Getting the workpiece straight in the chuck.

[Tailormade]

So, I've got a question so basic it seems no one else has even had to ask it. (Or if they did, I didn't know the right terms to search on)

In my 3 jaw chuck, I have yet to figure out a way to get the work piece even close to straight in the chuck.

I feel like there has to be some better way than what I'm doing. If there is some method that is well accepted for getting things aligned in the 3 jaw chuck, I am all ears.

What I *thought* would be the way would be to use a center finder, scribe some lines, and then center drill at the intersection. However, with the longer shafts I cant even drill there, the chuck is so far off. Longer as in, 15-20 inches.

I also have a four jaw chuck, but haven't tried switching the chucks just yet. I anticipate the same problem with this though, as I seem to be missing something basic about getting the shaft at least close to parallel to the ways perpendicular to the chuck face.

 

[Wreck™Wreck]

If I read your description properly you are trying to center drill 15-20 inches out. Is this correct?

 

[Frank Ford]

I use a centering roller mounted in my tool post:

Here's the full deal: http://www.frets.com/HomeShopTech/Tooling/CenteringRoller/centeringroller.html

 

[markba633csi]

Well first off, 3 jaw chucks (especially cheap ones) don't have great repeatability. If they did we wouldn't need collets and 4 jaw chucks.
What I do with mine is try inserting the piece in several times and see what happens. Sometimes it's right on the money. Other times it's all over the map. Another trick is "tapping" on the workpiece to help center it. Some people can do this with remarkable accuracy. But when it absolutely has to be perfect, use a collet or a 4-jaw.
Also for long pieces you must use a steady rest. I don't own one, but I suspect the day is coming soon when I'll have to break down and buy or make one.
Mark S.

 

[Tailormade]

Wreck" data-source="post: 483066" class="bbCodeBlock bbCodeBlock--expandable bbCodeBlock--quote js-expandWatch">

If I read your description properly you are trying to center drill 15-20 inches out. Is this correct?

Yes, it seems like a bad idea to me to, but the piece won't fit through the head stock, so I didn't see another option.

Sent from my SM-G900P using Tapatalk

 

[scwhite]

Yes, it seems like a bad idea to me to, but the piece won't fit through the head stock, so I didn't see another option.

Sent from my SM-G900P using Tapatalk

If you have a steady rest set it up for anything long .
I don't know what size lathe you have but it is most
Likely a small lathe like my 10" swing Clausing 4900
It can run about 2-7/8 dia. In the steady rest . And to set the steady rest on center and the right dia. You
Put a short piece os stock in the chuck turn it down to the size of you 15" shaft . Put you steady rest right up close to the chuck where you just turned the location to the size of the 15" shaft . Set your steady ready up on that short piece . Open it up do not move any of the jaws on the steady rest . Open the three jaw chuck and take out that short test piece you just set your steady rest to . Now in clamp the steady rest and move close to the other end of the shaft about 13" form your chuck . Put your shaft in the chuck
Snug it and best it on the bottom two jaws of your steady rest . Now you have to make sure you have you carriage on the side of the steady rest you plan on working . Close the top jaw on the steady rest . And clamp the bed clamp and the steady rest clamp .
Don't run any work in a steady rest very fast no faster than your back gear will run .
Check all of the jaws make sure you have them all
In the right slots . Each slot is numbered and each jaw is numbered and must go in the proper slot .
If you have two peace jaws the also should be a match with its number and should have the same number on it as the jaw slot.
You will have to take the all out a start number one first in the slot and the scroll must catch the number one jaw first then don't turn the scroll past number two slot make sure you catch number two the same thing on number three . Now you can screw them on in . Your chuck should be right now .
And just like markba633csi said I will tap on the face with the lathe in motion with a brass mallet
Don't run it to fast or to slow it should be about
250 to 350 rpms

 

[Tailormade]

I use a centering roller mounted in my tool post:

Here's the full deal: http://www.frets.com/HomeShopTech/Tooling/CenteringRoller/centeringroller.html

Oh that looks handy. I'll have to make one as soon as I source some ..would that count as square bar stock?

Sent from my SM-G900P using Tapatalk

 

[scwhite]

I use a centering roller mounted in my tool post:

Here's the full deal: http://www.frets.com/HomeShopTech/Tooling/CenteringRoller/centeringroller.html

I like that tool you made I will put it on my list
I had one years ago but I used mine for rolling
Metal into a bore that might be one or two thousands
To big . Or rolling metal on a shoulder the same way that might be turned to small a few thousands.
Mine was heavy duty a 1" cam lock roller .

 

[kd4gij]

I use a dial indicator and a soft mallet ton get the part running true. For a longer bar indicate out near the end first then check up near the chuck.
The roller posted me Frank works great on shorter parts.

 

[Glenn Brooks]

Here's a method I adopted from my master machinist friend, who learned this from from old time master machinists 35 yrs ago when he was starting out in the trade.

Loosely Chuck up your part in the three jaw, and turn on your machine at slow speed (50-100 rpm or thereabouts).

Lightly tap the high part with a light hammer 2 or 3 times as it spins around.

After you get the hang of it, this will true up the part 9 times out of 10. If not, loosen and repeat.

Tighten up the chuck enuf to hold the work.

I hardly ever use a dial indicator with my three jaw now, after I learned how to do this.

Glenn