Logan 200 Slow Half Nut Engagement?

[expressline99]

So on my Logan...being a clutch-less / plain apron design the movement of the carriage relies on the half nut. ...
Probably if you're reading this you already know that.

However, on my unit when trying to engage the half nut it doesn't seem to engage right away. Even with a super
high feed rate. I can't imagine trying to single point thread with it like this would even be possible. The lead screw is in decent shape. The threads aren't sharp or excessively worn from what I can see... I recall when I had the half nut off to clean everything up that it didn't appear overly worn either.

So what else could I look at or attempt to measure that could cause this? Or am I just out of my mind? Using other peoples lathes (OPLs) with clutch designs seem to engage quickly...

Paul

 

[wa5cab]

Paul,

It isn't clear whether you are saying that when you try to close the half nuts, it stops part way down for a while and then drops the rest of the way, or once it is all the way down, there is a noticeable time lag before the carriage actually begins to move.

If the former, use the threading dial to tell you when to engage the half nuts. Depending upon how much the nuts and screw threads are worn, for 80 to 90% of each lead screw revolution the nuts will not close.

If the latter, with the motor off engage the half nuts. With the carriage traverse hand wheel, rock the carriage back and forth. Axial movement of the lead screw shouldn't exceed about 0.005". If it is more than that, adjust the lead screw end float. Make a temporary U-shaped shim 0.002" or 0.003" thick to fit between the LA-166 Left Bracket and the LA-169 Collar. Loosen the set screw in the collar. With the shim in place, push the lead screw to the right, the collar to the left, and with your third hand tighten the set screw. Pull out the shim and repeat the carriage rock test. If it still seems excessive (I don't have any hard figures on this), investigate the half nuts (both threads and fit in the LA-351-1 Half Nut Plate (Guide)), lead screw threads and loose LA-351-1.

 

[expressline99]

Robert, Sorry I wasn't clear. This is when I'm trying to close the half nuts it stops part way down for a while. I will have to put the thread dial into position tomorrow and try this. I have it titled out to reduce wear I suppose?

I figured this would be a different issue than the lead screw adjustment and that's why I started another thread. I didn't ignore the adjustment you had given me before and I did that. It did tighten up the slack I had from before with the collar being put in it's place.

Maybe it will be more clear to me with the thread dial in place and giving me a reference point.

 

[Terrywerm]

Robert hit the nail on the head, but what is happening is when you try to close the half nuts, the high part of the thread on the half nuts are hitting the high part of the threads on the lead screw. When this happens, the half nut lever stops until the threads line up enough to allow the half nuts to drop fully into the lead screw threads. Long story short, what you are seeing occur is completely normal. Using the threading dial will help a little bit, as it will show you when the threads are lined up, allowing the half nuts to line up and drop right in.

 

[Bob Korves]

So on my Logan...being a clutch-less / plain apron design the movement of the carriage relies on the half nut. ...
Probably if you're reading this you already know that.

However, on my unit when trying to engage the half nut it doesn't seem to engage right away. Even with a super
high feed rate. I can't imagine trying to single point thread with it like this would even be possible. The lead screw is in decent shape. The threads aren't sharp or excessively worn from what I can see... I recall when I had the half nut off to clean everything up that it didn't appear overly worn either.

So what else could I look at or attempt to measure that could cause this? Or am I just out of my mind? Using other peoples lathes (OPLs) with clutch designs seem to engage quickly...

Paul

 

[eeler1]

For power feeds, you don't use the thread dial, or at least you don't need to. Normal, what you are going through. Been explained above why.

 

[wa5cab]

No, if you try to engage the half nuts at random, you are causing unnecessary wear on the nuts and to a lesser extent on the screw threads. It will feel like something is grinding until they suddenly engage. If you are concerned about wear on the threading dial gear, don't. It takes virtually no force to rotate it, and after 35+ years, there is still no appreciable wear. Assuming of course that you take the time to hit all of the necessary lube points every time that you use the machine.

 

[expressline99]

Well I set the threading dial and hitting the lines worked like a charm. I swear if something is too simple it will fly right by my grasp. Thanks to all of you for setting me
straight.

Great video there Bob. I haven't seen this guy before. Going to subscribe to his channel.

 

[expressline99]

No, if you try to engage the half nuts at random, you are causing unnecessary wear on the nuts and to a lesser extent on the screw threads. It will feel like something is grinding until they suddenly engage. If you are concerned about wear on the threading dial gear, don't. It takes virtually no force to rotate it, and after 35+ years, there is still no appreciable wear. Assuming of course that you take the time to hit all of the necessary lube points every time that you use the machine.

I do keep the lathe ways cleaned and lubed. The gears and all oil caps squirted. Today I got a new set of felt wipers to replace the old ones. I had cleaned the lead screw in detail last year when I painted this thing. I have to make a oil dauber to go in my tail stock. That hole needs the proper part in it.

 

[wa5cab]

Heh heh. I tend to be the same way. If a machine originally had a part, I want it to still have the part. Even if it's unlikely I will ever use it (I still have the lantern tool post and full set of holders that originally shipped with my lathe - and haven't used them since about two weeks after buying the lathe). But I will add one thing - the well in top of the headstock originally held the politically incorrect white lead. Which was routinely used on dead centers, before affordable decent live centers became common.