QMT High Precision Adjustable ER-40 ER Collet Chucks and 5C chucks in D1-4 and D1-5

In this discussion of 5C vs. ER it seems to me that (again, from research, not experience) there are two important considerations that would drive one's decision in addition to what has been mentioned. They may have both been brought up, but I don't remember at this point.

The first is whether the work that you will be holding is long enough to reach the back end of the collet in the case of the ER system or if you plan on holding short pieces. From what I can tell this is the major difference between these two systems. If your work is short and you can only hold a small portion of the piece then an ER collet will not work properly. In this case it seems to me that you have no other choice than to use a 5C system, if you are wanting to work with a collet, or go back to a jawed chuck.

The second would be production of numerous identical parts and you are in a time equals money situation. Then you would want the production value that is offered by a lever type collet closer with the 5C system. Of course you could use the various methods of speeding up the collet adjustment process such as drills, "speed spindles" or an Atlas chuck, but it seems that the standard production method is the lever.

I look at this as being the same as anything else in life, and that's a matter of compromises. As a newbie laying out a lot of money for what is now just a hobby, funds are limited and ER is cheaper, considerably. It will have limitations that I can see being hit, but in deciding what to purchase initially I need to look at what is likely going to be fitting the most needs for the money spent. It's a starting point.

I hope to sometime in the future, when I have gained enough experience, to procure one off work to help make some extra income and maybe pay for some of all this very expensive stuff! Should that day come then I have little doubt that I will likely end up with both systems.
 
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Larry$ said:
I got the 5C with adjustable back plate from QMT when I got my lathe 5 years ago. My chuck looks different and does not have the PM logo. It is a very nice chuck and I use it when the work will fit rather than a jaw chuck. The 5C collets will grip very short work. Disadvantage is the very limited range. On work less than 5/8"+- you really have to have 1/64" steps. My spin indexer and collet blocks are 5C.
Our CNC router uses ER32 from Techniques. They claim their collet nuts are superior to ball bearing ones. They also say to insert the bit to nearly the full depth of the collet. I've heard users say that isn't necessary. We had an employee put a bit in only about 1/2 the depth of the collet trying to reach deeper with a tool. He was lucky, when the 1/2" bit exited the collet at 16,000 rpm it just dented the wall.
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It is just what happens when using a cutter to go deeper when what is really needed is a longer cutter.
 
wrmiller said:
What does closer to the headstock get you?
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One disadvantage of having the collet chuck right up against the spindle is that you have to crank out the compound to part off (or do other operations) right up next to the chuck. This lowers rigidity since the tool is cantilevered out on the compound which is notoriously weak on a machine like the 1340. If the collet chuck is further out toward the tailstock, you can pull in the compound and position the tool post directly over the compound rotational mount which significantly improves rigidity (critically important for parting operations).

I started with an ER40 collet chuck on D1-4 mount from China. I also implemented a solid tool post which substitutes for the compound (unless cutting tapers) and vastly improves rigidity. But with the solid tool post, the carriage would not move close enough to the spindle to perform machining operations right up next to the collet as can be seen in the setup below:


IMG_5236.jpeg


I wasn't happy with the runout on the Chinese ER40 collet chuck either, so I decided to make my own replacement chuck with Set-True adjustability, and in the process lengthen the stick-out from the spindle nose so I could get right up next to the collet with the tool as can be seen below:

IMG_5231.jpeg
 
wrmiller said:
What does closer to the headstock get you?
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Put a piece of .125 stock in the chuck sticking out 3 inches then stick it out to 6 inches and see what happens when the lathe is started. The same happens when your chuck is stuck out that far.
 
Jake P said:
In this discussion of 5C vs. ER it seems to me that (again, from research, not experience) there are two important considerations that would drive one's decision in addition to what has been mentioned. They may have both been brought up, but I don't remember at this point.

The first is whether the work that you will be holding is long enough to reach the back end of the collet in the case of the ER system or if you plan on holding short pieces. From what I can tell this is the major difference between these two systems. If your work is short and you can only hold a small portion of the piece then an ER collet will not work properly. In this case it seems to me that you have no other choice than to use a 5C system, if you are wanting to work with a collet, or go back to a jawed chuck.

The second would be production of numerous identical parts and you are in a time equals money situation. Then you would want the production value that is offered by a lever type collet closer with the 5C system. Of course you could use the various methods of speeding up the collet adjustment process such as drills, "speed spindles" or an Atlas chuck, but it seems that the standard production method is the lever.
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Both points are valid Jake. In practice, I have found that the work piece needs to be inserted at least half-way into the ER40 collet to get a repeatable grip with consistent TIR. I would never chuck up a tool in that manner, but for workholding, 25mm or 1" is sufficient - anything less will be hit or miss on TIR. I know Mark really likes and uses the 5C short-grip potential.

Also, in a production setup, where a 5C quick-release collet closure is employed, presumably the volume of product being produced is high enough that machining a 5C emergency collet to closely fit the material would be justified and resolve the off-nominal gaps in the collet sequences.

There is no "right answer" here - it really depends on the kind of work you intend to pursue. Lots of people don't even stop to consider something other than 5C, or realize it comes with its own set of limitations.
 
I agree with David, it is a matter of preference and knowing the strengths/weaknesses of different work holding systems for the type of work you are using them for. They all have their place. As far as stick-out and TIR, it is all relative if you can adjust for it, granted the farther out you get very small axial difference are magnified. The advantage of the set-tru type chucks is you can compensate for it and it holds pretty tight tolerances moving away from the chuck. At least there are two quality options with the QMT/PM chucks that people can choose one or the other at a reasonable price.

ER-40 Set-Tru readings are in 0.0001" per increment
 
Dave,

my 14 x 40 Jet goes right to the collet face, with out extending the compound.
 
I don't use my compound but when I did I'm pretty sure mine did too although my lathe is a little larger.
Anything that sticks out from the spindle is going to be less rigid.
 
Buffalo21 said:
Dave,

my 14 x 40 Jet goes right to the collet face, with out extending the compound.
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Right. I’ve used a couple other lathes where the carriage isn’t as restricted as the PM-1340GT when advancing toward the spindle. This is a case where the 1340 might be peculiar - the carriage butts up against the feed rod connections on the side of the Norton gearbox well before a tool centered over the compound rotation collar is anywhere close to the collet.
 
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