4 Jaw Self Centering Chuck Question

[kingmt01]

4-jaw scroll chucks (self centering) are still produced). The only advantage I see with a 4-jaw scroll chuck is if you work with square stock often with the ability to still hold round stock. As noted it can't hold hex stock. It will also hold thin walled work with less deformation than a 3-jaw but not as great as a 6-jaw. It can't hold rectangle though.

I don't work with square stock often so I opted for a 4-jaw independent for the accuracy. I use a 6-jaw the most, with a 4-jaw independent second, & 3-jaw coming in third.

There are also 4-jaw combination chucks that function both as a scroll chuck & independent. Awesome chucks but not useful enough for to justify the high cost.

I can't say I've ever tried it but I'd think by clamping two jaws on the same side(only two sides clamped), using a center, light cuts, & very low RPM that you could get retangle stock cut. If it isn't bigger then the chuck you can shim it to be square. Hex can be done. Who doesn't get a 3 jaw handy tho?

The only reason it wouldn't hold round stock as well is if it isn't actually round. Rolled stock has a odd shape that wouldn't contact all the jaws. I usually turn my stock then flip it around in my chuck before starting my work with a scroll chuck. I don't do this when using an independent jaw.

 

[kingmt01]

I also twist & wiggle the stock to find the lowest spits to line up on the jaws.

 

[Rex Walters]

As noted it can't hold hex stock.

[Can't quite believe I'm correcting darkzero ....]

I think that was a typo - four-jaw scroll chucks can hold hex, square or round stock without runout. No scroll chuck can safely hold rectangular or irregularly shaped pieces without runout. I think Mr. Gelbart's point is that a 4-jaw is more versatile than a 3 or 6 jaw scroll chuck expressly because it can also hold hex stock.

As others have noted, a 3-jaw will safely hold out-of-round round stock (but not, of course, without runout). I use mostly cold-rolled and aluminum and have never acquired any out of round rod stock. Since I'm happy to use an independent 4-jaw to hold the occasional odd-shaped piece, I think Mr. Gelbart has a good point.

I'm still pretty new to machining, but I tend to have my smallest chuck on most of the time (a 4" 3-jaw scroll chuck), my 6" 6-jaw occasionally, and I use collets as much as possible (astonished myself when I realized just how small a part I could accurately turn even in a 74 year old lathe with a 3-C collet, a sharp tool, and good magnification).

Is there a recovery program for chuck addiction? Despite owning 5 (!) lathe chucks, including a recently acquired 5-C collet chuck (with 0.008" TIR to my annoyance), as well as large collections of 3C and 5C collets and closers, I'm semi-seriously thinking about getting a small four-jaw scroll chuck. Step one is admitting you have a problem....

 

[darkzero]

[Can't quite believe I'm correcting darkzero ....]

Not a rare occasion. I'm no pro or machinist by trade so I tend to say I may have no idea what I'm talking about at times. Corrections are always welcome.

 

[Tool-in-the-Box]

Thanks, great info. Like someone said above, must be an expensive chuck. Its a keeper for sure!

Here is a pic. Just need to remove old grease and repack.

 

[Earl]

I was once reprimanded for using grease in a chuck. I shrugged it off and went about my business. A week or so later I was having issues with the chuck - tight spots in the scroll. When my mentor saw it, I was reprimanded again for not cleaning the grease out when he originally told me about it!!! I have only used oil since that time and never had another issue with chips inside the chuck. Lesson learned. I have since heard from several sources not to use grease in a chuck.

 

[kingmt01]

I've never cleaned mine but heard of this & had forgoten all about it. Thanks for the reminder.

 

[Tool-in-the-Box]

Hmm, since the chuck doesn't look used I assumed the grease was from the factory. Should I just use oil then? If so what type would be best?

 

[chips&more]

I use grease in my chucks. And I think I see a grease nipple in your chuck on its face across from the logo. Chips/crap can get into every part of the chuck. I stuff easily tearable paper towels into the center hole of the chuck when I can. This helps prevent chips from getting into the scroll from the inside. And I keep a thin film of oil on the bare surfaces. Other than that, I clean & lube the chucks about every 6 months. The chuck is the heart of the lathe, take care of it!...Good Luck, Dave.

 

[mksj]

Some form of grease is what I have seen most chucks come with from the factory, the key is to put it where it needs to be and not putting on too much. I periodically put a light coating of way oil on the exterior surfaces and wipe it off, on the gears I use a very high viscosity teflon grease. Most chuck manufactures also sell chuck specific grease. I use a Bison 4 Jaw 8" combination, it is the about the same price as a 6J and for me a bit more versatile.