# ER32 or ER40???



## Canus (Sep 25, 2020)

Considering going to ER collets for my Bridgeport mill and my 16" Southbend lathe.  What are the pros and cons of each and which way would you go?


----------



## Buffalo21 (Sep 25, 2020)

ER 32 goes to ~3/4”

ER 40 goes to ~1”

If you want to use the system on a lathe, I’d go with the larger ER 40, for my mill I have ER 20, ER 32 and ER 40, rarely need the 40, I rarely need to use or really have the hp to run an end mill larger than 3/4”.


----------



## RJSakowski (Sep 25, 2020)

Cost is another issue.  ER40 collets run about 20% more than ER32 collets.


----------



## ttabbal (Sep 25, 2020)

I went with ER40 as my lathe has a 1.5" spindle bore so I can use the larger size. For the mill, I rarely go above 3/4" though.


----------



## mickri (Sep 25, 2020)

I would go with the ER40 because of the size of the bore on your lathe.  I went with ER32 because my lathe only has a 3/4 bore.  I also went with metric collets because there is no gap in coverage.  Imperial collets have gaps in coverage.  I mostly use my 10 mm and 13 mm collets to hold 3/8 and 1/2 end mills.  You will need to make a collet chuck for your lathe.  Not hard.  If I can make one anybody can.


----------



## mikey (Sep 26, 2020)

Here is something else to consider. ER collets can be sprung when holding diameters that are far from their nominal size. Yes, ER collets can compress down about 0.040" and still hold but do this enough and their accuracy suffers eventually. On a lathe, in a hobby shop, we are often using stock that is off size or non-nominal so it is common to compress ER collets to hold them. Since this is the case, it is wise to use cheaper import collets on the lathe.

Now, on the mill, accuracy counts. ER collets are most accurate when holding tools at or very near to their stated sizes. Fortunately, most tools have shanks that fall on size and distorting a collet to hold an off size shank is not commonly encountered. Given that accuracy of the tool holding system has a major impact on tool life, accuracy and finishes it stands to reason that you should use high quality collets on the mill to hold your tools. Most of us who use ER chucks on the mill will own several sizes of chucks because no one chuck size fits all. Quite often, a smaller chuck is needed to gain access to a feature on a part that prevents the use of a larger chuck. I have an ER40, ER32 and ER20 because of this demand. This can get expensive because you have to buy separate sets of collets for each of these chucks. I happen to use Techniks collets for each ER chuck used on my mill and yes, that cost a lot but it cannot be helped.

My point is that for the lathe, an ER40 chuck with import collets makes sense. On the mill, I would go with an ER32 system (max shank capacity is 3/4") and add other chucks as needed. Buy high quality collets for use only on the mill and do not use them for work holding on the lathe.


----------



## Aaron_W (Sep 26, 2020)

There is more variety available for ER32. Collet blocks, spin indexers etc so if you don't really need the larger size ER32 has some pluses.


----------



## NortonDommi (Sep 26, 2020)

I'd look at DNA collets as well. I recently didn't bid on a full set of DNA 32 collets because I didn't know exactly what they were, now I do I want some!


----------



## Suzuki4evr (Sep 26, 2020)

Here are links to er ranges. I added ER50 so you'll have more options. 






						Tool Holders, Collets and Machine Accessories ER32 Collets - MariTool
					






					www.maritool.com
				









						Tool Holders, Collets and Machine Accessories ER40 Collets - MariTool
					






					www.maritool.com
				









						Tool Holders, Collets and Machine Accessories ER50 Collets - MariTool
					






					www.maritool.com


----------



## Canus (Sep 26, 2020)

Thanks for all the great input.  Not sure how often I would need to use collets in the lathe so will probably go with ER32.  Would appreciate any additional comments to help me solidify my decision.


----------



## mksj (Sep 26, 2020)

I agree with Mikey, although ER chucks have a wide clamping range, the accuracy diminishes significantly as one clamps them through the range and also the holding power. I do not advise a metric set because they claim that there is a 1 mm clamping range, this is a selling point from the vendors but you will find that using a 12 or 13 mm ER collet for a 1/2" end mill is going to have significant run out. Much better off with an imperial set for the mill.  On the lathe maybe a bit different if you are just doing a single op and then cutting off the piece, but the effective clamping range is much less then stated but still better than a 5C. The other significant factor is that an ER collet requires having the end mill or stock held the full length of the collet, otherwise the collet will distort and collapse on the back end as it is clamped.

You will also find that many of the higher end ER collets are for a specific size end mill, with a very small rated clamping range. So a 12mm collet is for a 12mm end mill a 1/2" collet is for 1/2" end mill. Try it any other way the you spring the collet and the run out becomes significant. When I need accuracy in my mill I use a high quality ER collet at the rated diameter.

Me recommendation would be to use an ER32 on the mill, it is more compact, and the diameter is significantly less. Typically the largest end mill one uses is 3/4". One exception would be if you have any 1" tooling that will not fit an R8. An ER32 collet is going to require less nut torque, but buying a good quality ER nut (either coated or bearing style) makes tightening significantly easier and also improves accuracy. End mills typically run in fixed shank diameters, I mostly used 1/4", 3/8", 1/2", 5/8" and 3/4" probably 99% of the time when using an ER32 chuck. You do not need a full range set for the mill, buy a few higher quality types or maybe a 1/8" increment set. Techniks are quite good at the price point, but look at some better quality ones for your mill. Decent collets are about $15 each. Get a power or bearing nut. I have both Iscar and and the higher end Shar's nickle plated R8 ER collets holder for my mill and they are all under 0.0002" TIR, almost not measurable on my 0.0001" indicator, but has been discontinued. On my mill my edge finder requires a high level of accuracy when centering, I can only do this with my ER32 R8 setup with a 12mm collet. Most R8 collets have too much runout/skew.








						buying er32 collets
					

My Beall Collet chuck arrived and what a work of art it is.  now to populate the collet rack.  er32 collets can cost from a little to a lot.  obviously "a lot" means different things to different people, but it is not my first choice.  So the question is, If one buys moderately priced collets...




					www.hobby-machinist.com
				








						Glacern Machine Tools - ER Collet Chucks
					

Glacern Machine Tools manufacturers CNC Machine Vises, Precision Tool Holders, and Indexable Milling Cutters for vertical and horizontal cnc milling machines.




					www.glacern.com
				




Lathe is a different kettle of fish. Unless you have a small lathe, most people use an ER40 collet system, Shar's sells a set-true style ER chuck (32 or 40) that is quite popular. On a larger lathe (12" or greater) I would go with an ER40. As mentioned ER collets work for stock that passes through the full length of the collet, and for high accuracy work, I would try to use them in a reduced clamping range. They do work well for odd size diameter work, so rough stock that is a bit oversized , threaded stock or knurled. On the lathe I have a 1/32 ER40 imperial collet set which has a bit smaller clamping range between collets. I use a less expensive set for my lathe, but they are still decent quality. I also have a few Shar's ER40 collets that are decent and were in the $7 a piece range.





						ER Collets, ER40 Collet, ER 40 Chuck Collets,
					

23 Pcs ER 40  Chuck Collets




					zlivecenter.com


----------



## Nogoingback (Sep 26, 2020)

I just went through the same choice for my lathe and decided on ER 40 rather than 32.  My lathe has a 3/4" spindle bore, so my initial
thought was ER 32, but I realized that I do jobs with short lengths of stock that don't have to pass
through the spindle anyway.  I have a job like that coming up that will use 1" diameter bar, so at that point the choice was obvious.
The ER 40 won't go as small at the bottom end of the range, but to me that isn't as important.


----------



## mikey (Sep 26, 2020)

Canus said:


> Thanks for all the great input.  Not sure how often I would need to use collets in the lathe so will probably go with ER32.  Would appreciate any additional comments to help me solidify my decision.



Any time you need to grab a precision ground rod or an already turned rod that you do not wish to mar, or a knurled or threaded surface that you don't want to distort, an ER collet is the answer. It will also grab nominal stock for general turning, although a 3 jaw is faster and just as accurate for a first operation/turning. 

I agree with the other guys - for the lathe, get the ER40. ER50 will go bigger but the collets and nuts are big bucks and not worth the cost. For the mill, go with ER32 (to start) and buy a good nut and high quality collets, at least in the sizes your tooling requires.


----------

