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Excessive friction when threading in reverse, but not in forward

Hi rimcanyon, thank you for the reply.

Yes, I realize that I need to keep the saddle and apron together to adjust the half nut clearances. And I know that the goal is to have an indicator show zero vertical deflection of the lead screw as the half nuts are engaged. But I don't know how the nuts actually get adjusted, and none of the reading I have done mentions how to do it. So I thought that I had no choice but to to drop the apron to try and figure it out. But if it is possible to adjust the half nuts with the carriage in situ, I would love to know how to do it.

I did answer Mike's question in the later part of Post #8: I do keep the hold down blocks adjusted tight and I fitted them with all new bearings. I admit that I didn't fully appreciate until now how reverse cutting inverts all the the cutting forces. But again, the original friction problem happened even with the tool retracted from the work, meaning cutting forces weren't a factor.
 
Adding to Michigan and M-luds thought train... In effect the work piece is pulling your tool into the work when you run in reverse upside down. Are you taking out the backlash by backing your tool away from the work when you make your settings? if not, your tool will be pulled tighter (deeper) into the work and possibly do what you're mentioning. Any tie you try something new its a process. Don
An exceptional good consideration Don points out..That that the tool/cutter's rake angles to be suited to the material, and how the actions should be best suited to position cutting forces in the best way.
 
Hi rimcanyon, thank you for the reply.

Yes, I realize that I need to keep the saddle and apron together to adjust the half nut clearances. And I know that the goal is to have an indicator show zero vertical deflection of the lead screw as the half nuts are engaged. But I don't know how the nuts actually get adjusted, and none of the reading I have done mentions how to do it. So I thought that I had no choice but to to drop the apron to try and figure it out. But if it is possible to adjust the half nuts with the carriage in situ, I would love to know how to do it.

I did answer Mike's question in the later part of Post #8: I do keep the hold down blocks adjusted tight and I fitted them with all new bearings. I admit that I didn't fully appreciate until now how reverse cutting inverts all the the cutting forces. But again, the original friction problem happened even with the tool retracted from the work, meaning cutting forces weren't a factor.

I think this will be the same for a 10EE

(post #20)

Also, removing the apron there may be an oil pipe to disconnect although ISTR that later 10EE's have a transfer port rather than a pipe.
Hope that you can get to the bottom of the problem.
 
Thanks for that, CarbideTip. I dropped the apron today and basically discovered the same adjustment mechanism as you describe: oversize holes in the half nuts. Probably not too difficult to set properly when the apron is taken to bits as yours was, but likely to be a bear to set on a fully assembled apron. So what I decided to do on my lathe is based on knowing that when the half nuts are engaged, the lead screw gets displaced downward visibly. So I simply loosened the top half nut and pushed it all the way upward before retightening. I then engaged the half nuts and checked that lead screw turned freely and had minimal play. Hopefully it will have acceptable alignment when the apron is reinstalled.

I also discovered that the four screws that hold the half nut retainer piece on the tailstock side (not the one with the reverse plunger interlock) were only finger tight. This is due to my own oversight from when I originally rebuilt the apron. So I am hoping that between increasing the upper half nut clearance and the tightening the half nut retainer bar, the original problem will be resolved. I will post results when I get the apron on, hopefully tomorrow.

BTW, this 1959 square dial has the oil transfer port, sealed by a little cork washer. I know I should replace it, but I don't have a spare handy, and this one looks to be in perfect condition, so back in it will go.

Cheers!
 
I got the apron reinstalled with no problems. Checking the lead screw deflection when the half nuts are engaged, I found that it now gets displaced upward a little. Fortunately, the lower half nut's lower adjustment nut is accessible with the apron in place. A little tinkering with it allowed me to adjust it so that there is only 0.002" deflection. There does not seem to be any significant play in the lead screw engagement, and the half nut lever engagement is now positive and locks nicely in the engaged position. It is quite possible my half nut adjustment had been too tight all along. I don't do much threading, so it is not something I would have encountered in normal use.

Now I just need to "clock" the chasing dial, since it is a little off. Any advice on how that is done? Hopefully without dropping the apron again!

Also, unlike CarbideTip's beautiful CVA, my EE doesn't have an oil tube feeding into the half nuts. I looked for hidden oil passages, but didn't find any. How does a '59 EE lube its half nuts?
 
Duh. I forgot to mention the most important part: the feed screw drives the carriage smoothly in both direction with no discernible straining of the motor drive! So I am going to call this issue resolved.

Thanks to everyone for their advice and comments!
Dave
 
BTW, Any checking of the adjustment of the half-nuts should be done with the carriage all the way to the right, where the half-nuts are closest to the bearing support and the leadscrew has the least ability to deflect. When the carriage is all the way to the left, the half-nuts are near the middle of the leadscrew, where it's the easiest to deflect.

You may also want to use indicator to verify that the leadscrew is parallel to the ways (mine isn't).

Cal
 
Also, unlike CarbideTip's beautiful CVA, my EE doesn't have an oil tube feeding into the half nuts. I looked for hidden oil passages, but didn't find any. How does a '59 EE lube its half nuts?

The top half nut has a hole that aligns with a hole in the back of the apron that itself is fed oil from the little sump on the top of the apron. When the drop the half nuts on the leadscrew the hole in the nut lines up with the hole in the apron and the oil drops out.

In my experience the hole in the half nut is often clogged.
 
Thanks, Cal. Yes, I did check the half nut adjustment with the carriage at the far tailstock end for just the reason you mentioned. But it never occurred to me to check for lead screw parallelism with the bed. It is a bit of a contortion to get an indicator on the lead screw, so maybe it finally time to buy that Noga holder I have been lusting after!

And thank you Russ for the explanation about oiling. I did pass a fine steel wire down the two oil passages exiting the little sump before reinstalling the apron. The tube to the feed gear was clear. The other passage seemed clear but I could not totally verify it, since I couldn't see the where the wire end came out. But I have been pretty careful to clean all of the oil passages on this apron, so I am hopeful the half nut passage is clear. And now that I know how it works, I can devise a means to test it. So thanks for that.

This apron had what I think was a QA lapse at the factory: one of the copper tubes was cut too long before being installed in the elbow that is fed by the oil pump, and that extra tube cut off the oil flow. It took me hours to figure out why the freshly rebuilt pump wouldn't deliver oil. Turned out the elbow was blocked, and trimming the tube back fixed it. So I am a little sensitive to this apron oil flow...

And now the last bit: how do I align the marks on my chasing dial, other than using a Sharpie to make new ones?
 
In my experience the hole in the half nut is often clogged.
Yes, both the aprons I took apart had the hole in the half-nut blocked with muck.

And you've saved me some time too ... It had never occurred to me that the thread dial could be out of sync. I will remember that when it goes back on.
Thanks.
 
Pilot error, sorry. I had another look and the chasing dial is fine. The half nut engagement point on the dial is just a bit different when the motor is running in reverse compared to running forward. I will chalk that up to 63 years of wear….

But as I think about it, I don’t think it is possible for the dial to be out of sync. It just displays the relative position of the carriage and an arbitrary reference point on the lead screw thread. As long as that relative position is an even multiple of the thread pitch you are cutting, the half nut engagement is correct. In other words, if the chasing dial gear is one tooth off the “correct “ engagement point on the lead screw, you would just have to engage the nut on the prior or next lead screw revolution. As long as it is the same from pass to pass, the threading works.

Or maybe I am mistaken. That happens frequently.
 
I can’t see how shifting the thread dial by a thread will do anything useful…

Re: adjusting the half nuts, when the half nuts are fully engaged, try and move the carriage from side to side with the hand wheel, check it with an indicator. Keep adjusting both half nuts until you have it dialed in.
 
The DRO currently shows 0.007" of lateral carriage motion with the half nuts fully engaged, which seems a bit much. Probably okay for the kind of home shop work I do, but I will try to improve it. It is a Monarch after all, and it has its pride. People would talk...

Any idea of the original factory spec for this? Tenths I would imagine.
 
I was able to readjust the lower half nut to reduce the lateral carriage motion to about 0.0015” when the half nuts are engaged, so I think I will end the repair project here. Thanks again to all of you for the advice.
 
OK so i am confused. OP stated that he was attempting to cut left hand threads by turning the tool upside down and running the spindle in reverse....
Correct??????
So the tool and carriage is moving toward the head stock, yes....Therefore the lead screw is rotating as though you were cutting right hand threads, and
therefore the thrust is the same as cutting RH threads....the end gearing at the spindle is in reverse, and the spindle is going in reverse.....but the
gears in the QC box are turning normally as in RH threads. Thrust on the screw is also unchanged from RH threads...
Think you got to look elsewhere....The half nuts are working same as normal RH threads, if that was working normally on RH thread work, then i suspect the issue is
further upstream.....Does the spindle run fine in reverse if not threading?
Cheers Ross
 
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OK so i am confused. OP stated that he was attempting to cut left hand threads by turning the tool upside down and running the spindle in reverse....
Correct??????
So the tool and carriage is moving toward the head stock, yes....Therefore the lead screw is rotating as though you were cutting right hand threads, and
therefore the thrust is the same as cutting RH threads....the end gearing at the spindle is in reverse, and the spindle is going in reverse.....but the
gears in the QC box are turning normally as in RH threads. Thrust on the screw is also unchanged from RH threads...
Think you got to look elsewhere....The half nuts are working same as normal RH threads, if that was working normally on RH thread work, then i suspect the issue is
further upstream.....Does the spindle run fine in reverse if not threading?
Cheers Ross
pretty sure it is threading away from hdstock
 
pretty sure it is threading away from hdstock
Your correct, He was threading away from the headstock.

First paragraph, post #1, this thread.
DaveC said
I experienced an odd problem with my 1959 10ee. Having watched Joe Pie's YouTube video on the subject, I tried cutting a standard right-hand thread with the spindle in in reverse and a single-point tool upside down in the tool holder. Everything seemed fine at first, but as the carriage proceeded toward the tailstock, the motor began to struggle as if under a high load


In JOE Pie's videos he always threads away from the headstock.
 
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