# Chuck diameter question



## borjawil (Jan 28, 2017)

New to metal lathes. Reading around I've read that the diameter of the middle of the chuck (spindle) limits the diameter of a piece you can work on. However, that doesn't make sense since the chuck will hold much bigger a size. So I'm missing something here. Any one care to elaborate?


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## T Bredehoft (Jan 28, 2017)

If you want to bore out the chamber in a rifle barrel, you have to put the barrel through the spindle.  If you want to make a dozen 2" pieces from bar stock, the bar has to go through the spindle. If you don't want to do either of these, the diameter of the through hole doesn't matter, you can chuck as large a piece in the chuck as it will hold.


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## mikey (Jan 28, 2017)

Not sure where you read that but it is wrong. Your chuck can extend its jaws only so far before they don't grab properly; typically this will be 2/3 of their travel. If you extend the jaws to this max and the jaws don't hit the ways then that's the max diameter you can turn in front of the cross slide. Then there is the diameter that will fit over the cross slide; that is the max your lathe can turn from end to end.


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## Bob Korves (Jan 28, 2017)

The spindle is not the chuck.  The spindle is what the chuck attaches to.  Most lathes have a hole through the spindle.  The size of that hole determines the size of stock you can put through the spindle, which is a very useful thing to do.  I have put a 20 foot length of 1/4" bar through my spindle so I could make a 1/4" - 20 pitch LEFT HAND thread because I did not have a die for the job.  It requires considerable thought and care to make sure the 1/4" rod does not whip around and hurt somebody (I contained it in a pipe that was securely anchored), but it works just fine if you do it correctly.  I was threading a longer piece, several feet, but by having the stock through the spindle you can make one short piece after another, pulling the bar out of the chuck for the next part.  Much scrap is avoided by this process, and much wasted time as well.


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## borjawil (Jan 28, 2017)

Ah I see. Well lets say i need to make bushings or spacers from bar stock where the diameter exceeds what will fit in my spindle, however I only need the spacer to be 1" long. Can I put a 4" piece of bar stock in the chuck, center it, face it, etc. And turn it to my specs? Why or why not


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## Bob Korves (Jan 28, 2017)

Sure you can,  That is a primary use of the lathe.  Welcome to Hobby Machinist!


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## T Bredehoft (Jan 29, 2017)

Depending on the distance between the chuck and a live center in the tailstock, you can turn a piece that long. It can be as big around as twice the distance from the center of the chuck to the top of the saddle/crossfeed.


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## borjawil (Jan 29, 2017)

Ok, so if I'm able to do what I want to, then whats with the site of the spindle and getting a piece through that diameter? I think I'm missing the point of that.


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## francist (Jan 29, 2017)

Well for one, there are practical limitations to doing what you want to do. You can't just take a one inch bar of twelve inches long, say, and chuck it by one end and have it. It's going to go sideways on you and ruin your day. Anything more than about 3 diameters sticking out of the chuck and you want to start thinking about second means of support -- like a tailstock or steady rest. And if you want to bore or face on the end of your part, having the tailstock sticking in there is going to create a challenge. Hence the desire to pass the work through the chuck and spindle, so that you can stick out of the chuck a safe amount to do your work on the end, part your piece as desired, and then advance more work through the spindle and out of the chuck for the next piece. 

-frank


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## Bob Korves (Jan 29, 2017)

borjawil said:


> Ok, so if I'm able to do what I want to, then whats with the site of the spindle and getting a piece through that diameter? I think I'm missing the point of that.


Look at my post #4 again.  Smaller work up to the size of the spindle bore can extend all the way through the spindle and beyond, the part made and cut off, quickly and without wasting stock, often all in one setup.  Any time you have to remove a part you are working on and then remount it, you lose the accuracy of the single setup and introduce errors in the part.  If you use a longer piece of material just to hold it in the chuck, the stub in the jaws becomes leftover scrap metal at worst, a remnant at best.


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## borjawil (Jan 30, 2017)

Ah ok. Well most of what i want to do is going to be 1-2" in diameter, from 1" to 10" in length, and will need to be bored as well. So anything over 3" past the chuck I'm going to want something to support the work. Ive seen different options such as the steady rest or using the pointed thing on the tail stock. What are the pros and cons of these different devices and when are they best used? As I'm looking for a replacement tool rest i also need to find the tooling I will use.


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## Bob Korves (Jan 30, 2017)

Make sure you understand how to set up a steady rest, so the work is held properly and so the work does not want to walk out of the chuck.  It takes some understanding and care to get it right.


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## brino (Jan 30, 2017)

Hello @borjawil and Welcome to the site!

Here's a couple of PDF books you might find useful:
http://hobby-machinist.com/resources/sb-how-to-run-a-lathe-1966-27th-edition-56-pdf.2909/

http://hobby-machinist.com/resource...r-and-electrical-shop-bulletin-no-7-pdf.2866/

-brino

EDIT: hhhhmmmmm...Southbend bulletin #7 is supposed to be a booklet on making bushings, but the document linked above is NOT the full booklet. I will try to look around at home and see if I have the full document. Anyone feel free to PM me a reminder if I don't post back with a day or two. brino.


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## markba633csi (Jan 30, 2017)

Doing long pieces can be tricky cause you would need to support the work with the tailstock center (the pointy thing) to do the outside turning and then switch to a steady rest to do the boring.  Which can mess up the outside finish of the part- unless you use another gadget called a "cat head"... tools to make tools to make tools...
Mark S.


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## willthedancer (Jan 30, 2017)

If you're doing long bushings, you might consider buying DOM tubing and having it honed to size, mounting on a mandrel between centers to finish the OD and faces. Might save you some grief. You also might be able to buy pre-finished material with the bore already honed to size. (Think hydraulic cylinders).


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## brino (Jan 31, 2017)

Hello,

As promised in post #13 of this thread I found and uploaded the SouthBend bulletin #7 "How to Make Bushings for Automobiles, Buses and Trucks". It is nothing earth-shattering(only 12 pages), but it mentions/shows all the required steps and tooling, and gives some tolerance numbers for press and running fits.

You can find it here:
http://www.hobby-machinist.com/resources/southbend-bulletin-7s-how-to-make-bushings.3165/

-brino


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## borjawil (Feb 1, 2017)

Awesome thanks for all the info! Most of the bushings or spacers will be 2" long tops I believe. Steering stems are generally hollow as well but the OD is the important part to press into triple trees. If I can find spacers with an ID that works then of course Ill go that route, however, most of my spacers are for swapping motorcycle front ends that require a different sized bearing and the bearing race needs to be a slip fit, tolerances pretty tight.


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