Stopping with the clutch?

[pntrbl]

More questions from yesterdays fumbling.

I was handfeeding the carraige up to a shoulder that I set with a carraige stop. Is it OK to do this with the power feed and depend on the clutch to slip when the carraige hits the stop? Is that what the clutch is for?

SP

[A.K. Boomer]

I think this depends on the type of machine you have... some have an actual clutch type material, others rely on a loaded ball and an indent, I would not put the latter through any of those phases as i think its more for "just in case", if you really start useing this type for that senario you may find it starts slipping when your just trying to feed...

[JCHannum]

The clutch is not designed to slip when a shoulder or other obstruction is hit. The clutch feed is a separate feed that is driven from the key in the leadscrew or separate feed shaft, and is the means to engage and disengage that feed. It is designed as a positive feed, not as an overload protection.

The standard practice is to engage the clutch and feed to about the last 1/8" or whatever you are comfortable with, disengage and finish by hand feeding.

[pntrbl]

Thanx guys. My Logan has a clutch pack but I'm not sure about the LeBlond I was fooling with yesterday. In any event, I'll follow "standard practice". I'm just glad I have a place to find out what the standard practice is.

Thanx again.

SP

[A.K. Boomer]

The clutch is not designed to slip when a shoulder or other obstruction is hit. The clutch feed is a separate feed that is driven from the key in the leadscrew or separate feed shaft, and is the means to engage and disengage that feed. It is designed as a positive feed, not as an overload protection.

The standard practice is to engage the clutch and feed to about the last 1/8" or whatever you are comfortable with, disengage and finish by hand feeding.

I really think it depends on the machine, some are meant to give a good finish all the way to the end of travel without getting manual with it, at least thats how my friends hardinge chucker is, and thats how he taught me to use it, its not a ball detent machine, its has clutch material and i also think its lubricated... He's been useing it this way for decades...

[John Stevenson]

I don't think there is a standard.
My small TOS just has a spring loaded clutch to break drive in the event of a crash.
My CVA has adjustable clutches so they could be run as to a stop but not sure if they were designed to be used this way.

The big TOS, SN series, has a trip loaded clutch that when it hits a bed stop [ or headstock ] it disengages drive and throws the feed lever into neutral.
This is designed that way and on a few jobs I do like a big thru bore I set the bed stop with a micro switch on it and allow the machine to hit the stop and switch at the run off point.
This way I can set it on auto, walk away and come back when I hear it stop to fit another part to bore.

[ No pic's, the camera is counting to 100............... ]

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[JCHannum]

I really think it depends on the machine, some are meant to give a good finish all the way to the end of travel without getting manual with it, at least thats how my friends hardinge chucker is, and thats how he taught me to use it, its not a ball detent machine, its has clutch material and i also think its lubricated... He's been useing it this way for decades...

As Sir John mentions, Hardinge and other machines have trip mechanisms that will disengage when a preset stop or other obstruction is contacted. This is a quite a bit different than counting on the usual hand clutch to slip. The lathe in question, pntrbl's Logan, is a slip clutch, and has no trip mechanism.

Most lathes do have some form of safety device to prevent serious damage in the event of a crash. Some have shearpins in the leadscrew drive. Plastic or phenolic gears that will self destruct in the event of a jam are another common safety device. Atlas lathes have a shear bracket designed to fail when the leadscrew jams. I am sure there are many others as well.

If you do not know how your machine is set up, it is best to find out how to properly operate it.

[Timleech]

My DSG has a spring loaded clutch on the feedshaft, designed to slip when you hit a stop. AFAIR my old Harrison L5 had the same. Lots of Colchesters had an adjustable trip on the apron.

Tim

[DR]

My 11" Colchester will automatically disengage the feed lever when it hits a hard stop.

Not sure if it's recommended to run up against hard stops though. It's not exactly a "graceful" disengagement. There may be some adjustment in the apron to set the amount of pressure to activate the disengagement, if there is it isn't obvious.

[Timleech]

My 11" Colchester will automatically disengage the feed lever when it hits a hard stop.

Not sure if it's recommended to run up against hard stops though. It's not exactly a "graceful" disengagement. There may be some adjustment in the apron to set the amount of pressure to activate the disengagement, if there is it isn't obvious.

Some of the Colchesters, with a lever sticking towards you from the apron which you lift to engage the feed, the adjustment is by screwing the actual knob in or out.

Tim