I have a Chuck issue

[Al Slitter]

Hello All;
I have a 7" x 12" Mini lathe and have been having an issue with my 3-Jaw chuck not holding the work well.
The lathe came with a small chuck wrench which I use however when doing projects when working with steel the part which is chucked often rotates making an awful mess of the finished surface.
I have tried tightening up the chuck with as much force as I am able to deliver but still have this issue.
Should I make up a new chuck wrench which has longer arms to allow me to put much greater pressure on the work piece? Or is there an issue with the chuck?

Thank you!

 

[Sharky]

It could be any of a number of issues, what size stock are you holding, inside or outside jaws, are you tightening at all 3 points? A pic of your setup may help too.

 

[Al Slitter]

Using inside jaws, diameter of the piece held by the chuck is 3/4".
Will take a picture of the item and add it a little later.
As mentioned it is a 3-jaw chuck so all jaws tighten at once. My procedure is to tighten the item, then check
that the item is running true then tighten again using another jaw tightening hole.

By the way this problem came as a result of my attempt to bore out a Slitting Saw Mandrel to 1" .

 

[Al Slitter]

Here are two images of ther part. The first shows the damage the second image shows the boring that I was doing.





Hope this helps ?

 

[stupoty]

I normaly shim the jaws with some pieces of copper to protect a finished surface and also can help with grip.

were you drilling or boreing the hole? Normaly my tail stock loses grip on a tool first.

stuart

 

[Al Slitter]

I was boring out the 1/2" hole that I drill in an attempt to get to a 1" ID on this fixture.
Am not there yet as the mandrel just poppet out of the chuck, so took a break!

 

[John Hasler]

The damage makes it look like you were only gripping the last inch of the part. Did you not have the part fully seated? If you did your chuck may be bellmouthed.

 

[Bill Gruby]

As already stated by John, if you do not have a full depth grip on the part in the chuck it will slip under load. As I see it that is a long part and needs all the support it can get. If you are not holding full depth it could push back under load and then spin. This looks like what happened. You might try it again this time using a steady rest for the added support needed.

"Billy G"

 

[Sharky]

3/4" wont fit thru the chuck without modding the chuck, bore is 5/8" I bored mine to 3/4 thru hole which make a big difference. Youre only holding the end and youre springing the jaws. I'll look for the details on modding the chuck, but basically disassemble it and bote the chuck to .755, trim the back screws and reassemble.

 

[Al Slitter]

I have now finished the mandrel and cleaned up much of the damage done to the shaft end by the chuck!
Not only is this project finished but I have learned so much by having this problem. Firstly the problem with the work disengaging from the chuck
was caused when I was removing the boring tool without backing it off, I thought the back stroke would make the cutting process go faster. (No!)
I learned from others that the 3-Jaw chuck is the poorest one to use when doing work that requires pressure.
I learned that it is important to tighten all of the jaws on this chuck and if gripping a small area to use sandpaper applied to the the part gripped.
Using these techniques I was able to finish the project with out any slippage in the chuck.