Does my PM 1236t lathe have a power feed torque override clutch?

[TonyBen]

I was turning a part on my lathe using a collet and I was powerfeeding in the long direction. I had 6 inches of gap between the tool and the collet. Then the powerfeed stops and I hear clicking! Dammit! I didn't realize my carriage/apron ran out of travel and was hitting the the housing that holds the on/off lever shaft and switch!

I shut off the lathe and disengaged the feed. I moved it back and the feed seems to work. Did I damage anything or is there a powerfeed safety clutch that releases under overtorque? To be clear, it was the powerfeed, not the threading half-nut that was engaged.

Definitely a mistake I won't be making again.

Tony.

 

[a smile]

So adding a limit safety switch is necessary!
In my experience, you can add a photoelectric switch or a mechanical travel switch near the chuck to control the spindle motor relay as a final safety barrier.
I think safety is always the first!

 

[Ischgl99]

Yes, it has a clutch and functioned exactly as it should. It’s designed so you can use a feed stop to stop your feed at a set distance, but I’m not sure I am trusting enough to do that. There are two detents with spring loaded balls for the clutch, adjusting the tension on the balls by screwing the set screws in or out is how you adjust when the clutch slips.

Think of it this way, you tested the clutch and know it works!

Edit: added a picture from the manual showing the clutch and the adjusting screws.

 

[TonyBen]

Thank GOD! I always wondered how those micrometer carriage stops worked! I guess I know now.

Tony.

 

[jwmay]

! I always wondered how those micrometer carriage stops worked!

Micrometer carriage stop has nothing to do with it. Don’t use that carriage stop as a stop against power feed.

 

[RaisedByWolves]

Micrometer carriage stop has nothing to do with it. Don’t use that carriage stop as a stop against power feed.
View attachment 496121

This.

The power feed will likely just push the stop out of the way on most machines.

 

[tq60]

Some "real" lathes or production machines have this as a feature.

Our 16-inch L&S has multiple shafts across the front in addition to the lead screw.

One is a stop bar with sliding collers, set the coller, and the drive gets kicked out when the carriage hits it.

The micrometer stop is for HAND FEED. You go until you bump it.

If power feeding you pay attention, turn off power feed and go by hand. Otherwise, something must give when it hits.

Sent from my SM-G781V using Tapatalk

 

[Ischgl99]

Micrometer carriage stop has nothing to do with it. Don’t use that carriage stop as a stop against power feed.
View attachment 496121

I’m not saying I would trust it, but on this lathe, the clutch is designed to stop the power feed by using a movable stop. The set screws for the clutch are adjusted to give you the break away torque needed for that. You still need to shut the lathe off, but it is designed to stop carriage motion when feeding.

 

[jwmay]

I’m not saying I would trust it, but on this lathe, the clutch is designed to stop the power feed by using a movable stop.

I see now what you’re talking about. They do expect that someone may use it that way deliberately, as described in the manual. Oops!

 

[Ischgl99]

I see now what you’re talking about. They do expect that someone may use it that way deliberately, as described in the manual. Oops!

Surprised me as well when I got my lathe. I haven’t tried it yet, and probably never will. I built a proximity stop for threading and would use that as a feed stop before using this. My fear is if you don’t use it often enough, will it release when you need it to?

I was turning a part on my lathe using a collet and I was powerfeeding in the long direction. I had 6 inches of gap between the tool and the collet.

Were you using a collet in the spindle taper? This lathe design leaves the tool too far away from the collet face to do any machining of short pieces in the collet in the spindle, so I ended up getting a 5c collet chuck. It has been working well, but it can be a PITA screwing the collet open and closed on multiple parts. I’m thinking of taking the scroll out of the chuck and using it as a collet nose with a lever collet closer. I’ve had my eye on an Ortlieb lever collet chuck, the price new is not that bad, but it would get pricey getting collets for it instead of the significantly cheaper 5c and ER. https://www.ortlieb.net/fileadmin/o...uadro_Druckspannfutter/Schnellspannfutter.pdf