"Precision" or "does NOT do what it says on the tin"

In the context of this thread, the problem is that the collet refuses to hold the piece inline with the headstocks axis of rotation because the tailend of the collet is (was) too small and unsupported, hence it wobbles. If the collet and chuck were accurate, the test piece wouldn't wobble. The headstock axis not being parallel with the lathe bed is a different issue which would cause any workpiece to be turned tapered but it would be a true running taper. I'm making a huge assumption that you might be not understanding the problem so apologies in advance if you're just posing a question about checking parallelism generally.

Hmm, did I get something wrong here too? Afaik a C type collet has a very similar form to the more usual W types in use here in my country. I was thinking that these collets are centralized by the front cone and not by the tail end ( which anyway finally is guided by the draw tube). I never checked the tail diameters of my collets (and the inside spindle dia. of the lathe), maybe I will have to do that...

Greetings, Hansrudolf

Someone wrote somewhere in site that ‘Cheap Chinese lathes’ should be regarded as a kit of parts and will need building up.  The same is true of collets sets, chucks etc. My big Chinese lathe took nearly 6 months of patient cleaning, scraping etc. to get it right. I had my hooks on a Dean Smith and Grace which used in my name sake’s tool rooms before they built the main engines for old Noah’s Ark. I could not bring it out of the UK because it was not on the DTI’s data base of machines and I was damned if I was going to provide a full set for drawings for it.

As Mr. Bogstandard says you have to fit the collet-holders to your machine and get them true.  For this reason I only buy collets and make my own holders. I bought a set of second hand Russian collets 4mm to 14mm by 0.5 mm steps for about £25.  I then made a holder and they are 0.005 mm max run out. I also do a standard alignment check on my lathes once every 3 months and again before I am going to have to do something which requires great accuracy. I only takes 5 or so minutes to do.

As to spending more money, well some western companies can turn out pretty good junk at times.  No one does 100% inspection and as the chief Chinese inspector Mr Wun Thou Wong says ‘You no gettee light allee time”.

Edited By Bogstandard on 21/06/2010 06:17:32

Hi bogs ,
                   I totally agree with you
with hobby machines you have to spend time or money having parts fitted before you can use them.
closer to home , the prescot watch makers rested on  their lorals and look what happend to them.
an error repeated time and time again in this country.

I am starting off with a cl300 lathe  that needed  the speed control fixing
having reverse engineered the pcb ,thats now working. ( the day job helps with this bit )
Now the hard part , I have decided to change / upgrade the spindle bearings , before I start to use it
I think this  will help to make the parting off tools last longer for one thing.
 i don't think an inverted parting off tool will help with this machine

having read a number of related threads on this forum i have a long list of mods to do

with hobby machines the term "precision" is miss used in the same way as "HiFi" to describe  cheap audio amplifiers.

most of the time you only get what you pay for

                                                                      john

Edited By john swift 1 on 21/06/2010 14:52:22