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Leblond lathe feed rod issue.


Dec 21, 2023
Hello all,
Backstory: I recently purchased a Leblond 14x30 servo shift toolmakers lathe. I’m new to machining but was hoping to go the buy once cry once option with this nice old American made lathe. When I inspected the machine everything seemed tight it took every gear first try and the ways had only the tiniest amount of appreciable wear. The machine did have 14k hours which scared me but it was as much as I could justify for ranch work.
Problem: After getting the machine home and running it for some small jobs it missed its first gear. Since then, has missed gears regularly but I can get it into gear by shifting it around. Anyway I was making a few cuts, shifted gears and the feed rod stopped turning. There is no movement in the feed rod or leadscrew. No matter what I gear I try. The coupler at the change box is turning so I don’t think it’s the shear pin there. Anyone have any ideas? The users manual says something about a safety overload device on the feed rod but it is pretty vague. Thanks in advance!
By shifting gears, I really hope you are turning the machine off, then wiggling the chuck or feed screw or other moving parts during a gear change. You can't just change speeds or gear ratios while something is running like you would a car with stick shift.
You did get the manual for that, didn't you? You can find manuals for the servo shift on line for free.

I do not have a servoshift, but I think the deal with them is that you can change the speed while the lathe is running and it will shift to the selected gear once the spindle stops. Could be wrong on that.

There's a push in collar by the gear box to engage/disengage the lead screw. You generally only have that engaged (pushed in) when you're cutting threads.

I'm not quite clear here. You say the collar outside the gearbox is turning but the feed rod isn't? Make sure your feed selection and the appropriate headstock selectors are engaged. They might have gotten jogged a little; it doesn't take much to disengage the gear train.
It might be a handle isn't engaged all the way. Put it in a higher spingle speed turn off the power and wiggle turn the chuck back and forth and try moving the small levers to the extremes. If the feed and tread rods aren't turning I suspect there is either a key sheared inside the quick-change, a key is sheare, or a gear is disengaged on the on the swivel on the left that feeds the quick-change (im getting forgetfulness on what it's called. One of the others can help withe name). You will have to remove the quick-change if the swivel deal is engaged and turning the gears. Many times if a feed gear key is sheared, the gear is buggered up and still turns, I would use. 2 flat blade screw drivers to hold and pry to turn the gears to find the sheared key.
Appreciate the feedback sorry If I wasn’t clear the feed rod is stationary all the way to into the gear box including the collar it goes into. I always put the brake on while the machine is shifting. I have shifted the gears on the speeds and feeds into many different orientations and nothing. If I engage the feed rod while the machine isn’t turning it freezes the carriage indicating to me that the feed rod is in gear….I guess I’m going to have to get into the quick change gear box 😬
Remove the large cover at the LH end of the headstock.

There is a "porkchop" shaped casting that is radially adjustable to set the clearance between the input gears to the quick change gearbox.

Check that these gears are in mesh as the "porkchop" (known as the quadrant) may have slipped out of adjustment and the quick change box drive is no longer engaged.

If this is the case, place a dollar bill between the input gears (to ensure some clearance) and adjust/tighten the quadrant casting.

The LeBlond Tool & Diemaker lathe (which is what I glean from the original post) also has a length stop feature on the lowest feed rod.

There are rectangular clamp-on dogs at both ends of that feed rod, which can be set to contact the carriage and stop the longitudinal feed.

You should check these stop dogs to verify that they have not been activated by the carriage and also shift that lowest feed rod into a definite position, not floating between fully engaged and disengaged.

I think you'll see how this feature works when you pull the LH headstock cover as it works a lever that ultimately disengages a single tooth dog clutch inside the headstock.