4" 3-jaw chuck questions

[sed6]

I'm considering a lathe and have a few chuck questions.



The chuck above is described on the Micro-Mark site as "Larger capacity self-centering 3-jaw chuck with 7/8 inch dia. bore allows full use of hole through #82710 lathe spindle. Body dia. = 3.937 inches. Internal jaws clamping range = .078 to 1.181 inches. Internal jaws jamming range = 1.181 to 3.543 inches. External jaws clamping range = 1.181 to 3.150 inches."

So the green arrow is on the internal jaws and they can pinch something as small as .078 inches up to 1.181 inches and if the piece is less than 7/8 inches it'll fit into the bore of the chuck, correct?

It looks like those internal jaws should be able to expand quite a bit bigger than that, like up to 1.55" easily to hold a mag. It that right or am I missing something here?

I read people bore out their internal bore all the time to step up to a common size like 3/4 or 1" even. There is a lot of meat on this chuck, would it be possible to bore it out to 1.55" to take a mag? I've put some red lines to illustrate what I'm thinking.

I appreciate any input!

 

[Anglepoise]

I'm considering a lathe and have a few chuck questions.
!

You are going about this in the right way. Before purchasing a lathe it is very wise to have a good idea what you want to do with it. For us who will use a lathe for our flashlight hobby, lathe spindle hole size becomes very important.

In your chuck ilustration, boring out to the red line is not doable. even if it was, you still face a spindle bore that might be too restrictive for what you want to make or mod.

And in regards to holding diameter, as you spin out the internal jaws, there becomes less and less holding power as jaw teeth disengage from the scroll.
When gripping oversize items, grip very gently so as not to damage the chuck or switch to external jaws.

Good luck in your quest......................

 

[gadget_lover]

The reason that the movement is limited is the engagement of the teeth on the bottom of the jaw with the scroll. Move them too far out and you end up with only a tooth or two engaging the scroll and it might come lose.

The "internal jaws' are meant to fit inside the hollow body of the flashlight. The rounded steps on the outside of the jaw hold the work. You will note that the 3 steps will allow it to hold an object more than 4 inches ID even if the jaws only moved an inch.

I most often use the long serrated portion of the "internal" jaws to hold parts under 2 inches or so.

Boring it out would be a questionable task. First, the chuck is hollow and there are moving parts inside the chuck. There is a good chance that you will hit something while boring it.

Second, the process of boring it will likely weaken it in some way, and you don't want it failing while you are using it.

3rd, there are ways to hold big objects besides fitting them all the way inside the bore of the chuck. If you are only doing external work, then supporting the far end with a center will hold it much better than inserting it into the 3 or 4 inch deep chuck.

Welcome to the brotherhood of tool lust. Lathes are FUN

Daniel

 

[gadget_lover]

And the other thing about opening the jaws further... A 7x12 lathe has only 3.5 inches from center of the bore to the table. Take a 4 inch chuck and extend the jaws more than 1.5 inches and you hit the ways.



Daniel

 

[sed6]

Thanks for the good advice and encouragement everyone! Hopefully soon I'll be making metal shavings of my own!