Southbend toolpost, terrible finish

[Naiveambition]

Name of the thread says it all. I'm trying to learn a new to me, lathe and so far the turning finish is just plain bad. I've been using the Latern post, even when resetting multiple times for center adjustment.

I've noticed that my tool holders also hold an angle on the tool itself, plus the included rocker position without shimming . This seems excessive rake to me,, should I just block it up to level center?

Thinking hard on just building a 4 way toolpost from steel and bypass the problem . But would like to know how to use the lantern.
Or am I just missing something. It's an updated south bend 9 from the 30s

 

[goldstar31]

I think that your reference to the 30's is a bit wrong but if the old fashioned Armstrong tool holders are used, the correct height and tool angles can be maintained by shimming . I confess that my Armstrong tool holders are 'somewhere' in my collection. Probably in the next cage to my White Elephants.

Having said that, it would be easy enough to fabricate 4 way tool holders by bolting up three bits of steel plate and move onto a system more in keeping with today.

Of course, no one knows if your 'paint' restoration described earlier was sufficient to get your lathe to turn to a fine finish- once you have got the tooling properly sorted.

The correct way- methinks- was to see if the lathe actually worked.

I took a wrecked Myford Super7B to probably better than factory but note that the paint work leaves much to be desired.

So I look forward you seeing what improvements are made

Regards

Norman

 

[ShopShoe]

Naiveambition,

I would probably buy or build a quickchange toolpost myself.

For starters, trying a 3 or 4 position holder might also be an option to see if you like that better.

And then, I won't ignore the tangental tool users either, might be worth a try.

If you are really interested in the lantern tool post with Armstrong holder approach they are discussed by mrpete222 on YouTube: I'm sorry I can't recommend individual videos as he has so many. He uses many different lathes with different setups and on some of the older videos he describes more about machining and spends less time presenting his views on life (!!!??).

--ShopShoe

 

[Niels Abildgaard]

Sounds like when I got my Boxford many years ago.
A photo of Your setup will be helpfull.
I had at least three ways to improve finish.
First was a banded regular pattern using power feed cut structure be it facing or normal longitudinal.
It disappered when turning handles by hand.
Disconnected drive from spindle to gearbox and turned the system with a low speed electric screwdriver.
It was binding regularly but not in phase with leadscrew.Phew ,no bent leadscrew, but a very mistreated wheel in gearbox.
A little work with a file and bands disappered.
Next improvement was putting lathe on a rock and this gives a dramatic improvement on chatter resistance and overall wellbeing of subject,lathe and me.
If You have a southbend on a thin piece of wood or tinplate it will not be giving what it really can.
A canadian did the same for a Myford and was impressed enough to admit it.

http://www.homemodelenginemachinist.com/showthread.php?t=15300&page=6


The third avenue was to make some ultrarigid toolholders for normal and parting of .

In Your case I would remove compound slide and support a tool stifly direct on crosslide and see if it surface improves.

 

[packrat]

Try and find a quickchange toolpost for your South Bend. I think you will be much happier. Keep your old Lateran post for some work, it may come in handy.
Do you have copy of South Bends HOW TO RUN A LATHE..? lots of information there about lathe cutting tools. A four way tool post is also hard to get the center height right you are always trying to find a shim to put under the tool to get center height..In faked I have one you can have cheep..

 

[428Bird]

I bought a Chinese CXA quick change for my lathe and I am extremely happy with it. For what I'm doing, it's excellent.

Britt Bettell

 

[john_reese]

It is not a necessity to buy a new toolpost. If your lantern style toolpost has a properly fitted ring and rocker it will be rigid enough. The cause of poor finish is improper sharpening or presentation of the tool. If you do not have it find "How To Run a Lathe" by South Bend. Lots of digital copies on the net. The old style tool holders pretty much limit you to using high speed steel bits. Some old style holders held the bit parallel with body of the holder. These were designed for solid or brazed carbide bits. Small lathes generally work best with positive rake tooling. The high speed steel bits can be ground to optimize cutting angles for the material being cut. Modern toolholders like the Aloris clones are very convenient, as are carbide insert toolholders. I find it difficult to make very light ( a couple thou) cuts with carbide inserts. Most have a small negative rake hone at edge. I do have quick change tool holders for my lathes. Recently I made tangential tool holders for the BXA that let me present a dead sharp bit at a high rake angle. I use them regularly for finishing cuts. I also made a holder for the CXA toolpost on my 13" lathe. It holds a HSS bit on a 12* back rake. The front edge of the bit is relieved 8*. The top has a narrow groove that provides a 15* side rake and acts as a chipbreaker. I use it as a finishing cutter. If you do choose to go the route of a QCTP and carbide insert holders I suggest using inserts designed for aluminum for finishing, CCGX, as an example. They are ground to a sharp cutting edge and provide a positive cutting rake.

 

[Hopper]

On an old lathe like that, poor finish can be caused by a number of factors. The lantern toolpost will provide a perfect finish on a perfectly set up lathe. You do have to be careful not to have too much tool overhang. A pic of your set up would help determine this.
Other factors could include worn bed ways, gibs, dovetails, headstock bearings and chuck. A fancy toolpost will not compensate for any of these.

 

[goldstar31]

I recall writing on this subject some 20 years ago and also some 10 years ago on 'wear' and understandably don't wish to have to repeat myself for the umpteenth time.

The simple test of bad finish is probably to see what happens when the tool is advanced on an offset by say 12 degrees on slide and see what happens. A tool advanced by one thous should produce an almost
imperceptical dustting of swarf which can be crumbled in the fingers and which doesn't necessitate the use of a sterilised needle to remove the swarf!

If the latter persists , all the paint and fancy tool posts will be of no avail.

My take which you may or may not accept but it follows Connolly in his Machine Tool Reconditioning book which, if my memory recalls, deals with a SouthBend

Norm

 

[packrat]

Here is some good information on putting the lathe tool on center...
[ame]https://www.youtube.com/watch?v=1MrjnIcscxI[/ame]

 

[PopAlexandra]

I bought a Chinese CXA quick change for my lathe and I am extremely happy with it. For what I'm doing, it's excellent.

Britt Bettell

I second that. Works just fine for my small projects. Good quality/price ratio.

 

[Blogwitch]

N,

There is usually more to problems than the obvious.
Because you have a fairly old machine, have you checked for flatness of the toolpost mount and the flatness of the under surface of your lantern holder? If they aren't totally flat, your toolpost could be minutely wobbling on it's mount causing the centre height to change as you start cutting. I had to surface grind the top of a Myford ML10 topslide because of that type of problem. After he fitted a QCTP onto the reground surface, everything was perfect.

Are your gibs adjusted up and lubricated correctly? If not, that can cause the tool tip to rock up and down.

One thing you shouldn't do is hold tipped tools in a lantern type of holder. Tips are ground or moulded to exact angles for optimum performance and are designed to work when the tip toolholder is perfectly horizontal. Your type of holder doesn't allow that, as it has the tip height adjust on it. OK for HSS ground tips that can be altered by grinding to give a few extra degrees of clearance but not for the exact angles required by tungsten tips.

John

 

[goldstar31]

My comments deleted

Regards

An older N

 

[Naiveambition]

If I can remember correctly, I tried a high speed steel , and a carbide bit. Carbide tip was worse.

My toolset came with a bunch of high clearances bits so ima try that. As for the machine, the bed is dated 1929 but the rest of the parts are variously dated up thru the 50s. The bes as a whole still has all frosting marks on it except the high traffic area.
Admittingly I have no experience to relate to except my 7x10 that's nice, quite, and do the job slowly.... Whereas the south bend can be super aggressive, loudish, shakes the table🤓🤓. The shaking is from the pulley system as it rotates it bounces the tension plate for the motor. I've tried to soften it by weight . And while better, still needs addressed. This setup is not typical unless you mount the countershaft on the wall.

The Latern toolpost does have a rocker shim and I am using the Armstrong tool holders. I think all of them have some degree of rake built in.
The south bend manual is kinda vague on instructions so. Is the rocker the center adjustment or do I also shim on top of the rocker?

 

[goldstar31]

As I can claim being part of a pre-WW2 generation and sort of still feel at home with flat belts and hard and fast pulleys and all the delights of having graduated in the University of Hard Knocks, you might do a lot worse than forget '7 by whasits' and carbides and all that Jazz and load up your printer with 500 +sheets and print out Robert Smith's Advanced Machine Tool Work which is still available as a pdf. YOUR machine and its multitudes of set ups is there.

No photos or that sort of thing but decent write ups an d sketches on procedures.

In a fit of idiotic charity, I donated my copy of the book and have regretted it ever since.

Forget those with 'wise saws and modern instances' and immerse yourself in sheer practical engineering.

Regards

the Ancient N

 

[doc1955]

Here is a very easy way t set your tool height on the lathe. And nothing special is needed.

[ame]https://www.youtube.com/watch?v=vpCu56O8AJ0[/ame]

 

[kuhncw]

What material are you cutting when you get the poor finish?

Chuck

 

[Naiveambition]

I also am a super fan of all things old , quite simply cause they work well and are well made. So when I am not figureing out why it won't do what I want, I am usually missing one little thing, and then it's bliss.
I was turning stainless I think, possibly a good tool steel.
Same with the lathe. I'm hoping it's just a rake issue. I just can't understand the need for rake built into the holder vs being level.
What's the disadvantage or advantage of this system. The tooling used in my book are different from what I have. So again no real reference. I will look at the book goldstar suggests

I like the smallness of the Latern , but only accepts 1/4 in. Bits, so if I can I will use it often. Will build a toolpost for other bigger toolbits I can use.

 

[kuhncw]

A good finish on some types of stainless steel, 304 for example, can be a challenge. Have you tried test cuts in 6061 aluminum, brass, and perhaps 12L14 steel?

Chuck

 

[10K Pete]

I'm hoping it's just a rake issue. I just can't understand the need for rake built into the holder vs being level.

Tool holders with a built-in rake angle are for just that purpose. Saves you having to grind the second angle on the rake surface.

The no-rake holders were for brazed carbide tools.

I wish I had a set of Armstrong holders in 1/4", 5/16" and 3/8". There are some jobs where they are much easier than a QCTP.

Pete