Author Topic: Chinese CZ300A Lathe - How do I ?? question  (Read 9486 times)

Offline Deek

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Chinese CZ300A Lathe - How do I ?? question
« on: October 10, 2012, 06:04:17 PM »
G'day all.

I am very new to your forum after Googling away for possible answers to my questions & coming across it. I have used the search function but haven't found a match to what I seek. Recently I purchased a cheap hardly used 10 year old Chinese lathe [CZ300A] for $500. After setting it up in the workshop of a friends local service station we discovered that it wasn't such a bargain after all.
The drive rack & pinion for the carriage/saddle is badly damaged & needs to be removed & replaced. So far I cannot find any helpful info on the best way to remove the carriage/saddle & apron, so as to replace the damaged parts.

Actually finding replacement parts is also proofing a challenge at this stage, but I figure if I can get them off I should be able to get new parts made somewhere.

Any helpful tips or info would be much appreciated.

Cheers

Deek
Western Australia.

Offline hopefuldave

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Re: Chinese CZ300A Lathe - How do I ?? question
« Reply #1 on: October 10, 2012, 08:04:22 PM »
Hi Deek,
 Sorry to hear you found some problems - though I think my QC gearbox full of old coolant probably beats it, rusted-out 60-year-old bearings, not made for 40 years... Yes Sir, said Timken, we can make you our minimum order of 500 at £525 each....

To get to the rack:

It's not a quick job, but not a really difficult job either!

Best way to start (as I've found when doing it a few times, similar machines):

disconnect from power!
remove the tailstock (may first need to unbolt the stop at the end of the bed, between the ways);
move carriage all the way to the headstock end ;
remove three plastic bungs covering the ends of the 3 shafts and remove any nuts / fixings / thrust bearings on the outboard end;

remove the socket screws from the shaft bracket, and the taper pins if fitted (not essential, but you'll need to pull the bracket out further from the bed otherwise);
*firmly and confidently* lever bracket out from side of lathe bed (easiest to put a pry-bar behind one of the shafts with a wood/copper pad or two to prevent damage) and slide off shafts - you may have a ball and spring that drops out of the fwd/rev shaft's detent latch and a thrust bearing or two on the ends of the leadscrew and feed shaft;

Slide the carriage to about half-way along the ways;
remove taper pins (AKA shear-pins) from the feed shaft and leadscrew at the gearbox end;
back off the grubscrew/s holding the switch cam on the shaft;
*engage half-nuts*;
slide carriage towards tailstock - this should pull the feed shaft and leadscrew out of the collars at the gearbox end;
The carriage and apron should now be free to slide off the end of the bed!

When you slide 'em off, beware of gibstrips etc. that are going to fall out - note where from (usually rear shear) and which way around - you'll need to slacken the gib adjusters to get 'em back into place before sliding everything back together when you're done!
 Once the carriage is off, you can carefully remove the three shafts, being aware of keys that will drop out once you do (e.g. the feed worm holds the key for the feed shaft - the slot in the worm is blind-ended so it needs to be in place before fitting the shaft back in etc.).

You may not need to take the whole carriage off, just the apron and if so just unbolt it once you've freed the shafts at both ends (usually half a dozen capscrews from the top surface of the saddle wings, beware of the slide lock that drops inside if it's unscrewed too far!)  - Bear in mind that the crossfeed gear (for power feeds) sticks up above the apron to engage a gear on the crossfeed shaft in the cross-slide!

Once the rack's off, you'll probably find it's a standard pitch - either DP or Module, depending on whether it's Imperial or metric, should be findable as a stock item (not specific to your lathe) even if you have to drill for mountings?

Hope that helps, Your Machine May Vary!

Dave H. (the other one)
Rules are for the obedience of fools, and the guidance of wise men.

Offline Deek

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Re: Chinese CZ300A Lathe - How do I ?? question
« Reply #2 on: October 11, 2012, 12:13:22 AM »
Thanks for the reply Dave.

I will just get familiar with the correct name & location for the different parts of the lathe & see how we go.  :thumbup:

Cheers

Deek

Offline hopefuldave

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Re: Chinese CZ300A Lathe - How do I ?? question
« Reply #3 on: October 11, 2012, 04:05:25 AM »
Hi Deek,

If you don't already have it, the operation manual's available from http://ebookbrowse.com/cz300a-lathe-manual-pdf-d303471398, for free download - should name the parts, at least? Being a Chinese manual, it's a bit rough and ready and doesn't go as far as a parts/assembly diagram, if Grizzly in the USA perhaps rebadged it under their own brand name their manual's likely to be a lot better! BusyBee in Canada also used to stock it as their B2070 - they may have a manual that's better than the one I found online!

Good luck, and have fun!

Dave H. (the other one)
Rules are for the obedience of fools, and the guidance of wise men.

Offline RotarySMP

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Re: Chinese CZ300A Lathe - How do I ?? question
« Reply #4 on: October 11, 2012, 07:27:02 AM »
When I first read your post I thought it was the generic Sieg 7x12 sort of lathe. Since I CNC'd mine, the rack and pinion are in a box under my bed. Unfortunately yours is a differnt bigger machine, sorry.

Most of this chinese stuff is sold under various brands, so I am sure you will find a some one (probably in the states) who stocks parts.
Best regards, Meilleures salutations, Mit freundlichen Grüßen, Cu salutari
Mark
https://www.youtube.com/c/RotarySMP

Offline 75Plus

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Re: Chinese CZ300A Lathe - How do I ?? question
« Reply #5 on: October 11, 2012, 03:42:28 PM »
Deek,

The quick change set up is a different but I believe you will find that all the carriage and apron parts are the same on this Grizzly lathe. The manual can be downloaded and I believe parts can be ordered from Grizzly.

http://www.grizzly.com/products/12-x-36-Gear-Head-Cam-Lock-Spindle-Gap-Bed-Lathe/G4003

Joe

Offline Pete49

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Re: Chinese CZ300A Lathe - How do I ?? question
« Reply #6 on: October 11, 2012, 10:31:34 PM »
As Joe says go and look on the grizzly site. My chinese lathe (new) came with a basic (very) manual but the Griz one is very informative and probably the only difference is theirs are imperial thread as opposed to my metric version but the change gears are the same for both machines. Once cleaned up and adjusted they are not much different to the older non chinese lathes and can hold accuracy as well as the old hercus lathes
Pete
oops..........oh no.........blast now I need to redo it

Offline Deek

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Re: Chinese CZ300A Lathe - How do I ?? question
« Reply #7 on: October 13, 2012, 02:41:18 AM »
Guys, thanks very much for all your suggestions. I will follow up on the info given.

Cheers

Deek

Offline Miner

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Re: Chinese CZ300A Lathe - How do I ?? question
« Reply #8 on: October 17, 2012, 04:44:21 PM »
Deek,
Due to a variety of reasons, and most would involve part tollerence's and interchangeability. You quite likely wont find a direct replacement rack and/or pinion that will drop in and use the same screw holes as your current one does while still having the correct mesh. So I'd almost bet you'll end up off setting the rack and drilling and tapping new mounting holes at the correct locations anyway. There's more than a few gear suppliers around that offer various rack and pinion combinations. So that's another route you could go. You can set the mesh you want or need by using something as simple as plain paper. Everything from .001 thick cigarette hand rolling papers to typing paper or even thicker. The paper gets squeezed between the pinion mounted in the lathe at the operating position and the rack to set the clearance or lash, then clamp your rack in place, move to the other end and do the same, then use the rack mounting holes as a drill jig. Obviously the holes need to be drilled and tapped very accurately. And especially so if they use the common counter sunk vee type screw head.

For a real good example of that part tollerance or interchangeability. You could have a look at Rob Wilson's thread on this forum about what he's found on his 626 mill while CNCing it.

Pete