Does one have to make their own chuck center for turning between centers?
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  1. #1
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    Default Does one have to make their own chuck center for turning between centers?

    Ive seen a lot of talk about the dog when turning between centers, but what about the center for tge chuck? All my centers are tapered and i have no adapters or anything to use them in the chuck. Obviously i could cut my own, but do I have to do that? Is there a center for this premade?

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    in fact ,the lathe spindle will have a tapered bore that will hold a centre of some suitable size......might be big one ,like #5 Morse,so the lathe will also come with a spindle bush ,whic is #5 Morse on the outside ,but only #2 on the inside...to take a #2 centre.......notice that no chuck is involved so far.....Now normally ,you will also have a catch plate which will have one or more slots to drive a bent tail dog....a straight tail dog will need a stud out from the plate face............now a chuck can also be used as a catchplate ,if you dont have one.....with a bent tail dog,simply remove the jaws ,and use the slots.........a straight tail dog ,can use a chuck jaw to drive the dog......hoever you need to leave on opposite jaw in to balance the chuck,and be careful it doesnt catch anything as it rotates......this will incluse your knuckles.......All this is explained in the South Bend "How to use a lathe "book....which is available free online

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    There's more than one way to skin a cat. Depending what you have on hand, or what you want to buy.

    If we are talking a 9a, which I think you have. Then you probably have a common taper in your spindle nose #2 or #3mt I would guess, but you need to check.

    Then buy a dead center to fit taper, plus check the length of center to make sure it will pass, or correspond well with whatever you are using for a drive plate. Those centers come in all different lengths, so you might need to figure it out.

    Your best shot of it being really true would be to touch up the angled point anyhow. . .

    Which explains some other options. Like putting a piece of round stock in your chuck. Cut your own point. It will be true till you remove it from chuck. When you re-install it, touch it up again so its true again. . .

    Also using a chuck as a drive plate is not terrible. Let the arm of dog ride against one chuck jaw is all.

    Or buy a back plate and use as a drive plate. Or buy a drive plate. . . Lots of ways of doing things, and using what you have.

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    For turning between centers, the chuck isn't involved (other than for center drilling the stock). Looking at your available tooling, you already have everything you need for turning between centers. The tailstock will take a live center with a MT#2 taper and the headstock will take one of your centers with a MT#3 taper. Stick a piece of stock between the centers, add a drive plate and dog and you are all set to go.

    One thing I DON'T see in your tooling is a drive plate. It is a plate that screws onto your spindle and has a slot in it where a drive dog will sit.

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    What is there in case that is unknown

    sb-spindle-dims.jpg

    All you larger (than 9A / 10K ) owners - note that there IS NO direct fit for any MT - you have to have the SB supplied bushing

    In case unknown, here resides the MT specs

    Standard Tapers

    have fun

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    I'm guilty of using a chuck jaw to drive a dog on a larger lathe, especially when I don't want to remove the chuck. Just chuck up some scrap, cut a quick taper to true it up and rock on.

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    And of course you can buy a soft MT2 centre to go in the headstock taper (which was described as a live centre when I was an apprentice, the tailstock centre which doesn't turn with the work being the dead centre)and turn it down ever-so-slightly to give absolute concentricity.

    George B.

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    If you use a shop made center in the chuck, instead of using just a straight piece rod, make it with a shoulder so that it cant slip back into the chuck jaws. If you mark it to a jaw, when you use it again there wont be much dressing off needed.

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    I almost always use the same idea as MilGunsmith does. A piece of scrap turned half way down it's length to leave a step, flip it 180 degrees with the step against the jaws, then turn your 60 degree point. It's then as concentric to the spindles C/L as your bearings will allow. I just use the side of one of the chuck jaws to drive the lathe dogs tail. Any time it's used after that I take a few thou clean up cut on the point to retrue it. There expendable pieces of tooling given enough time, but they work and run as true as the first time you made it. With an older lathe there can be dings or score marks in the taper and even the best hardened and ground center may not run as true as a shop made one will with the added bonus of not needing to remove whatever chuck happens to be on the machine.

    Turning between centers seems to be rarely used today in commercial shops. That's not because it's a poor method, it's just the opposite. The only reason it's not used more is because it limits the depth of cut and feed rates to what the lathe dogs grip on the shaft can handle verses what a chuck can withstand. It's also an excellent method for use in a home shop while using a between centers boring bar with the part fixtured to the cross slide.

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    Quote Originally Posted by johnoder View Post
    All you larger (than 9A / 10K ) owners - note that there IS NO direct fit for any MT - you have to have the SB supplied bushing
    It might not be a FULL MT#3 socket, but a standard MT#3 center will fit (perfectly) in a 9" spindle. It has a 0.602"/ft taper, same as a standard MT#3. Even the spindle opening of 0.938" (without the bushing) is the same as the big end of a MT#3.

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    Turning between centers fell out of favor in big shops when the CNC turning centers came into play. Before that the centers were the reference as work was passed from one machinist to the next. Each would have a specific operation that his lathe or mill was set up to do. There are some good old WW2 era training videos around that show the process.

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    read post #7 again.

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