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ER40 versus 5C Collets - Considerations and Trade-offs
- Thread starter davidpbest
- Start date
- Joined
- Dec 21, 2018
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- 2,136
We've been over this territory before. I've got both horses in this race: ER or 5C (+R8). Fact of the matter is both have advantages & disadvantages. The claim that 5C only holds well on work that perfectly matches the collet bore is a bit dubious, since the likelihood of a perfect match is minimal But close enough of us who aren't working to .0001.
I have noticed that Joe Pie very often uses Enco 5C collets in his videos in spite of his apparent preference for ER in this video.
About one type having greater holding power, likely true BUT both have "enough" for their intended purpose. AS for the bearing ER nut claim to fame of being easer to tighten/loosen, Do you actually use less force when you use the bearing type? Or do you just get a lot more holding power than what is required for the job at hand. We've run some pretty massive tooling on our CNC with ER32 collets and as long as the tools are fully seated into the collet and the nut properly torqued (we use a fixture and torque wrench) everything is happy.
Personally I use the 5C on the lathe way more often than the ER40. I will hold very short insertion depths in a 5C that will not work in an ER40. The disadvantage, for me, is the limited holding range of the 5C, requiring lots of collets for the full range. (Which I don't have.) I do have a few hex & square 5C collets & one external hold, all of which can be very handy. PS, you can go broke buying every collet there is!
My person preference for the 5C is likely due to the fact that it was the first system I got. Lathe chuck, collet blocks, tool & cutter grinder, & spin indexer all in 5C. I do have an ER40 chuck and R8 to ER40 adapter. All my collets are imports. My chucks are of the "Run-Tru" type, so if I'm feeling fanatical, I can get ± dead on when reversing work.
I have noticed that Joe Pie very often uses Enco 5C collets in his videos in spite of his apparent preference for ER in this video.
About one type having greater holding power, likely true BUT both have "enough" for their intended purpose. AS for the bearing ER nut claim to fame of being easer to tighten/loosen, Do you actually use less force when you use the bearing type? Or do you just get a lot more holding power than what is required for the job at hand. We've run some pretty massive tooling on our CNC with ER32 collets and as long as the tools are fully seated into the collet and the nut properly torqued (we use a fixture and torque wrench) everything is happy.
Personally I use the 5C on the lathe way more often than the ER40. I will hold very short insertion depths in a 5C that will not work in an ER40. The disadvantage, for me, is the limited holding range of the 5C, requiring lots of collets for the full range. (Which I don't have.) I do have a few hex & square 5C collets & one external hold, all of which can be very handy. PS, you can go broke buying every collet there is!
My person preference for the 5C is likely due to the fact that it was the first system I got. Lathe chuck, collet blocks, tool & cutter grinder, & spin indexer all in 5C. I do have an ER40 chuck and R8 to ER40 adapter. All my collets are imports. My chucks are of the "Run-Tru" type, so if I'm feeling fanatical, I can get ± dead on when reversing work.
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- Dec 18, 2022
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- 2,564
I have and do like the nuts with the bearing, I like them because they do not apply a twisting/rotational force to the collet.
- Joined
- Dec 26, 2015
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- 2,138
Well, I haven't noticed anyone here saying that the work has to match the bore of the 5C collet to a tolerance of ±0.0001. The published spec is +0.000/-0.003". But you are correct that both systems have their advantages and disadvantages.
After my .0001" .I only bought my 5C collet chuck because I had some short pieces I needed to hold, I much prefer the ER40 chuck for most of my work. The biggest disadvantage is what David posted, the 0 to -0.003” tolerance of the work piece for a 5c collet. If there was a better system, I would ditch 5c in a heartbeat. There is a chuck I would like to get, the Ortlieb chuck is exactly what I would like to have, compression collets like the ER system, and 5c style collets for short pieces. It is well out of my price range, but maybe some day…
- Joined
- Feb 21, 2022
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- 844
What happens when a 5C collet is used for smaller sizes than its recommended diameter range?
Do the changing diameter differences between the collet & the nose as they migrate into the taper, have an effect on the parallelism of the bore?
Let's consider the following parameters, using round figures where possible.
Chosen major diameter of the collet – 38mm – Chord length between slots – 32.1333mm
Chosen minor diameter of the collet – 34mm – Chord length between slots – 28.6662mm
Distance apart – 11.3426mm – Derived from the 10 degree angle & 2mm difference in radii.
Slot widths – 1.5mm
Nominal clamping diameter – 20mm
Undersize clamping diameter – 19.8mm= 0.2mm or ( 0.008” ) smaller.
The collet needs to be drawn into the nose taper by 0.3017mm to allow its bore to touch the undersize rod perimeter. At this position, the major chord ends touch the nose taper at a diameter of 37.8936mm and the minor chord ends touch the nose taper at a diameter of 33.8929.
The difference in the two diameters is 4.0007mm, the nominal difference used was 4mm.
These calculations relied on having a sharp corner between the end of the chords and the slot edges. Adding a tiny radius at the ends of the chords will theoretically have quite a large effect on these results.
A force often overlooked is the rod diameter acting on the bore, this also has an effect on the collet jaw angle, not just the nose taper. There are demonstrations attempting to prove otherwise. They only show the initial contact, not the remainder of the clamping operation where the final seating occurs & the jaws conform to both the taper & the bore.
In conclusion:
Using a 5C collet way below its intended range still clamps parallel within 0.0007mm ( 0.000027” ) over a distance of 11.34mm.
For the bore to still remain parallel within 0.7 microns ( 1/3rd of a tenth ) so far out of its working range. Can it be assumed, within reason, that the major and minor diameters close in equally, retaining the included angle & therefore the bore parallelism?
This small amount of flex required in the collet flexures is easily accommodated in the design, & is one reason why they are so long.
Do the changing diameter differences between the collet & the nose as they migrate into the taper, have an effect on the parallelism of the bore?
Let's consider the following parameters, using round figures where possible.
Chosen major diameter of the collet – 38mm – Chord length between slots – 32.1333mm
Chosen minor diameter of the collet – 34mm – Chord length between slots – 28.6662mm
Distance apart – 11.3426mm – Derived from the 10 degree angle & 2mm difference in radii.
Slot widths – 1.5mm
Nominal clamping diameter – 20mm
Undersize clamping diameter – 19.8mm= 0.2mm or ( 0.008” ) smaller.
The collet needs to be drawn into the nose taper by 0.3017mm to allow its bore to touch the undersize rod perimeter. At this position, the major chord ends touch the nose taper at a diameter of 37.8936mm and the minor chord ends touch the nose taper at a diameter of 33.8929.
The difference in the two diameters is 4.0007mm, the nominal difference used was 4mm.
These calculations relied on having a sharp corner between the end of the chords and the slot edges. Adding a tiny radius at the ends of the chords will theoretically have quite a large effect on these results.
A force often overlooked is the rod diameter acting on the bore, this also has an effect on the collet jaw angle, not just the nose taper. There are demonstrations attempting to prove otherwise. They only show the initial contact, not the remainder of the clamping operation where the final seating occurs & the jaws conform to both the taper & the bore.
In conclusion:
Using a 5C collet way below its intended range still clamps parallel within 0.0007mm ( 0.000027” ) over a distance of 11.34mm.
For the bore to still remain parallel within 0.7 microns ( 1/3rd of a tenth ) so far out of its working range. Can it be assumed, within reason, that the major and minor diameters close in equally, retaining the included angle & therefore the bore parallelism?
This small amount of flex required in the collet flexures is easily accommodated in the design, & is one reason why they are so long.
- Joined
- Dec 21, 2018
- Messages
- 2,136
I suspect you are correct. I know I have used 5C collets on under sized work (successfully±) within limits of course. The larger the collet size the more deviation it will tolerate. My set stared out as 1/32" increments. But on the smaller sizes I found they did not tolerate much under size work. The result is I've added 1/64ths collets on most things under 1/2". If I had it to over, I'd buy the full - by 1/64ths set.
About the idea that using a collet on under-sized work will damage it by permanently deforming... may be true - if too much under-sized. But I haven't seen it on my set--- so far.
My original set came from PM (Quality Tool). I keep them clean in their plastic containers.
I had modified an old, cheap battery drill to spin a stub chuck key. It died and I really don't change collets all that often so replacing it is an "on my list # 79." To change out work, it is faster in a 5C collet than in an ER, but of little matter in hobby work.