# How important is lathe chuck run out?



## Pcmaker (Oct 16, 2018)

I know it's not an accurate way to measure run out, but I indicated the surface of my 3-jaw chuck and I get around .007 run out. 

If I put an end mill in the chuck and indicate about an inch away from the chuck, I get more than that. 

How important is chuck run out?

I tried loosening the nuts holding the chuck and moving it around, retighten it, but that didn't do all that much. 

Also, if you take out your 3-jaw chuck, is there a process you have to do to get it back on or do you just slap it on there after cleaning the mating surfaces and tighten the nuts?


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## BaronJ (Oct 16, 2018)

Hi Guys,

7 thou is not that bad !  If you want accuracy use a four jaw chuck or a collet.
However if you are going to complete the job with removing it from the three jaw then it probably doesn't matter.


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## markba633csi (Oct 16, 2018)

7 thou is a bit on the high side- my Shars 4" is about 3 thou.  If your chuck is mounted to a backplate sometimes you can improve the fit by taking off material and tapping the chuck into position
m


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## Pcmaker (Oct 16, 2018)

Is the backplate where the chuck bolts into? Or is that a separate part from the chuck and where the chuck mates to onto the lathe?


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## WarrenP (Oct 16, 2018)

Thats what I did, I separated the chuck from the backplate on the back of the chuck and took material off the backplate so it could be adjusted more. Then the chuck a bit loose still, tap it on the high side until you get it in position and tighten. I can get mine down to less than a thousand that way, ( I think more if I wanted to cut more off). If you have a piece of round stock you know is actually round (ground , etc) you can put that into the chuck and measure it.


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## WarrenP (Oct 16, 2018)

Pcmaker said:


> Is the backplate where the chuck bolts into? Or is that a separate part from the chuck and where the chuck mates to onto the lathe?



I took the back plate off the chuck on mine. If you cut the ridge a little then the outside of the chuck can move more for adjustment. That's how mine was anyway... if you posted a picture with the chuck off everyone could be sure on it.


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## Dabbler (Oct 16, 2018)

I never worried about run-out in my 3 jaw chuck.  It is a great practice to plan your work so you can do as much as possible usign a single set up so rechucking is not on the table.  In all my time machining, I seldom, if ever had to indicate in a piece of work for a second operation.


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## RJSakowski (Oct 16, 2018)

First, which surface are you referring to?  If it is the OD of the chuck body, don't worry about it.  If it is the flat face, it would be desirable to have minimal runout as it is useful to use that face as a reference surface.  The biggest concern is run out in the jaws.  It is ideal to have zero runout in the jaws to permit removing and remounting work as to work on both ends of a part.  

I check jaw runout by mounting a dowel pin or similar ground surface in the chuck and measuring the position of the surface as I rotate the chuck.  The TIR or total indicated runout is the difference between the minimum and maximum readings.  The readings are usually made close to the chuck jaws and at a distance of a coouple of inches from the jaws.  The first TIR value is usually considered to be radial runout while the second also includes angular runout.  Radial runout is considered to be due to a difference in jaw position due to a poor jaw grind or to wear in the scroll or both.  Angular runout is caused by the jaws not being parallel to the spindle axis.

Because of the design of a scrolling chuck, it is difficult to obtain zero runout for all diameters.  .003" is not uncommon, even in a new chuck.  There is a type of chuck called a "set tru"  where the chuck can be centered for zero runout at one particular diameter.  Usually, if zero runout is desired, a four jaw chuck is used.  A four  jaw chuck can correct for radial runout but it will nit eliminate radial runout.  Another way is to run your work on centers.  This will ensure repeatable zero runout on your workpiece even with removal and reseating from the lathe.

You can work with a chuck with runout.  As Dabbler said, try to set up your work sequence so all of critical turning is done in a single setup.  This sometimes requires some out of the box thinking.  I believe that Joe Pieczynski on YouTube showed a workaround for obtaining zero runout from a chuck with runout.


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## benmychree (Oct 16, 2018)

A sloppy 3 jaw chuck is nearly worthless, you should be able to chuck up a round part and have it run within no more than 3 thou.  If it was mine, I'd buy a new chuck.


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## pacifica (Oct 16, 2018)

For several years I used collets and 4-jaw chuck only, then I got a 3 jaw with under 1 thousanths tir and now usually it is all I use, Convenience wins out.


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## Pcmaker (Oct 16, 2018)

I've wanted to get 4 jaw self centering chuck anyway. This is my lathe:

http://www.grizzly.com/products/Grizzly-7-x-12-Mini-Metal-Lathe/G8688

It comes with a 3" chuck with 3 jaws. 

Can I upgrade my lathe to use a 4" or larger chuck? How do I know it'll fit my lathe? I see some chucks on Amazon, but not sure which one would fit my lathe and also which one would be an "upgrade"  with less runout


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## higgite (Oct 16, 2018)

Pcmaker said:


> I've wanted to get 4 jaw self centering chuck anyway. This is my lathe:
> 
> http://www.grizzly.com/products/Grizzly-7-x-12-Mini-Metal-Lathe/G8688
> 
> ...


Littlemachineshop.com sells a 4” 3-jaw scroll chuck with adapter to mount on your 3” spindle flange for $132 + shipping. They claim .003” max radial runout. No affliation, just a satisfied customer.

Tom


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## magicniner (Oct 16, 2018)

Pcmaker said:


> How important is chuck run out?



It's not. 
As stated above well planned work obviates the run out.
In addition any run out means reversing work will have a visible artefact in the finish so anything but perfect is a pointless ambition


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## BaronJ (Oct 16, 2018)

Hi Pcmaker,

Why not measure the run out at say three different diameters and see what you get.  You should find that at one particular diameter you have a minimum figure.


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## Pcmaker (Oct 16, 2018)




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## BaronJ (Oct 16, 2018)

So in that video, he is getting 8 thou !  No big deal !


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## Pcmaker (Oct 16, 2018)

I hope that endmill is a good enough indicator for that


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## ChrisAttebery (Oct 16, 2018)

The run out on the 6” 3 jaw on my 13x40 had .012”TIR . It was a PITA to deal with. A lot of my lathe work is second ops. I just bought a new 6” 3 jaw with integrated D1-4 Mount from Shars and it has .0015”TIR. It’s taken the dread out of lathe work and made it fun again.


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## mikey (Oct 16, 2018)

PCMaker, here is some basic info that might give you some insight.

Run out on a 3 jaw chuck has numerous sources - the accuracy of the spindle, how the chuck mates to the spindle register, how tight your bolts are that tighten the chuck to the spindle, the accuracy of the machining of the chuck body/jaws/scroll and probably several others that I can't think of right now. They all add up to your TIR, or total indicator run out. The way to check how much is there is detailed in RJ's post.
All scroll chucks have some run out, although high end chucks typically have less than cheap ones. Now, the very first time you chuck up a work piece and turn it is called a First Operation. In a first op, no matter how much run out your chuck has the work piece will turn on the center line of your spindle and the work will be accurate as long as you do not remove the work piece from the chuck. What matters is that the jaws hold the work solidly and that you do not remove it from the chuck. This is a good thing because much of the stock we start with is not truly round to begin with, but it is once we turn it.
It is only when you remove the work from the chuck for some reason and then try to re-chuck it that your run out matters because the likelihood of being able to get it re-centered or aligned with the spindle centerline are nil unless you have a chuck that allows you to dial it back in. You can use a 4 jaw chuck or a scroll chuck with an adjustable position (set-tru, adjust-tru, whatever) or possibly a collet chuck to get it close to or back on the spindle centerline. When you re-chuck a piece (that has already been turned) for further work on the lathe, this is called a Second Operation and the accuracy or run out of the chuck used for a second op is where you need minimal TIR. This is really where a 4 jaw comes in handy. It is the potentially the most accurate chuck you can have; it is also the slowest to use.
The bottom line is that it is pointless to check run out on a 3jaw scroll chuck provided the jaws are intact, in good shape and grabs the work tightly. For first op stuff just use it. For second op stuff, get a 4 jaw.

As for how big a chuck to get, use the smallest chuck you can that will do the work you need it to do. Big chucks hold bigger stuff but weigh more, wear the spindle and spindle bearings more and the jaws have the potential to contact the ways if extended far enough. I would think the largest you should go is a 4" without worrying about hitting the lathe with the jaws. A 5" will work but will not gain you much more capacity (because of the jaw hitting thing).


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## Cooter Brown (Oct 16, 2018)

You can grind the inside of the jaws with a die grinder on the tool post......I have a friend that did this to his chucks he said he got better results using a carbide burr instead of a grinding stone...


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## Pcmaker (Oct 16, 2018)

I really want a 4" 4-jaw chuck that's compatible with my lathe... that also has little run out. 

Or I'll just save up money and get me a Precision Matthews 10x22 lathe

Something more ridgid than my 7x12... something that can part with no issues and something that comes with DRO installed.


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## mikey (Oct 16, 2018)

Give LMS a call and see what they can do for you re the 4 jaw. 

If you're thinking of stepping up to a 10, why not go a little further and go with the PM 1127? It has all the features a good lathe needs at a price that is really, really good for what you get, including a D1-4 spindle that makes buying chucks simple.


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## Pcmaker (Oct 16, 2018)

mikey said:


> Give LMS a call and see what they can do for you re the 4 jaw.
> 
> If you're thinking of stepping up to a 10, why not go a little further and go with the PM 1127? It has all the features a good lathe needs at a price that is really, really good for what you get, including a D1-4 spindle that makes buying chucks simple.



We'll see how much I get from the tax man next year.


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## higgite (Oct 16, 2018)

Pcmaker said:


> I really want a 4" 4-jaw chuck that's compatible with my lathe... that also has little run out.


Runout on a 4-jaw is immaterial. That's the beauty of a 4-jaw. You can adjust it for near zero work piece runout.

Tom


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## Pcmaker (Oct 16, 2018)

higgite said:


> Runout on a 4-jaw is immaterial. That's the beauty of a 4-jaw. You can adjust it for near zero work piece runout.
> 
> Tom



Are you talking about independent 4 jaw chucks? I was thinking of getting one, but I figure it's a pain you have to zero it every time you put work piece in.


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## higgite (Oct 17, 2018)

Pcmaker said:


> Are you talking about independent 4 jaw chucks? I was thinking of getting one, but I figure it's a pain you have to zero it every time you put work piece in.


Sorry, yes, I should have said independent. When I think 4-jaw, I don't think scroll. Like was said earlier by others, you can use a 3-jaw and have zero runout on a finished piece that you can turn in one operation. But, if you have to do what Mikey called a second op on the work piece, that's when you will need the 4-jaw IF you want to maintain concentricity of your cuts. Before I got a collet chuck, my 3-jaw got most of the ride time on my lathe because it could handle most of the stuff I did. The 4-jaw only came in from the bullpen when the 3-jaw couldn't finish the game. Yes, a 4-jaw does get tedious if you use it for everything. But, if you want zero runout on a multi operation part, as a famous philosopher once said, their ain't no free lunches.

Tom


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## Pcmaker (Oct 17, 2018)

what's a second op?

I'll get a 4 jaw independent chuck, but it'll probably be a specialty chuck that won't be used too much.


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## ddickey (Oct 17, 2018)

Removing after finishing your first operation(s) then reinserting your work piece into the chuck. This is second operation.


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## Dabbler (Oct 17, 2018)

I use my 3 jaw 80% of the time, but the 20% I use my 4 jaw - well those things just can't be done any other way, that I know of.  In all the years (38? 39?)  I've owned my lathe, I've never used the face plate.  (I've mounted it a few times and spun it up, just to see it go!) 

Your mileage may differ.  I consider the 4 jaw independent chuck to be far more indispensable than a 3 jaw scroll chuck.  You can do everything with it, even things that are usually done by a 3 jaw, but a little slower.  Remember what I said about doing as much as I can in one set up?  With a 4 jaw independent, it only adds 3 or 4 minutes to that set up...  food for thought, maybe?  

a quick example:  I was making a multi cavity mold out of a piece of 5" aluminum.  I mounted it in my 4 jaw independent chuck and made the cavity.  I then indexed the work piece by rotating it in its offset position and completed a ring of cavities.  I then advanced toward the centre, and made some  more.  Impossible in a scroll chuck, trivial in a 4 jaw chuck.  (not one of the cavities was in the centre of the aluminum)


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## ddickey (Oct 17, 2018)

I remember last summer or spring some guys here bought four jaw independent chuck's that could also be used like a scroll chuck.


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## BaronJ (Oct 17, 2018)

Hi Guys,

There are a few three, four and six jaw scroll chucks available in a range of sizes.
A friend of mine has a six inch six jaw scroll chuck, he says is great for thin stuff.  He also has a set of soft jaws for it, for when he needs high second op accuracy.

I also use soft jaws on my three jaws scroll chuck when I need to, such as boring out a gear.


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## RJSakowski (Oct 17, 2018)

Pcmaker said:


> I've wanted to get 4 jaw self centering chuck anyway. This is my lathe:
> 
> http://www.grizzly.com/products/Grizzly-7-x-12-Mini-Metal-Lathe/G8688
> 
> ...


  Be aware that a 4 jaw self centering chuck has the same runout issues as a 3 jaw chuck.  Most use a 4 jaw chuck because of the the ability to adjust each jaw independently and thus achieve zero runout.

Aside from the ability to accurately set up second operations, another use for the four jaw would be to mount previously machined parts for remachining.  An example might be a shaft that needs a bearing surface remachined.  It is important that the new surface be concentric with the original machining and the 4 jaw chuck permits that alignment.

A four jaw chuck still has the potential for angular runout.  You can zero runout at one  position on the work, usually near the chuck jaws.  If there is angular runout, you will see see it at positions other than the adjustment position.

Kieth Fenner has a number of excellent YouTube videos on setting up work in a 4 jaw chuck.


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## pacifica (Oct 17, 2018)

ddickey said:


> I remember last summer or spring some guys here bought four jaw independent chuck's that could also be used like a scroll chuck.


They’re nice but expensive;a 4 jaw scroll chuck with a set-tru ability


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## Dabbler (Oct 18, 2018)

Marc LeCuyer makes some great points about work holding in his 2 part video:


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