I am trying to decide what lathe chucks to buy, and was wondering which is better to own. A 6" chuck or a 8" chuck. Also is it better to have a 3 jaw or a 4 jaw? I mostly turn 12" long 1" to 1-3/4" round pieces of 4130, 4140, 4340, etc. moly/chromoly steel. Precision and error of .001 & .0001 are ok with me
My other questions concern which is better, D style mounting, threaded spindle, or L taper mount? Would it be better to have a collet chuck or a 6 or 8 Jaw precison chuck? Consider that the lathe is a 9" to 13" size.
Chuck diameter is best determined by the work you'll do. Large chucks are more difficult to use with small materials, and will generally not grip very small diameter stock. Needless to say, small chucks can limit material size on the large end, but the hole in the spindle tends to govern there, not the chuck.
3 jaw or 4 jaw? That's not really a fair question. It's like asking if you should buy a pickup or a sedan. If you intend to run round stock and want to be able to grip it without spending any time getting it to run true, a three jaw with soft jaws is the solution. If you intend to machine irregular shaped objects, a 3 jaw can become impossible, or at the very least very difficult to use for the purpose. All depends on the nature of the part, and if it lends itself to being held in an irregular fashion. Facing a part, for example can be accomplished even if the part isn't running true with any given feature.
If you'd like precision to less than a thou, a three jaw is unlikely to make you happy, even with soft jaws. That level of precision is best governed by the use of a 4 jaw, where you have the option to alter how the part is held by the chuck. Again, the nature of the work will dictate. They don't really interchange with one another. You really should have both types of chuck-----but if you are limited to one only, with no prospects of getting another, make your choice a 4 jaw. It will be somewhat slower to use for round materials, but there's almost nothing you can't grip with one, as opposed to a three jaw.
Avoid a threaded spindle like the plague, assuming you have the option. They work, but are primitive as compared to any of the other spindle types. The most convenient and common is the D series. It's fast and easy to install or remove, and readily available when you rise above home shop type machines. It's the spindle of choice for manual machines, although the A spindle may be somewhat more popular with CNC's. Dunno------I'm not a CNC person, but I realize they used that spindle on some turret lathes. Don't have a clue why the D type wasn't the choice instead.
One of the negative features of a threaded spindle is the risk of the chuck coming off when using the machine in reverse. Many home shop types will tell you that you don't run lathes in reverse, but that's because they have no clue about the advantages. There are times when reverse running can serve a good and valuable purpose, and that includes plug reversing, such as when tapping. That operation poses a great risk of losing a threaded chuck. Again, if you have options, try to get a machine that is reverse capable, and make sure the spindle is compatible if you do.
Again, depends on the work you intend to do. If you do small things that can be difficult to grip, collets are a very nice addition. Truth be told, if you buy a three jaw with master jaws (two piece jaws, or an optional set of jaws that allow for soft jaws), you can usually machine soft jaws to grip almost any part you desire, with the added feature of machining stops that locate parts laterally. You can produce multiple parts easier if you have a reference point that repeats. Collets often don't allow for that due to how they grip the part in question. Small parts tend to move closer to the headstock than do larger parts, a function of the collet closing in to grip the smaller diameters. Collets are not a requirement, but can make your life a lot easier. The one real advantage is that a collet chuck usually has nothing that can hang you up, so if you're making small items and have to hang over the spindle, you don't run the risk of getting whacked by jaws the way you would by running a chuck instead. You'll use all of them if you have them.. You can survive with only a 4 jaw. Takes more time, but it does work.
You need to decide on a lathe before considering the chuck. Any chuck larger than 1/2 the swing must be carefully considered. Precision of .001 can be done (not that easy), forget about .0001 unless you are an expert with loads of money and experience.
Harold sez: (whole buncha good stuff) !! Thanx Harold. Very informative as per usual. RCM is fortunate to have your wise and learned counsel from time to time. Keep it up -- better yet, write a book. I want to be your agent.
============= The only *R*E*Q*U*I*R*E*D* workholding fixturing for a lathe is a faceplate and centers/drivers. Of course a collet closer makes things much quicker, and some 3 jaw and 4 jaw "set-tru" chucks are very handy.
Before you spend a ton of money on chucks, ask yourself what you are going to be making/doing. One possible alternative that may be better than a chuck is a block you bolt to the face plate, and bore to the exact diameter of the part you wish to clamp. If the block is split with clamp screws or even a set screw, you can then adjust for minimal runout. From the sizes of parts you describe, you should be able to use 2 pieces of 1-1/2 X1-1/2X6 or
8 inches of square steel, or for occassional use aluminum.
Many of the tools, fixtures, etc. you see in the catalogs were developed for the production shop/machinist, where time is money. This is not generally the case for the home shop, and in any event, setting up and machining one and only one part may not be much, if any, quicker with the expensive production tooling.
(1) Get some of the old time machining books from Lindsay and see how machining was done before the wide introduction of production fixtures and attachments, such as bolting angle irons and v-blocks to the face plate. It is true these types of setups don't allow heavy feeds and high speeds, but are more than adequate for 99.44% of home shop projects. see
a good overview and first book I suggest
careful you don't spend all your money on books! :-)
(2) Consider mounting what is called a collet vise to your face plate. While you can't run long barstock through the spindle, this provides an inexpensive 5c collet set-up that you can adjust to 0 TIR if you want to spend the time. [Be sure and unscrew the tightening handle from the ring before starting the lathe! :-) ] for examples see (Enco frequently has these on sale also )
?ProductID=900-0012note that 5c collets are available as stock items with hex and square holes.
If you open the center hole up in the faceplate large enough to allow a center to be installed in the spindle, you won't need to remove it when turning between centers. You will need to use straight tail dogs and fabricate a driving block to bolt to the face of the plate.
Then machine a bunch of stuff, and decide what *Y*O*U* need.
As far as the "best" spindle nose. Unless you are changing chucks frequently, turning left hand threads, or abruptly stopping/reversing the spindle (both of these to unscrew a right hand threaded spindle) I don't think it makes much difference.
It does appear from looking at the catalogs that the D-camlock chucks seems to be more available and lower in price, however if you have a threaded spindle, it is much easier to make your own tooling. One trick is to use nuts with the spindle thread [you may have to call around to the fastener stores, the hardware stores won't have these] and weld/braze to the fixture. Unka' George ================ When we are planning for posterity, we ought to remember that virtue is not hereditary. Thomas Paine (1737-1809), Anglo-American political theorist, writer. Common Sense, ch. 4 (1776).
If he's asking, D, threaded spindle or L, then he DOESN'T have a lathe, yet.
Threaded spindle stuff is the cheapest and most commonly found. You can't do heavy turning in reverse, and have to be careful anytime starting in reverse or stopping abruptly, that the chuck doesn't unscrew.
I happen to like the D-Camlock system, because my lathe has that. The accessories are a bit more expensive, and it would be VERY tricky to make a camlock backplate as it needs a taper and a flat to match up so that both seat at the same time. I think it is true that you will never get a machine with a larger through hole on a threaded spindle than you can get with Camlock. I have a 15" Sheldon with D1-6 camlock, and it has a 2.25" through hole.
A collet chuck is a great accessory, especially if you do a lot of small shaft-like parts, and need to chuck them in and out quickly. Up to 1" and a little larger, you can get 5C collets. But, if you are doing a lot in 1.75" diameter, I don't think there are commonly available collet chuck systems that go up that big. If so, they'd be VERY expensive.
Hi! First of all thank you for all your replies so far.
Well, here are so more items from my thoughts. I probably won't be gripping parts smaller than 1/2" or 3/4", as most of my parts are not smaller than that.
I intended on also having a faceplate, and also centers too for both head and tailstock.
My current lathe, although I am thinking of purchasing or building my own lathe, is a 9" Model A South Bend from 1941. I don't see my self having much more room than that would be required for a 13" lathe.
I do also turn some 2024, 6061, and 7075 type aluminum under 1" dia. and never longer than 12". I've never had to make parts from that stock longer than 6" but, sometimes had to make a few parts from the same drawing.
I've been told that you should have a large through hole for stock to pass through, and to avoid small dia threaded spindles. I've seen 2" and larger threaded spindles on some lathes but they were larger lathes.
I have lots of Royal brand 5C collets at hand as I purchased them early on when setting up my shop, so I have the basic sizes all at hand.
I also figured on having a toolpost grinder as well in my setup as well as steady and/or follow rests One of the things I do very regularly is drill 17/32" dia holes in round stock, then either bore a larger hole from that or ream it true
Off on a small tangent, has anyone ever seen dimensioned drawings of the D1-4 / D1-6 spindle?