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Books are great but they don't make really basic things clear

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jbmauser

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#1
From the get go I turn with moving the carriage by hand. I have never used the the leadscrew to make cuts and I always get a rough finish. I am working on tool shape. I know about carriage stops, don't have one for my SB 9C lathe but what is the point? by hand you can hit a hard stop but turning with the leadscrew moving the carriage would be a disaster? Do the half nuts pop open when they hit a stop? I don't know and am not prepared to try it.
 

jwmelvin

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#2
For lathes without a clutch on the carriage drive (like my import 10x22), you are right that you do not want to power feed into a hard stop. Doing so will break something (generally the shear pins on the lead screw but possibly gears, etc.). But you can stop just short of the hard stop and feed the last bit by hand. You can mount a dial indicator so that you can see the end of travel approaching with more accuracy than just a narrowing gap, if you prefer.
 

stupoty

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#3
From the get go I turn with moving the carriage by hand. I have never used the the leadscrew to make cuts and I always get a rough finish. I am working on tool shape. I know about carriage stops, don't have one for my SB 9C lathe but what is the point? by hand you can hit a hard stop but turning with the leadscrew moving the carriage would be a disaster? Do the half nuts pop open when they hit a stop? I don't know and am not prepared to try it.

Hello,

You would stop the power feed before the hard stop and move to the hard stop by hand. Some lathes do have clutches for emergency situations and some have auto disengage for the power feed using adjustable stops of some sort.

You might use a hard stop if you were doing repeat parts for example, plus many other uses too :)

A soft stop implies some sort of dial indicator that you use to see where you are.

Stu
 

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#4
Greetings, i suggest you start using the power feed and no carriage stop. The difference in finish quality is like night and day.
 

markba633csi

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#5
Kinda primitive, isn't it jb? Actually requires some input and attention from the operator, imagine that :big grin:
 

Janderso

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#6
You will gain confidence by using your lathe as intended. Take your time, pay attention.
That's my experience anyway. I use my auto feed all the time on my 13" SB., release the clutch when I hit my spot.
Threading, release the half nuts, in your relief area. Pull the carriage back one turn and rinse and repeat.
You will get it.
 

homebrewed

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#7
If you're really worried about crashing the carriage while power feeding you could turn a run-out groove in your work, similar to what is often done while threading. Just make it a bit deeper than the final diameter you want in the piece. Of course, this will only work if you have some extra material to work with. If you are turning a piece on both ends, or need to turn it around to finish it, you can't use this method. But see below.

I have a lathe I modified by adding a hand crank to the lead screw. Engaging the half-nuts and slowly turning the crank produces a pretty decent finish, and I can feel when the carriage hits the carriage stop. And there is no danger of breaking a gear.
 

jbmauser

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#8
Kinda primitive, isn't it jb? Actually requires some input and attention from the operator, imagine that :big grin:
HEY watch that primitive stuff.... it is only a few years older than me.....
 

jbmauser

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#9
Can you cut threads at very slow speed using the back gears? Enough torque?
 

markba633csi

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#10
Of course, one of their main usages, to give slow speeds with good torque
 

Hawkeye

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#11
I made a hard stop for each of my lathes with a dial indicator included. I have it set so that the needle starts turning at the 1/2" point before the hard stop. I can disengage the clutch at about the 0.005" point and finish by hand.
 

rock_breaker

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#12
Yes books are great and I enjoy the ones I have but I am not sure the operators manuals discuss the basic controls thoroughly, sorta like learning to drive different automobiles.
Are you using a small radius on the tip of your cutting tool? I have fond this helps even when hand feeding. Try as we might it is difficult to move the carriage small distances uniformly per revolution of the spindle when hand feeding but the lead screw will do that extremely well.
A lot has been said in the pre-cedng posts about fixed carriage stops, believe every word about potential damage. IMHO metal working machines are like an automobile, they won't drive themselves!
Have a good day
Ray
 

MrWhoopee

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#13
I don't know a lot about SB 9's, but doesn't it have a star-wheel just below and to the right of the carriage hand feed wheel?

Like this:
1540522313710.png
If so, that star-wheel engages the feed clutch, which is used for turning. The half-nuts are only used for threading. The feed clutch is a little more forgiving, it will slip if you crash up against something hard.

Of course, I could be completely wrong. Your 9 may not have a clutch.
 
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Tozguy

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#14
Not sure if I understand your question so must ask if you are looking for a good book on lathe operation?
Using the power feed and lead screw are well described in some books.
I suggest that you set up some practice runs for both operations so that you can build your confidence in using the half nuts and feed clutch/engagement on your lathe. You do not even have to make chips, just run the lathe within safe limits.
To me it was about breaking the ice on both operations as opposed to breaking the lathe. You are wise to want to understand the pitfalls and avoid crashes but this should not prevent you from getting the full use from your machine.
 

projectnut

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#15
One key to a good finish (even when advancing the carriage by hand) is to have the radius of the tool larger than the distance it is advanced with each turn of the spindle. Secondly match the spindle speed (surface speed per Minute) with the material being turned. Also keep in mind one cutting profile does not work for all materials. The profile for copper and aluminum will be different than one used for stainless or cast iron.

Here's a quick tutorial on the different tool profiles used on different materials:
http://www.steves-workshop.co.uk/tips/toolgrinding/toolgrinding.htm

Here's a link to a quick tutorial on speed and feed rates for different materials:
http://www.engineeringenotes.com/in...turning-problems-industrial-engineering/27210
 
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