# Help with finish Please.



## bronson (Feb 15, 2013)

Hi i have notice that when cutting the length of a chuck of bar steel alum drill rod what ever i get a threaded look highs and lows of about .0005 i am guessing on that. Spindle speeds and feeds don't seem to change this much. I have checked spindle bearing adjustment. Apron adjustment, cross-feed gib adjustment compound gib adjustment different lathe bits different tool posts and i am now at a lose. I run a 1953 southbend 9" model b. When you cut left to right looks like a right hand thread and right to left left hand thread. Please Help :wall::wall::wall:

Bronson.


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## aonemarine (Feb 15, 2013)

.0005" on a 60 year old machine???  You should be happy!!!  I have a 1942 SB 10 K and doubt Im any better than you are...
 the highs and lows are usually the lead screw but for the amount you are talking about, i Would just consider normal for the age.
 to improve upon what you have would take alot of hand scraping and refitting....


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## bronson (Feb 15, 2013)

This is happening just by feeding by hand with no feed screw on i am sorry if i wasn't clear it just looks like threads but i am not threading. Or using auto feed.


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## aonemarine (Feb 15, 2013)

Do you mean that you are facing? or cutting the length of the bed?   Honestly .0005" aint bad at all...


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## aonemarine (Feb 15, 2013)

How about a picture??


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## cwkelley75 (Feb 15, 2013)

Tailstock flexing maybe?


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## Lakc (Feb 15, 2013)

Depends on what your cutting mostly, but you said it happens with everything, so my best guess its the radius on your cutter.


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## bronson (Feb 15, 2013)

It is cutting the length and it will happen on a 1" dia bar stock stuck out 2" no tail stock or a foot long piece with tail stock. I will get a pic tomorrow thanks for all the replies.

Bronson


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## aonemarine (Feb 15, 2013)

cwkelley75 said:


> Tailstock flexing maybe?


 
Doubtful...  Just need to figure out exactly what he is taling about...
funny he said he gets the same results in brass though, tool geometry would effect everything but brass (in a sense).  So now im curious....


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## aonemarine (Feb 15, 2013)

Do you have a quick change gear box?  can you feed automaticly? and how are you engauging the feed on the apron? with the half nut?
Feeding by the handwheel on the apron wont cut it....


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## bronson (Feb 15, 2013)

It doesn't matter how slow i feed with the hand wheel it still happens. If i use the auto feed with the half nuts or the clutch it still happens give me a few minutes i will go make a cut and take a pic be back soon. Thanks again.

Bronson


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## aonemarine (Feb 15, 2013)

OK im here.... I just tried to take a pic of some brass cut with  0' rake bull nosed and 316 ss 15' rake pointed but I cant really get a good shot of it....  will try with other camera....


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## aonemarine (Feb 15, 2013)

facing cuts on 316 ss and 360 brass


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## bronson (Feb 15, 2013)

My facing cuts look just like yours its when i am cutting the length of the bed sorry taking so long for the pics i took a few plugged in the camera and my wife has 6000 photos she hasnt cleared waiting to load.


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## bronson (Feb 15, 2013)

This is going as slow as i can spindle speed as fast as the lathe goes. The tool i did it with.


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## aonemarine (Feb 15, 2013)

It will be hard to judge much from feeding manually by the carrige wheel, feeding by the clutch or half nut will give me a better idea of whats going on.  have you tried snugging up the collar on the back of the spindle.  (this pulls the spindle back against the caged ball bearings)???
 they also tand to get some garb in them that could be your problem....   waiting for pic to  give me more insite...


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## bronson (Feb 15, 2013)

I will check the collar and use auto feed with clutch and get you a pic thanks for the help.


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## aonemarine (Feb 15, 2013)

AHH I see.....  Thats really not tooo bad.... some deflection going on....  looks like 8 to 10 deg rake??   try taking it to 15 and sloow the spindle speed a bit. (biggest head stock pulley)

  Flat belt I assume???


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## aonemarine (Feb 15, 2013)

What alloy???


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## Lakc (Feb 15, 2013)

Just guessing here but:


Loose drive pulley
Worn key or keyway
Motor unbalanced
Chuck unbalanced
Worn leadscrew
bad 3 phase converter
Motor windings
It looks like some kind of vibration is resonating in the bar from the machine, see how the frequency gets higher the further you get from the chuck?


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## t_ottoboni (Feb 15, 2013)

How tight is the belt and how tight is the motor mount?
You may be having trouble caused by 2-phase motor vibration

To read a bit more about it: single-phase-motors-can-effect-lathe-finish-cuts


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## bronson (Feb 15, 2013)

Aonemarine you got it. it was the collar at the end of the spindle i gave it like an 1/8 of a turn did two cuts and it is gone Thank you very much that was great. Love this site. One more question i have two collets one says southbend and has the number 2 on it and is twice the size of a 3c collet do you know what this is for? Thanks again.

Bronson.


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## aonemarine (Feb 16, 2013)

Lakc said:


> It looks like some kind of vibration is resonating in the bar from the machine, see how the frequency gets higher the further you get from the chuck?


 

 I feel this is more deflection from a lite weight machine.. seen it in mine as well.... there is ways around it.... back rake and tool tip radius are critical....sometimes you have to go against the rules... Im talking 20' back rake...  Yea it sounds nuts but works....

 Thats provided the spindle collar is snug and not bumpy when rotated by hand with some drag applied...


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## aonemarine (Feb 16, 2013)

bronson said:


> Aonemarine you got it. it was the collar at the end of the spindle i gave it like an 1/8 of a turn did two cuts and it is gone Thank you very much that was great. Love this site. One more question i have two collets one says southbend and has the number 2 on it and is twice the size of a 3c collet do you know what this is for? Thanks again.
> 
> Bronson.


 
Heck no!!  I have 10 K collets and im still after 20 years trying to figure out what they are!!


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## aonemarine (Feb 16, 2013)

bronson said:


> Aonemarine you got it. it was the collar at the end of the spindle i gave it like an 1/8 of a turn did two cuts and it is gone Thank you very much that was great. Love this site. One more question i have two collets one says southbend and has the number 2 on it and is twice the size of a 3c collet do you know what this is for? Thanks again.
> 
> Bronson.


 
 Glad I helped you out, these old lathes can still kick some butt! ;D


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## bronson (Feb 16, 2013)

That thread about the single phase motors was very interesting. I have replaced my motor about one year ago i run 110 volts 3/4 hp. The belt i run is an automotive ribbed belt which made a hugh difference. My stand for my lathe is not that ridged i need a new one. Thanks again.


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## aonemarine (Feb 16, 2013)

I will have to read that thread... but if the feed is controlled directly by the motor speed I really dont see where it would come into play... except for varying load..hmmm    still shouldnt matter...  speed and feed the same... Geared...


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## Swifty (Feb 16, 2013)

Maybe chuck jaws are worn and not gripping part properly. Some thing is definitely playing up.

Paul.

Should have read last page of posts, I see that it's fixed.


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## chipenter (Feb 16, 2013)

My lathe is a 1930s Faircut Senior that gives a good finish , It is more likely to be tool geometry , the harder the material being turned the more top rake is required on the tool , the larger the radius on the cutter the better the finish with really light cuts , and dead on centre ,  face of without leaving a pip and you know it's right .


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