitt (UK)