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Chinese Lathe


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  #1  
Old 10-29-2018, 01:38:28 AM
cobbadog cobbadog is offline
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Default Chinese Lathe

Some time back I bought my first metal cutting lathe and as I spend more time on it I am getting more comfortable on it and a little more adventurous.

This lathes does not have a thread chasing dial on it and apparently Mr China never made one to suit. So I thought about adapting one from another lathe to mine.
So my lathe has a 20mm OD lead screw, (square thread) with a 3mm pitch (1 thread each 3mm).
I do have a thread chasing dial from another lathe but the gear that engages the lead screw has a fine thread on it and is not compatible with my lathe.

What size gear and how many teeth should the bottom gear have to suit a 20mm OD lead screw?
and
Is it a feasible thing to do, adapting another dial?

Sorry for any silly questions but it is how I learn, I hope.
Cheers John
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Old 10-29-2018, 12:16:24 PM
Pete Spaco Pete Spaco is offline
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Default Re: Chinese Lathe

Wow! I had no idea that this was such a complex issue.
See:
https://www.practicalmachinist.com/v...-screw-227592/

Pete Stanaitis
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Old 10-30-2018, 02:09:36 AM
cobbadog cobbadog is offline
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Default Re: Chinese Lathe

Thank you so very much for that link Pete.

I need to study it a lot more and try to work out what it is they are saying.
Initially I thought it was going to be a simple exercise and make a single gear to do the job but now I know I will need at least 3.
I will also have to retrace any mathematical skills I once had to do the formula. One of the posts shows a list of pitches and gear size but also another number that does register for me but all of those numbers suit a 4mm pitch and mine is that awkward one 3mm. I will persist and read on.
Thanks once again.
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Old 11-04-2018, 12:17:01 AM
cobbadog cobbadog is offline
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Default Re: Chinese Lathe

Getting closer to a result. Now I'm looking at the idea of having the gears made using a 3D printer. Time will tell.
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Old 11-07-2018, 11:49:17 PM
cobbadog cobbadog is offline
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Default Re: Chinese Lathe

I signed up with the practical machinist forum and have been posting questions for about a week now and getting some positive results until yesterday when someone in authority read me the riot act about not asking questions about Chinese made lathes and that i would be banned if I continued.
I thought that this is a nice way to meet and greet people, NOT!
then some of the other members replied that it was a good question and deserved an answer. They said if the term Chinese made lathe was removed from my initial question apparently there would not have been an issue.

No matter where you go you get this kind of responses, dont you!
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Old 11-08-2018, 01:02:02 AM
Beanscoot Beanscoot is offline
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Default Re: Chinese Lathe

I wouldn't bother with trying to install a thread chasing dial, just keep the halfnuts engaged until you are done with the thread.

When you get to the end of the thread, pull the tool out, stop the machine, and use reverse gear to go back to the beginning of the thread.

More importantly, it sounds like you got the wrong lathe - for working on old engines you need to cut proper threads, not those dreadful metric ones.
Or did your machine come with this capability?
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Old 11-08-2018, 01:55:30 PM
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Default Re: Chinese Lathe

Just what brand of Chinese lathe do you have? I have a 1997 Chinese lathe (13" X 40") sold by Enco formerly in Chicago, IL - no longer in business. I could take pictures of the thread chasing dial assembly if you think it might help.
Check back in a couple of days. Have to go out of town for a bit...
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Old 11-09-2018, 01:19:59 PM
Pete Spaco Pete Spaco is offline
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Default Re: Chinese Lathe

Hello John.
Just a small point, but I am pretty sure that Enco was bought out by MSC.
They took two or 3 years to transition away from the Enco name, IIRC.

I liked the Enco outfit since they had a store about 50 miles away. Sorta like Harbor Freight, but more focused on metal.

If there's a need for parts, I'd suggest contacting MSC. They have always been responsive to me.

Pete Stanaitis
----------------

---------- Post added at 11:19:59 AM ---------- Previous post was at 10:58:22 AM ----------

I just googled "Enco" and found that MSC still has Enco lathes for sale!

Pete Stanaitis
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Old 11-09-2018, 09:59:34 PM
slip knot slip knot is offline
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Default Re: Chinese Lathe

Practical machinist can be a bit harsh. its not really for beginers. I gave up on it years ago.
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Old 11-10-2018, 12:53:02 AM
cobbadog cobbadog is offline
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Default Re: Chinese Lathe

Hi Guys,
Thanks for the replies. I too am away until Monday so will post a pic and brand of the lathe then. I think I might have the right number of teeth required for this lathe and have contacted a supplier and will see how that goes also.
The option of leaving the half nut engaged is good but I would prefer to not have to stop the lathe and then reverse it then go forward again, it is a time thing plus this lathe does not have a brake on it and it you get too close to the end of your cut and stop it it just winds down, quickly but not quick enough so for a beginner I feel it is unsafe.
Yes slip knot not a very friendly site at all except for those who considered my question based on the theory not the machine. It was mainly one who had a bee in his bonnet. If you spoke to members like he does on any other site I visit he would be the one that gets booted.
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Old 11-10-2018, 09:26:47 AM
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Default Re: Chinese Lathe

Machinist sites in general tend to be populated by trolls and assholes. . . I gave up on all of them eventually. (Except this one, of course)!
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Old 11-12-2018, 05:30:17 PM
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Default Re: Chinese Lathe

OK - Have some pictures and information that may or may not pertain to your lathe.
My lead screw appears to have 3mm thread pitch. The thread chasing dial gear has 16 teeth and measures 18mm dia.
Maybe this helps. Maybe not.
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Old 11-13-2018, 01:08:19 AM
cobbadog cobbadog is offline
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Default Re: Chinese Lathe

Hi John,
Yes that does help a lot, thank you. I have ordered a couple of smaller gears a 10T and a 14T to try out as these numbers allow me to divide the teeth numbers equally by either 1.25 and 1.75 pitch.
What size metric pitch does the 16 teeth suit please? I will order one now and put it in with the other gears as well.
Thank you for your informative reply and the pictures too.
Cobba
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Old 12-09-2018, 01:40:19 AM
cobbadog cobbadog is offline
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Default Re: Chinese Lathe

This is what I have made and have gears to suit the metric threads I want to do as a beginner. Also got some Tefolex to put on the metal to aid the cutting process.
Mr Chinaman seller of the gears told me that the gears I chose would engage correctly to a 20mm OD lead screw with the 3mm pitch and he was correct.
I assembled what I made and bolted it onto the lathe and gave it a run to ensure that it did rotate when the carriage is not moving and stopped when the half nuts were engaged just like the real thing.
Ran out of time today to do the marking up of the dial so will do that next chance I get so I put a bit of paint on my achievement and will continue with the project soon.
You can see the gears and the mounting bolt in one pic, all the components in another and a coat of paint on the body, not mine.
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Old 04-10-2019, 08:33:13 PM
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Default Re: Chinese Lathe

Tons of machining forums out there that are more Asian friendly if not primarily based on again machines. Find one and ask how many teeth are on their machine that you have. There are a few write ups and you tubes on making these gears out of brass using a tap. My Sheldon has a home made one by the previous owner. I wouldn't call it accurate by why means but it does work.

I also had the same experience on practical machinists when i joined and asked questions about my Sheldon. Pretty uppity crew over there. Once I bought a Hardinge and quized them about it they were all ears.
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Old 04-11-2019, 02:09:09 AM
cobbadog cobbadog is offline
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Default Re: Chinese Lathe

G'Day Fig,
thank you for your input as well. I did end up buying 3 gears to start with. they are so cheap to buy I can't justify the cost of buying the extra tooling to then make the gears and on top of that I do not have the machinery or ability to make a gear.
Using the gears I bought and the very simple thread chasing dial I made I have been successful in knocking up some metric bolts and when I get some time I want to test the theory of making some Whitworth threads with the combination of gears for the head end.
Each time i use the lathe I am feeling more confident but always keeping in mind not to be too cocky about what I am doing. So when turning stuff up I always take my time and keep improving my "skills". It is almost therapeutic if you are a sicky like me!
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Old 04-11-2019, 08:41:09 AM
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Default Re: Chinese Lathe

Join the club Cobba. There are few things as therapeutic as carving something from raw metal. I have a long piece of 50x75 steel 50cm long that needs a slot cut in it on my mill. Yesterday I fabricobbled a machine jack to support the length outboard of the vise. A couple hours on the lathe turning and single point threading I wound up with this. It just needs a couple flats milled in it for spanners.

Of course I could have bought one for a few bucks but what fun is that.
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