Pm1236 1-3 speed selection froze

[FTlatheworks]

There's two of us, and you've worked with both. I've never seen an issue like this one where the gears don't want to slide. Unless I hear a good diagnosis, we'll just replace that whole shaft and gear assembly to be safe.

what’s the lash supposed to be on those?
Please email the cost of those parts. Also, I I’ll try to pull mine and fix them myself, but I’m hesitant to do any boring, or real work on them. I’d be more likely to send them to someone that has more tools and knowledge and could possibly save them for me.

 

[FTlatheworks]

There's two of us, and you've worked with both. I've never seen an issue like this one where the gears don't want to slide. Unless I hear a good diagnosis, we'll just replace that whole shaft and gear assembly to be safe.

So the right side 1-3 gears have no play in them. If the left side gear set is meshed on a-c then the 1-3 won’t mesh without major force, or opening the lid and pushing on the gear opposite of where the shift fork applies its leverage. So the 1-3 gear set has one or two gears that have shifted and bound up on the key and shaft and stuck in that crooked position permanently. So if I disengage a-c gear transmission gear set, 1-3 can be engaged easier, but still not the way it should be.

I think it may only be one of the gears inside diameter and key seat have become too large and allowed the gears to slide at an angle, so the only way to get it to move is pushing on both side of the gear so the bore remains linear with the shaft. When I open the snap ring holding them together a little, they move a bit easier, but this may just be due to me applying pressure closer to the center of the gear, so it isn’t pushed at the angle created by the shift fork.

Whatever it is, it possibly can be taken apart and cleaned up, but I do worry about the fact that a gear or two will not be running concentric and perpendicular to the axis of rotation. I don’t believe I will need to purchase the whole assembly anymore. I think the max will be a new gear on the 1-3 idler/trans gear, or gear set. The minimum will be removing them and running a bushing, or something.

Here is a video showing The number 3 gear can be pushed on and one side and the 180 degrees away from the point I push on will move away from the #2 gear it’s seating against with a snap ring.

 

[mattthemuppet2]

My guess is a burr on the key is causing the problem. You need to remove the shaft and both sets of gears, then you can see what’s going on

 

[markba633csi]

Agreed- there must be an issue with the fit of the gears on the shaft. I suspect the shift fork mech is a contributing factor also, since
he mentioned it doesn't engage the gear near the shaft but instead, toward the outer diameter. Any tendency to jam up will be magnified
as the parts wear

 

[FTlatheworks]

Here’s an update for everyone. They offered to cover the shaft and gear assembly. They said the factory believe it’s a burr, or due to a crash. I explained when the speed selection stopped working I didn’t crash the lathe, but I have had one crash in 2021 while turning square stock. I had the chuck jaws opened wide enough to hit my compound.

I told them if there’s a chance that it was my fault I can’t have them pay for it, even though they insisted. Thanks to all for the help.

 

[ShawnR]

I started a to make a thread about this issue and the engine pointed me to this one.. I am having the exact same problem, switching speeds with the 123 knob. Have pulled the cover off twice now to see what the heck is going on inside. I emailed Tech support just a few minutes ago, before finding this thread. One thing I noted was the shifting lever on the back of the gear looks like it is contacting the teeth of the smaller gear. I tried sticking a piece of paper in there to see if it was binding but it was inconclusive. I am wondering if this is causing a binding in the whole shifting assembly. Also noted the main shaft is not super, glass like, so maybe catching a bit (binding) but I would think that this would have improved with use, wearing it smoother, not showing up after 4 years. I could not detect any slop between gears, as pointed out in the OP videos. But the more I play with it, it does seem that the gear assembly does not slide on the shaft as I would expect, rather than binding due to a misalignment, even when just trying to slide them by hand instead of the knob. Or maybe a burr somewhere as mentioned. I will keep exploring but hopefully tech support will get back to me.

Here is a video. You can see in the video that I "tap" the lateral slide using the change knob and the gears move.

 

[ShawnR]

Here’s an update for everyone. They offered to cover the shaft and gear assembly. They said the factory believe it’s a burr, or due to a crash. I explained when the speed selection stopped working I didn’t crash the lathe, but I have had one crash in 2021 while turning square stock. I had the chuck jaws opened wide enough to hit my compound.

I told them if there’s a chance that it was my fault I can’t have them pay for it, even though they insisted. Thanks to all for the help.

Wondering if you received the new gear assembly, if you found any difference in fit or finish of the new one over the old one, and if it resolved your issues?

 

[xr650rRider]

You should be turning the spindle by hand when you try to change the speeds.

 

[woodchucker]

I agree about moving the spindle.
I also think while the gear is in one location, put a few drops of teflon (liquid) on the shaft , then move the gear over and put a few drops on the other side. Make sure you rotate the shaft so the teflon gets all around. Teflon will make it more much more easily.
The gears need to rotate to sync up. Just a fact of life.

 

[ShawnR]

You should be turning the spindle by hand when you try to change the speeds.

Thanks, yes, been trying that. The issue is the binding on the shaft, not the gears meshing. Sometimes, the gears are not even touching (side to side) and the lever will not move. I believe my issue is the same as what the starter of this thread had. I was just adding my experience to the thread in case this is a common issue with the 1236.

I agree about moving the spindle.
I also think while the gear is in one location, put a few drops of teflon (liquid) on the shaft , then move the gear over and put a few drops on the other side. Make sure you rotate the shaft so the teflon gets all around. Teflon will make it more much more easily.
The gears need to rotate to sync up. Just a fact of life.

I have never seen liquid teflon but will see if I can find some. Thanks