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School me on collets for the Atlas lathe, 3c, 3at,or both?

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Uncle Buck

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#1
I understand the benefits of using collets on the lathe and their greater accuracy instead of chucks, but I have always had a poor memory regarding the Atlas lathe and collets. As I recall Atlas/Craftsman lathes when made were supposed to take 3at collets and not 3c collets. Unless I am mistaken 3at collets can be hard to find and are expensive when they are found these days. Could a guy use a 3c collet instead? If not, why not, do they simply not fit the closer and flop around?

Anyway, if you are in the know on collets maybe you might further my knowledge some. It would be appreciated. Clarity on the whole Atlas collet thing in particular would be greatly appreciated.
 

Uncle Buck

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So far 27 people have looked at this thread and not one knows anything more than I do about Atlas collets for lathes? Man, I am some disappointed guys.......
 

wa5cab

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#3
Uncle Buck,

Since my father-in-law went into hospital a month ago, and then died, my wife has been stuck in San Antonio caring for her mother. And I've been out there about 3/4 of the month (three trips so far). So I'm not keeping up with anything fun much. :-(

Anyway, the collets that Atlas originally supplied for the 10" and 12" machines were the 3AT. They aren't too difficult to find. I have a complete 1/32nd increment set plus extras all acquired within a few weeks. What's hard to find are 1/64th increment ones. I found that Bass Tool here in Houston still stocks them and in 1/64th increments. Downside is that price is about $21 each. The draw tube is a little harder to find but not unavailable. There was a guy making an adjustable length one with ball thrust bearing that I bought first. It works fine. I later found two originals from different decades.

The differences between the 3AT and 3C are (a) 3C is about 3/8" shorter than 3AT so a fixed length draw tube that works with one will be too long or too short for the other. This can be solved by having two different length thrust bearing/centralizers. (b) threads are the same pitch and only 0.003" different in OD (3AT is the smaller) so a draw tube tapped for 3C works fine on 3AT. (c) closer taper is significantly different (3C is shorter) so to use both, you need two adaptors. Both type adaptors to fit 3MT spindle taper show up frequently on eBay.

All that being said, I do not like the 3C. I have some because of the afore mentioned problem finding 1/64th increment 3AT collets. But probably due to the shorter closer taper they seem always to jam in the adaptor when tightened. When you loosen the draw tube, you have to bang on the handwheel to get the collet to release. The 3AT ones release just by loosening the draw tube.

So you can use either or both so long as you have the proper adaptor and proper length draw tube.

The lever type closer for the 12" is extremely difficult to find. The actual draw tube assembly is the same for both 10" and 12" but the lever and the mounting brackets are different. I have most of a 10" model (everything that works with 12") but have been looking for nearly a year for the lever and brackets to convert it. I have the Atlas drawings and may eventually give up and make them.

Robert D.
 
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Uncle Buck

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Thank you, that was what I was looking for!
 

Artemetra

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This thread isn't too old so I'm posting another question: I have some Precision Brand collets that don't work in my collet closer. My Royal, Hardinge, Sutton collets work fine. I see the Precision Brand collets are a little longer, maybe .08" measured in the collet adapter. What is the deal with the Precision Brand collets? Do they make a taper adapter for them that's different?

Also, here's a little more info from a nice ramble by D. Turk on another site, 2008:

The 3AT (atlas) has a different taper on the front of the collet so a 3 AT will not work in a 3C nose piece and vise versa. There is about .05 to .08 difference in the thread diameter also but the same pitch thread. What I have found is that the grater taper on the 3AT collet requires a lot more force to close and hold a work piece. The 3C collet on the other hand has a less taper and so takes significantly less draw bar force to hold the work piece. I am not sure if the steeper angle of the 3AT collet affects accuracy much but in my mind it has to. One thing that is different is because the of the grater angle on the 3AT collet it takes less movement to close it. In the cast of the 3C it reacquires more travel of the collet to close it. Just some odd thoughts about the two collets.

I personally do not like the 3AT but do like the 3C. Then I am predigest as the 3C 4C 5C collets were patent by Catarac which led to Hardinge. Least I know the 5C was patent by Catarac which Hardinge acquired when they purchased Catarac. That patent by the way ran from 1920 to 1927 and as Hardinge wonted big royalties for the use of there 1 inch collet no lathes other than the Wade 8A used a 1 inch collet till 1938 when the patent time had ran out. By the way Wade got around Harding patent by patenting there own collet. What Wade did was lengthen the thread 1/2 inch but other than that was exactly the same as the Hardinge collet. In fact Wade offered two draw bars for their lathe so you could use either there long threaded collet or you could get a longer draw bar and use the shorter Hardinge collet. The wade 8A came out in 1928. Ya and I have one. Just a little history guys that I think for the most part is correct.
 

VSAncona

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I have a set of NOS Precision brand 3AT collets that I bought for my lathe and I've been curious to know where they were made and by whom. I don't think they are quite as nice as the name brands like Hardinge, Sutton, Royal, etc. but they seem to be adequate and are pretty common on ebay. My collet adaptor is also a Precision brand.
 

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These are not 3c collets, bt I figured I would post anyways. These are called EC collets and you can sometimes find them and the chuck for a reaonsable price. I use them on my atlas lathe quite often when I need to turn and part off pieces in a succession or really want the accuracy and the ease.

IMG-20130206-00032.jpg
 

wa5cab

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#8
Artemetra,

My 3AT collet collection includes Precision and half a dozen other brands. After you posted your question, I compared the Precision ones to several of the others and the others among themselves and find quite a length variation. Both between collets of the same brand and between different brands, and both in LOA and in the length of the taper. I have 3AT collet drawings from three different sources, Logan, Hardinge and unknown. None agree on all dimensions. None show how long the threaded area should be. And aside from the Hardinge, the other two are missing some other dimensions. So my take on all of this is that if you have two alike with different brands or of different ages, it's a minor miracle! I found three distinctly different versions made by Precision. I didn't compare each of the other brands among themselves but wouldn't be surprised to find some of them don't exactly match.

I have never seen what I would call a collet chuck for a 3AT. Only handwheel operated and lever operated draw tubes. Aside from the little European ER types and the rubber-flex types, all of the collet chucks I've seen have been for collet sizes too large to fit into the spindle bore (like 5C). Where did you find it? Could we have a photo? As for the difference in length making some of the collets unusable, I have a 5C collet chuck for my Atlas, and it would easily handle the length variation that I found (about 1/8" total) if it were for a 3AT. It would be inconvenient to have to readjust it but the lever type closer I have would also have the necessary range. And the handwheel one would just screw on a few more threads.

Two comments on the D Turk paragraph that you copied in. I don't find that the difference in taper (about 3 deg. per side) makes the 3AT any harder to close than the 3C. I do find that the 3AT collets are self releasing and that the 3C are not. With the handwheel closer, to release a part held in a 3AT, I just have to loosen the handwheel. With several 3C's, after loosening I have to hit the handwheel with something to get the collet to release. Consequently, despite the better availability of 3C, I decided to go with 3AT. Second, his statement about the difference between the threads is approximately the difference in millimeters. He should have said so as at first I thought he was 'way off in left field.

Robert D.
 

Artemetra

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#10
Here are pics. Logan 820, 1946, I think the collet closer came with the lathe. No markings on it. The other pictures show both of my collet types. Left is the Precision Brand collet. Obviously longer. The Precision collet sticks out of the adapter too far even when fully threaded, unable to cinch down on the work. The closer has a stepped diameter, which is the depth stop. Now I'm thinking of machining a ring to "lengthen" the step and put the closer back by the longer diameter. If that works I'm golden.

Logan Collet Closer 1.jpg Logan Collet Closer 2.jpg Precison Brand vs Hardinge Brand 1.jpg Precison Brand vs Hardinge Brand 2.jpg
 

wa5cab

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#11
Artemetra,

Thanks for the photos. That is a fair amount of length difference. But about the same as the max delta-L out of the assortment of 60 odd collects that I have. For reference, all three of the collet drawings that I have agree that the length from the left (threaded) end to the large end of the taper should be 2-5/16" AKA 2.313".

However, if that amount means the difference between working and not working, the spacer/pilot/thrust bearing next to the handwheel on your closer is too short or thin for your spindle. I have three handwheel type collet closers. Two are Atlas originals, one early and one late, that I finally found after some time looking. The first one that I bought has the handwheel and spacer adjustable. So I can use it on 3AT or 3C collets. My rule-of-thumb for adjusting it is that when the draw tube is screwed about half-way onto the collet (typically 7 or 8 threads) the pilot should be against the end of the spindle and the collet should be fully in the adapter but not squeezed any. If you make a spacer to go between the thrust bearing and the wheel of a thickness such that the above rule is met for the rest of your collets, the Precision ones will work fine. You will probably need longer flat head screws.

Robert D.
 

Artemetra

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#12
Thanks Robert, interesting thoughts. Basically I think I can work it out now - but not quite like you put it. The thrust bearing on this setup isn't doing anything. Maybe that tells me that the wheel collet closer isn't original to this lathe. Somehow, the tube hits a shoulder inside the spindle, and that is the stop. The thrust bearing is a couple inches back from the rear of the spindle, not touching anything when you have a collet with workpiece tight in it. If you were to somehow push it all the way in, the wood would rub on the cover anyway. So Maybe I can make a larger spacer for behind the spindle that will use the bearing, or just a little sleeve that goes inside the spindle. I'll post when I get to it.
 

VSAncona

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#13
I have three handwheel type collet closers. Two are Atlas originals, one early and one late, that I finally found after some time looking.

Robert D.
Robert -- Do you have any photos of your early Atlas handwheel type closer. I'd like to find one for my Atlas lathe and it would be helpful to know what I'm looking for. The one I have now works okay, but I don't think it's original to the lathe. It's an inch or two too long.
 

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#14
Artemetra,

Either you collet closer wasn't made for the lathe you have or it is missing a part. Or both. All handwheel operated drawbars and collet closers I have ever seen for any make machine take the thrust against the left end (or the top on a vertical mill) of the spindle, not against some shoulder down inside the spindle. I think that your closer is missing the actual thrust bearing. Possibly the nose of the draw tube is stopping against the left end of the adapter. I never saw any hollow lathe spindle that wasn't the same ID throughout.

Try this. First, with the adapter loose, load one of your shorter collets into it. All threads and the relief groove should be visible. If not, your adapter is too long. Then, put the adapter into the spindle nose, load a collet into the adapter as far as it will go without pulling on it, slide the drawtube into the spindle, and screw it onto the collet 7 or 8 turns. Pull lightly to the left on the handwheel and measure the distance between what I was calling the thrust bearing on your handwheel and the left end of the spindle. As a check, push to the right on the handwheel and the collet should come out of the adapter a little ways. This confirms that the drawtube nose isn't hitting the adapter when it is where it belongs. Make a steel or stainless steel thrust bearing about 1/4" larger in diameter than the drawtube and a little longer than the measured distance mentioned above. Bore it until the ID is .005" larger than the diameter of the drawtube. Bevel one end at 45 deg., leaving just a barely visible flat on the end, and gently deburr. Temporarily assemble everything and tighten the drawtube until the collet is just beginning to compress. Mark the top of the handwheel so that you can count turns and back it off until it comes loose. Shorten the thrust bearing until the answer is between 7 and 8 threads engaged when it goes tight. That should allow you to use all of your collets.

Robert D.
 

wa5cab

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#15
VSAncona,

I have in Atlas catalogs of various dates seen three different Atlas 3AT collet drawtubes. The photo shows what I think are the second (left) and third (right) variants. The first was very similar to the second except that the handwheel was round instead of octagonal. The thrust bearing on #2 is crimped or swaged so tightly to the tube that it is immovable. I may end up having to machine it off. I am not certain how #2 was made. One would assume that probably the handle was cast, the tube machined from heavy wall tubing, and pressed into the wheel. But in the bore I cannot see a parting line so it could have been cast as one piece and then machined. In #3, the wheel is cast aluminum. The alloy steel tube was pressed in and secured with a short Allen set screw. The thrust bearing on #3 was actually made by the person whom I bought the drawtube from but looks like the photos. It is a bare slip fit on the tube, about .002" running clearance. #2 is probably cast SS. I do not know the purpose of the two holes in #2's wheel. They may not be original as they are sloppy and both need deburring both sides.. The OD of the two draw tubes are not quite the same. #2 is 0.772" and #3 is 0.745".

Robert D.

Atlas Draw Tubes 2 and 3.JPG
 
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iron man

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#16
Forgive me for asking but I have never used a collet in my life if I could not four jaw it and get it accurate I would give up. But I still find it interesting, since the Atlas has a MT3 tapper cut into the head why cant you use the much cheaper MT3 mill collets??? they seem to come in all sizes and making a rod to tighten them up would be a walk in the park.. Ray
 

VSAncona

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Forgive me for asking but I have never used a collet in my life if I could not four jaw it and get it accurate I would give up. But I still find it interesting, since the Atlas has a MT3 tapper cut into the head why cant you use the much cheaper MT3 mill collets??? they seem to come in all sizes and making a rod to tighten them up would be a walk in the park.. Ray
You certainly could use the MT3 collets with a drawbar for short workpieces. The advantage of the 3AT collets is that they tighten with a hollow draw tube, so you can have a long piece of stock passing through the tube. If you're making a bunch of identical small parts, it's easy to simply turn a part, part it off, loosen the collet and slide your stock through for the next part, re-tighten the collet, and start turning. There's no indicating required.

- - - Updated - - -

Robert -- Thanks for the photos. Mine looks different than both of those. I'll try to take a photo my setup and see if anyone here can identify it.

Vince
 

Artemetra

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Robert, that's hilarious! I made the very part you describe, with those exact details, before your post. It works like a charm. All the collets, not just the long Precision ones. You're right, there was something missing. Thanks for the help!
Btw, I wanted to get the collets going for this lathe because they are the WAY TO GO! Iron Man, try the setup (buy the parts you need if you don't have them) it's a sweet way to go. If your lathe can use a lever-style drawbar/closer, well then you're in the money if you have to make more than three pieces or so.

Collet spacer 1.jpg Collet spacer 2.jpg Collet spacer 3.jpg Lathe 3_8 to 5_16 turning w live ctr.jpg
 

Restorer

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#19
View attachment Collet Adapters.pdf

The attached PDF shows basic dimensions for each collet configuration.

Manufacturers take liberties and change dimensions especially in Asia.

Hope this helps. Perhaps Nels can copy the drawing to the lathe download section.
 

wa5cab

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#20
Ray,

In addition to what has already been written about long stock, there is one other issue between 3MT (or 2MT) and 3AT (or 3C) collets. AFAIK, no one makes 3MT collets in increments smaller than 1/16". If your need or interest in collets is for holding milling cutters, neither that nor the drawbar being in the way is any issue. It's relatively easy to buy end mills in 1/64" increments with shanks in 1/16" increments. And the 2MT or 2MT collet sets are cheaper both because they are easier (and cheaper) to make and there aren't as many of them in a full set. But if you need collets for holding small work pieces, 1/16" increments just isn't good enough.

Robert D.

Forgive me for asking but I have never used a collet in my life if I could not four jaw it and get it accurate I would give up. But I still find it interesting, since the Atlas has a MT3 tapper cut into the head why cant you use the much cheaper MT3 mill collets??? they seem to come in all sizes and making a rod to tighten them up would be a walk in the park.. Ray
 

wa5cab

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#21
Restorer,

I just put your file into Downloads, along with three others that I have found in various places. They are under Atlas\Collet Specs.

Robert D.
 

wa5cab

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#22
Yep, that is funny. One comment to add - Atlas spindles are all countersunk on the left end. Hence the 45 deg. taper on all of the thrust bearings. Looking at one of the photos of your lathe, it appears that your spindle isn't countersunk. So you were quite right to leave the end of the thrust bearing straight.

As the subject of drawbars and MT collets came up, I'll add that most of the drawbar thrust washers I've seen (including an original from Atlas) have also been beveled. However, back when I started adding various collet types to my 3996, the first drawbar I found was aftermarket. The person who made it made the thrust bearing about the same length and about the same OD as the factory one I later acquired. But instead of beveling one or both ends, he cut a 3/4" dia. step about 3/16" long on one end. I find that this design is actually more comfortable to use with a drawbar than the beveled ones. On a lathe (at least on an Atlas 10" or 12", the drawbar is much smaller in diameter than the hole through the spindle. When you loosen the drawbar to remove the collet, cutter or workpiece, the weight of the handle, thrust bearing and drawbar causes the tapered thrust bearing to follow the handwheel to the left and drop out of the bevel in the spindle unless you hold it up in the bevel with one hand. You almost always have to bang on the handwheel with something to loosen the collet. And when you do, if the bearing isn't still up and concentric with the spindle hole, you tend to bang the bearing against the end of the spindle and aren't pushing on the collet axis. With the stepped bearing, everything stays in alignment and it just feels better.

Robert, that's hilarious! I made the very part you describe, with those exact details, before your post. It works like a charm. All the collets, not just the long Precision ones. You're right, there was something missing. Thanks for the help!
 

robinj66

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Forgive the thread resurrection but I'm hugely confused about setting up milling cutters in my 10F Atlas (TV36).

I have attached pictures of the items that came with my lathe which appear to be those mentioned at p168 "Manual of Lathe Operation" (described as a "drawbar, sleeve and an arbor for straight shank cutters").

My first query is that my drawbar is solid with an external thread but everyone else seems to have a hollow tubular drawbar with an internal thread (even the one in the manual on close inspection). Does this mean I am missing a drawbar?

With the solid drawbar & arbor, do I need cutters that have an indent on the shank (so that the grubscrew fits into the notch) or is the friction of the grubscrew simply enough to hold a smooth shank cutting head?

Does the "sleeve" act as a spacer? And if so, does it go at the rear or the front (chuck side) of the headstock spindle?

Am I correct in thinking that my arbor will not hold 3AT or 3C collets?

Even as I'm writing this it strikes me that I might be confusing myself about the use of collets - I understand that they provide superior "gripping power" over chucks (especially with smaller diameters) but do I need them to mill on my lathe?

Sorry for so may questions - I'm sure there will be many more:dejected:
 

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#24
Can you tell us what thread your drawbar has? You might have a drawbar for MT2 or MT3 collets.
 

wa5cab

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#25
Robin,

Machinists, expecially new hobbiest ones, have a tendency to be sloppy about nomenclature. In fact, hobbiests in general are bad about this. Generically, there are two types of threaded devices that work by sticking them through the hollow spindle from the left end. They are called draw bars and draw tubes. Draw bars are (almost always) solid, and have male threads. Draw tubes are hollow and have female threads.

The most common draw bar in the English speaking world is 3/8" in diameter and has 3/8"-16 threads. There is no "standard" draw tube. They are identified by the collet type that they fit, most of which are of different outside diameters with different pitch threads.

What you probably have is the Atlas cutter holder set for 3MT (or MT3). It consists of a 3.8"-16 draw bar. a 3MT to 1/2" diameter cutter holder with set screw, and four reducing bushings. And I will throw in here that you never ever want to use a Weldon style (with the set screw flat ground on the side of the shank) cutter other than one with a 1/2" dia. shank that does not require a bushing. Those are safe to use. But if you put a smaller shank diameter one into the appropriate reducing bushing and tighten the set screw onto the flat in the bushing with the flat on the cutter right under the set screw, you will probably never manage to remove the cutter and bushing from the 3MT cutter holder.

Anyway, this setup is used only for holding milling cutters whose shanks fit the holder or one of the bushings. It could be use to hold a short work piece of the proper diameter, but the set screw will mar the surface. So you do not want to try to use it for that.

The draw bar is made for tightening tools that have a taper that matches the taper in the lathe or milling machine spindle. The only collets that it will tighten (close) on your machine are 3MT collets, which only come in 1/16" diameter increments. You can use 3MT collets for holding short work pieces but the work piece diameter must be withing about +/- 0.007" of the collet diameter.

If you want to do mill work with the Atlas milling attachment mounted in place of the compound, it sounds as though you have what you need so long as your cutter shank diameters are 1/4", 5/16", 3/8", 7/16" or 1/2". But if you want to use collets for holding work to turn, face or thread on the lathe, aside from short work pieces in the range 1/16" to 3/4" by 16ths that 3MT collects come in, you need something else.

The three collet types that are commonly used on an Atlas 10" or 12" are 3AT (which is what Atlas/Clausing used to sell), 3C, and any of the European type ER collets. The first two require a matching draw tube and a 3MT to 3AT or 3MT to 3C closer adapter. The ER collets require what's usually called a collet chuck, of which there are two types, those that screw onto the spindle threads (and allow the work piece to extend back through the spindle) and those built onto a 3MT arbor secured by a draw bar (that don't).

The pro's and con's of these three types of collets is another subject (which I think this thread was originally about).
 

robinj66

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Thanks for the replies.

Terry - my drawbar has a 3/8" UNC thread (16 TPI)

Robert - thanks, that's cleared up some issues for me.
The ER collets are much more readily available over here (UK) although there is a used set of 3AT collets currently on US Ebay in Massachusetts.

I have provisionally tried out my set up on the lathe today and it seems to lock the cutter holder in the headstock (and a 1/2" cutter is surprisingly tight in the holder (I just assumed it would spin).
 

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#27
Thank you for bringing this thread back to life. It is some very helpful information.
 

robinj66

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#28
Unfortunately I have now gone and broken the wheel on the end of my drawbar . Any idea how I go about removing the stub from the bar?

My initial thought is to heat it up and "persuade" it to part company with the bar. Is it just a friction fit or is there some hidden fixing that I'm not aware of?
 

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#29
Robin,

The handwheel is pinned to the stud with probably a grooved taper pin. I can see one end of it in your third photo. Determine which is the smaller end and drift it out with a pin punch. The handwheel is the same as I think the one on the milling attachment, except without the handle and probably not keyed (I never noticed on mine).
 

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#30
Thanks for the replies.

Terry - my drawbar has a 3/8" UNC thread (16 TPI)

Robert - thanks, that's cleared up some issues for me.
The ER collets are much more readily available over here (UK) although there is a used set of 3AT collets currently on US Ebay in Massachusetts.

I have provisionally tried out my set up on the lathe today and it seems to lock the cutter holder in the headstock (and a 1/2" cutter is surprisingly tight in the holder (I just assumed it would spin).
Robin,

Milling and cutter shanks are finish ground to tight tolerances, as is the hole in the cutter holder. So they are a snug fit. Otherwise, the set screw would tighten them off center and the hole that they would cut would be oversized.

I think that the ER collets would be your better bet. Certainly cheaper. And if the size family that you choose is the ER32, can handle parts up to 3/4" diameter through the spindle (if you get the screw-on chuck). If you do opt for the 3AT or 3C collets, they go from 1/64" to 1/2" because the draw tube must slide through the 25/32" spindle bore. And although I have both for reasons I won't get into, you don't need both. The draw tube effective length is different for the two types because the collet lengths are different.
 
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