Threading with an AL320G Lathe

[Maryak]

Hi Guys,

For some time I have been less than happy about the change wheel combinations supplied with this lathe. In the handbook the change wheel chart is overpasted with an ammended version which is less than stellar.

Yesterday I went through a long and labourious process to try and find the best setups for both metric and imperial threads using the as supplied change wheels.

Attached is a spreadsheet showing the best available setups and an increased range of threading for this lathe based on a 3mm pitch leadscrew.

I know I'm not the only owner of this lathe so I hope my fellow owners will find this useful.

Best Regards
Bob

Edit, yet more improvements..........new excel file attached

View attachment Hafco.xls

 

[rodw]

Bob, thanks for this. After setting up according to the sticker for a M12 x 1.75 thread, I got a 0.7 thread so now I know why you went through this exercise!

I hope I have more luck with you settings

 

[Varmtr]

Thanks for this chart Maryak I have been looking at getting this lathe. As I will need to do 1"x14TPI 60 degree thread for a project I'm doing.
Cheers
Rossco

 

[rodw]

Thanks for this chart Maryak I have been looking at getting this lathe. As I will need to do 1"x14TPI 60 degree thread for a project I'm doing.
Cheers
Rossco

Rossco, just note that this chart is missing metric threads that are on the factory data sheet that are below 1.0 pitch. Also I think the feed rates are for when the lathe is in threading mode (half nut lever down), not in general turning mode (half nut lever up which engages the cross feed/long feed selection lever on top of the saddle). Therefore, it is not a complete replacement for the factory data sheet but has some very useful info on it for BA threads etc.

 

[Maryak]

Rossco, just note that this chart is missing metric threads that are on the factory data sheet that are below 1.0 pitch. Also I think the feed rates are for when the lathe is in threading mode (half nut lever down), not in general turning mode (half nut lever up which engages the cross feed/long feed selection lever on top of the saddle). Therefore, it is not a complete replacement for the factory data sheet but has some very useful info on it for BA threads etc.

Maybe you should take another look.

Best Regards
Bob

 

[rodw]

Maybe you should take another look.

Best Regards
Bob

Bob, I had a closer look at this and there are two standard metric threads missing in your spreadsheet being 0.70 and 0.80 pitch.

There is a difference in feed rates for some entries on your spreadsheet when compared with the factory data. I have not been able to get my head around this.

The standard turning feedrate (24x60, 24x50, 25x48 ) recommended for general turning operations agrees, but if you look at say a Metric 1.75mm pitch (using the 24x60 MXN gears), you say 0.583 and the book says 0.612. I figure there is some other gearing within the saddle somewhere but have not got my head around it.

If I scratch a 1.75mm thread with the half nut lever in the up position (eg. Not in threading mode), the pitch is around 0.7.

 

[Varmtr]

I mostly deal with imperial threads 95% of the time and the odd BA threads on the projects I do. But with the BA threads I mostly use a tap as most parts are already supplied with bolts just need to drill the holes.

Rossco

 

[Maryak]

Bob, I had a closer look at this and there are two standard metric threads missing in your spreadsheet being 0.70 and 0.80 pitch.

There is a difference in feed rates for some entries on your spreadsheet when compared with the factory data. I have not been able to get my head around this.

The standard turning feedrate (24x60, 24x50, 25x48 ) recommended for general turning operations agrees, but if you look at say a Metric 1.75mm pitch (using the 24x60 MXN gears), you say 0.583 and the book says 0.612. I figure there is some other gearing within the saddle somewhere but have not got my head around it.

If I scratch a 1.75mm thread with the half nut lever in the up position (eg. Not in threading mode), the pitch is around 0.7.

Firstly, my apologies you are correct 0.7 and 0.8 mm pitches were missing but so are those below 0.35mm and those above 4mm. I have added those to a newly attached chart.

As far as the feeds go, it would appear the basic difference between the half nuts and the feed gears is 1:3, i.e. 3mm on the lead screw gives 1mm on the longtitudinal feed through a worm drive and some compounding in the saddle. From this point, the same formulae are applied to each susequent line. Where the same thread may be cut using either set (24/60 or 28/35) the end results of the triple compound are the same. I am happy they are different from the original chart because IMHO that chart is grossly inaccurate.

I used a program called "nthreadp" to find the combinations for my chart.

Best Regards
Bob

View attachment Hafco.xls

 

[rodw]

Bob, apologies are not required. It is great you added the feed rates to you spreadsheet, I was going to put up a suggested revision to your work and could nail the missing entries but was completely stumped with the feed rates so decided not to do half a job.

It was only because of operator error on my part that I looked closely at your tables and the maths behind it. Fortunately, the label on my lathe seems to be spot on but I have not gone through your revisions in detail. Something to do with a glass or two of red wine on a Friday night!

I am a firm believer that collaboration results in better decisions and information so thanks very much for the update. I think I will get it laminated and keep it in my shop!

 

[rodw]

Maryak, thanks again for this. I had forgotten all about this spreadsheet until I tried to cut a M10 thread this week and then I finally remembered this was here! So much for making up a laminated copy when I said I would. NOT! Maybe I will get something happening now!

 

[dave57]

hi there, i have an al320g lathe an can not work out the thread chart would somebody be able to tell me which gears to use to cut a 26tpi 60degree x3/8 bscy
would appreciate any help/tips
cheers dave :wall:

 

[Swifty]

You are best to take a pic of the threading chart and post it so we can see what is shows. I am assuming that it has a metric leadscrew, so that means for any TPI you will have to use a 127 tooth gear on a compound gear train.

Paul.

 

[dave57]

this is the chart that came with the al320g lathe

 

[Swifty]

A bit of a strange set up, 6 gears involved. What they have is called a compound gear train, it is a bit hard to read the figures on the chart, but I will give it my best go. You want to cut 26 TPI, on the chart 26 is in the left hand column, so you will have to set up gear M 24 tooth and gear N 60 tooth as shown at the top of that same column.

Next you will have to set up gears A B C D, as you move across the row for 26TPI you will see that it shows the gears to use for this. Gear A 32 teeth, gear B 35 teeth, gear C 32 teeth, gear D 35 teeth. I can only assume that they have supplied all these gears with the machine. You will see from the sketch on the side that gears C and D are on the outside.

On my lathe, I only have to worry about 4 gears, the rest is sorted out be the lever positions on the feed box. As I said in an earlier post, I have to use a 127 tooth translation gear for imperial threads. If I could be bothered doing the math with your gears, somewhere in there would be the same ratio.

I've probably confused you totally now, ask any more questions that you like and I will see if I can explain. By the way, where about's are you located?

EDIT, I just noticed that Maryak has a chart on the first post showing completely different gears to be used, I can see why he became so frustrated by the supplied chart, it's nothing like what he has worked out. You may have to ignore all that I said above and use the gears shown on the spreadsheet.

Paul.

 

[rodw]

You've probably forgotten to engage the threading lever on the saddle. Do that and the factory table is 100% correct. Read my Rods Aussie Shed thread. The guys here talked me through my first thread on the AL320G near the beginning of it. The bottom diagram on the label is the most useful. Sketch it on a piece of paper, label every gear and build it.

and you probably don't need to change M&N again one you set them up the right way for the type of threading you do.

 

[rodw]

EDIT, I just noticed that Maryak has a chart on the first post showing completely different gears to be used, I can see why he became so frustrated by the supplied chart, it's nothing like what he has worked out. You may have to ignore all that I said above and use the gears shown on the spreadsheet.

Paul.

But if you look at his chart, part of it agrees 100% with the factory specs. What he's done is list other options using the combinations of M&N. I think his chart would be useful for identifying BA threads and stuff like that. Its almost a case that too much information overwhelms.

 

[dave57]

thanks for your help gentlemen, but i have had no luck with making my own thread ,going by the lathe chart i ended up with a very very fine thread with the maryak chart i could`nt get the gears to fit,gear C interferes with gear A mounting shaft , i`m going to give it a rest for a while maybe buy a die .
cheers dave

 

[Swifty]

Dave, where about's are you located, maybe a member is near by and can help you.

Paul.

 

[rodw]

Dave,

2 things....

If the half nut lever is not in the position shown, the thread will be very fine. (Abour half what you want)



The shafts position is adjustable. You will note that there is a flat on the end of it. Stick a spanner over it, loosen and move the shaft along the slot so everything fits. You may also have to play with the supplied shim washers to get the gears aligned laterally.

 

[rodw]

This shaft is the one I mean..

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I will say however, for small threads, it is so much easier to use a die. I've bought a few sets from Trade Tools Direct and they are good quality, under $50. I think H&F have them too, hit them up for a discount seeing you have their lathe.