Thread: AL250G threading problems. Any AL250 owners with ideas

I am a bit lost here..... The first picture is very small when you click on it...

What bit is the nut coming loose on?

It is it the driver or the driven gear and I had to guess I would guess the gear is missing a key and is slipping under load and winding the nut off as it slips..

All driver and driven gears have to have a positive drive to the shaft they connect to..

Originally Posted by .RC.

I am a bit lost here.....

Same here, pictures make no sense.

Wild stab in the dark. When the nut is tight is the idler gear free to rotate on its shaft?

Did you change the gearing from what you were using that was working?

Stuart

This is the gear train to drive the power feed.

The idler gear runs on a shaft.
The shaft has collar, and one end is threaded to go through an adjustment arm where it is held in place with a nut.
The gear runs on the other side of the collar and is retained with a washer and circlip .
The gear runs freely on the shaft.
When the power feed is engaged, the idler gear shaft seems to 'unwind' out of the retaining nut.

I might be seeing things that arent there but the left hand side of teeth on that gear look a little messed up.
Is that first picture how it runs or what it looks like when the nut is undone?

Stuart

The first picture is still very very small...

I would say your problem is a missing bearing or a washer that is too big and hitting up against the outer ring of a bearing... When you tighten it all up I take it the gear goes tight as well.. When everything is tight the gear should spin free as a bird...

Undo the banjo, let it flop out of mesh with the others gears... Tighten it up as in use and give the gear a spin... I imagine it will be tight..

Hi Stewart,
Here are some better pics.
The gear in question is the second one from the bottom. in the pic 4010543
The teeth are intact

I removed the gear and shaft so you can see where it fits and both ends of the shaft.
You can see the nut in the slot of the adjustment arm in pic 4011551
The presented problem is that when the power feed is engaged the 'idler' gear ( the one in question) somehow manages to unwind the threaded shaft.
Beats me how.

So the gear you are holding in your hand spins freely around the shaft when its off the lathe and also when the shaft is attached to the lathe.

HI RC,
Thanks for your interest.
I understand what you are getting at, but the gear does spin free as a bird on the shaft when everything is tightened up.
The only change I have made is to replace the 8mm thread with a 10mm with a finer pitch to try and create more anchor when the nut is tightened.

I also rang Hare and Forbes and spoke to the 'lathe man' and he understood what I was explaining but said he has never heard of this happening before.

How much clearance are you leaving between gears?

The quadrant appears to have some damage which many explain the uneven wear I think I am seeming.
It may result in some side load that undoes the bolt?
Whats the Diameter of that collar and width of the slot? machining that slot from 8mm to 10mm gong to reduce the clamping area you have greatly I would think.
Do you have clearance between the large gear and the collar?

I'd be tempted to put it together and then take the e-clip off that shaft and see if the gear gear works its way off or the shaft still comes undone......... but I'm really clutching now.

On my lathe when I got it the alignment of these gears was ....."not good" it did take some tweaking but then it wasn't coming undone.

Stuart

Stewart,
I transformed the thread to a M10 x 1.25 left hand thread and nut this afternoon. (That's a story in itself.)
It seems to have fixed the problem
BUT what you are recommending has merit.
If you say that the gears might need 'tweaking' than I can appreciate how this may play a big part, and I will get a little stool to sit on now, and take the time too get everything running 'true'.
I will remove the circlip and washer on the idler gear and turn things over by hand and see if that encourages the gear to walk along the shaft.
Thank you for your guidance.
I guess I have something to think about over Easter.
warm regards
Brian

Use a nylon collar lock nut.

The only way the spindle can come undone is if the gear is binding on the spindle. Looking at the damage on the backing plate I would say the spindle may be seating in the damaged area so throwing the spindle/gear off at an angle. Any tendency for the idler and spindle to be thrown off skew may only show up under load, so before checking you will probably need to load up the gear train by engaging half nuts, lightly engaging the cutting tool, turning the chuck by hand and then checking with feelers. Given the damage on the backing plate, I’d say the problem is either at the bottom between the idler gear and the backing plate and/or at the top between the idler gear and the gear behind
Stuart may well be right, but my experience tells me any gear not secured will come off the spindle anyway - almost always when you are almost finished cutting a thread.

Thanks Sacc---good point, something for me to look at in the morning
regards
Brian

Nearnexis,
The first thing I tried--right at the start was a nyloc nut--no difference--it just unscrewwed