collets on a lathe

Better precision than a chuck, faster setup for multiple parts, less likely to mar the work - there's a lot of reasons. Can you give us any details of what the nature of your question is?

no, just didnt understand why you wouldnt use a chuck. i thought it might be for light duty milling but not when so many used lathes come with collets..thanks for your reply..tony

Tony,

Do a search in this discussion group; this topic has been addressed extensively.

Wolfgang

T> why would you use collets on a lathe? thanks tony

"Tony" wrote in news:guudnfjd-IQRSVLZnZ2dnUVZ snipped-for-privacy@comcast.com:

When you want to turn something, you use a chuck. When you want to turn something accurately, you use a collet. Collets are typically considerably faster for part exchange. Collets grip virtually the entire circumference of the part, instead of

3/4/6 points. When clamped in a collet, the material is true to the spindle to a high degree, there is no need, nor, really, possibility to 'indicate in' the part. This saves tons of set-up time.

I had to turn down a small piece of round nylon. A chuck could not have held it well enough without deforming to make cuts in it. Respectfully, Ron Moore

In addition to the other answers, you can use a collet when you want to turn something in reverse on a lathe with a threaded spindle. The chuck might unscrew itself but a collet won't.

Best Regards, Keith Marshall snipped-for-privacy@progressivelogic.com

"I'm not grown up enough to be so old!"

Thanks for that explanation - I was unsure myself (being new to this) - so, correct me if I am wrong - the collets come in sets, with overlaps to hold different sizes of work. Is it a common holder, and the different sizes attach to the holder - and the shaft on the collet holder is tapered to suit the headstock on the lathe? - have I got it right? ie, its not the right thing to just clamp it into the existing 3 or 4 jaw chuck?

I need to buy some for a little job that just WONT go in the 3 jaw chuck on the lathe - even though I am in Australia, would you have a link (please, if its not too much trouble) to a online tools shop that would have a picture and specifications of a set?

Andrew VK3BFA.

Good point Keith. I had never considered that. Thanks.

Ivan Vegvary

According to Andrew VK3BFA :

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Absolutely not to be done. That defeats most of the benefits of a collet.

Let me try to describe just how it is on my 12x24" Clausing, which is similar to most lathes, but not all:

1) The spindle has a large enough bore to clear a drawbar to fit the collets. In the case of the most common size of collet, "5C", this requires a through bore which will clear 1-3/8" (pretty close to 35mm). 2) The spindle has an internal taper which is enough larger to accept an adaptor (called the "closer"). For 5C collets, the minimum spindle taper is the Morse taper 4-1/2. (Not really a standard *Morse* taper, but an addition to the series when it was incorporated into the ASA series of tapers.) 3) The closer is placed in the spindle's taper -- ideally with a combination spindle nose protector and closer remover placed on the spindle nose first. The closer has a flange at the open end which is pressed by the nose protector to remove it, since it tends to firmly wedge itself into the spindle in use. 4) The closer has a cylindrical through bore, with a taper at the open end which matches that on the collet, so when the collet is drawn into the bore, the taper forces it to close down onto the workpiece. 5) The closer also typically has a pin sticking into the cylindrical bore which engages a keyway on the OD of the collet, to keep it from rotating when things are being installed or removed. This is *not* to drive the workpiece, which is accomplished by the taper inside the closer, but for convenience when the collet is loose. 6) A tube (drawtube) passes through the spindle, and has an internal thread which matches the external thread on the back of the collet. (The collet also typically has an internal thread at the back to allow mounting a stop so a series of workpieces will all go in the same depth.) 7) The drawtube either simply screws onto the back of the collet, drawing it in (done by a handwheel on the other end of the drawtube), or has a lever and cam mechanism to allow the collet to be drawn in to tighten it. The lever mechanism is more expensive, but more convenient, especially for a large number of parts in a batch run

In the case of the lever, you turn the end of the drawbar until it is screwed far enough onto the collet so the lever will move it to just the right position to lock it (and the workpiece) in place.

A long workpiece can be fed through the spindle and a part machined from it, then the lever releases it, and it is advanced to the right position to make another identical part, and so on. Usually, this is done with a turret on the lathe bed, so you don't have to keep changing tools, but for short runs it can be done with a quick-change toolpost or even a turret toolpost.

For really long stock, there can be a support tube with provisions to feed the stock automatically -- often with compressed air pushing a piston in the tube.

Now -- not all lathes need the closer. Hardinge lathes are designed with the spindle nose to have the right tapers for the 5C collets (or some other sizes) which were originated by Hardinge to start with.

Also -- Watchmaker's lathes, and the next size up as well, have spindles designed to directly accept their collets -- WW size for the watchmaker's lathe, and "D" for the next size up.

Now -- some lathes don't have a big enough spindle bore to accept a drawtube for the 5C collets, so you may be stuck with smaller collets (e.g. 3C for a 6x16" Atlas/Craftsman lathe), or you may need an add-on collet chuck (not nearly as accurate) to use the 5C collets on a machine which has perhaps a 1-1/2x8 spindle nose. If you have to get one of these, get the adjust-tru version (Bison makes them, among others), and take the time to tune it to run on center with that adjust-tru. And to loosen or tighten the collet in this, you need to use a key similar to that on a normal lathe chuck. And because the collet is moved totally outside of the original spindle, you lose some rigidity, and some of the distance between the spindle nose and the tailstock.

Well ... first it would help to know what size of lathe you have. What is the spindle's internal taper, what is the bore, and who made it.

Usually, for most lathes, you need a collet closer made to fit the spindle nose, and a lever drawtube assembly designed to mount on that lathe. Even if you use the handwheel type of drawtube, you need to know the spindle nose's internal taper, and the length of the spindle from one end to the other.

Note that the lever style tends to be quite expensive as an aftermarket add-on.

But -- once you are set up for collets, especially in the 5C size, you can get collets in round, hexagonal, or square sizes within the range of what will feed through the drawtube.

Good Luck, DoN.

Let me give you a real-world example: I own an electronics assembly service. One product for a customer contains a humidy sensor made in Finland. The price each has recently gone from $175 each to $225 each. Each sensor is in a threaded stainless steel housing with a vented cap. The connection to the sensor is via a three-pin threaded brass housing on the back-end. By design, there is not enough room in the product for a connector, so we have to solder wires to the three pins.

To get access to the pins we use a small Prazi lathe, with a collet chuck, to turn off the portion of the bass housing around the pins, but not touch the pins inside.

The collet grips the thin stainless steel housing all the way around without marring the surface. If it's marred or marked, we just bought it, and I sure don't have any use for an expensive humidity sensor! I wld not even think of clamping the sensor in a three-jaw chuck.

Changing from one type chuck to another on this lathe takes quite a while. Other lathes may be quickly changed.

Paul

I hadn't either but I recently bought an old Craftsman 12" lathe with a 1

1/2" x 8 TPI spindle. My previous lathe was a JET 9 x 20 with the same spindle but it had a groove in the spindle between the threaded portion and the headstock and the chuck's backplate had a set screw that was tightened in that groove to keep it from unthreading itself in reverse. The Craftsman doesn't have the groove so I commented to a friend on that being something I didn't like about the new lathe and he promptly informed me that's why I need a set of collets! :-)

Best Regards, Keith Marshall snipped-for-privacy@progressivelogic.com

"I'm not grown up enough to be so old!"

Hi Don, thank you for your usual comprehensice answer - going to have to look up a few things there, but thats ok - thats what the textbook is for.....(including the specs for my lathe...)

Andrew VK3BFA

If it's just a 'little' job you can cheat. I take an Al tube (bar)and bore the ID to size and mark the orientation (usually at the chuck key) and slit the tube. Will hold stuff that size well pretty accurate as long as you hold orientation. Better than regular collets to hold stuff that is slightly tapered. If you need lots of sizes buy a collet set instead.

============= Lots of good suggestions. Most of these are for the advanced user with lots of money. A full 5-c collet adapter to fit you lathe is the ideal, however it is also the most expensive, and the lever operated styple can be a pain to install/remove.

For low volume or one-time use several alternatives exist. Bear in mind that these alternative may not allow the using of long length of bar stock through the spindle. [Which can be a safety hazard.]

If you have a face-plate, one of the cheaper alternatives is to buy what we term a collet vise in the United States, and bolt this to the face plate as required.

By clamping a long 1/2 dowel pin in both the tail stock drill chuck and in the collet vise, the collet vise can be centered on the faceplate within a few thousandths TIR. This can then easily be adjusted with an indicator to as close as you like.

Prices in US$ for the collet vise are 30$ and 5$ for each 5C collet. 5C collets are the most common in the US and come in hex and square as well as round. Emergency [soft] collets that you can machine to size in brass, nylon and steel are also available. Downside is the range for any one collet is limited, and the stock can't extend through the collet into the spindle. You can also use the collet vise on your mill.

You can also use what is called a tumble block fixture by using an angle plate to bolt to the face plate. Same comments about 5C collets apply and this will be a harder set-up [but more flexible]

Another alternative is the use of a morris taper collet holder using ER collets. ER collets have a wider clamping range per collet, but generally cost more than the 5C and do not seem to be available in hex and square.

Depending on the spindle nose specifications of your lathe, ER collet holders may be available that will allow long bar stock to extend through the collet and into the spindle. These are expensive, and are generally considered specialist tools.

for example of horizontal/vertical collet vise you can bolt to face plate see:

For an example of a "tumble block" fixture that you can bolt to a faceplate using an angle block and also use with a mill see For an example of the morris taper MT collet holders [it may be cheaper to buy just the holder and the collets you need rather than the entire set. calculate prices] see ?ProductID=900-0005-061 that the lathe spindle may have a "stub" morris taper specification that will not accept a full length MT tang. My Emco Compact-10 is like this and I had to get a #5 to #2 reducer, and cut the back half off the reducer, and use a #2 collet holder. (#3 would have worked also but tail stock is #2 as is mill head) Be sure to get the draw bar style adapter and use the drawbar.

Another alternative, is to use a drill chuck mounted to the spindle. If you do this be sure to use an adapter with a drawbar to prevent the drill chuck from pulling out of the spindle and use a key closed [Jacobs style] drill chuck as the keyless [Albrecht style] may tend to open.

For even cheaper alternative, bolt a block of material to the face plate, and bore the required hole. Block can be equipped with set [grubb] screw or split with clamp bolt to retain part. You can drill face plate and block for dowel pins for quicker set-up. You can also tap the hole if you need to hold threaded parts, even taper [pipe] threads [if you have a tap...]

Good luck and welcome to the trade.

If you look at history you'll find that no state has been so plagued by its rulers as when power has fallen into the hands of some dabbler in philosophy or literary addict.

Desiderius Erasmus (c. 1466-1536), Dutch humanist. Praise of Folly, ch. 24 (1509).

An interesting and inexpensive alternative to a collet chuck, but wouldn't one need to worry about balancing something like this - especially at higher speeds?

Peter

============= One needs to check the balance of *ALL* face plate work. Be reminded that the closing handle unscrews from the cap. Even with the horizontal mounting flange the balance when centered on the face plate was not a problem at typical home shop lathe speeds [slow]. I modified a driver plate to take two 1/2 grade bolts and used that. Found I could leave the collet vise mounted as I don't do much between centers work anymore.

Also a horizontical/vertical unit was shown. There is a vertical unit only that has better weight distribution. see:

or you can machine the flange on the side for horizontal operation off for more clearance which is what I did. Simply bolt to a right angle iron for use on the mill when you need horizontal orientation.

Look for sales of both the collet vises and collet sets for a better deal or go for the whole skippie and get the hex/square fixtures also.

For the capabilities this added and set-up time it has saved me, this has got to be one of the best tooling investments I have made.

If you look at history you'll find that no state has been so plagued by its rulers as when power has fallen into the hands of some dabbler in philosophy or literary addict.

Desiderius Erasmus (c. 1466-1536), Dutch humanist. Praise of Folly, ch. 24 (1509).

thanks to everyone for the replies, i have learned alot over the years from this group..thanks tony

According to F. George McDuffee :

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[ ... ]

The original installation -- yes. However once that is done, simply removing a stripper bolt allows me to pull out the lever-style mechanism and replacing the bolt with it upside down allows it to rest against the back of the headstock. The stripper bolt *should* have a nut, but it is held in place nicely by gravity. I do this fairly often for putting larger diameter chuck-held stock through the spindle. (In particularly -- the largest hex size which will fit through the spindle without the collet drawtube in place.

Yes -- that is one reason for the support/feed tube which I mentioned for long stock extending out of the back of the spindle. Anything which sticks out more than perhaps ten times its length is likely to turn into a dangerous flail if unsupported. But it does not take much to support it. I use white PVC plumbing for the purpose. As long as it prevents the free end (and the middle) from getting very far off center, it prevents the problem.

That can work. Beware getting the faceplate very much off balance, as it will cause the lathe to walk around the shop.

Agreed for all.

You can also hold the six-sided one in a 3-jaw chuck, or the four-sided one in a 4-jaw chuck -- but this makes getting to the part which locks the collet in rather difficult. It can be useful for a one-shot job, but not for one where you are making a lot of parts. Especially considering that in a 4-jaw you will have to re-true it each time you change parts.

Agreed. Let me mention here that you have mis-spelled the name of the taper -- it is "Morse", not "morris". This could result in problems when he is trying to find such things in a catalog. "Morris" is a UK car make -- part of the MG series from some time ago.

The ER collets have the advantage that they cover a much wider range per collet, so it takes fewer to cover the entire range. A *full* set of 5C collets can be quite expensive, even at $5.00 per collet for the cheap ones. Usually, a set in steps of 1/16" is sufficient for holding stock of standard (inch) dimensions, and if you need to hold partially machined parts, you pick up a single collet to fit that size as you need it. 1/16" to 1-1/8" adds up to 18 collets, or $90.00 at $5.00/collet. Double that for 1/32" steps, and again for 1/64" steps. And when you get to the 1/64" steps, you are probably going to be limited to the vendors which charge on the order of $35.00 per collet, instead of $5.00/collet.

The ER collets which I have for my Compact-5/CNC lathe each cover a 1mm range, so the total count is a lot lower.

Agreed.

Hmm ... that is a fairly reasonable price, and I can get the holder to fit my 40-NMTB Nichols milling machine.

I believe that the 4-1/2 Morse Taper which my Clausing uses in its spindle is in reality a "stub", using the narrow end of the Morse taper #5. But ASA has declared it to be a "standard". :-)

This will mar soft workpieces, just as a 3-maw would do.

An interesting approach.

Enjoy, DoN.

Thanks.

Peter