A Sennca Falls Lathe questions

"It is apparent after using it briefly that the apron has NO lockout that prevents one from simultaneously engaging the longitudinal feed and the half nuts."

DoN, I am not sure what I would look for. I had always used the half nut lever to engage the carriage meovement. It was only after getting a couple of old books on lathe operation that I learned I wasn't susposed to do this. I actually find it easier to use the lever. I have to think which way to turn the star knob to stop the carriage. That scares me when it gets close to the chuck or face plate.

John

I seem to recall that the feed is a slip engage type not a hard set half nut. If both were engaged (as is on my Sheldon it is possible) the half nut would easily win.

The longitudinal feed as you say is a Friction feed as I know.

Martin

With the lathe stopped, see whether it is possible to engage the half-nuts lever while the power feed selector is in either of its extreme positions -- for either cross-feed or longitudinal feed.

And, with the half nuts engaged, it should not be possible to move the power feed lever into either the cross or longitudinal feed positions. But that presumes the existence of a neutral central position, which may not exist.

Another possibility might be some kind of interlock to prevent tightening the clutch star wheel, even though the direction selector is in one of the active positions.

I can understand that. Though the star knob can be adjusted to allow the drive to slip when it hits a stop (say a bed mounted micrometer adjustable carriage stop). You can even adjust it light enough so you can stop the handwheel by hand while your other hand backs off the star wheel. Test this out some distance from anything important, and at a slow speed (ideally, in back gear) -- since your star wheel *might* simply engage a dog clutch, with no slip.

Hmm ... as for which way to turn the star knob to stop -- I presume that it is CCW. Which direction does it turn while feeding towards the headstock/chuck? It might be that all you need to do is to grip it under these conditions and it will loosen. And for the cross-feed (which you can't do with the half-nuts anyway), check which direction it cross-feeds when the settings are right for longitudinal feed towards the chuck. Mine will feed out under those conditions, so I have to reverse the tumbler to face in from the OD.

Better than my Clausing there, since it has direct gears with no clutch. But the Clausing has a lever which slides and rotates in a slot like this:

Thank you DoN for the info. I will look at it and experiment with the lathe in the morning. As I recall, the half nut lever will drop out pretty easily. I sometime have to hold it up or it drops and the carriage stops moving. Maybe I done have something adjusted correctly. I really haven't done much with it. I wish I had learned more while my father was still alive. I am more of a woodworker, so that is what I used it for. I just replaced my Sears wood lathe with this lathe when I inherited it.

Over the last year I have been designing and building a T-38 flight simulator cockpit. In 1972 Uncle Sam actually paid me to go to USAF pilot training. I have loved the T-38 ever since. I am trying to make the simulator match my 30 year old memory of what it felt like to fly. My goal is to trailer mount it and bring it to Civil Air Patrol, Boy Scout meetings and allow young people to get a taste of flying a jet.

In my quest for simulated authenticity I have had to learn how to weld and do simple machining in order to build the rudder pedals and flight control stick. They are now done and I have started building the cockpit itself. That should be easy. The hard part for me will be the electronics.

Now that I have gotten a taste of machining, I would like to do more.

Jim Rozen what is the spindle threads and taper for your lathe? Also, what taper do you have on the tail piece? I thought mine was something like =BD" to the foot. I made a couple of centers on the lathe using =BD" to the foot taper. They seem to fit. They hold and I have to drive them out with a piece of =BD tubing I stick into the backend of the spindle and tap with a ball peen hammer. For the tail stock, I tried a MT2 it didn't fit. However, my dad use to wrap a piece of thin copper around the MT2 dead centers and they held. I do the same. I know admitting this will probably get me burned at the stake for blasphemy.=20

LOL

John

Trust me on this, Martin. I know what happens when both are engaged, and the spindle starts up. It rips the right hand leadscrew bracket off the machine.

Jim

The spindle is 1.125-12 thread. It's an oddball I know. The lathe came with a faceplate and a chuck. I've adapted a four-jaw to fit that spindle.

Both the spindle taper and tailstock taper seem to be Morse number two. I suspect that at some point in its life, somebody modified them to be MT-2, because I think those machines came with Jarno Tapers in them.

Not at all. I think you can still purchase jarno centers from MSC. The nice thing about centers like that is that in principle they have excellent accuracy, and using the copper as a bodge will degrade that, as well as reduce the rigidty of the setup. Old lathes like this can still do some nice work.

One thing I have not mentioned about my lathe is that the crossfeed handle has *no* graduations on it. If yours is the same then you will be severely hampered by it when it comes time to actually use it to do any serious work, because you will be unable to turn diameters to a tolerance of better than about ten thousanths of an inch.

If your machine was factory-fitted with a graduated dial (a close friend has one which is a bit more recent, and that is so-equipped) then you can disregard the comment. However if you don't have any graduated dial, I would suggest the following approach - if you want to use the machine for serious work:

1) carefully remove the entire crossfeed screw, handle, and bushing. The bushing unscrews from the front of the carriage, pad the wrench so you don't twist up the hex, mine seemed to be almost hand-filed into a hex, not a standard size really. 2) remove the nut from the cross slide. 3) fabricate a new nut, and obtain another crossfeed screw and dial assembly from something like a logan or a south bend. 4) you will have to modify the threaded bushing of the newer assembly to fit into the carriage of your machine I suspect. This would mean either turning it down and re-threading if it is larger, or making up an ID/OD threaded bushing if it is too small.

But this sort of transplant does two things: it allows a modern graduated dial so your machine can be counted on to hit diameters within a thousanth or so. And it preserves the original part which could be re-installed in the machine to put it back into the condition it was in when you got it.

A former owner of my machine was obviously hampered by the lack of graduations, because there are a few that are hand-scratched into the ball handle and the nose of the bushing.

Jim

LOL Jim it sounds like you know this from experience?

I went out and experimented with my lathe. I tighten the star wheel CW and got the carriage moving right to left. I slowly moved the half nut lever upward and watched the half nuts. The nuts would start to close on the turning screw then I would feel a pressure trying to force them open. I think I could override this force and keep the nuts closed manually with the carriage moving but, for obvious reasons I didn't try.

John

No Jim, I do not have a graduated dial on my cross feed. I had to laugh when you said, "you will be unable to=AD turn diameters to a tolerance of better than about ten thousandths of an inch." If I can do two to three hundreds of an inch tolerance I will be happy.

My lathe's spindle measured 1 3/8" by 10 TPI. I believe that too is a non-standard thread. I have a 4 jaw chuck and have considered getting a three jaw. However, I never see any adapter plates with 1

3/8" by 10 threads.

Thanks for the input on changing the screw and adding a graduated dial. I have been thinking of maybe just having a new cross slide with "T" slots made. If I do, I will follow your advice.

However, don't look for that to happen soon. I am busy with my T-38 simulator project. I could build and equip a workshop for what this thing is costing.

John

Oh. I guess you are unaware of the purpose of the funny little hook-latch that is on the front of your apron, in line with the hole in the cross slide. Of course not, looking at your photo I see that you are missing the threaded, graduated shaft that goes in there, like I am.

You can do some moderatly accurate turning this way. It is supposed to have threaded rod with two locking thumbnuts on it, that goes into that hole in the cross slide. The latch flips over and the thumbnuts bear on the outer surface of it, so that the depth of the slide can be controlled much the same way that a drill press depth stop can be used to control the quill feed. It's a tolerably fine thread and has inch graduations on the upper, flat surface.

I know this is what goes there because my friend's star lathe (which *does* have a graduated dial) has one. I've been meaning to copy it for mine. Now there's another reason to borrow it and take some photos/measurements.

Interesting, the serial numbers are pretty close - and I would have suspected that they would *increase* the spindle diameter, not decrease it. You will have to thread backplates single-point if you want to add to your tooling supply.

The nice thing about lathes like that is, you can use them up to and including their ability. And if you want to improve them, there's always a chance later for a side project. Of course this leads to owning more than one lathe, because you need the second one to work on the first one.... etc.

Jim

Eastburn

Then you don't have a friction version or it is set way to hard. Martin

Remember, this a very vintage lathe. It has a bunch of features that might be considered "non-optimal" to the modern lathe user.

The clutch cannot be "set." It is either tight or loose, and it doesn't run in an oil bath. The other salient fact here is that the left-hand side leadscrew bracket is pretty flimsy on this machine. John's lathe is pretty much the clone of mine, so his clutch will behave the same under normal operating conditions.

Which means that simultaneous engagement of power feed and half nuts effectively locks up the leadscrew.

Modern lathes are built to prevent this with a lockout on the half nuts - they cannot be engaged unless the feed control is in neutral. My guess is, if that lockout were somehow defeated in a modern machine, there would be expensive noises if the same thing were done, in spite of the slip clutch.

Jim