on bed design.


john kling
 

Most lathe have v ways (or combinations of v and flat ways). A few inexpensive lathes (such as Atlas) used flat beds. I imagine that this is a cheaper design to manufacture. A big mill and a big surface grinder would seen to provide efficiency in manufacture. But some precision lathes also have flat beds. So the design evidently is not all about cost savings.

Is there a reason that the majority of manufactures of lathes chose v ways?



Guenther Paul
 

You say a Atlas lathe was inexpensive well check the selling prices of the atlases you change your mind. I admit
the atlases/craftsman are not near as precise as a south bend. I have both
 
GP




From: "jkling222@... [SOUTHBENDLATHE]"
To: SOUTHBENDLATHE@...
Sent: Thursday, December 31, 2015 5:03 PM
Subject: [SOUTHBENDLATHE] on bed design.

 
Most lathe have v ways (or combinations of v and flat ways). A few inexpensive lathes (such as Atlas) used flat beds. I imagine that this is a cheaper design to manufacture. A big mill and a big surface grinder would seen to provide efficiency in manufacture. But some precision lathes also have flat beds. So the design evidently is not all about cost savings.

Is there a reason that the majority of manufactures of lathes chose v ways?




Jim B. <btdtrf@...>
 

For a given amount of bed space the v way provides more wear area and for a given amount of wear the v bed has less tool drop. 

Jim B,

On Dec 31, 2015, at 5:03 PM, jkling222@... [SOUTHBENDLATHE] <SOUTHBENDLATHE@...> wrote:

 

Most lathe have v ways (or combinations of v and flat ways). A few inexpensive lathes (such as Atlas) used flat beds. I imagine that this is a cheaper design to manufacture. A big mill and a big surface grinder would seen to provide efficiency in manufacture. But some precision lathes also have flat beds. So the design evidently is not all about cost savings.

Is there a reason that the majority of manufactures of lathes chose v ways?



rjitreeman0909@...
 

The V way give more consistent location of the tail stock and saddle.. By design the flat ways require clearance between the two ways allowing the saddle and tail to float by several thousanths and therefore have an increase variability from setting to setting while the V way of the saddle and tail simply settle to the same alignment with repeatability.


Guenther Paul
 

No on a v way bed the v is the guide for the carriage and tail stock, a lot lot more accurate.  A flat bed uses the edges of the bed for a guide
 
GP




From: "rjitreeman0909@... [SOUTHBENDLATHE]" To: SOUTHBENDLATHE@...
Sent: Thursday, December 31, 2015 7:54 PM
Subject: Re: [SOUTHBENDLATHE] on bed design.

 
The V way give more consistent location of the tail stock and saddle.. By design the flat ways require clearance between the two ways allowing the saddle and tail to float by several thousanths and therefore have an increase variability from setting to setting while the V way of the saddle and tail simply settle to the same alignment with repeatability.



john kling
 

I see some flat bed lathes (Hardinge -flat with beveled edge) and some German and swiss flat beds have reported high accuracy. -This is the source of my puzzle.


On Thursday, December 31, 2015 8:32 PM, "paulguenter@... [SOUTHBENDLATHE]" wrote:


 
No on a v way bed the v is the guide for the carriage and tail stock, a lot lot more accurate.  A flat bed uses the edges of the bed for a guide
 
GP




From: "rjitreeman0909@... [SOUTHBENDLATHE]"
To: SOUTHBENDLATHE@...
Sent: Thursday, December 31, 2015 7:54 PM
Subject: Re: [SOUTHBENDLATHE] on bed design.

 
The V way give more consistent location of the tail stock and saddle.. By design the flat ways require clearance between the two ways allowing the saddle and tail to float by several thousanths and therefore have an increase variability from setting to setting while the V way of the saddle and tail simply settle to the same alignment with repeatability.





Mark R. Jonkman
 

I think hardinge uses a dovetail way that is flat on top but the dovetail provides the accuracy. 

The carriage on an atlas uses a gib on the back to keep it tight but ta the tailstock slides between the ways where as vee ways might give it more repeatability. 

Which would be better if comparing two lathes would most likely come down to which one has more wear. A heavily worn vee way lathe would probably not be more accurate then a flat way lathe with limited wear.

It really depends on personal preference.

I've had both types of lathes and i could create very accurate things with both. Due to wear, my Atlas 6" was at times more accurate then my SB Heavy 10 depending on what i was doing.

Sincerely 
Mark R. Jonkman

On Dec 31, 2015, at 9:51 PM, john kling jkling222@... [SOUTHBENDLATHE] <SOUTHBENDLATHE@...> wrote:

 

I see some flat bed lathes (Hardinge -flat with beveled edge) and some German and swiss flat beds have reported high accuracy. -This is the source of my puzzle.


On Thursday, December 31, 2015 8:32 PM, "paulguenter@... [SOUTHBENDLATHE]" <SOUTHBENDLATHE@...> wrote:


 
No on a v way bed the v is the guide for the carriage and tail stock, a lot lot more accurate.  A flat bed uses the edges of the bed for a guide
 
GP




From: "rjitreeman0909@... [SOUTHBENDLATHE]" <SOUTHBENDLATHE@...>
To: SOUTHBENDLATHE@...
Sent: Thursday, December 31, 2015 7:54 PM
Subject: Re: [SOUTHBENDLATHE] on bed design.

 
The V way give more consistent location of the tail stock and saddle.. By design the flat ways require clearance between the two ways allowing the saddle and tail to float by several thousanths and therefore have an increase variability from setting to setting while the V way of the saddle and tail simply settle to the same alignment with repeatability.





Anthony Rhodes
 

John,
 
I'm coming to this quite late due to being busy with other matters. I've read your message and the 6 responses, and I'm interested in machine tool design, so I thought I might contribute.
 
The issue at hand is, firstly, to control the location of the cutter relative to the work piece with as much precision as possible. Where there may be a loss of such precision, it is preferable to take the loss where it will have the least detrimental effect on required accuracy of the work piece.
 
There is a mathematical benefit in a narrow guide way, On most lathes with inverted V-ways there is one such for the carriage and one different one for the tailstock. The narrow guide way, by its geometry, reduces the amount of skewing of the controlled element, ie the carriage or tailstock, as it is traversed along the bed. Even with vertical wear of the V-way the carriage or tailstock tend to stay at the same distance from the axial center of the bed. It has been calculated that vertical displacement below or above the axial center of the work piece has much less effect on the accuracy of machining, more effect on small diameter work pieces and much less on large diameter ones.
 
The above being said, there are many forms of bedways, dove tail and flat (or box ways in the modern terminology) being a couple of them, There are also single Vs, triple Vs, and four Vs, in addition to the common two V pattern. Common examples are small Asian lathes, as well as the AA 6" for single Vs, Monarch 10EE and Rivett 1020 for 2 Vs, South Bend and it's clones for 3 Vs, and American Standard for 4 Vs. Atlas and Myford use flat ways and Hardinge uses dove tails. There are, of course, many more for each form. There are also various displacements of the bedways. Slant beds are pretty well known, which provide benefits in clearing the bed and carriage of chips and lubricants or collants, and while I'm not aware of over head bedways for the carriage, I do know of such for the tailstock.
 
Each form of bed had some benefit in the eyes of the designer and manufacturer. In the end, there is probably more benefit in the choices of and processes used on the materials, and the care taken in precision of manufacture, than all the theoretical benefits from geometry. And care in use, maintenance, and adjustment will do more, than anything done before installation in the shop, to provide superior performance over a long, useful life. Ham fisted and ignorant people can destroy the best machine in a couple of days, whereas a considerate, knowledgeable user can make the lowliest machine turn out quality work over a long time, far beyond the reasonable expectations placed upon it from the day it left the manufacturer.
 
Anthony
Berkeley, Calif.
*************************************************

In a message dated Thu Dec 31, 2015 2:03 pm (PST), jkling222 writes:
Most lathe have v ways (or combinations of v and flat ways). A few inexpensive lathes (such as Atlas) used flat beds. I imagine that this is a cheaper design to manufacture. A big mill and a big surface grinder would seen to provide efficiency in manufacture. But some precision lathes also have flat beds. So the design evidently is not all about cost savings.

Is there a reason that the majority of manufactures of lathes chose v ways?


john kling
 

Looking at pictures of Hardinge lathes that have what looks somewhat like a wide flat bed, I see that they have angles on both the front and back side. In a sense this like having a single inverted V  - with several inches of metal where the peak would otherwise be. So I will take the Hardinge off of the precision flat bed lathes. I have seen pictures of 1900 Drummond lathes with a tube type bed. The pictures do not reveal a slot in the "tube" - which I assume must be there to make any sense as a design.


eddie.draper@btinternet.com
 

Round bed Drummonds have a slot at the bottom of the tube, and the leadscrew is inside it.  There always seem to be a few on ebay UK.  Probably controversial, but I'd put them in the category of "exhibit" rather than "tool" nowadays, although it is fair to say that a great many were made and sold and doubtless did good work.  Many had treadle drive.  My first lathe work was on a later flat bed Drummond.  Drummond eventually were bought out by Myford.

Eddie




From: "john kling jkling222@... [SOUTHBENDLATHE]"
To: "SOUTHBENDLATHE@..."
Sent: Tuesday, 5 January 2016, 8:17
Subject: Re: [SOUTHBENDLATHE] on bed design.

 
Looking at pictures of Hardinge lathes that have what looks somewhat like a wide flat bed, I see that they have angles on both the front and back side. In a sense this like having a single inverted V  - with several inches of metal where the peak would otherwise be. So I will take the Hardinge off of the precision flat bed lathes. I have seen pictures of 1900 Drummond lathes with a tube type bed. The pictures do not reveal a slot in the "tube" - which I assume must be there to make any sense as a design.



Gregg Eshelman
 

On 1/5/2016 1:17 AM, john kling jkling222@yahoo.com [SOUTHBENDLATHE] wrote:


Looking at pictures of Hardinge lathes that have what looks somewhat
like a wide flat bed, I see that they have angles on both the front and
back side. In a sense this like having a single inverted V - with
several inches of metal where the peak would otherwise be. So I will
take the Hardinge off of the precision flat bed lathes. I have seen
pictures of 1900 Drummond lathes with a tube type bed. The pictures do
not reveal a slot in the "tube" - which I assume must be there to make
any sense as a design.
Before Hardinge went to the dovetail bed they used a flat bed with outward sloping sides and a slot down the middle. Commonly called a split bed. The exact same profile was used on at least two other makes of lathe so accessories are interchangeable.

The split and dovetail bed lathes mostly do not have any kind of a conventional saddle/carriage or any type of leadscrew or power feed. Accessories like cross slides or compound slides are movable along the bed but get locked in place while in use.

The lathes are intended to work on small areas of the workpiece. When they do threading, it's with an attachment that does thread chasing with a follower on a master thread mandrel, usually mounted on the left end of the spindle. Thus they cannot do things like cut long tapers or very long threads. Nor can they easily make full length turning cuts for doing things like rounding rough stock. Usually they're fitted with collets in the spindle for starting with smooth stock.

Some of the Hardinge lathes with dovetail bed have power feed, and the most desirable HLV-H model can also do threading without a chaser attachment. Their earliest dovetail bed lathes were essentially the same as the split beds with a different profile on top. Same accessories but also altered for the dovetail. Some accessories for the split bed had removable alignment blocks that could be swapped for ones to fit the dovetail.