Is There A Definitive Article On Collets

[savarin]

The title says it all.
Is there a definitive article on collets anywhere?
The information I'm after is something like:-
what are the different sizes
what are they for
different methods of holding the bits
types of lathes they are suitable for
suitability for differing jobs etc
and any other information that may be of use to the newbie wanting to select a set.

 

[JimDawson]

The short answer is: It doesn't seem that what you want exists on the Internet. Google Collet Types that's the best I found.

 

[RJSakowski]

The title says it all.
Is there a definitive article on collets anywhere?
The information I'm after is something like:-
what are the different sizes
what are they for
different methods of holding the bits
types of lathes they are suitable for
suitability for differing jobs etc
and any other information that may be of use to the newbie wanting to select a set.

Not an expert but here goes:
Collets are usually available in both SAE and metric dimensions. SAE are typically made in fractional increments and metric in mm increments but they can be any size. Some collets are made to be custom machined by the user. Collets also come in other geometries than round; e.g. square and hex.

Collets are used to hold work in a lathe or tools in a mill. They hold work or tools by virtue of a taperd surface with slits which mates with a tpered socket. As the collet is drawn into the socket, the socket collapses and grips the part or tool firmly. Their claim to fame is their ability to hold with minimal runout.

Use on a lathe can be directly with the spindle socket as in Morse taper collets or with a collet chuck mounted to an adapter or to the spindle chuck mount. R8 collets are common on mills.

There are many different collet types. Morse, C5, R8, and the ER series are common ones.

 

[Uglydog]

I've always found this helpful.
http://www.hardingeus.com/usr/pdf/collet/2351.pdf

And this article interesting, especially when I had some cheap collets & endmills that were slipping and walking.


Daryl
MN

 

[David S]

I have some MT2 metric collets for my lathe. I find that these collets require the piece to me held to be the same diameter as the collet. I.E. 12 mm collet for a 12.0 mm shank.

For the clock work that I do to hold arbors I have a set of ER collets (Extended Range). This means a reasonable number of collets can handle a wide range of diameters..

David

 

[brino]

Hi Savarin,

I initially read your topic and thought "what's to know; they are collets!". But then after seeing your questions, the useful answers above and having it sit in my brain a while I realize it's not that simple......there are a number of details about mounting, size ranges, use that are definitely NOT obvious.

I have never seen a detailed guide to collets. I originally just liked the advertised concentricity and repeatability and jumped in and started buying/using them. The first set I got was ER-32 for my old lathe, then some MT4 ones for my mill, then some MT3 ones for my rotary table, and then some 5C ones for an indexer....wow, they do add up! They have been very useful, and I have a few thoughts to add...

The collets that fit directly into your spindle taper should be the most accurate as the spindle taper itself was turned on the spindle centre. Any extra taper adapters, nose-thread adapters will necessarily add more room for error and decrease repeatability; you may not get them reinstalled the same way a second time.

My big mill has a Brown and Sharpe #11 taper. I cannot find tooling in that size, but was able to find a B&S#11 to MT4 taper adapter and I can use MT4 collets in that to hold end mills.

My lathe has an MT3 spindle taper and 1-1/2 x 8tpi nose. I could use MT3 collets directly in the spindle with a draw bar to tighten....but I usually don't for two reasons:
1) the holding range of the MT3 collets is limited to small diameters

2) I dislike using the threaded drawbar.....it tightens up great, but loosening it feels so stone-age! I need to tap the end of the bar to shove the collet out of the spindle taper. I put a long coupler nut on the threaded bar to spread the force over more threads and use a soft-faced hammer...but I still hate the thought of hammering on the threads.

There are special collet closers you can add to a lathe, either handwheel or lever operated, but they necessarily reduce the maximum diameter thru the spindle.

I have found ER-32 adapters for my lathe that I really like. Beall tool makes them in the USA:
http://www.bealltool.com/
http://www.bealltool.com/products/turning/colletchuck.php
They advertise them as being for wood-working; I've never used them for wood, they work great for metal.
Their set of collet sizes are limited, but the adapter is standard ER-32 so you can buy more anywhere.
They used to offer a larger set (ER-50?) as well, but I don't see it there now.......

For me the beauty of the ER-32 collets is in overcoming those two issues above:
1) I can get and use ER-32 collets in a huge range of sizes right up to the maximum thru hole of my lathe spindle!

2) the loosening....the nut has as an off-centre ring that locks into the groove on the collets. You actually have to install the collet into the nut before putting the nut/collet onto the tapered nose adapter. http://www.bealltool.com/pdfs/collet_chuck.pdf


It is tightened and loosened with pin wrenches. That allows the collet to be pushed out of the taper when loosening. No hammer required!

Even though the more do-dads you add between the spindle and the collet the less accurate it gets the above have always met my needs.
However, if you start making pieces for NASA's next telescope, you may need to reconsider........

Jeez...this is turning into a book...I'd better sign off.
Keep having fun!
-brino

 

[savarin]

Thanks Brino, good one.
So would I be correct that none of the collet systems allow long lengths of material to protrude through the back or do some of the er chucks have a through hole?

 

[brino]

savarin,

Some collets do allow long bar stock thru them.....if either:
1) they have a nut that compresses the collet into the taper
or
2) they can use a hollow draw-bar tube

My ER-32's are of the first type. Here's a couple shots of a 3/4" collet on a bar; that's the max size that will fit thru my lathe spindle.




The adapter on the left goes onto my 1-1/2"x8tpi spindle like this:




My MT2 and MT3 collets require a 3/8"-16tpi draw bar. Since that draw-bar is such a small diameter, it is solid. That limits the gripped depth to about 1-1/2".
Yet another reason I like the ER-32's better.



The 5C collets that I use on my indexer have thru holes and are drawn in by a hollow tube that grabs the collet external threads.
So they should fit the marked size right thru up to their limit....which I'm not sure of...I know my largest is 1-1/8".


I have no R8 collets. Someone else will need to comment on those.

another book, but at least it's a picture book.........

-brino

 

[savarin]

Hmm, I wonder if I'm competent enough (somewhat dubious) to make the collet holder to fit my spindle.
Then if its made in place it should (should being the operative word) be spot on and I can use ER32's with a purchased nut.
If I purchased the adapter to screw onto the nose of the lathe I would assume it would not be as accurate as one made on the spindle.
Damn, another project for the future

 

[brino]

And this article interesting, especially when I had some cheap collets & endmills that were slipping and walking.

Daryl,

Thanks for posting that paper on preventing collet slip. A very interesting read!

-brino