# lathe runout?



## penzen (Sep 14, 2006)

How does one test the runout of a lathe or a mandrel.  As a new owner of a Jet Mini VS with extention, I would like to know how true my lathe is.  The live center in the tailstock meets very close with headstock spindle but this is only a visual check. All comments appreciated.

Tom


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## Rifleman1776 (Sep 14, 2006)

I'm not sure what you mean by the term "run out". If you are referring to correct alignment, the point of a tailstock live center should meet exactly with the point of a drive spur. Anything less than exact is unacceptable.


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## chigdon (Sep 14, 2006)

I am not sure how to measure it but wood lathes are going to be horrible compared to metal lathes.  That being said for a small inexpensive lathe, a Jet mini should be much better than most.  Someone like Bruce Boone would be more qualified to answer this.


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## Chuck Key (Sep 14, 2006)

Even when the points meet exactly, if you rotate the spindle 180 degrees they may not.  If not run out.



> _Originally posted by Rifleman1776_
> <br />I'm not sure what you mean by the term "run out". If you are referring to correct alignment, the point of a tailstock live center should meet exactly with the point of a drive spur. Anything less than exact is unacceptable.


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## Rifleman1776 (Sep 14, 2006)

> _Originally posted by Chuck Key_
> <br />Even when the points meet exactly, if you rotate the spindle 180 degrees they may not.  If not run out.
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> 
> ...



Agreed, but I think with a wood lathe visually 'exact' would suffice. Some would call it a "sweet spot" when they meet at one point but not another. That is [explitive deleted] nonsense. I was told this by someone who claims to be very knowledgable then checked with many acknowledged master turners. The string of 'explitive deleteds' comments was scorching. There simply is no such thing as a "sweet spot", don't be mislead otherwise. The lathe is true or it isn't. Accessories (mandrels, etc.) that don't meet exactly are defective also.


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## Mudder (Sep 14, 2006)

> _Originally posted by Rifleman1776_
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Iâ€™m a little confused by your question. 

If you want to measure â€œrunoutâ€, I would define that as how well your mandrel or center runs compared to the centerline of the latheâ€™s rotational axis. In order to make this kind of measurement you will need a dial indicator or a test indicator and a way to mount it.

First thing I do is see if the mandrel is true by holding the rod in a vee block and setting the indicator to check any deviation from zero at several points along my morris taper.
(that is assuming that you are using a tapered mandrel)  Once I am satisfied that my mandrel is running correctly I mount it in the lathe and check the deviation from zero at several places along the mandrel rod.


The other measurement that I take is one of alignment (both vertical and horizontal). I have checked lathes running from the cheapest import up to and including Novaâ€™s, Powermatics and Oneways and I have found that it is possible to **** the tailstock on each and every lathe and throw it out of alignment to one degree or another. Contrary to what Frank says I have found that latheâ€™s do in fact have a â€œsweet spotâ€ and this is how I find it. 

When I set up to drill I always bring up my tailstock up and while the tailstock is unlocked I bring the point of the drill into contact with the material that Iâ€™m drilling while the lathe is spinning and allow it to find centerâ€¦â€¦Also known as the â€œsweet spotâ€. I also do this when I bring the tailstock up to support the end of my mandrel for penturning. The only time that I cannot use this method to find the â€œsweet spotâ€ is when Iâ€™m turning between centers using a spur center in the headstock and in that situation you will be roughing the wood and creatiog your own centerline.

In summation, unless you find that your lathe is GROSSLY out of alignment but does have little runout I would not worry too much because using the methods above you can indeed find that a lthe has a â€œsweet spotâ€.


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## bonefish (Sep 14, 2006)

A crude way to do it is to mount the mandrel, and while the lathe is turning, support a magic marker on something and very slowly and gently, bring it to the mandrel and lightly touch the spinning mandrell.

If the magic marker only touches in one place, then that is the high side of the mandrel, and the lathe is not running true. 

If the marker makes a mark all the way around, that means the mandrel is close to center, as close as this crude method will indicate. I know this method is not precise and has its limitations, but it will give you a general idea.

The only sure way is with a dial indicater and/or a center finder.

Mudder, I don't understand the 'sweet spot.' There might be one spot that you find that is 'sweet', but that doesn't mean that the remainder of the mandrell or drill is. If you adjust the tail stock and are able to get the mandrel running true, then, yes you have what you referring to as a sweet spot. 

If there are places that are not 'sweet' they are going to cause either an oversize or off center hole if you are using a drill, or an oval if you are turning with a mandrel.

I can only give you the benefit of my experience, but finding the center, or sweet spot by running the drill up to the spinning part and letting it find it'own center, I have never been able to drill a hole in the exact center by doing this. You can get closer by using a center drill to start the hole, but it still isn't exact.

Bonefish


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## Paul in OKC (Sep 14, 2006)

> _Originally posted by Mudder_
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I would agree with you here, Mudder. The cost of making dead on alignment for a wood lathe would drive the cost up. There is enough play in the tail stock as you said to make the alignment off a bit at any given time you slide it up and lock it down. I agree with checking the headstock using a indicator on the morse taper part and see if there is any 'runnout'. The only time slight mis-alignment is an issue, in my opinion, is if you drill your blanks on the lathe. This could cause a slightly tapered hole, being larger at the entry piont than at the end. Just my .02


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## Paul in OKC (Sep 14, 2006)

> _Originally posted by bonefish_
> <br />A crude way to do it is to mount the mandrel, and while the lathe is turning, support a magic marker on something and very slowly and gently, bring it to the mandrel and lightly touch the spinning mandrell.
> 
> If the magic marker only touches in one place, then that is the high side of the mandrel, and the lathe is not running true.
> ...



This may not be totally accurate. Such a case would be if your mandrel is bent. I rely very little on my mandrel for telling me that my lathe is true. The taper could be fine and your mandrel slightly out, either by the threads or being bent, and you could chase forever and 'out of line' problem.


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## bonefish (Sep 14, 2006)

Paul:

If the mandrel is bent, putting it in the head stock and leaving the other end free and turning on the lathe will quickly indicate if it is bent.

The end will wobble.

Bonefish


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## Paul in OKC (Sep 14, 2006)

> _Originally posted by bonefish_
> <br />Paul:
> 
> If the mandrel is bent, putting it in the head stock and leaving the other end free and turning on the lathe will quickly indicate if it is bent.
> ...


And your point is.....The discussion here is runnout. You  can not judge runnout by the mandrel, is what I meant. The 'far' end of my mandrels have never run dead on when loose from the live center, but everything is true when the center is in, that's what matters to me.


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## Mudder (Sep 14, 2006)

> _Originally posted by bonefish_
> <br />I can only give you the benefit of my experience, but finding the center, or sweet spot by running the drill up to the spinning part and letting it find it'own center, I have never been able to drill a hole in the exact center by doing this. You can get closer by using a center drill to start the hole, but it still isn't exact.
> 
> Bonefish



I don't know if we are talking about the same thing. By running the drill up an allowing it to find center you are indeed in the "Sweet spot". You are drilling on the centerline of the rotational axis. If I wanted to drill dead center in a blank then I would indicate the blank to be sure that the outside of the blank is zeroed to the rotational axis of the lathe. I often put a blank between centers and turn it round, then put it into the collet chuck which I know is true to the centerline of the rotational axis of the lathe and then bring up the tailstock and allow it to find its "sweet spot", thus drilling dead center of the blank.

When I jump on one of the 12 lathes at work I never have to worry about the tailstock because our tool room lathes have dovetail beds and the production lathes run on other systems that guarantee accuracy. I would also drill as close to the collet or chuck as I possibly could and indicate the work to be sure that all my alignments are correct in relation to the rotational axis of the machine.

Basically speaking, the â€œsweet spotâ€ of a lathe is dead center of the rotational axis.


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## txcwboy (Sep 14, 2006)

lots of "quoting" going on here ! Phewwwwwwwwww


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## Paul in OKC (Sep 14, 2006)

> _Originally posted by txcwboy_
> <br />lots of "quoting" going on here ! Phewwwwwwwwww



[]


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## bonefish (Sep 14, 2006)

Mudder:

We are talking about something different. 

I was talking about if a drill were chucked in a tailstock that is out of alignment.

Yes, a drill that is true to the axis of rotation will start in the center of the rotional axis of a piece of material mounted in the headstock.

I have never heard it referred to a sweet spot, though.

I also though we were talking about a sweet spot in the live or dead center, or a drill in the tailstock. 

In this instance, I don't believe there would be a sweet spot in the tailstock. I also don't think the drill would start in the center of the axis of rotation of the material in the headstock.

If I wanted the hole dead center, I would first drill the hole, then mount the material between centers, and turn it until the hole was in the center.

Bonefish


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## Paul in OKC (Sep 14, 2006)

> If I wanted the hole dead center, I would first drill the hole, then mount the material between centers, and turn it until the hole was in the center.
> 
> Bonefish



Huh?  If you run it between centers, the hole is already in the center, you don't have to turn it til it gets there.[]


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## bonefish (Sep 15, 2006)

Paul:

Mounted between centers, the hole is in line with the axis of rotation. The outside of the material probably isn't, because a drill seldom drills straight, even the gun drills which use a deep hole boring head.

The barrel, or whatever the object being made will not have the same amount of material on each side of the drilled hole. To get the same thickness of material all around the drilled or reamed hole, the hole is placed between centers, using a live and dead center, and material is removed until the outside surfaces are parallel to the center axis of the hole.

I think this subject has been beaten to death. This will be my last post on this subject.

bonefish


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## Mudder (Sep 15, 2006)

> _Originally posted by bonefish_
> <br />Paul:
> 
> ......... because a drill seldom drills straight, even the gun drills which use a deep hole boring head.




Guess it's all in the setup.

We make an 8mm Z stroke rack for a company that is 18" long and we gun drill a 3mm hole through it, consistently holding true position within a diameter of .001â€. I don't know about you but I would consider that a pretty straight hole over that distance.


Getting back to the "sweet spot". The tailstock is considered by a great many turners as to have found it's "sweet spot" when it is aligned with the rotational axis of the lathe (The place where it will do the best). Your lathe tools also have a "sweet spot", the place where they cut the best (you wouldn't try to make a cut using the top wing of your gouge would you?). A baseball bas has a "sweet spot", where it will hit the ball the farthest; I'm also told that golf clubs also have a sweet spot.

In the end I guess it just might boil down to what we choose to refer to the same thing. Is it a paper bag or is it a paper sack? A can of soda or a can of pop? Etc, etc.


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## ctEaglesc (Sep 15, 2006)

How amny angels can dance on the tip of a live center?


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## Mudder (Sep 15, 2006)

> _Originally posted by ctEaglesc_
> <br />How amny angels can dance on the tip of a live center?



3542.889649 [] + one more in a pink frock []


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## Paul in OKC (Sep 15, 2006)

> _Originally posted by Mudder_
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I am glad you added the extra one, other wise I was going to question your calculations[]


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## Jerryconn (Sep 15, 2006)

The one in the pink frock... Is that one any kin to Fanger [][}][]
Seriously the answer is ........however many want to  (OK, Ok, I'm kidding)[}]


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## ctEaglesc (Sep 15, 2006)

Do you guys really worry about this stuff?
GEEZE! believe me when I tell you that when I get a wobble I let out a few curse words and then continue turning the pen.
You are worried about a measurement that is less than a thickness of paper over a 6" span.
This aint rocket science.If it were I would find something else to make in my shop.


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## Paul in OKC (Sep 15, 2006)

> _Originally posted by ctEaglesc_
> <br />Do you guys really worry about this stuff?
> GEEZE! believe me when I tell you that when I get a wobble I let out a few curse words and then continue turning the pen.
> You are worried about a measurement that is less than a thickness of paper over a 6" span.
> This aint rocket science.If it were I would find something else to make in my shop.


Like little pink angel frocks[]


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## Mudder (Sep 15, 2006)

> _Originally posted by ctEaglesc_
> <br />Do you guys really worry about this stuff?
> GEEZE! believe me when I tell you that when I get a wobble I let out a few curse words and then continue turning the pen.
> You are worried about a measurement that is less than a thickness of paper over a 6" span.
> This aint rocket science.If it were I would find something else to make in my shop.




I'm not worried, are you?  []


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## clewless (Sep 15, 2006)

> _
> This aint rocket science.If it were I would find something else to make in my shop.
> _


_
Eagle, you took the words right out of my mouth![][]_


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