Carriage stop

[BelgiqueB]

Novice question here, how do you use a carriage stop, do you actually let it autofeed into the stop and rely on the 'clutch' system in the carriage feed, or do you stop it before it touches and handfeed it into the stop?

I've been stopping before and hand feeding it in, but you can see a difference in surface finish then, haven't been brave enough to let it autofeed into the stop .

Thanks, Christof.

 

[mtt.tr]

Test yours by spinning the chuck by hand. Depends on the lathe you own

 

[Spark plug]

I always stop before the carriage stop, it’s the way I was shown at collage and have continued ever since.

With practice you get used to stopping the feed very close to the stop and seamlessly continuing the feed by hand.

 

[brightspark]

if your not happy in case of hitting the stop just slightly tighten it sufficient to hold so if you do hit it under feed it will move.cutting close to the chuck gives you a good incentive to get it rite

 

[Agroshield]

If the lathe manufacturer provides an auto-trip facility in the machine, why would you not use it? Look at leadscrew dog clutches used for screwcutting in high-end stuff. Are they not working on the same principle?

See date on frontspiece of this for an idea of how old the concept is:

https://archive.org/download/machinestopstrip00hornrich/machinestopstrip00hornrich.pdf

As matt.tr says, if you do want to drive into it, you would be well advised to service and lubricate the trip mechanism in the apron and verify its operation is 100% reliable* cutting air. You also need to work out how hard to tighten the stop and ensure the securing mechanism is also reliable. Put a dial indicator downstream of it and drive into it a few times. It should not move.

* that means testing it over a representative selection of the feed rates and spindle speeds your machine does.

 

[Pete.]

If you've got adjustable clutches like my Monarch then you could set them to slip but then it might slip during heavier cuts too. I just stand in attendance and feed the last few thou.

 

[BelgiqueB]

The manual states 'A safety mechanism on the feed drive disengages in case of overload both the main and the crossfeed carriage', unclear if this is meant only in case of 'cockup' or to be used regularly.

I'll give it a try as suggested here by hand and see what happens.

 

[addjunkie]

The manual states 'A safety mechanism on the feed drive disengages in case of overload both the main and the crossfeed carriage', unclear if this is meant only in case of 'cockup' or to be used regularly.

I'll give it a try as suggested here by hand and see what happens.

Shear pin?

 

[mtt.tr]

What lathe is it?

 

[ryan2020]

Novice question here, how do you use a carriage stop, do you actually let it autofeed into the stop and rely on the 'clutch' system in the carriage feed, or do you stop it before it touches and handfeed it into the stop?

I've been stopping before and hand feeding it in, but you can see a difference in surface finish then, haven't been brave enough to let it autofeed into the stop .

Thanks, Christof.

you need to say what lathe you have?

 

[BelgiqueB]

Staral (Jones & Lampson) 190

 

[Agroshield]

The manual states 'A safety mechanism on the feed drive disengages in case of overload both the main and the crossfeed carriage'

If it is described as a 'safety' mechanism in case of 'overload', it is NOT meant to be relied on for routine, everyday use.

Do you use the breaker in your consumer unit to switch off the coffee machine? Do you trigger the ABS in your car every time you stop at a traffic light?

The exploded diagram of the apron from the manual would show the trip mechanism (if any). The safety mechanism is likely to be in another place altogether, a shear pin as suggested above, that will require some disassembly to access and repair.

 

[Pete.]

The manual states 'A safety mechanism on the feed drive disengages in case of overload both the main and the crossfeed carriage', unclear if this is meant only in case of 'cockup' or to be used regularly.

I'll give it a try as suggested here by hand and see what happens.

'In case of overload' suggests unintended use.

My Denford had a collar on the feed shaft that you could set with an allen key. I think it was meant to prevent you from running the toolpost or compound into the chuck. It was a sprung-loaded dog in the gearbox. My Monarch also has the feature but I've yet to investigate how it's activated, it seems to me that it relies on you never moving the compound. I guess for production runs it could be handy if the operator is busy de-burring or something.

 

[RichardM]

My Boxford works as above, BUT the stop (in picture) is moveable along the lathe bed and has an adjustable micrometer as well.

Slipping load is set on the apron for this.

 

[BelgiqueB]

Plan of the carriage drive system below, looks like part 3/42 might be a spring loaded gear that disengages when there is too much torque on the shaft.

3/14 is the half nut shaft, 3/17 is the carriage drive shaft.

 

[Pete.]

It does look like an overload with no facility to se it. My guess is that the feed rod is sprung loaded the other end as there doesn't seem to be room for a spring in that housing.

Perhaps some tentative testing is in order - after you've verified that the rod does slide and isn't gummed up.

 

[Gritineye]

Just put a dial indicator next to the stop, zero it to match the stop position.

Then you can see when you're within a few thou of the shoulder on the part you're turning, then the difference in the tiny hand fed surface won't show.

Here's the combined one I made, easy project for a beginner, which I was at the time.

Threaded screw is the stop.

 

[Kram]

Depends on the lathe. I have added a switch to my carrage stop that fits on the micrometer so its got fine adjust, which instantly shuts off using the vfd fast stop.

 

[Agroshield]

That is for sure an overload device for the feeds. It looks as if it works on the same principle as RichardM's Boxford above. The zig-zag line is the spring, pushing the balls outwards, which probably locate in dimples in the outer part. When the force overcomes the spring tension, balls go inwards towards the shaft centre and the clutch slips. Same as in a cordless drill but radially instead of axially.

The feed shaft and leadscrew are not numbered on that diagram. It stops at the gearbox output and at the parts that belong to the gearbox. The shaft and screw will be on another drawing. Trace the line for 3/17. It is not the shaft but the big lump under 3/6.

The difference between a safety overload and a trip device is that on a trip device, you can walk away from the machine and when it trips the machine will just stop cutting with no pressure/load on anything. The overload clutch will just keep turning and slipping until you come back and disengage the feed to take the pressure off.

If you find the manual for a Colchester Bantam or Chipmaster or Harrison 10AA, you can see details of an auto-tripping one.

On your machine, it would be worth a good study of the manual, and if it is text-searchable, look for 'shear pin'. That is normally the way the leadscrew safety overload is done. There is not one immediately obvious in your drawing above, but it is worth finding it and checking it is of the proper specification (soft steel or brass) before you crash the machine. Sometimes it has been known for the shear pin to be replaced with something inappropriate - the 4" nail equivalent of a 5A fuse.

 

[Pete.]

That is for sure an overload device for the feeds. It looks as if it works on the same principle as RichardM's Boxford above. The zig-zag line is the spring, pushing the balls outwards, which probably locate in dimples in the outer part. When the force overcomes the spring tension, balls go inwards towards the shaft centre and the clutch slips. Same as in a cordless drill but radially instead of axially.
.

Of course it is. I imagined the saw-tooth to be triangle engagements.

I checked out the feed trip on my Monarch, it pushes the rod axially against a spring until a drive spline slides apart.