Ceriani David lathe: change gears

[MyrtleLakeParticipant @myrtlelake]

inch conversion ratio?

[MyrtleLakeParticipant @myrtlelake]

I don't find much discussion of these lathes online. That said, they are a consistent advertiser in MEW, so possibly some members here own one.

I have looked through the manual of the David 203 manual. It can be found on the Ceriani website:  www.cerianimu.com  I still cannot determine what exact gear selection is utilized for metric to inch transposition. it is obvious (it seems to me) that there is not a 127 tooth gear, so it must be a close approximation. Does anyone know which it is?

Edited By MyrtleLake on 11/04/2016 20:28:42

[Michael GilliganParticipant @michaelgilligan61133]

Not much help but; for investigators, here's a link to the product page.

**LINK**

MichaelG.

[Clive HartlandParticipant @clivehartland94829]

Pro Machine Tools are the UK agent, I would ask them for details. See advert at the side here.

Clive

[JasonBModerator @jasonb]

Without knowing what driver is on the spindle, leadscrew pitch and the lever ratios its a bit hard to tell. From the manual there are two gear trains one for metric, the other for imperial but working them out I can't get anything that is related to 127, 63, etc

A good photo of the chart on the front of the machine, what the driver and what the leadscrew pitch is and could have a go at working it out.

For an expensive lathe I have seen better manuals on far eastern machines

[JasonBModerator @jasonb]

Got it. There is some error for example

 

11tpi would be 2.3091mm pitch but the lathe cuts 2.3077mm

14tpi would be 1.8143mm pitch but lathe cuts 1.8132mm

18tpi would be 1.4111mm pitch but lathe cuts1.4286mm

As there is no change of the driver or on the gearbox then they are just using the nearest possible gear train from the provided change gears which do not seem to include 63 or 127.

 

Also shows that people could easily fall into the trap of thinking that they are paying for a gearbox full of pitches when infact they will have to be swapping change gears for almost any change of metric, Whitford (as they call it) and Mod. Even then the range of pitches is quite low compared to similar size far eastern machines

 

Edited By JasonB on 12/04/2016 08:19:18

[Neil WyattModerator @neilwyatt]

Jason's calculations show errors less than a thou.

I suspect that '11' setting for the gearbox on the Whitworth chart is part of the solution

The manual does pose the problem of being in Italian, but the change gear setup itself seems straightforward enough:

[Brian WoodParticipant @brianwood45127]

I don't know if it is much help, but a translation gearing of 37/47 gives a good approximation for 100/127

Brian

[JasonBModerator @jasonb]

Neil, the "11 setting" is the desired pitch eg 11tpi and not a setting, the manual is just a reprint of the top line of the chart from the front of the machine.

The gearbox setting is the first Leva (lever) column and that can be moved to position D changing 0.5mm pitch to 1.0mm pitch and 11tpi to 22tpi so a simple 2:1 gearbox

The diagram of the gears is what was throwing me last night as it looks to show the 60 driving the 75 and the 65 driving the 30. but it should be 60 driving 65 and 75 driving 30 giving 0.923 and 2.5 multiply those together to get pitch of 2.3077. On the metric side a simple 60T idler so 35T driving 70T = 0.5. Note both these pitches use the gearbox in exactly the same "C" position so there is nothing in the box to give better imperial ratios

 

Edited By JasonB on 12/04/2016 10:06:26

[Neil WyattModerator @neilwyatt]

Aha!

I assumed the inverted vee was a picture of the two levers, not the crest of a thread!

I thought you could only cut Whitford pitches on a Myworth lathe

Neil

[John Stevenson 1Participant @johnstevenson1]

Posted by Neil Wyatt on 12/04/2016 09:07:42:

Aha!

I assumed the inverted vee was a picture of the two levers, not the crest of a thread!

I thought you could only cut Whitford pitches on a Myworth lathe

Neil

.

But only with a 63 ½ tooth gear.

[MyrtleLakeParticipant @myrtlelake]

JasonB – thank you for working those out for the various pitches. I was reading the drawing the same, but it seemed really very odd to me. 65 / 75 is a poor translation ratio to use, I would think.

[JasonBModerator @jasonb]

You need to look at the whole gear train for each pitch not just two of the 4 gears being used in a particular train.

Comparing the result for 11tpi the gear train gives to the true pitch I would say its a very good result, 0.0014mm per turn or 0.06% error is negligable unless you are making long screws

[MWParticipant @mw27036]

Posted by Neil Wyatt on 12/04/2016 09:07:42:

Aha!

I assumed the inverted vee was a picture of the two levers, not the crest of a thread!

I thought you could only cut Whitford pitches on a Myworth lathe

Neil

Thats only because it's an imperialo lathe.

Michael W

[MyrtleLakeParticipant @myrtlelake]

Okay, I follow your math now, at least. You're calculating (60/65) x (75/30). You expressed this in an earlier post as "0.923 and 2.5." I believed I understood compound gear train calculations, but you've proven me ignorant. Having just skimmed Screwcutting in the Lathe by Cleeve and Machine Tool Operation by Burghart for review, I'm clearly lost.

Some quality time with the books are needed for me on this one.

[JasonBModerator @jasonb]

I divide the driver by the driven so

60 divided by 65 = 0.923

75 divided by 30 = 2.5

 

Then multipy these two together

0.923 x 2.5 = 2.3077

 

Or as you have written (60/65) x (75/30) = (0.923) x (2.5) = 2.3077

 

Luckily in this case that equals the pitch, in most cases the driver on the spindle and the lead screw pitch come into the equasion too.

Edited By JasonB on 12/04/2016 20:38:59

[MyrtleLakeParticipant @myrtlelake]

Here is the context driving my interest in the matter. It may be helpful to the discussion to mention it.

My workshop functions around Schaublin W20. There are two 102 lathes which use W20 collets and chucks (M37.6 x 3 spindle thread). My milling machine also uses W20 collets, and its accessories accept W20 collets and lathe chucks. The Ceriani is the only lathe I know of that is available with this spindle option. Even if I found a Schaublin 102-VM or 102N-VM, getting it into my basement shop is not in my future.

One of my 102's is set up for thread cutting. It uses a watchmakers' type telescoping shaft to drive the top slide. There are a few issues that are less than ideal. The longest thread I can cut is 70 mm without having to move the compound slide and pick up the thread again. The cutting tool advancement is only able to be advanced straight in (90 degrees) to the work.

The final issue that an engine lathe such as the Ceriani would alleviate is longer turning operations. Anything longer than 150 mm requires the compound to be moved laterally along the bed. Then the cut must be accurately picked up at the same diameter. Here is an example: a drawbar I made.

Hence, the main focus for another lathe in my shop is turning and screw cutting longer diameter work. To a lesser extent, it would also allow faster, simpler threading operations. When feeding a cutting tool directly in during threading operations is problematic, an engine lathe would be a useful option.

While most of my work is metric — as is my preference — it seems inch threads are required often enough to warrant the attention to accuracy. To a far lesser point, I also like that the Ceriani is truly metric on its cross slide, top slide and tailstock screws. I am in North America, and finding a native metric hobby lathe is very limiting. (Yes, a DRO is an option here)

Having a lathe that is native W20 would mean work could be transferred in one chucking between lathe/lathe or lathe/mill. Being able to use my existing array of collets and lathe chucks is practical too.

Those are the draws that keep bringing me back to considering the Ceriani David. I've always found myself, though, a little underwhelmed by its draw. I don't know what to say beyond that.

Edited By MyrtleLake on 12/04/2016 21:05:34

[BazyleParticipant @bazyle]

Is there an agent in the USA or are you importing it? If the latter it would be worth looking at the possibility of finding a metric version of a typical Chinese lathe from eg Germany plus an ER collet set. Even if the cost is greater the resale value will be vastly higher, spares could be available in country as they mostly follow the same pattern.

[MyrtleLakeParticipant @myrtlelake]

There is no agent in the USA. I got a quote from Ceriani a while ago. The shipping costs were significant but within reason.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by MyrtleLake on 12/04/2016 21:01:33:

Here is the context driving my interest in the matter. It may be helpful to the discussion to mention it.

My workshop functions around Schaublin W20. There are two 102 lathes which use W20 collets and chucks (M37.6 x 3 spindle thread). My milling machine also uses W20 collets, and its accessories accept W20 collets and lathe chucks. The Ceriani is the only lathe I know of that is available with this spindle option.

…

Having a lathe that is native W20 would mean work could be transferred in one chucking between lathe/lathe or lathe/mill. Being able to use my existing array of collets and lathe chucks is practical too.

Those are the draws that keep bringing me back to considering the Ceriani David.

.

Bazyle,

Given this scenario ^^^

I am struggling to follow the logic of your suggestion … [quote] it would be worth looking at the possibility of finding a metric version of a typical Chinese lathe from eg Germany plus an ER collet set. [/quote]

Could you please elaborate ?

MichaelG.

[JasonBModerator @jasonb]

Well I suppose the flange mount of the typical far eastern offerings would make it fairly easy to make a spindle nose adaptor that you could cut the M37.6 x 3 thread onto and at the same time make the bore suitable to take the W20 collets. Though I don't think that was what Bazyle was thinking.

J

[Author]

Posts