Three-jaw chucks, of the same general type used to hold bits in most power drills, are also common equipment on metalworking lathes. Though it is not necessarily so, three-jaw chucks are so commonly of the self-centering variety, in which the jaws are not independently adjustable, that “self-centering” is generally assumed from the term “three-jaw chuck.”
But there are distinct advantages to using a four-jaw chuck (which is generally assumed, contrariwise, to have independently-adjustable jaws), and though a three-jaw chuck is nice to have for convenience and for use with hexagonal stock, most machinists find the four-jaw chuck to be more versatile and useful in the long term.
This table is adapted from a list by Bruce Simpson, as quoted on Frank Hoose’s excellent lathe-work site.
16 thoughts on “Three- vs. Four-Jaw Lathe Chucks”
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Actually you can buy 4 and 6 jaw self-centering lathe chucks, this is nothing new. More info on BISON-BIAL site. And 3-jaw version can also achieve high precision, expensive but possible.
There are 4 jaw scroll (what the trade calls a self centering) chucks. Most wood lathes come with them.
For handling thin tube, there are 6 jaw chucks, which hold at lower pressures.
Scroll chucks tend to hold the same centering for pieces that are the same diameter. That leads to the “Set-Tru” chuck – its a regular scroll chuck, with the ability to move it around relative to the spindle center. It makes for fast centering when doing repetitive work.
For precision work on a metal lathe you generally see only 4 jaw independent and 6 jaw chucks.
If you are going to spend the cash on a decent self centering chuck it might as well have six jaws because it wont be much more than a 3 or 4 jaw and they don’t mar thin tube and soft materials as badly. Any aluminium surface finish gets chewed up pretty badly by a 3-jaw.
As well, generally only companies who actually know what they are doing make six jaw chucks so you won’t get trash.
Yah, with the work I’ve done in precision machining you’re either using a 6 jaw chuck to lessen the deformation on the material, or you’re in a collet. Not so much the 3 jaw, but they do have their use if precision isn’t a big deal.
You have marks on aluminium or copper because you use hard jaws, for
soft metal you need to use soft jaws. And precision of 3-jaw can be
0.005mm (this is like 0.0001 inch ?).
6-jaw chuck is used for thin wall materials (better load distribution). Many people forget about basics, when we use hard and soft tools.
I’ve made a square block using a 4-jaw. For practical use though, the 3-jaw and the collet holder are the ones that stay on the machine.
Great info! I love Make, and it’s great to see some lathe Chucks getting some love on here too! Very cool!
If you’d like to compare and contrast the whole range of lathe workholding approaches, I’ve made up a table that might be helpful:
http://www.cnccookbook.com/MTLatheHolding.htm
Best Regards,
Bob Warfield
http://www.cnccookbook.com