Cutting a thread with Hafco AL320G

[dougsshed]

Hi! I'm new on this forum. I'm pretty ignorant about all things related to machining. However, I retired a few years ago and, over time, have equipped my workshop with a number of toys. Some have been good/great decisions. Some have not. The jury is still out on my AL320G metal lathe. When I bought it, it was quickly apparent that it had been shipped with no lubrication whatsoever other than the oil in the headstock. I see that others have had similar problems.
I've been using it for about a year on this and that but I have studiously avoided thread cutting as it seemed a very daunting task. I have this set of spare gears and a gear/thread cutting chart that were a mystery to me and I always found a way to not need to cut threads.
Well, I decided that being scared is a very non productive thing to be. I worked through the chart and the gears and found a project that entailed cutting an M30 x 3.5 thread. I set up the gears, worked out the use of the half nut and started with a very light cut. I did not disengage the half nut at the end of the first run. I put the lead screw in to neutral, backed off the cutter, reversed the lead screw back past the start of the cut, brought the cutter back in and resumed the cut. The second run was very slightly out but the third cut was halfway past the first cut.
Research on the net showed that lead screw end play and/or half nut free play would be the likely culprits.
The half nut was tight as a drum. The lead screw, however had lots (and lots) of end play. I know this is not a top of the line lathe but it's still expensive enough that it shouldn't have that much play. There doesn't seem to be any capacity for adjustment so I have made an adjuster as per attached pic.
Having adjusted the end play, I was frustrated to find nothing had changed: the first run was out a few thou, the second run was way out.
Help!!! Anyone? I feel like I've been sold a lathe that can't do what it was advertised as being able to do.

 

[Niels Abildgaard]

Hello Dougsshed

Do not reverse or disengage the leadscrew.
Working sequence is;

Cut
Stop
Take tool out of material diameter with cross slide handle.
Run lathe backward,stop and change to forward
Put crosslide to former position and give a small amount of feed with compound.
Pray
Repeat until thread is fine
As beginner do not play with leadscrew tumbler gear or thread dial indicator,even if Your leadscrew is metric andYou are cutting a metric thread.For imperial threads never.
I would take that homemade leadscrew endplay adjuster off.

You will be fine

http://www.machineryhouse.com.au/L141


Have looked up Your lathe and is green with Envy.
Had a part time alcoholic electrician fool around with a variable frequency drive that fell off a lorry and ended up paying him more or less what You have given for lathe complete .
Lathe was 1000 Aud and QC gearbox was bad,but makeable.
Was thrown out of church due to language used repairing
A very nice faceplate from ebay uk 200 Aud but nice
A new three jaw fitted to new backplate 200 Aud
Got so tired of the chatter and sound quality that I put the whole thing on a piece of granite .200 Aud with transport and handling.
2000 Aud to electrician
My lathe is not two times the worth of Yours.
Congratulations and it is to heavy to steal singlehanded.

Congratulations

 

[Swifty]

Hi Dougsshed, I do the same as Niels has told you, I never disengage the half nuts, just pull the tool out and reverse. One great feature of my lathe is that it has a foot brake, this means that I can screw cut at a reasonable speed, retract the tool and stop the lathe very quickly. My lathe is an AL540.

Paul.

 

[dougsshed]

Thanks guys. The problem is solved. I think I had misunderstood instructions previously given in that there are two ways to reverse the direction. I hadn't disengaged the half nut. I knew that was possible but asking for trouble. But I was reversing via the lever that engages the lead screw (not the half nut lever). This lever can engage the lead screw in fwd or reverse. After reading Niels instructions, something in my brain (I do have one of these) clicked and I realised it might work better if I used the forward/reverse power switch instead (which I had forgotten was an option....I always just turn the lathe on in the one direction).
Raced down to the workshop and gave it a try. Perfect cut alignment each time
Thanks again. At least my lead screw no longer has end play. In the end, I'm not sure if fixing that was necessary but it felt like a good thing to do.
Best rgds
Doug
For all you married guys out there.... 'It is better to apologise than to ask for permission' LOL

 

[Swifty]

Doug, it may help to know what was wrong with your method. Disengaging the lead screw selector (not the half nuts), and then turning the leadscrew back, besides being a bit of a job, as you would have had to move the saddle back while turning the leadscrew, when the selection lever is engaged again the gears will just mesh in the next available tooth. The relationship between the main spindle and the leadscrew via the gear train, must always remain the intact. By using the half nuts, the relationship is maintained, but you have to know when to engage the half nuts. With my lathe, I have 2 different gears to choose from to fit to the chasing dial (thread indicator) right next to the half nut lever, once upon a time when I was much younger and probably did things by the book, I would use the chasing dial, but it sure spins fast while you are waiting for the correct mark to match up. Now that I'm much older and hopefully wiser, I just reverse the lathe after pulling the tool out.

By the way, any end play in the leadscrew should be taken up as the saddle starts to move, so trying to remove it is not necessary.
Paul.

 

[JimDobson]

I feel like I've been sold a lathe that can't do what it was advertised as being able to do.

Pretty quick there to blame the tool.

 

[dougsshed]

Actually, Jim, I wasn't quick to blame the tool at all. Although the initial post was a fairly short story, the process of trying, not succeeding, researching on the net, trying what was suggested on the net etc was quite a long one. It was only after that process had gone on for quite a while that I began to feel that it might not be my ignorance that was to blame. Even so, had I been quicker to blame the tool, there was some justification for doing this as there have been some items about the lathe that definitely weren't up to scratch, some minor and some more significant.
As I said in my initial post, the lathe had been shipped 'dry'. I was told by Hare & Forbes that it was 'ready to use'.
Several stickers on the lathe peeled of almost straight away. These included the reference mark on the saddle hand wheel and on the thread chasing dial and the large sticker for the fwd/rev control lever.
The lathe does not appear to have been primed with undercoat. You hardly need to touch it and the top coat peels off leaving bare metal exposed.
The (riveted on) scale for the compound table is approx 1 1/2deg out.
The optional stand that I bought is only top coated on the outside. On the inside of the cupboards, it only has overspray that feels like 120 grade coarse emery. Not nice to store things in.
These and other items of 'Chinese quality' might well predispose one to 'blame the tool' prematurely. All things considered, I think I have been quite patient
Sorry if this sounds a bit snappy but I think you were equally quick to make your judgement on the operator.

 

[rodw]

Doug, if you go to my Rod's Aussie shed starting on page 5 is a very good tutorial on cutting threads on the AL320G from guys on the forum who guided me. It remains my first and only thread.

http://www.homemodelenginemachinist.com/showthread.php?t=19885&page=5

One problem I did wrong was not to engage the threading lever so the gearing was wrong. As said, just stop and reverse the tool using the power switch, not the gearbox and for metric threads, don't use the chasing dial. If you search for AL320G on this forum, you will find a spreadsheet with all the available threads but the ratios in the manual are definitely correct (if you remember to engage the threading lever).

The problem regarding your empty gearbox does not surprise me, but mine had oil in it! The problem is the plastic sight glass that ships with them. Mine let go just sitting in the carport before I installed it and oil went everywhere. I'd say yours let go in transit. Hare and Forbes were really good about it and airbagged a replacement overnight and gave me 5 litres of oil. The second one let go overnight after I fitted it and dropped the oil a second time.

I got a replacement sight glass with a metal thread from http://www.bolt.com.au here in Brisbane. From memory, it is 16mm x 1.5 mm thread but don't quote me on the pitch! I know it is the same as the bung on the table of my Seig SX3 mill which I used until I got it sorted.

In all honesty, I think it is a good lathe. I have done a few things to mine like adding a collet chuck, coolant, long feed stop, light, DRO etc. If I had a bit more room, I might have gone a bit bigger but for the bread and butter stuff that paid for it, it lets me pop out parts in half the time as my previous lathe.

I have documented all my mods in my shed thread so read on (and make sure you bolt it down if you are using the factory stand).

As far as the paint goes, I got some engine paint as touch up paint mixed roughly to match the grey at Bunnings. Just take the back panel from the switch with you when you go. You will see why I needed a fair bit of paint if you read my thread.

 

[dougsshed]

Thanks for that, Rod. Your experience seems to tally up with mine in a number of ways. Now that I've sorted the threading issues, I'm a lot more confident in the lathe and in what I will be able to do with it. The first thing I did when I bought it was bolt it down. I agree, it seems, overall, to be a competent lathe. BTW, here's a pic of the finished job once I worked out the thread cutting. It's also the first Morse taper I've done and it fits very snuggly in my dividing head

 

[rodw]

Doug, looks good. What will you use the threaded end for?

I was saved a job cutting a taper for my rotary table because a mate bought the same rotary table I did at the same sale and cut me a MT2 taper when he was set up on his CNC lathe.

Here was my shortcut to taper cutting. Works well.

http://www.homemodelenginemachinist.com/showthread.php?t=23268

 

[dougsshed]

Doug, looks good. What will you use the threaded end for?

I was saved a job cutting a taper for my rotary table because a mate bought the same rotary table I did at the same sale and cut me a MT2 taper when he was set up on his CNC lathe.

Here was my shortcut to taper cutting. Works well.

http://www.homemodelenginemachinist.com/showthread.php?t=23268

Hi Rod, the thread is specifically to hold a wood lathe chuck but I also have a nut to fit that will hold a thinner work piece such as a disc in place while I machine it on the rotary table/dividing head. I am in the process of making an ornamental lathe/rose engine and I will need this to make the index wheel and possibly the vernier plate. I have no doubt it will be handy for other things as well. These forums can take up your whole day if you aren't careful You read something and follow a link. The destination has another interesting link and then that destination.........etc, etc

 

[Jinxy Jones]

Hi to All
I'm new to the forum AND metal lathes. I have bought a Hafco alg320, and attempted my first thread (8x1.25mm) today, or a least i was hoping to. BUT, when trying to change the gearing using the sheet within the door, it seems that, either I don't understand the instructions, or the reference sheet may be wrong. The recommended gearing is as follows:
M=24
N=60
A=30
B=32
C=40
D=36

For some reason C & D won't mesh i.e. Too big.
What am I not understanding about the instructions?
Am I putting the gears on the wrong shafts?

 

[priceyk]

Hi Jinxy, Looking at the manual you need to loosen both the locking nut (in the curved slot) and the nut holding the gears C & B . The locking nut should allow the whole pack to swing down and the Tee bolt holding B & C should then be able to slide to accommodate the different gear sizes.

 

[Jinxy Jones]

Hi Jinxy, Looking at the manual you need to loosen both the locking nut (in the curved slot) and the nut holding the gears C & B . The locking nut should allow the whole pack to swing down and the Tee bolt holding B & C should then be able to slide to accommodate the different gear sizes.

Hello and thank you for the advice "priceyk".
It helped me. Can't believe I did not see the "flats" on the idler shaft to move it for the correct tolerance. Both gears now mesh without binding. THANKS!