Tool Review: ER40/R8 collet chuck

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Well-Known Member
May 24, 2008
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ER 40 Collet

A couple weeks ago I set about getting opinions on the ER32 collet chuck sold by LMS. During the discussion I changed my mind about the size collet system and the vendor, so I ordered an ER40 set from 800watt on eBay. It arrived earlier this week and today I had a chance to use it and see exactly what I had purchased.


First Impression

The first thing I noticed is that nowhere has the country of origin been marked. Of course, the first assumption is China. However, except for the case, the pieces seem of pretty good quality so it could be India or possibly even somewhere in Eastern Europe. My guess is somewhere in Asia.

The case is made of yellow pine, or something very similar, and of very poor quality construction. It was broken and falling apart when it arrived. It’s wobbly and all the pieces fit poorly. The corners are “reinforced” but there is only a nail or two holding the corner covers on.


Upon opening the case my first impression was good. The ground finish on the chuck seemed of good quality, no chattering or burn marks. All edges were properly finished, I didn’t find any burrs or snags anywhere. Even the threads on the nose had a ground finish.


Some slight burrs on the collets are evident, but then I didn’t really expect to have the edges of the longitudinal slitting finished. All the outside edges have a decent finish, though they could have done a better job around the ring slot.


The chuck and all the collets are laser or acid etched indicating the size of each. Hopefully this will prove more durable than the ink markings I’ve come to expect.


For the sake of those who don’t know, the ER collet systems are a self-extracting collet that allows stock to pass completely through it. The collet is held in the nut by an eccentric ring, the collet slips in at a slight angle then “snaps” into place. The nut is then screwed onto the nose of the chuck, pressing the collet into the taper in the chuck. No drawbar is necessary such as might by used by an R8 or Morse Taper collet. Of course, the R8 portion of the chuck prevents pass-through, but I won't be needing that feature on a mill.



Let the testing begin

First up, the mill spindle. As expected it came out dead-nuts on the money. No surprise there, this is old American iron, after all.


The chuck came out with about .0005 run out. Not bad for a inexpensive Asian tool.


So, I put a 3/8 end mill in a collet and tightened up the nut. I got about .00125 run out on the side of the end mill. Not great, but on the edge of tolerable.


I then tried a 1/2 inch end mill and collet. The results were much better at about .0005, about the limits of the chuck. This is also what I got using an R8 collet with the same end mill.


Last Impressions

I have no illusions that this is a “high quality” tool. I did not have any accuracy problems with the mill, so I didn’t expect this to “correct” anything. What I did want was a little more convenience and flexibility and I think I got that, only time will tell. I may end up replacing the 3/8 collet from another vendor, that hopefully will correct the high runout experienced there. I still have to check the other collets but I expect similar results from them.

Overall I think it is a good, not great but good, addition to the shop.
Next up is to create a chuck for the lathe. Someday.

I think that unless you spend big bucks you won't get runout any better than you are getting.

I have also found that the collets do need a little 'bedding in', all because of the little bits of roughness you noticed. Once that is worn or knocked off, I found my collets were starting to get very accurate indeed, and mine are the same sort of source as yours, unknown.
So if I was you, I would wait a while, and recheck them after they have had a bit of use before going out and buying new ones.

The one thing you might consider is a ball raced collet nut. They really do make these ER collet chucks much more user friendly, and you can get a real good grip on the tool with them, you can almost do it by hand tightening. The people who have taken my advice and purchased one are usually over the moon with how much easier they make tool changing. No more three handed juggling.

You should be able to source them in the US if you are lucky.

If you are going to make a nose fitting for your lathe, maybe this part of an article I wrote might help a little. It is for an ER 32, but the technique is the same.

A very nice write up by the way. It does show that far eastern tooling is really getting a lot better compared to what it used to be.


Thanks John.

I was wondering if maybe the slight “roughness” of the collet is what was throwing it off. Time will tell, I’m in no great hurry to replace it.

Years ago I would tell people that Chinese goods had two levels of quality; pretty good, which was extremely rare and extremely poor, which was all too common. There was very little middle ground. Over the past few years the middle ground has expanded. To be sure, there is still a disproportionate level of crap being distributed from China, but the common grade of quality has steadily improved. These tools are evidence of that, if China really is where they are made. It’s nice to pick up a tool and not feel like you just grabbed a handful of razor blades.
As I recall, it was the 3/8 collet I had to replace, as well. Someone must have made a large run with the same problem. I've used the ER40/R8 for a year now and wouldn't want to be without it. I added a set of R8 collets over Christmas for those times when head clearance is an issue, but the ER40 is first choice.

Similar experience with an 800 watt Er32 collet chuck. The chuck itself was a little better than 5 tenths for me ( 2'ish). I found one collet that was pretty far out, and the rest very good. At the time, I tossed the collet and ordered a new singleton, but perhaps I should have tried to give it some TLC.

I also have collet chucks from Glacern and Maritool, and a set of Maritool collets. The latter is a nice step up if you want to spend a bit more on the collet set. I use these things as toolholders on my CNC, so that's why I need so many (4) collet chucks and 2 sets of collets.



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