Mini Lathe Unwanted Taper?

[ShagDog]

To preface, I am a lathe junkie. I do not need another. However, I am intrigued to some degree with Mini Lathes. For me, the most important criteria for a lathe is the ability to cut repeatably with no taper. I am referring to turning with no tailstock support. A basic rule I follow is to have no more than about 3x the diameter of the material sticking out from the chuck.

I am interested to know about your experiences with your mini lathes and whether you can achieve repeatability in turning with no taper repeatably. By "repeatably", I mean from one day to the next and from one material (like steel) to another (like aluminum) or any other definition you would like to give it.

 

[markba633csi]

Good question- I'd be interested in knowing that too, although I'm not currently in the market for one
Several factors can cause taper besides the alignment of the headstock to the ways
Poorly fitted carriages, rigidity and toolholding issues can all introduce errors

 

[mac1911]

Do you have a limit on your taper ?

How mini if a lathe are you intrigued by ?

 

[ShagDog]

Do you have a limit on your taper ?

How mini if a lathe are you intrigued by ?

Yes. As close to zero as possible. About .0003" max over 3" length on 1" diameter for example, so about .0001" per inch. Am I asking too much? Is anyone getting close to this number?
As to mini lathe, 7x to 9x.

 

[markba633csi]

That's a tall order for any mini lathe- curious to hear what others say
Especially on the cheapie lathes like Vevor (provided they stay running long enough to finish the cut)

 

[ShagDog]

My feeling is you wouldn't reach that with any mini lathe-
-- but
If you were taking very light cuts with a very sharp tool- you might get close
You are talking Monarch or Hardinge performance numbers

Actually, I should have specified. I am talking about very light finishing cuts with the appropriate tool. Maybe I am asking too much, but, I am interested to know whether it can be done consistently with a very small lathe. I don't think one needs a Hardinge or Monarch to achieve these numbers. Blondihacks can do it on her PM 1022 (seen in her video on lathe alignment).

Here is the Blondihacks video:

 

[homebrewed]

To a large extent it depends on the particular lathe. The bed could be warped or twisted, which would put a lower limit on what you could get by aligning the headstock. The spindle bearings aren't of particularly high quality so that could be a factor as well. They aren't tapered roller bearings, they are deep-groove types. The lathe chucks that come with the lathes have TIRs in the .002-.003" range (quoting from the LMS catalog).

Issues like this can be addressed. Assessing the situation is key to determining the limiting factors and coming up with a plan to fix or minimize them.

 

[RaisedByWolves]

Yes. As close to zero as possible. About .0003" max over 3" length on 1" diameter for example, so about .0001" per inch. Am I asking too much? Is anyone getting close to this number?
As to mini lathe, 7x to 9x.

Yes and no.

With carbide tooling and a heavy cut you’re doing good at .003 over 3” on a 7” chineses lathe. In fact I would say that would be exceptional.

A good lathe in the same size range with a properly ground HSS tool bit might get you what your looking for, but that is wholly operator dependent.

 

[WobblyHand]

Think it's possible, but you probably have to do some tweaking, like alignment of the head stock. My LMS mini had a slight taper, but I managed to align the head stock a little better. Don't think it's at 0.0001"/inch though. Haven't measured it in a couple of years, but I'd be surprised if it was that good. Most of the time I don't need that level of performance!

 

[ShagDog]

Yes and no.

With carbide tooling and a heavy cut you’re doing good at .003 over 3” on a 7” chineses lathe. In fact I would say that would be exceptional.

A good lathe in the same size range with a properly ground HSS tool bit might get you what your looking for, but that is wholly operator dependent.

Did you mean .0003" or .003"? I am actually referring to a very light cut like maybe a couple thou to finish to size. I would probably also use HSS instead of carbide.