Help with finish Please.

[bronson]

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.

 

[aonemarine]

.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....

 

[bronson]

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.

 

[aonemarine]

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

 

[aonemarine]

How about a picture??

 

[cwkelley75]

Tailstock flexing maybe?

 

[Lakc]

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

 

[bronson]

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

 

[aonemarine]

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....

 

[aonemarine]

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....

 

[bronson]

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

 

[aonemarine]

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....

 

[aonemarine]

facing cuts on 316 ss and 360 brass

 

[bronson]

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.

 

[bronson]

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

 

[aonemarine]

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...

 

[bronson]

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

 

[aonemarine]

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???

 

[aonemarine]

What alloy???

 

[Lakc]

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?