# Shenzhen Lathe problem - Hare & Forbes AL-335

Hi All
Can anyone help shed some light on this problem?
Aussie link http://www.machineryhouse.com.au/Products?stockCode=L183 #
Hare & Forbes Lathe code=L183
http://www.metalworking.com/dropbox/Shenzhen_CQ6230B_Lathe.JPG
Background Info ---------------------
Leadscrew = metric 3mm pitch
Change gears 1 Set: M=1.25 (pitch) Z"T, 44T, 26T, 52T, 38T
Lathe: Shenzhen CQ6230B
FWIW the chinese manual that comes with the lathe is poor reading, sure that are not designed to teach but they must convey a clear message/instuction when referencing any information therein.
Down the left side of the lathe (headstock gearchange cover) there are 5 tables of information.
1. REVS/MM 2. REVS/INCH 3. THREADS METRIC PITCHES MM 4. THREADS IMPERIAL PITCHES 1/INCH 5. INDICATOR TABLE
Q1. In the top most table (revs/mm) Under the column titled "position" Third column from the left, there are two symbols (one demonstrating horizontal, one demonstrating vertical)
horizontal ----^VW^--- vertical |

< |
What is their meaning (are they important, or can they be ignored)?
Q2. In the third table (THREADS IMPERIAL PITCHES 1/inch) Under the column titled "position" Second column from the left, there is the letter Z (directly underneath are MII and MI) Any clue as to what the letter Z means? (I did find in the chinese manual that one of the change gears was referred to as "Z"T" as in a 22 teeth gear)
Are they trying to tell me that the 22 teeth gear is also known as the Z gear?
Q3. In the third table (THREADS IMPERIAL PITCHES 1/inch) Under the column titled "position" First column from the left, (you may need to zoom in)
There is a small image on the table face where the image shows in part
48T (being on top)
(no in between gears)
Z ( being below it, is this referring to the Z gear ie: 22Teeth?)
Q4. In the third table (THREADS IMPERIAL PITCHES 1/inch) Under the column titled "position" Second column from the left,
If I wanted to produce a 24tpi thread, should I be selecting the levers A and 3 with 48T on the top change gear and 22T gear on the bottom?
Thanks DazFNQ
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...
... Chinglish dictionaries are hard to find. I don't think you can get much help from anybody.

Sounds right, give it a try; see what thread lead you get.
Have fun learning to run your new toy.
FWIW, I have a SuperMax manual written in chinglish on a mchine I just got. Using it to figure out the maintenance lube schedule and points to lube was a REAL treat.
Karl
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On Mon, 16 Jun 2008 06:29:41 -0500, "Karl Townsend"

Does you Supermax have Turcited rectangular ways? If it does, what's an appropriate bribe for a copy of the instructions on adjusting the gibs? Not how to make the adjustments, but how to tell when they're properly adjusted. The combination of 3(?) gibs per axis (as opposed to one gib for dovetail ways), and the low coefficient of friction of the Turcite, makes it difficult to tell the difference between too tight and too loose.
--
Ned Simmons

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Ha It gets better, in the Hare & Forbes brochure it says theat the leadscrew is metric, but another source of information for the same lathe says that it is an imperial leadscrew.
Have discovered that its pitch is 3mm and it has 8tpi (butress thread)
I'll just keep digging.

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Can't be both. 8 tpi is (1/8)(25.4)= 3.175 mm pitch, not 3.000 mm pitch.
It's close enough that a thread pitch gage may have difficulty distinguishing unless one takes the leadscrew off the lathe.
A better way to measure in place is with a dial indicator stuck to the bed indicating horizontal travel of the carriage with half-nut engaged while manually turning the leadscrew and counting turns.
Joe Gwinn
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When you start cutting a thread make the first pass barely scratch the work and check the pitch or modulus with a thread gauge.
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I'll try that thanks Jim
DazFNQ
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wrote:

Thanks Joseph, it was late afternoon, little overcast (cloudy) and hard to see.

Measuring a buttress thread with a "V form" thread gauge is slightly imperfect.
Thanks once again DazFNQ
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----- Original Message -----
Newsgroups: rec.crafts.metalworking Sent: Monday, June 16, 2008 11:25 PM Subject: Re: Shenzhen Lathe problem - Hare & Forbes AL-335

Joe thanks for the tip.
After measuring the carriage travel based on leadscrew revolutions
Leadscrew Revs Dial Indicator Gauge 1 0.125 2 0.250 3 0.375 4 0.500
So you were correct, thanks. More importantly these bloody chinese documents really are crap as they go on to say that the leadscrew pitch is 3mm 8tpi.
Thanks DazFNQ
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Bingo: exactly 8 tpi. Welcome.

I bet the Chinese-language manual is no better. Attention to detail is language-independent, and arabic numbers are used in both languages.
I would make a xerox working copy of the manual, and start to annotate the copy in pencil. The reason to do this with pencil on a copy is that not all discoveries will hold up, so one needs to be able to edit. After a year, things should have stabilized, and one can use ink in confidence.
Joe Gwinn
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Looking at the threading charts, it looks as though it is using transposing gears (typically 100 tooth plus 127 tooth) to drive the leadscrew for metric threads, but direct (just an idler, which is likely to be the larger of the pair of transposing gears) for imperial threading, which suggests that it is an imperial leadscrew, not a metric one.

Interesting. Do you have the machine directly available? (I guess so, given the photos). Why not cheat and try *measuring* the leadscrew's pitch? Of course -- it might be possible that it has two leadscrews, one of each pitch.
And normally for Imperial that would be an Acme thread, not a buttress thread. IIRC, the included angle of the buttress is 30 degrees, and the Acme is 29 degrees, so that part would be pretty difficult to tell without really precise measuring tools. :-)

And *confirm* things by *measuring* what you can get to. No matter what lies the "manual" may tell, you can tell which is the truth by actual measurement.
Good luck,         DoN.
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wrote:

Checkout the image of the standard gear setup:
http://www.metalworking.com/dropbox/Shenzhen_CQ6230B_Lathe_Standard_Gears.JPG

This is now not correct, calcs originally based on the chinese manual:
After measuring the carriage travel based on leadscrew revolutions
Leadscrew Revs Dial Indicator Gauge 1 0.125 2 0.250 3 0.375 4 0.500

Yep, with a Unified 60 degree pitch gauge measuring over an acme square thread can be problematic but does appear to be 8TPI as nothing else comes remotely close.

Your absolutely right, those chinglish manuals are crap.
Therefore, based on my original message <snipped>
Leadscrew = metric 3.125 pitch
Change gears 1 Set: M=1.25 (pitch) Z"T, 44T, 26T, 52T, 38T (Where it appears that Z = Z axis )
Simple gear train of Driver 24T Intermediate 127T Driven 48T
Im not sure as to which calc method from my reference book to choose here. Is there a resource on the net that can answer these questions?
Thanks DazFNQ
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On 2008-06-17, DazFNQ <djimpsfnq> wrote:

[ ... ]

O.K. The 127 tooth gear serving just as an idler at the moment.
[ ... ]

So -- precisely 8 TPI.

O.K. And that is confirmed by your measurements vs leadscrew rotation.

Nope -- Leadscrew is imperial -- 8 TPI -- which converts to 3.175mm metric pitch.

Right.
Well ... first off, you can ignore the 127T idler, because both gears mesh with it. You could just as well use the 100T as an idler, except that it makes things more difficult to change at need, since the 127 tooth one would overhang the 100 tooth one. The only thing the idler does -- other than space the other gears apart a bit more -- is to assure that the driver and driven rotate in the same direction.
So -- for 2 revolutions of the spindle (and driver), you get one revolution of the driven (and input to the geartrain inside the headstock).
There is someone who has a program on the net -- a regular here. I tend to not remember the URL because the programs are compiled for Windows (which I don't use), and use enough private libraries to make it difficult to compile them on a unix box.
But IIRC, his program is set up for a geartrain from the spindle direct to the leadscrew, without taking into account the gearbox in the headstock. With that, or an external quick-change gearbox, you don't really need the program most of the time.
Enjoy,         DoN.
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Probably blocked for me -- if it is truly in China. I've had too many attacks from sites in China.

Got that one.

Typically, you get a different feed rate along the bed (shown as horizontal), and across the bed -- along the cross slide (shown as vertical). The precise values probably don't matter unless you are aiming for a particular surface finish, but the approximate range do in determining how much metal you remove per revolution (and how hot the chips will be. :-)

I think that they are calling the gear on the leadscrew (or feeding into the quick change gearing) 'Z' for the "Z-axis" -- the length of the carriage. The cross feed is usually the "Y-axis".

I think that Z is whatever is fed into the internal gearbox. A change of this will change the selection of pitches.

Also the "I --- II" knob in the "II" positions. Don't use the levers, use the knobs at the bottom. I think that the levers at the top are for selecting RPM of the spindle, not threading details. And the smaller one with the lever pointing down selects CW or CCW spindle rotation. I think that the "M --- S" knob on the bottom panel may be for selecting right-hand or left-hand threads by reversing the threading leadscrew .
But select what you think is right, and try it -- with a very light cut, and a thread pitch gauge in hand. Ideally -- paint the workpiece with layout dye, then make a very shallow cut, and compare what you got with the proper leaf on the thread pitch gauge to make sure you get what you should.
Note that some parts of the tables are still difficult to read, mostly thanks to the information thrown away by the lossy compression used by jpeg. In particular, the drawings to the left of "Threads Metric" are pretty well blurred. A separate close-up shot of that one table would help.
I'm not at all sure what the "Indicator table" is -- perhaps the dial usually present to guide when to engage the threading half-nuts. Normally, these work only on metric, or only on imperial threads, depending on the machine. They may have switchable threading dials on the carriage (which isn't shown in your photo).
Looks like a fun machine once you get use to it. But it doesnt' cut one thread which I need -- 27 TPI.
Good Luck,         DoN.
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DoN thanks for assistance todate, got me working now.
DazFNQ
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Hi All
Have uploaded a text file (best viewed in notepad wordwrap off) regarding the Lathe tables, and todate can confirm now that the gearing supplied performs screwcutting correct.
Sorry for not replying sooner, I had to do some work, yuk!
Thanks to all for their help
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