Thread: HELP with HAFCO AL336D Lathe - leadscrew gears.

Originally Posted by mandcbrown

Thanks Hanks heaps for the pictures and further information - that really helps understand what should be going on (though it actually isn’t ding what it’s supposed to).

You are correct - it’s not a problem with the threaded leadscrew- that’s doing what it should. It’s the slotted feed rod that will not engage when the S/M dial is in the M position. You may be on to something noting that the dog thingy should be moved by the selector to switch between the screwing and machining gears. It may well have a problem in its alignment or something as it will only engage a gear in the S position - not the M position - in the M position the slotted rod just free spools by hand and does nothing when the machine is running. When in the S position, the change gears on the side are mechanically linked to that slotted rod and move together driving the cross feed or horizontal travel of the saddle - sorry if my terminology is a bit screwy as I’m only starting out with this.

On consideration of this, and looking at the photo you have kindly given of the fear assembly with the front cover removed, I am thinking it might be necessary to remove that front cover to investigate what is going on in there. What would you think about that idea ? Are there any important points to note if I go ahead and do that ?

Your assistance is greatly appreciated.

Regards,

Mark.

I think the cover comes off easily from memory. As i mentioned, move the knobs fully clockwise and try to see what the rack gears are engaged into. That last picture should help. I think there is a drain plug on the side of the gear box and a full plug above that. When you break the seal of the gasket, try to use a paint scraper or something to peel it off on one side so the gasket doesn't rip. Just clean up the gasket and use some blue hylomar or similar. Even if you do break the gasket the sealer will get out out of trouble, or make a new gasket if you have material. While I was in there, i squirted clean hydraulic oil over the gears with a glass syringe to wash out any casting sand.

Just in case I am making a huge blunder here and missing something very basic, I will go through how I ended up at this point thinking that something was not working - gosh I hope I’m not that stupid though.

i have used the horizontal and cross feed to turn and face off material and all went well, using the small black lever on the saddle, and the S/M gear selector in the S position. I am 90% sure that the halfnut lever is not engaged while doing this.

I then wanted to try cutting an external thread - so looking at the tables on the left hand cover of the machine it looks like I need to set (for a 20 tpi thread) the feed box dials to A4 MII. Doing so I found there to be no horizontal movement of the saddle at all. Moving the black selector lever on the saddle doe nothing, and putting this into the neutral position and engaging the half nuts did nothing as well.

Sorry if if this confuses the issue further - aaahhh !

Is there a shear pin in the leadscrew that has let go? I love the leadscrew covers but they can be a pain at times.

Phil

Grizzly in the US have very good online manuals for all of their products. They will have sold, may still be selling, this same lathe but under a different name.

I just had a check and you can't select drive to the saddle at the same time you have the half nuts engaged. There is a mechanical interlock which will prevent the levers moving once the other is selected.
I think you are right about what dials to select. I put a photo below which shows the dials where they should be. If you have them like this, the drive shaft for the saddle can spin by hand and is disconnected from the gearbox. The threaded leadscrew is under the spring covers so you cant see it here but if you look near the thread gauge at the other side of the saddle (right hand side where the shaft leaves the apron), you can see the lead screw. You need to make sure that is turning if you want to cut a thread. Have all the levers on the saddle in neutral and see if that shaft is turning when the chuck is turning. If it is, then you are ready to cut a thread. As soon as you engage the halfnuts the saddle will move. There is no clutch so just select it positively by pushing down quick. If you have the lever for selecting the drive to the threading gearbox in the position shown on my lathe, then the saddle will move towards the chuck, if the motor is going forward (chuck is going anticlockwise). Move it to the other side and it will move the saddle away from the chuck. 20tpi is quite a coarse thread so the saddle will move fairly quickly. try it when you are in the lowest gear on the chuck gearbox so you don't give yourself a fright. Just pull up the halfnut lever to disconnect and the saddle will stop again.

If that threaded leadscrew under your spring covers is not turning then you can't cut a thread. Remember the slotted shaft should be disconnected and free to spin by hand. It plays no part in cutting a thread.
So if the leadscrew is not turning you need to make sure the drive to the threading gearbox is OK first. I take it you understand how to select the change gears to drive the threading gearbox at the right speed. note that in my photo I am using 127/120 but you use just 127/127, ie the 48tooth gear which drives the threading gearbox should be on the 127 tooth gear, not the 120 one as it is on mine. For 20tpi you use 24 tooth and 48 tooth, same as mine has just now (but as i said the 48tooth one is on the wrong part of the idler gear for 20tpi)

So in my picture of the change gears, I would set all the levers as indicated and leave the halfnut disengaged (That means you can move the saddle with the handwheel while the lathe is turned off) and check if that last gear is turning. If it is, and the leadscrew is not turning, AND you have checked there is a key between the shaft and the 48 tooth gear, then that means you have something wrong with the gearbox. Hope i haven't made it more confusing.

D

Originally Posted by sossity

I just had a check and you can't select drive to the saddle at the same time you have the half nuts engaged. There is a mechanical interlock which will prevent the levers moving once the other is selected.
I think you are right about what dials to select. I put a photo below which shows the dials where they should be. If you have them like this, the drive shaft for the saddle can spin by hand and is disconnected from the gearbox. The threaded leadscrew is under the spring covers so you cant see it here but if you look near the thread gauge at the other side of the saddle (right hand side where the shaft leaves the apron), you can see the lead screw. You need to make sure that is turning if you want to cut a thread. Have all the levers on the saddle in neutral and see if that shaft is turning when the chuck is turning. If it is, then you are ready to cut a thread. As soon as you engage the halfnuts the saddle will move. There is no clutch so just select it positively by pushing down quick. If you have the lever for selecting the drive to the threading gearbox in the position shown on my lathe, then the saddle will move towards the chuck, if the motor is going forward (chuck is going anticlockwise). Move it to the other side and it will move the saddle away from the chuck. 20tpi is quite a coarse thread so the saddle will move fairly quickly. try it when you are in the lowest gear on the chuck gearbox so you don't give yourself a fright. Just pull up the halfnut lever to disconnect and the saddle will stop again.

If that threaded leadscrew under your spring covers is not turning then you can't cut a thread. Remember the slotted shaft should be disconnected and free to spin by hand. It plays no part in cutting a thread.
So if the leadscrew is not turning you need to make sure the drive to the threading gearbox is OK first. I take it you understand how to select the change gears to drive the threading gearbox at the right speed. note that in my photo I am using 127/120 but you use just 127/127, ie the 48tooth gear which drives the threading gearbox should be on the 127 tooth gear, not the 120 one as it is on mine. For 20tpi you use 24 tooth and 48 tooth, same as mine has just now (but as i said the 48tooth one is on the wrong part of the idler gear for 20tpi)

So in my picture of the change gears, I would set all the levers as indicated and leave the halfnut disengaged (That means you can move the saddle with the handwheel while the lathe is turned off) and check if that last gear is turning. If it is, and the leadscrew is not turning, AND you have checked there is a key between the shaft and the 48 tooth gear, then that means you have something wrong with the gearbox. Hope i haven't made it more confusing.

So after your descripton of the functions of all the levers and levers and what drives what, I went back to the lathe and put in the setting you suggested for threading - and - wallaa - things actually work as they should.

A bit bit embarrassed to admit it but - I don’t think I had the full understanding of the different drive required to thread as opposed to turning.

For turning and facing one one needs to have the half nut disengaged (in neutral) and use the feed drive for apron and cross feed movement - shift the little black lever in the centre of the carriage / saddle either up for lateral movement, or down for cross feed. This also requires the S/M feed box dial to be set to S, causing engagement of the slotted feed drive shaft.

For threading, the little black feed selector lever in the middle of the apron is set to neutral, and the lead screw is engaged using the half nut lever - minding that you have the direction of rotation selected correctly using the small lever on the top left of the main headstock ( I experimented with the saddle set away from the chuck so as not to crash the thing by selecting the wrong direction). Now here is where I thought there was a problem initially - this also requires the S/M selector dial on the feed box to be set to M - this disengaging the slotted feed drive shaft - you only need to use the half nut to get the carriage movement required to create a thread.

My humblest apology for not knowing this in the first place, but I did spend a good deal of time trying to nut this out myself, and unfortunately as previously noted the instruction manual for this lathe was of no help in providing enlightenment on this either.

THANKS SOSSITY FOR YOUR PROMPT HELP AND INFORMATION THAT HAS LED TO GIVING ME AN UNDERSTANDING OF HOW THIS LATHE FUNCTIONS - and finding that in fact there is no problem with the lead screw or feed drive gears after all - I just didn’t understand their use - Duh 🙄😳.

Thanks to everyone else who contributed as well.

I managed to turn and inside and outside thread that fits pretty well for a first go - though is a bit scrappy looking being PVC (but cheap to practice on).

Cheers.

Mark.