# Apron can be picked up off the ways by about 1/8 inch; is this OK?



## twooldvolvos (Dec 4, 2020)

Well, I am to the point to where I figure there is nothing to it but to do it with my new-to-me lathe.  So in the process of trying to flare a 3/4 inch copper pipe for a Mr. Pete style cutting oil can, I noticed that my apron can be lifted about 1/8 inch off of the ways.  (please don't ask me to explain).  I am just wondering if that is normal.  I will grant you that my flaring technique was most likely not by the book.  I am thinking that in normal lathe operation, the apron is forced against the ways so the fact that I am able to lift it a small amount is not an issue.  Any wisdom?  BTW, I have attached a pic of my finished cutting oil can.

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## Jim F (Dec 4, 2020)

My 9C is the same way.


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## Bi11Hudson (Dec 4, 2020)

There must be a confusion about terminology on my part. I know the "apron" as part of the cross slide that contains several gear trains and knobs and handwheels and such. What is there varies from model to model. In any(all?) cases though, the apron is rigidly attached to the cross slide. 

The cross slide is a point of registration. It should move in only two directions, that being the "X" axis or longitudinal and the "Y" axis or front to back. There should be no other motions. There may be a half a thou in the "Z" axis, or less. Just enough that the slide is not hard fixed to the ways. Call it room for oil or lubrication.

There are "shoes",_ I don't know the proper term_, on the underside of the cross slide that clamp against the ways to hold it tight. If there is slack in these shoes, the apron, attached to the cross slide, can be moved in the "Z" axis. i.e. vertically. This must never happen. When it does, the "shoes" must be tightened. 

Every machine will have different methods for attaching the "shoes". But there will be some method to tighten them solid and then relieve that pressure to allow movement and lubrication. I have an Atlas built machine and a Grizzly Chinese machine. In addition, I have had several smaller machines over the years. Every one had a different system, but each one had some method to hold the cross slide to the ways.

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## markba633csi (Dec 4, 2020)

I think you mean "carriage" rather than apron?


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## Jim F (Dec 4, 2020)

On a lathe Z is the longitudinal axis, X is crossfeed, Y is a milling attachment.


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## Jim F (Dec 4, 2020)

markba633csi said:


> I think you mean "carriage" rather than apron which is the "control panel" part of the carriage facing you


I knew what he meant, like I said mine moves in the Y axis, also.


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## twooldvolvos (Dec 5, 2020)

Bi11Hudson said:


> There must be a confusion about terminology on my part. I know the "apron" as part of the cross slide that contains several gear trains and knobs and handwheels and such. What is there varies from model to model. In any(all?) cases though, the apron is rigidly attached to the cross slide.
> 
> The cross slide is a point of registration. It should move in only two directions, that being the "X" axis or longitudinal and the "Y" axis or front to back. There should be no other motions. There may be a half a thou in the "Z" axis, or less. Just enough that the slide is not hard fixed to the ways. Call it room for oil or lubrication.
> 
> ...


Thanks for your comment.  I am referring to where the hole apron assembly attaches to the ways.  In other words, When I lift up on the assembly, the felt scrapers will lift off the V ways about 1/8 inch.  BTW, my lathe is an older South Bend 10K.


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## Bi11Hudson (Dec 5, 2020)

Jim F said:


> On a lathe Z is the longitudinal axis, X is crossfeed, Y is a milling attachment.



Being mostly self taught, I take the machine motion axes the same as from plane trigonometry. Looking down at a basic "unit circle" drawn on paper, X is the left-right axis, Y is the up-down axis and Z is toward or away from the viewer. Looking down at a machine, any machine, from above, I take the axes the same way. It may not be the "correct" way, but it is a way to keep the motions of the machine in perspective for me.

I have seen different axes represented different ways by different people. I never went to "high school", having had a remedial math class in the mid-'70s. The background I took into the class was nautical navigation, knowing a few formulas from "solid" trig, (third dimension) All such axes reference a different direction on different machines. By keeping the same references as I keep navigation, it simplifies anything I encounter in life. It may not be correct, but it allows me to present a solution to a LOOSE cross slide in terms that can be understood.

What it comes down to is that the cross slide should move "left-right" or longitudinal, as well as "in-out" for depth of cut. It should never lift off the ways, being loose enough to move smoothly and nothing more. This applies to a lathe, a mill, a shaper, or even the front door. It should move in only two dimensions. You choose which two.

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## DavidR8 (Dec 5, 2020)

There are gib screws on the far side of the carriage that can be adjusted to take out the play. 
I cannot recall if there is similar on the front 


Sent from my iPhone using Tapatalk


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## SLK001 (Dec 5, 2020)

Make of lathe?

Having the carriage lift like that is really no big deal, as all of the forces are down into the bed (not up into the air).  As David says, most lathes have a gib at the rear of the carriage (RE: directly across from the cross slide dials) that can be tightened to lessen this "lift".  If you have a South Bend lathe, you'll probably find that the two bolts are fairly loose.  Just tighten them by hand until you're more comfortable with the amount of upward play.  Just know that if you get them too tight, the carriage may bind while in use.


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## Jim F (Dec 5, 2020)

SLK001 said:


> Make of lathe?
> 
> Having the carriage lift like that is really no big deal, as all of the forces are down into the bed (not up into the air).  As David says, most lathes have a gib at the rear of the carriage (RE: directly across from the cross slide dials) that can be tightened to lessen this "lift".  If you have a South Bend lathe, you'll probably find that the two bolts are fairly loose.  Just tighten them by hand until you're more comfortable with the amount of upward play.  Just know that if you get them too tight, the carriage may bind while in use.


I think he has a 10K, I have a 9C.


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## Manual Mac (Dec 5, 2020)

I first noticed this on my SB9C years ago when parting.
The blade stuck into the shaft I was cutting off, stopped the spindle, and the carriage lifted in the rear.
Since then I have kept the gib in the back of the carriage finger tight (still loose) but still not able to lift.
Never had that happen again.


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## machPete99 (Dec 5, 2020)

Most lathes will have some guide blocks bolted under the carriage to keep it from lifting up. There are typically shims in there to take up most of the play.


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## Al 1 (Dec 5, 2020)

I agree with Jim.   Forces are down. Al


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## Jim F (Dec 5, 2020)

Manual Mac said:


> I first noticed this on my SB9C years ago when parting.
> The blade stuck into the shaft I was cutting off, stopped the spindle, and the carriage lifted in the rear.
> Since then I have kept the gib in the back of the carriage finger tight (still loose) but still not able to lift.
> Never had that happen again.


Fixed mine.


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## NortonDommi (Dec 5, 2020)

SLK001 said:


> Having the carriage lift like that is really no big deal, as all of the forces are down into the bed (not up into the air).


Sure about that?  I bore with a LH tool and part off with an inverted,(from conventional),blade from the front so in those cases the resultant forces are upwards.
  As Bill Hudson has made note much depends upon perspective.


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## savarin (Dec 5, 2020)

Got fed up playing with shims on mine so made a push pull set of screws to adjust the play.
It make adjusting the play easy.


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## SLK001 (Dec 5, 2020)

NortonDommi said:


> Sure about that?  I bore with a LH tool and part off with an inverted,(from conventional),blade from the front so in those cases the resultant forces are upwards.
> As Bill Hudson has made note much depends upon perspective.



Well, the lathe is _designed_ for the forces to go into the bed - not into the air.  I suppose that you could mount the lathe upside-down on the ceiling and use it like that, but that's not how it was designed.  We often hear, _"I part backwards, standing on one leg with my eyes closed and it works for me..."_  All that tells me is that their lathe isn't set up properly for parting, or their technique is bad.  And why would someone routinely bore with a LH tool?  Every "lift" of the carriage will change the bored radius (not much, but it does change).  If you're using carbide, boring with a LH tool seems like a recipe for fracturing the insert.


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## Jim F (Dec 6, 2020)

SLK001 said:


> Well, the lathe is* designed* for the forces to go into the bed - not into the air.  I suppose that you could mount the lathe upside-down on the ceiling and use it like that, but that's not how it was designed.  We often hear, _"I part backwards, standing on one leg with my eyes closed and it works for me..."_  All that tells me is that their lathe isn't set up properly for parting, or their technique is bad.  And why would someone routinely bore with a LH tool?  Every "lift" of the carriage will change the bored radius (not much, but it does change).  If you're using carbide, boring with a LH tool seems like a recipe for fracturing the insert.


Yeppers.....
He is on the other side, so it may work there.....
the whole flushing water thing.......


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## NortonDommi (Dec 6, 2020)

SLK001 said:


> Well, the lathe is _designed_ for the forces to go into the bed - not into the air.  I suppose that you could mount the lathe upside-down on the ceiling and use it like that, but that's not how it was designed.  We often hear, _"I part backwards, standing on one leg with my eyes closed and it works for me..."_  All that tells me is that their lathe isn't set up properly for parting, or their technique is bad.  And why would someone routinely bore with a LH tool?  Every "lift" of the carriage will change the bored radius (not much, but it does change).  If you're using carbide, boring with a LH tool seems like a recipe for fracturing the insert.


I'm already upside down according to your world view!
No, I keep my eyes open when parting and I usually sit down or stand on both feet facing the lathe.  The reason I use an 'upside down' parting tool and run the chuck clockwise is that the chips or swarf falls down and it just works better.  I part at nearly the same speed I turn at, fast and hassle free.
  I was incorrect when I said I use a LH tool for boring though, I use a RH tool upside down from conventional cutting on the rear side of the lathe as it allows me to see what I am doing easier if I am doing something narly.  If you ever have to bore out a track roller some genius has decided to blast weld into after a non-maintained bearing has collapsed and done so without removing all the broken bearing I can assure you that being able to observe the cut is pretty much vital. 
 I have never had any problem boring to size.


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## Jim F (Dec 6, 2020)

NortonDommi said:


> I'm already upside down according to your world view!
> No, I keep my eyes open when parting and I usually sit down or stand on both feet facing the lathe.  The reason I use an 'upside down' parting tool and run the chuck clockwise is that the chips or swarf falls down and it just works better.  I part at nearly the same speed I turn at, fast and hassle free.
> I was incorrect when I said I use a LH tool for boring though, I use a RH tool upside down from conventional cutting on the rear side of the lathe as it allows me to see what I am doing easier if I am doing something narly.  If you ever have to bore out a track roller some genius has decided to blast weld into after a non-maintained bearing has collapsed and done so without removing all the broken bearing I can assure you that being able to observe the cut is pretty much vital.
> I have never had any problem boring to size.


Some of us have screw-on chucks, that gets hairy.....


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## NortonDommi (Dec 6, 2020)

P.S. For upside down parting off the forces are downwards into the apron. I have a reasonably sturdy lathe but on lighter lathes lack of rigidity is what cause parting problems due mainly to the lifting forces on the toolpost which is why long before I was born people started mounting parting blades on rear toolposts. 
#  Having worked with ancient lightweight clapped out badly worn small lathes  I can tell you that parting upside down makes a huge difference.


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## SLK001 (Dec 6, 2020)

NortonDommi said:


> P.S. For upside down parting off the forces are downwards into the apron.



Are you sure about _*that*_?  If the tool is upside down in the rear, the spindle is rotating CCW into the tool.  It is used this way because any catch will move the tool *away *from the cut (as opposed to parting normally, when a catch will try to pull the tool into the work, thus a broken blade).  It is the vertical play in the carriage that allows the tool to lift out of the way when used upside-down - not possible if the forces are downwards into the apron.


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## twooldvolvos (Dec 6, 2020)

SLK001 said:


> Well, the lathe is _designed_ for the forces to go into the bed - not into the air.  I suppose that you could mount the lathe upside-down on the ceiling and use it like that, but that's not how it was designed.  We often hear, _"I part backwards, standing on one leg with my eyes closed and it works for me..."_  All that tells me is that their lathe isn't set up properly for parting, or their technique is bad.  And why would someone routinely bore with a LH tool?  Every "lift" of the carriage will change the bored radius (not much, but it does change).  If you're using carbide, boring with a LH tool seems like a recipe for fracturing the insert.


Intuitively I would have guessed exactly what you are saying.  Otherwise the manufacturer would have gone to the same lengths with the underside of the ways as they did on the top side.


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## NortonDommi (Dec 6, 2020)

SLK001 said:


> Are you sure about _*that*_?  If the tool is upside down in the rear, the spindle is rotating CCW into the tool.  It is used this way because any catch will move the tool *away *from the cut (as opposed to parting normally, when a catch will try to pull the tool into the work, thus a broken blade).  It is the vertical play in the carriage that allows the tool to lift out of the way when used upside-down - not possible if the forces are downwards into the apron.


Yeah, pretty sure.
  I even went out this morning and knocked up a mock-up out of a couple of pieces of wood and a bit of bar to check I am not as deluded as most suspect me to be! What was that saying about levers?
  In turning from the front there is a lifting force at the base of the toolpost. This is countered by the lever arm of the cross slide, the mass of the cross slide and tool post and the gibs on the dovetail which transfer forces to the apron and on into the mass of the lathe.
  I am sure someone smarter than me will now demolish me mathematically. 
On another note I think that with parting lack of rigidity, tool geometry and that heinous backlash contribute most to problems.

As to *twooldvolvos *original question I think that has been answered.  Adjust cross slide gibs and apron anti-lift pads/retainers?


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## SLK001 (Dec 6, 2020)

NortonDommi said:


> Yeah, pretty sure.
> I even went out this morning and knocked up a mock-up out of a couple of pieces of wood and a bit of bar to check I am not as deluded as most suspect me to be! What was that saying about levers?
> In turning from the front there is a lifting force at the base of the toolpost. This is countered by the lever arm of the cross slide, the mass of the cross slide and tool post and the gibs on the dovetail which transfer forces to the apron and on into the mass of the lathe.



Well, you have the drawing correct, but you interpreted it wrong.  The force is coming from the WORK, so in the front toolpost, the force is going INTO the bed.  Inversely, the force from the work in the REAR toolpost is going into the AIR.


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## NortonDommi (Dec 6, 2020)

SLK001 said:


> Well, you have the drawing correct, but you interpreted it wrong. The force is coming from the WORK, so in the front toolpost, the force is going INTO the bed. Inversely, the force from the work in the REAR toolpost is going into the AIR.



  I think the simplest thing is for you to take two pieces of scrap wood very roughly in the same relationship size wise to your lathe cross slide and toolpost and nail/screw the smaller to the larger.  attach something be it another piece of wood , a bit of steel rod as I did to the 'toolpost' piece, pivot the whole about the base directly under the 'toolpost' and apply a force downwards on whatever is representing your cutting tool.
  Visibly observe which way the base tilts. 
  Go back and look at the drawing again.
  I know it seems counterintuitive but hey!  Perhaps physics work differently up here? I mean just look at how water goes down the plughole backwards where you are.


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## SLK001 (Dec 6, 2020)

Here's a simplified free-body diagram of the front toolpost (there are rotational moments that just complicate things).  The rotating work imparts a downward force F1 into the toolpost (I don't show the work force).  The toolpost resists this force by exerting an upward force also of F1.  To prevent the toolpost from flying off into space, a corresponding downward force F2 (equal to the work F1) into the bed.  A free-body diagram is complete when ALL vertical and ALL horizontal forces sum to zero.

The same diagram can be used for the rear toolpost, except the forces are opposite.


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## Mitch Alsup (Dec 7, 2020)

SLK001 said:


> Are you sure about _*that*_?  If the tool is upside down in the rear, the spindle is rotating CCW into the tool.  It is used this way because any catch will move the tool *away *from the cut (as opposed to parting normally, when a catch will try to pull the tool into the work, thus a broken blade).  It is the vertical play in the carriage that allows the tool to lift out of the way when used upside-down - not possible if the forces are downwards into the apron.



Let us start by ignoring bending moments on the tool post.
Let us, instead, concern outselves with how the force on the part is being absorbed by the machine.

Tool at front, CCW, the work on the part is pushing the cariage onto the ways at the front of the lathe
Tool at rear, CCW, the work on the part is lifting the cariage away from the ways at the back of the lathe

The bending moments in the tool, its holder, the QCTP, the compound, and the cross slide are small compared to the forces mentioned above.

Tool at front upside down, CW, the work on the part is lifting the cariage from the front ways--this arangement is used in common threading application where DoC is light.


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## SLK001 (Dec 8, 2020)

Mitch Alsup said:


> Tool at front, CCW, the work on the part is pushing the cariage onto the ways at the front of the lathe
> Tool at rear, CCW, the work on the part is lifting the cariage away from the ways at the back of the lathe



Isn't this what I said?  If not, that is what I _intended _to say.



Mitch Alsup said:


> Tool at front upside down, CW, the work on the part is lifting the cariage from the front ways--this arangement is used in common threading application where DoC is light.



When is this setup _ever_ used?  I've never threaded, common or otherwise, like that.  All that mounting the tool so that the forces are UP does is _decrease _rigidity.  

SETUPS IN ORDER OF RIGIDITY:
1)  TP front, tool up, CCW
2)  TP back, tool up, CW  (#1 and #2 are equal)
3)  TP front, tool down, CW.
4)  TP back, tool down, CCW.

#3 is more rigid than #4 because of the lever arm of the carriage, since the front of the carriage has little vertical play.


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## Bi11Hudson (Dec 8, 2020)

Seems to me that power up or down is not the primary concern here. If the cross slide is run on dovetails, as most of them are, lifting of the cross slide will affect the depth of cut. The Atlas (and Craftsman) machines notwithstanding, the dovetails keep the cross slide in position on its' longitudinal travel. When there is a gap, or potential for that gap, the cross slide can move in or out.

Since the work is the power in this scenario, and the dovetails (or diamond slides) have the mating surfaces at an angle, it seems to me that any movement would be attempting to move the tool outward, while at the same time the power is driving down. That, to me, generates "chatter" or inconsistant radius of cutting. 

I base my theoretical thinking on a smaller machine, out of Taiwan. (a G-1550 Grizzly) The Atlas, with its' flat ways, uses the pressure from a vertical surface against the inside of the ways. The thoughts are theoretical because I am not willing to loosen the "shoes" that keep the machine tight.

.


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## Mitch Alsup (Dec 8, 2020)

SLK001 said:


> When is this setup _ever_ used?



9:30 into 






> SETUPS IN ORDER OF RIGIDITY:
> 1)  TP front, tool up, CCW
> 2)  TP back, tool up, CW  (#1 and #2 are equal) I would argue that this is slightly (slightly) less rigid than #1
> 3)  TP front, tool down, CW.
> ...


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## SLK001 (Dec 8, 2020)

Bi11Hudson said:


> Seems to me that power up or down is not the primary concern here...


Yeah, we have strayed off the thread starter's original concerns.


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## SLK001 (Dec 8, 2020)

Mitch Alsup said:


> 2) TP back, tool up, CW (#1 and #2 are equal)
> 
> I would argue that this is slightly (slightly) less rigid than #1



I agree that it is _probably_ less rigid than #1 (on most lathes), but I don't have any evidence to prove it.  However, some lathes have mounting points for tools at the rear, so the rigidity differences are probably small.


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## Superburban (Dec 8, 2020)

I think it all really depends on the lathe. I do not recall any with decent gibs to spread the forces on the underside of the front way. The ways and saddle spread out the forces pretty well, and are also easy to oil. How do you oil the underside? Granted, using a cutting tool is different then normal operations, and you generally are not moving the carriage, so wear on the underside is not as much a concern, but if all there is on the bottom, are a screw on one side, and the carriage lock on the other, that is not much. I think if I were to do much backwards cutting, I would make a second carriage lock for the left front of the carriage. Then you can lock down both sides of the front end when cutting. 

My second concern would be the dovetails on the cross slide. How strong are they in the upwards direction?


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## Mitch Alsup (Dec 8, 2020)

SLK001 said:


> I agree that it is _probably_ less rigid than #1 (on most lathes), but I don't have any evidence to prove it.  However, some lathes have mounting points for tools at the rear, so the rigidity differences are probably small.



The front way have that vertical ^ along with the flat _ way so 3 surfaces locate the fron of the cariage.
The back only has the flat _ way so only 1 surface locates the back side of the carriage.

Thus the front is better "located" in X and Z than the back, but since the forces go into the flat _ way the ^ is only used for longitudinal support.


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## Jim F (Dec 8, 2020)

Mitch Alsup said:


> The front way have that vertical ^ along with the flat _ way so 3 surfaces locate the fron of the cariage.
> The back only has the flat _ way so only 1 surface locates the back side of the carriage.
> 
> Thus the front is better "located" in X and Z than the back, but since the forces go into the flat _ way the ^ is only used for longitudinal support.


Depends on the lathe.
My SB9 has a V front and back, with a flat in front and a V in back for the tailstock.


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## SLK001 (Dec 8, 2020)

Jim F said:


> Depends on the lathe.
> My SB9 has a V front and back, with a flat in front and a V in back for the tailstock.



Ditto with my South Bend Heavy 10.  Vees on both front and back of carriage.  The tailstock has a vee up front and a flat at the back.


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