Morse Collets In Spindle Vs Er Collet Chuck?

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Stereo Joe

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I'm wanting to add some collets to my lathe and for about the same price, I can get a set of MT3 collets and a drawbar to fit in the spindle or an ER-32 collet chuck and collets.

Can anyone comment on the pros and cons of these options?

My priority is the least amount of runout possible and the ability to hold small, delicate parts without damage.
 
Hi Joe. If the parts you work with are of nominal size that will fit the MT collet almost perfectly then the MT collets will potentially be more accurate than the ER collets. The reason is that there is only one interface, that of the collet in the spindle. With ER collets you must have a chuck and the chuck to spindle mount interface and the ER collet fit itself will introduce some runout, small though that may be. Bottom line is that the MT collets will give you the least potential runout of just about any other type of collet (unless you have a native 5C spindle, in which case you would use 5C).

On the other hand, if the ER chuck is mounted very accurately and you use good ER collets you can get runout down to about 0.0002" or so. The key advantage to the ER collets is that you can grab onto parts that are non-nominal size, which is usually what us hobby guys work with, so ER collets are very popular.

Neither the MT collet or ER collets will tend to mar the work piece, although if you cinch down hard enough you can cause some distortion of threaded areas.

Personally, I use ER collets. I have a 5C adapter with Royal 5C collets and its pretty accurate but useful only when I work on nominal sized parts, which isn't that often and especially once it is turned and needs to be chucked up again. The flexibility of the ER system is worth what little runout I have to deal with.
 
Thanks, Mikey! That's very helpful. I suspected the Morse collets might be a little more accurate for the reasons you said. I'm making stuff of my own fancy, so I can pretty well stick with nominal dimensions on parts that will be held in the collets.
Is there a specified tolerance for the MT3 clamping range? The set I'm looking at has collets in 1/16th increments.
My only other concern is the potential to damage things in the spindle by constantly whacking on a drawbar to release the collets..
 
I have a set of 3MT collets for my lathe. I made an er40 collet chuck . The MT's live in a drawer, they are to much of a pain. With the ER's I have through hole so not limited to length.
 
Stereo Joe said:
Thanks, Mikey! That's very helpful. I suspected the Morse collets might be a little more accurate for the reasons you said. I'm making stuff of my own fancy, so I can pretty well stick with nominal dimensions on parts that will be held in the collets.
Is there a specified tolerance for the MT3 clamping range? The set I'm looking at has collets in 1/16th increments.
My only other concern is the potential to damage things in the spindle by constantly whacking on a drawbar to release the collets..
Click to expand...

I'm not sure what it is for the MT collets. For 5C, they have to be within about 0.005" of nominal diameter. Normally, these collets are intended to hold tooling, which have shanks very close to the size of the collet. They are not usually used for work holding. In order to have enough flexibility, you would need a rather large collection of collets and that can get expensive.

An ER collet is also meant for tool holding but many of us use it for work holding in the lathe. They are more flexible on size and like kd4gij said, you can pass long stock through the spindle while it is held in an ER chuck. A full set of import ER collets is fairly cheap and will cover 1/16" up to 3/4 for an ER 32 set and up to 1" for the ER 40 set.

If I were you, I would go for an ER chuck and collet set. It will do all you want to do and it will hold the parts more securely. A MT or 5C collet only has about 1/2" area that clamps down. An ER holds with the entire collet.
 
Great info, guys. Thanks a lot.

I have read that the ER collets are not as good for clamping at the nose only - they require the front and back of the collet to both engage the tool/part. Would the MT3 collets be any better in this regard? I would likely be clamping short parts quite often.

Another question: how would a face-mounted collet chuck compare with a taper shank collet chuck (other than losing the through hole advantage)? I found a good local deal on a MT3 to ER-32 collet chuck set that is tempting.
 
An ER collet needs to clamp down on at least 3/4" to hold a part accurately and securely. Normally, this is an easy thing to do but if the part is really short then it can be a problem. Then again, it will be a problem for any kind of holding device if its really short.

A spindle mounted chuck on the lathe is better than a taper mounted one simply because of the loss of the pass through capability as you said. This is one of the key advantages of an ER chuck and I personally wouldn't want to lose it. Taper mounted chucks are better used on a mill, not a lathe.

On the other hand, if you are absolutely sure you are only going to mount short work pieces then a taper mounted ER chuck would probably work okay.
 
I use MT3 collets on my mill. I can't find any numbers on the clamping range but I know from experience that it is quite small. The collets are often unable to get an adequate grip on drill bits, for example. Oversize parts won't go in at all.
 
Thanks again, everyone.

A more specific question now: anyone know about "HORMA" brand tools? I can't find much about them other than they are from Spain, I think. I found a deal on a like new MT3/ER-40 collet chuck and 10 collets for $150 CAD. Seems like a good price to me compared to the Chinese stuff.
 
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