ER40 versus 5C Collets - Considerations and Trade-offs

[davidpbest]

Are you considering a collet setup for your lathe or mill for workholding or toolholding applications, and confused about the trade-offs between ER, and 5C systems? If so, the attached document might help understand the differences between the R8, ER40, and 5C collets and related chucks for these systems.

This is a topic that has been extensively discussed in various threads here on H-M, and the attached document is my effort to demystify the topic, summarize the various points of view, and contrast the pros/cons of each system.

 

[Nesse1]

Thanks for posting this Dave. I'm someone trying to decide what to buy for my "new to me" lathe, and this sort of info helps (I've seen it previously in one of your recent posts.)

Since cost often matters, the following video, and it's part 2, sheds light on the quality, or lack there of, of the common generic china made 5C chuck making the rounds on eBay and similar. Hint: the softness of the pinion gears is concerning. Which brings the next question: is the Precision Mathews version better?

 

[dbb-the-bruce]

Great stuff Dave, I always look forward to your posts.
I spotted one mistake at the top of page 9:

chuck and use a $20 ER collet nut to tighten the setup, I can speak with authority that your TIR will not be disappointing and get worse the more you tighten down on the nut.

Pretty sure you meant "will be disappointing" - but it's not clear to me. Sounds like you are trying to say that using a $20 nut on a precision setup will lead to bad results. A great point - consider the whole setup as a system. I had never considered that a bad nut would push a good collet out of alignment.

Another thing I didn't see addressed (and perhaps it's a no-brainer for most people) is the ability to use long stock in the collet and keep feeding it out as you make multiple parts. I'm curious if there is much difference doing this with different collets or if it's more a matter of the machine/setup. In other words you only do this on a lathe so it's a non-starter with R8. Personal experience is that some ER holders do not provide for through hole stock. Do most lathe ER chucks/holders support through stock?

-Another Dave.

 

[RJSakowski]

I bought a 5C collet chuck for two reasons. I already had a 5C collet set, albeit only by 1/16ths, and I liked the slim nose on the 5C chuck which allowed me greater flexibility for certain operations.

A down side is the lack of grip range of a 5C collet which will require minimally a 1/32" set of collets and preferably a 1/64" set. The cost of a full set of 5C collets would exceed the cost of a set of ER32 or ER 40 collets. Changing out collets on my collet chuck also requires a full 32 turns of the chuck key, which can be annoying.

I disagree with the idea that 5C collets only grip the work at the nose of the collet. Were that true, the work would be unstable in the chuck. When a 5C collet is closed, it first contacts the the work at three points ,H in the left drawing, at the nose of the collet, as the collet jaws bend in a simple arc in region B in the upper right drawing. The collet also makes contact with the 5C socket at point D with a slight gap at E. The work is only in contact at C in the drawing.

As the chuck is further tightened, the simple arc in region B changes to a S shape with bends at F and G as shown in the lower right drawing, closing the gap E. Fully tightened, the collet will be in contact with the socket all along the surface between D and E and the region A will again be parallel to the collet axis, gripping the work along three axial lines along H and stabilizing it.

The limit governing the ability to grip an undersized cylinder will be determined by the three gaps in the collet. The amount of force required to close a collet will increase as the difference in size between the collet and the work increases. In the case of using a lever type collet closer, the available force may very well be insufficient to that required to fully close on the work, resulting in a three point grip on the work rather than three lines.

 

[paradox_pete]

One of the often mentioned disadvantages of the ER series collets is the inability to hold short work. I have found a work around which has proven quite effective for my purposes.

The trick is simply to place a piece of like diameter material in the back of the collet while chucking up the short work piece in the front. Ideally the back piece would be exactly the same diameter as the work piece, but I have found that in practice a slight difference (a few thou maybe) is workable.

A common situation for me would involve facing off a piece I have just parted. In this case, simply turning a little more of the parent stock down than strictly necessary for the piece leaves an identical (to very close tolerance, at least) stub I can use in the "back" of the collet. Of course, if making multiples of a part, one can simply use the duplicate parts.

I'm sure there are a number of downsides to this, but in practice I have found it pretty effective. I've used the trick on both the collet chuck on the lathe and with collet blocks on the mill. It seems like a dead obvious thing to try to me, but I have not seen it mentioned anywhere, so perhaps not as obvious as I think?

-Pete

 

[Beckerkumm]

Great thread. I can't add to the science but I've gotten some sort of collet chuck and collets with my used lathes. I suspect that leads some to their choices since they have a start when collecting. My first lathe had a 5C taper in the spindle and a draw bar set up with a lot of collets. Since i knew no better, I decided 5C was the way to go. I scrounged and found an almost complete set of NOS Lyndex 64th collets and added some Hardinge and NOS Royal. Then I found the draw bar needed work or it introduced runout when tightened down so I worked on that. Then I found the ways introduced variation because there was so little wear near the spindle vs a few inches outward so I found a NOS Bison set tru chuck to span the distance. Second lathe had a Sjogren type 5c chuck that was good and ran true within .0005 and a lot of not so great used collets so that made my earlier decisions less dumb.

The point here is that if buying a lathe now I would not put value on collet chucks or tooling when purchasing unless everything looked almost new and was top shelf. Adding to existing tooling can be a rat hole. Turns out I like the 5C for the work I do since most bar stock comes in standard increments but I shouldn't have based the decision on what came with the machine. You want high quality 5C collets so they are not cheap for a full collection. I suspect a Rego Fix Er set up isn't for the faint hearted either but precision is the point of collet work so it looks like a worthwhile expense. I like used stuff but in the chuck and collet world, there is a lot of risk so almost new is as old as I will go.

This comparison is useful and I hope others add to it. I got some TG 100 with a mill so that info would be helpful as well. Dave

 

[davidpbest]

Great stuff Dave, I always look forward to your posts.
I spotted one mistake at the top of page 9:



Pretty sure you meant "will be disappointing" - but it's not clear to me. Sounds like you are trying to say that using a $20 nut on a precision setup will lead to bad results. A great point - consider the whole setup as a system. I had never considered that a bad nut would push a good collet out of alignment.

Another thing I didn't see addressed (and perhaps it's a no-brainer for most people) is the ability to use long stock in the collet and keep feeding it out as you make multiple parts. I'm curious if there is much difference doing this with different collets or if it's more a matter of the machine/setup. In other words you only do this on a lathe so it's a non-starter with R8. Personal experience is that some ER holders do not provide for through hole stock. Do most lathe ER chucks/holders support through stock?

-Another Dave.

Another Dave,

Thanks for catching the typo. The document has been corrected and reposted.

As for long stock feeding, this is more of a workholding and machine setup discussion than it is specific to which type of collet. You can feed long stock through the spindle and secure it with either 5C or ER40 at the spindle nose (provided the material is sufficiently small in diameter to fit through the spindle and collet). I think you'll find that most people who are feeding bar stock through the spindle on a regular basis will prefer a 5C setup simply because it's faster to open/close the collet when moving from one part to the next (if not for other reasons such as TIR). Obviously, if your material is not a nominal size, that can complicated the decision. But I do reference on page 8 the fact that for production work a 5C collet is more convenient for bar-feed type applications. I employ a "spider" to support the bar stock, keep it centered in the spindle to improve TIR at the collet nose, and to reduce the chance for long stock to begin to whip uncontrollably which is a major safety hazard. You can see my implementation of a spider at this link, and there is an excellent discussion of another version at this link and elsewhere in various forums here on H-M.

David Best ( I go by David, Dave was my father. )

 

[davidpbest]

Which brings the next question: is the Precision Mathews version better?

I don't have experience with the PM 5C collet chuck, but there is a lengthy post on this subject at this link. At a certain level, the adage "you get what you pay for" applies here, so I wouldn't expect an industrial quality 5C collet chuck for $150 as James (Clough42) found out. You might call PM and ask them the country of origin - my guess is that it's made in Taiwan and probably good quality, but check with them.

 

[davidpbest]

Changing out collets on my collet chuck also requires a full 32 turns of the chuck key, which can be annoying.

You might consider making a speed handle for your collet chuck (@mksj version shown):

Or a cordless ratchet - lightly held so as not to over-tighten and distort the collet geometry:

 

[Ischgl99]

I'm driving my son back to college, so can't find the link right now, but I made a post about the 5c collet chuck I got from PM a while back. Definitely not Taiwanese quality, a bit rough as received, but it cleaned up well and works fairly well.