Checking runout on Sieg C6 lathe

[Blue HeelerParticipant @blueheeler]

Hi all,

Are these the correct method of checking runout on a lathe?

 

 

 

Edited By Jim Dobson on 28/05/2019 02:16:39

[Blue HeelerParticipant @blueheeler]

[HopperParticipant @hopper]

Yes and no.

The first test should include a reading off the large face (the one with the holes drilled in it) as well. If that is out, the chuck will "wobble".T

The second test tells you not a lot. The outside of the chuck body running true does not prove the jaws and the job they are holding is running true. The outside of the chuck body could be 3mm out of true but the jaws could be true.

Third test tells you nothing much at all. It tells you the lathe is turning round, not lobed or egg shaped, but a freshly turned cylindrical surface will always read zero like that that as the dial indicator is replicating the position of the tool that turned it. It does not mean there is zero runout between the smaller diameter held in the jaws and the larger freshly turned surface. That could be out by millimeters and still read zero on that set up.

What exactly is it you are trying to determine on your C6?

Edited By Hopper on 28/05/2019 05:40:54

[Blue HeelerParticipant @blueheeler]

Hi Hopper and thank you for the reply, much appreciated.

I've seen so many and read so many posts about run out on lathes (I've had this lathe for 6 years and its done everything I've asked it to) so I suppose your question to me " What exactly is it you are trying to determine on your C6?" is a good grounding question and one that should just get me back to turning and making things for my steam hobby instead of trying to find problems with 'Run out' that my skill set wouldn't even know how to rectify if I found it.

I suppose we're all a bit guilty of doing this now and again (though I shouldn't speak for anyone else so I'll just raise both hands for me, myself and I) of worrying about nought that we should be.

Jim

Edited By Blue Heeler on 28/05/2019 06:15:27

[HopperParticipant @hopper]

LOL, yes if it ain't broke, don't fix it.

There is also confusion between "runout" and "alignment" which are two different things.

But if your jobs are turning out satisfactorily, carry on lathing!

[Blue HeelerParticipant @blueheeler]

Thanks Hopper, I've just said your quote above as a mantra 10x LOL –

" yes if it ain't broke, don't fix it".

The most accurate thing I suppose I do on the lathe is make cylinders and pistons for model and toy steam engines and they turn out very good.

When I bought it I had a friend (who has now sadly passed on) with a machinist level set it up so there was no twist in the bed and he did some test cuts and miked it out till he was happy and he was a perfectionist.

I'd never even touched a lathe or mill till they were delivered off the back of the truck and taken out of their crates. Best tools I have EVER owned, I just wish I'd bought them a helluva lot of years earlier!

Thanks again for planting my feet back down firmly on earth, much appreciated mate!

[JasonBModerator @jasonb]

Posted by Hopper on 28/05/2019 05:39:41:

Yes and no.

The first test should include a reading off the large face (the one with the holes drilled in it) as well. If that is out, the chuck will "wobble".T

If backplate was turned on the machine and always goes back in the same place the chuck won't wobble if the backplate is out. Same applies to the register that locates the backplate that can be out but if backplate were turned on machine all will be well, hence not so worried about the second reading on my machine

[Blue HeelerParticipant @blueheeler]

Thanks Jason and thanks for posting the video up of your lathe (I've subscribed to your channel).

Cheers,

Jim

[HopperParticipant @hopper]

Plus there is no point in getting too fussy when most three jaw chucks are lucky to hold a job true to within two or three thou (.08mm) anyways. If you want a job to run dead true, use a four jaw chuck and dial indicator.

Or start with oversize material held in the three jaw and turn all diameters in one sitting without moving it in the chuck.

Edited By Hopper on 28/05/2019 08:57:23

[Neil WyattModerator @neilwyatt]

I would only add that those long multi-joint indicator stands are not ideal. I use a single pillar with a solid cross piece to minimise overhang and flex. Any movement can hide or exaggerate readings depending on the situation.

Neil

My SC4, silver steel in (a very clean) 3-jaw chuck:

[SillyOldDufferModerator @sillyoldduffer]

Jim's right to say we're all guilty of this. It's so tempting to measure a new lathe with that new DTI and micrometer. I've led myself up the garden path without a paddle more than once! Orgies of clumsy measuring of all the wrong things.

Trouble is measuring tiny distances with precision is full of pitfalls. There are so many things to go wrong including invisible dirt and temperature changes. Technique is all important; the most expensive kit in the world won't get the answer right unless it's used correctly. And you have to understand why taking the measurement is meaningful in the first place and the extent to which the result matters in the real-world. Or not.

New industrial machines are often set-up and tested by specialist installers. With hobby machinery and mixed-ability owners, I feel it's safer to detect trouble by using the machine to cut metal. Cutting metal generates clues in abundance. It avoids sticking a DTI on a machine, jumping to the wrong conclusion, and then messing up big-time by fixing the wrong problem. After cutting reveals there's an issue measuring can isolate the cause and confirm when it's fixed.

How to apply Schlesinger would make a good MEW article if anyone has the time and skills needed to put it together. This Stub Mandrel chap seems to know all about it. Like Superman and Clark Kent, Neil and Stub Mandrel have never been seen together…

Dave

[Blue HeelerParticipant @blueheeler]

Appreciate the replies one and all.

Cheers,

Jim

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