What would you consider a complete ER collet set

Now, I'm looking to build and adapter for the Sebastian lathe, and thinking that I might want to go with ER40, since my spindle will pass through 1 5/8". But, if I'm going to buy another set, even if it is the cheap set, I'd prefer there not be gaps in the holding range.

But, what would a full "able to hold anything in the range" set look like?
Have a look at the attached - it goes into this in detail.
 

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  • About R8 ER and 5C Collets.pdf
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I guess by now you figured out that everybody did what they needed at the time. Here is my setup. When I got my mill several years ago, I got a set of endmill holders and the Shars ER32 to R8 spindle and the Shars set of collets. I need about 3 or 4 to have complete Imperial, but I just haven't needed them yet. Will get them in Tekniks one at a time. When I got the lathe, I got a straight shank ER32 holder. Dial it in the 4 jaw and it works fine. The 3 & 4 jaw chucks just don't go down in size real good, so collets are a better choice.

Fast forward to the mill again and I got 5C collet blocks and spin indexter. Bought a set in 1/32" and that was a mistake. I am now adding all the 1/64" sizes in as the 5C don't compress as much. I added the 5C lathe collet chuck. Now I can pass long lengths through and do 2nd operations quickly. Eliminates dialing in the 4 jaw. I have added in 4-5 R8 collets for popular endmill sizes.

So, for about 4-5 years I used the ER32 collets all the time. Switching to R8 and 5C collets simply works better for me. The ER32 collets sit lonely in the drawer. I have only used them once this year. With repect to what has been posted. You might want to investigate Metric sizes vs Imperial. If I had to do it over again, I think I would have gone complete Metric and skipped Imperial.
 
I think David's document provides a good summary of all the aspects between ER and 5C collets. But as Chewy points out, this is not necessarily an either or question. You may end up wit both over time. I have 5c collets primarily for work holding on the lathe and after a while got the 64ths set PM is selling. I do some metric work as well so I added a metric one as well. Being restricted to certain sizes of 5c collets and not having a full clamping range is not that much of a restriction for me in practice. I just choose the diameter of the parts I am making accordingly so that i can grip them on second ops. And the ability to grip safely on just a few mm of a part has been useful (but David will just design with enough material left to clamp securely in his ER40s so that may not matter much to him). So combined with a quality 5c chuck (I first had a lemon from Bostar -- the PM's were not available at the time) this is the setup that basically lives on my lathe most of the times. Is this the most economical choice in the end? Certainly not but I feel I got value for the money and am very happy with the setup.

On the mill I have R8s and ER32 and ER16 holders. I decided against ER40 since is considerably more bulky than the ER32. I use them like an endmill holder and they give me repeatable stick outs in tool changes as opposed to the R8 collets. However, an ER40 set is certainly more budget friendly to start out as it can do double duty between lathe and mill.

One additional thing that makes 5c collets useful to me is the ability to use them in my Sheckel d-bit grinder. I just ground a 4mm step on a 7mm drill and it was really easy because I had a full range of 5c collets at hand to just pop the drill into.
 
Taking all this into consideration, I think I'm going to get me a 20-piece, metric, ER-32 set.
I'd go with ER40, but I've already got some ER32, and the 40 won't fit on the mill so well. So, I'll expand out the set I have.
I don't have a collet for the lathe, it is a short MT5 taper, with a weird spindle thread size (2 1/8" x 8), and no real ability to cut metric threads. I've already started building a chuck that will thread on. I'll cut the head off one of the cheap MT3 ER32 chucks, and shrink fit into the end of the spin on part. Then I'll mill either hex or square flats on it. The result will be a collet block that will spin onto my lathe spindle.

This would be so much easier if I could find an oversized collet block.
 
I think David's document provides a good summary of all the aspects between ER and 5C collets. But as Chewy points out, this is not necessarily an either or question. You may end up wit both over time. . . . And the ability to grip safely on just a few mm of a part has been useful (but David will just design with enough material left to clamp securely in his ER40s so that may not matter much to him).
Thank you @j-becker - I had a good laugh at those comments. Yes, if you’re not careful, you will end up like I did, with ER32, ER40, 5C, well over 250 collets, and every imaginable collet chuck for the lathe spindle, tailstock, mill spindle, rotary table, as well as square and hex collet blocks.
 
I have an ER-40 collet set from 1/16th through 1+1/8 in 1/32nds.
I have ER40 holder in R8 (Mill)
I have ER40 holder in MT5 (nose end of the lathe)
I have ER40 holder in MT3 (tail end of the lathe)
I have square sided ER40 holder
I have hex sided ER40 holder

I was lucky in that my cheapo ER40-R8 has no discernable runout in the indexed position of my mill spindle.
There is a radial orientation where my cheapo MT5_ER40 holder has less than 0.000,3 runout. (marked)
 
I have the same ER-40 setup per above, but made a D1-4 ER-40 set-true chuck instead of the MT5. I find a 1/32 increment has a little closer range then a 1 mm set, and fits my stock better. Not sure why, but many of the ER-40 1/32 increment sets have a few missing sizes that I needed to back fill. I still prefer the ER-32 collet size on the mill, I use the ER-40 for my 1" end mills. I primarily use my 5C on the lathe/indexer because I hold a lot of small short stock, but it requires a 1/64th 5C set. I do use my ER-40 collets in the tailstock with end mills for step cutting wear I need a square shoulder for a hole.

ER-40 collet set by 1/32 step 1/8-1", I back filled a few of the missing sizes with the Shar's and Techniks ER-40 collets. I rarely use this set, but in general ER collets tend to have tighter TIR tolerances then 5C, and the Techniks are very good and at a mid price point. I have an Iscar 1/16 increment ER-32 set for the mill, but I only use a few collet sizes, most endmills come with standard size shanks.
ER40 1-32 complete set.jpg
 
You got a better box than I did..............

But, yes, that is what a full set of ER40 collets looks like.
 
You need 1/32" increments to get all sizes according to this chart.

 
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