Thread: lathe autofeed overload?

Ive got the common 12x36inch lathe, (al960b) and was doing some cutting today, blunt tool, in stainless with a pretty harsh feed and depth of cut and the auto feed managed to stall out. Work piece was still spinning away no problem. I didn't hear any worrying noises, and once i changed the tool out to a sharper one it continued on no problems. Before i got tearing into the apron, is there some sort of overload mechanism in these to prevent damaged incase of a stall?

Thanks

Is there a shear pin where the feed rod goes onto the quick change gearbox output shaft?

Originally Posted by .RC.

Is there a shear pin where the feed rod goes onto the quick change gearbox output shaft?

feed rod was still turning from memory, but ill have a look tomorrow.

Its a while since I've had it apart but on my similar AL340 there is definitely a brass shear pin driving the feed screw. And I think also a rudimentary clutch arrangement before the pin. There used to be a yahoo group for this class of lathes, they knew all the ins and outs, don't know if it still exists.

NO there is no overload mechanism on the AL-960B. You have probably damaged a Gear, Pin or keyway, but somehow it can drive with less load ie Sharp Tool. The problem could be at the Apron or the Feed Gearbox. I jammed mine at one time and as a result had it completely apart. My problem was both in the Apron and the Feed Gearbox. You can download the Manual on the 'Machinery House' website if you don't already have it.

Heres the an AL-960 from H &F website.

Trap for young players.

Check that the shear pin IS made from brass. I found out the hard way that it was steel ( my lathe is a Steelmaster but nearly identical) and it bent the pinion that drives the apron along the rack.




Al-960B shear pin.jpg

It defiantly has a steel pin in the drive for the apron. Guess ill have to pull the apron apart and sus it out, though so far it has caused me no problems with sharp tool and taking heavy cuts.

brendanh,
You do not need to pull the apron apart to pull the shear pins.

I seem to recall jogging ( with the jog button) the lathe over and driving the pin out with a punch.Not that its easy it took a lot of jogs to get it just right

I marked the side(s) it drives in from so it will line back up to replacement (Brass pin). You never know if the bloody holes are drilled off center- and wouldn't align the wrong way around.hence the match marks.


It was not stated if you have one of the coiled flat spring thread cover thingies fitted.Watch out for em( on the head stock side) as they can coil up into a solid immovable block and it is possible to drive the carriage and jam up on them- this is what happened to mine to bugger the pinion .It bent before the steel shear pin broke.

The symptom of this will be a tightness every half turn while rolling the carriage up or down the length of the bed.

AL960B doesn't have the leadscrew covers thank goodness. It doesn't have a jog button but if you take the drive out of gear you should be able to turn it by hand.

When this occurred did you notice if the feed shaft was still turning?

Could the feed selector of possibly just jumped out?

If the pin has sheered there may be a bur that is catching and giving the drive.

Don't be surprised if it is the shear pin
This is mine out of a brand new AL340D

Phil
IMG_3054.JPG IMG_3058.JPG

I have the same problem with my Hardinge HLV. It came with a broken sheer pin. Unfortunately the lead screw had partially rotated so the old pin could not be driven out. Also some butch/macho dill had had a go at disassembling it previously and somehow had forced spacers and gears on the shaft in the gear box; causing a very hard time to disassemble it as gently as possible. The entire gearbox castings and leadscrew had to be removed for the repair. Hardinges are built for precision; not heavy roughing.

A tip from the Hardinge group site for checking the shear pin is to engage the half nuts then use the carriage wheel to force the apron to the right. There is enough clearance on the right end of the leadscrew for it to move about 1/2". Enough to show if the pin is broken or not.
The Hardinge sheer pin is steel and quite hard.

One thing that was drummed into me regarding sheer bolts on older small square haypresses is that the sheer bolt is made from a hardened steel that is designed to break at a certain predetermined pressure. A soft mild steel bolt of the same size will deform and try to bend before finally breaking at higher pressure than the unit was designed for. It is there to protect the other parts.

Time to gently ease the workboots on and hobble over to the workshop and do some more on the HLV.

Ken

Originally Posted by pipeclay

When this occurred did you notice if the feed shaft was still turning?

Could the feed selector of possibly just jumped out?

If the pin has sheered there may be a bur that is catching and giving the drive.

feed shaft was still turning.

Tried it out today, locked it into feed and i was able (with some moderate resistance) turn the hand wheel to advance it toward the chuck, which to me its something inside the apron.
Having said that i was tuning some 80mm steel bar taking heavy cuts, course feed with no issues again apart from getting burnt by flying chips.

It might have sheared the key that drives in the slot in the feed shaft. I have had this happen on a larger lathe before.

Turns out it is friction drive