Collet confusion.

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Collet confusion. Kevin(Bluey) 07-03-2008
Posted by David Littlewood on July 3, 2008, 11:36 am
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>
>All clear and understood.
>
>I had that link bookmarked , and will check it out again.
>
>Not sure I'll buy a set just yet ,I still have the Myford collet set
>,But these below would be able to fit my drill press and a future mill
>with the MT 2 chuck.
>I have some other tooling I want to get first
>
>Found this set on the Bay ,price is good ,not sure on the quality ,
>made in the Peoples Republic of C .
>
>http://cgi.ebay.com.au/FULL-ER25-COLLET-SET-15-PCS-CNC-MILLING-LATHE-NEW
>-A05_W0QQitemZ110265889934QQihZ001QQcategoryZ25294QQtcZphotoQQcmdZViewIt
>emQQ_trksidZp1742.m153.l1262
>and the MT 2 chuck ,
>http://cgi.ebay.co.uk/ER25-MT2-3-8-COLLET-CHUCK-CNC-MILLING-LATHE-NEW-A6
>8_W0QQitemZ110265134618QQihZ001QQcategoryZ12584QQtcZphotoQQcmdZViewItemQ
>Q_trksidZp1742.m153.l1262
>
>On the collet page if you scroll down he has a handy chart with all the
>collet sizes etc.
>
Well the price is certainly attractive. Some of the cheaper sets have
been reported to have slightly higher run-out (lack of concentricity)
than they should, but for the holders at least it is possible to clean
them up in the lathe you will be using it on (see correspondence here a
few months ago). Not much you can do if the collets are out of true. Try
looking at the seller's feedback to see if anyone has complained, or
asking around.

David
--
David Littlewood

Posted by Peter Fairbrother on July 3, 2008, 2:09 pm
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 Kevin(Bluey) wrote:
> David Littlewood wrote:
>>>
>>>> The great advantage of ER collets is that their double taper means
>>>> they can close down by 1.0mm (0.5 for the very small sizes) and
>>>> still maintain excellent grip and concentricity. Collets with a
>>>> single taper only work efficiently for material of the exact
>>>> diameter of the collet; even normal mild steel (usually a few thou
>>>> under nominal) can be a problem with single taper collets.
>>>> This means that a set of ER collets will grip anything within their
>>>> range - you don't need a metric set and an imperial set, for
>>>> instance. They will grip milling cutters effectively. The collets
>>>> themselves do need a drawbar as the double taper holds them in; it
>>>> is the collet chuck itself that needs a drawbar, at least when
>>>> holding milling cutters.
>>>> The different numbers are just sizes. ER25 (the set I use) goes
>>>> from 1.0 to 16.0 mm; the larger sets have a correspondingly larger
>>>> range.
>>>> David
>>>
>>>
>>> David ,
>>> Thanks for clearing that up .
>>> I thought it was some evil conspiricy to extract more folding green
>>> from our pockets by having to buy a set of each because of some
>>> manufactured difference.
>>>
>> Just to make sure there is no confusion, I should explain that the
>> different sets are different in size. They are not interchangeable
>> between sets. I think it would be unfair to say this is done to
>> extract more money, just that there is a set appropriate for your
>> equipment. Thus, for my lathe (S7) and milling machine (Emco FB2) the
>> ER25 size is about right; the holders for the larger sets would be
>> inconveniently large for the 2MT spindle. The "25" in ER25 refers, I
>> think, to the widest part of the chuck taper, the actual collets are
>> about 26mm at their widest point.
>>
>> Don't let the profusion put you off, just find the right size for your
>> machinery and buy a set, you will find them invaluable.
>>
>> See, for example:
>>
>> http://www.arceurotrade.co.uk/Catalogue/Collets/ER-Collets-Collet-Chucks
>>
>> Not sure, reading my previous post, that this was clear.
>>
>> David
>
>
> All clear and understood.
>
> I had that link bookmarked , and will check it out again.
>
> Not sure I'll buy a set just yet ,I still have the Myford collet set
> ,But these below would be able to fit my drill press and a future mill
> with the MT 2 chuck.
> I have some other tooling I want to get first
>
> Found this set on the Bay ,price is good ,not sure on the quality ,
> made in the Peoples Republic of C .
>
>
http://cgi.ebay.com.au/FULL-ER25-COLLET-SET-15-PCS-CNC-MILLING-LATHE-NEW-A05_W0QQitemZ110265889934QQihZ001QQcategoryZ25294QQtcZphotoQQcmdZViewItemQQ_trksidZp1742.m153.l1262
>
> and the MT 2 chuck ,
>
http://cgi.ebay.co.uk/ER25-MT2-3-8-COLLET-CHUCK-CNC-MILLING-LATHE-NEW-A68_W0QQitemZ110265134618QQihZ001QQcategoryZ12584QQtcZphotoQQcmdZViewItemQQ_trksidZp1742.m153.l1262
>
>
> On the collet page if you scroll down he has a handy chart with all the
> collet sizes etc.

Missed this post.

The cheap ones can be pretty good, I bought an ER25 set all of which
have a TIR within a single 1/100 mm division on a normal dial gauge.


Which is pretty darn good.

YMMV,

-- Peter Fairbrother

Posted by Peter Fairbrother on July 3, 2008, 1:50 pm
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David Littlewood wrote:
>>
>>> The great advantage of ER collets is that their double taper means
>>> they can close down by 1.0mm (0.5 for the very small sizes) and still
>>> maintain excellent grip and concentricity. Collets with a single
>>> taper only work efficiently for material of the exact diameter of the
>>> collet; even normal mild steel (usually a few thou under nominal) can
>>> be a problem with single taper collets.
>>> This means that a set of ER collets will grip anything within their
>>> range - you don't need a metric set and an imperial set, for
>>> instance. They will grip milling cutters effectively. The collets
>>> themselves do need a drawbar as the double taper holds them in; it is
>>> the collet chuck itself that needs a drawbar, at least when holding
>>> milling cutters.
>>> The different numbers are just sizes. ER25 (the set I use) goes from
>>> 1.0 to 16.0 mm; the larger sets have a correspondingly larger range.
>>> David
>>
>>
>> David ,
>> Thanks for clearing that up .
>> I thought it was some evil conspiricy to extract more folding green
>> from our pockets by having to buy a set of each because of some
>> manufactured difference.
>>
> Just to make sure there is no confusion, I should explain that the
> different sets are different in size. They are not interchangeable
> between sets. I think it would be unfair to say this is done to extract
> more money, just that there is a set appropriate for your equipment.
> Thus, for my lathe (S7) and milling machine (Emco FB2) the ER25 size is
> about right; the holders for the larger sets would be inconveniently
> large for the 2MT spindle. The "25" in ER25 refers, I think, to the
> widest part of the chuck taper, the actual collets are about 26mm at
> their widest point.
>
> Don't let the profusion put you off, just find the right size for your
> machinery and buy a set, you will find them invaluable.
>
> See, for example:
>
> http://www.arceurotrade.co.uk/Catalogue/Collets/ER-Collets-Collet-Chucks
>
> Not sure, reading my previous post, that this was clear.


AET stuff is nice, but for ER25 collets

http://cgi.ebay.co.uk/FULL-ER25-COLLET-SET-15-PCS-CNC-MILLING-LATHE-NEW-A05_W0QQitemZ120273119058QQcmdZViewItem?_trksid=p3286.m20.l1116

is pretty good quality, and a quarter the price - and at under £18 for
the full set there's no VAT or customs fees to pay.

(satisfied customer only)

-- Peter Fairbrother

Posted by Peter Fairbrother on July 3, 2008, 2:00 pm
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David Littlewood wrote:
>> Hi ,
>> I have been surfing sites like Chronos , RDG and RHR looking for some
>> tooling and I noticed the number of different collets available ,
>> this is leading to some confusion on my behalf.
>>
>> Just wondering why there are so many differnt collets , there are ER
>> 32, ER35, ER40 etc and probably a heap more that I have not seen or
>> heard off .
>> What are differences and advantages one over the other.?
>>
>> The ones I remember from my trade days were threaded and were drawn
>> into the lathe spindle using a draw bar and hand wheel on the out
>> board end of the spindle.
>> (Hope I'm not telling my age here.)
>>
>> I'm not looking to buy any , as I have a full set of what I think are
>> Myford collets and a chuck that came with the Super 7 . There is one
>> "ring in" in the set it has Hardinge stamped on it and is slightly
>> different in the profile (concave)on the front face.
>> I don't use them a lot ,but if you are machining lots of parts from
>> small diameters they would make life easier.
>>
>> Thanks .
>
> The great advantage of ER collets is that their double taper means they
> can close down by 1.0mm (0.5 for the very small sizes) and still
> maintain excellent grip and concentricity. Collets with a single taper
> will only work efficiently for material of the exact diameter of the
> collet; even normal mild steel (usually a few thou under nominal) can be
> a problem with single taper collets.

I'm not sure that it's the double taper so much as the fact that there
are eight gripping segments, rather than three in a normal collet.

In a three-segement collet the inside of the segments is round, and if
it is used to grip a tool which is slightly smaller than the hole then
each segment will only touch the tool on a thin line.

With eight (or perhaps sixteen) segments an ER collet will grip on 8 or
16 lines, rather than 3.

Also, as there are 8/16 gaps, they can close up more than i=f there are
three gaps.


-- Peter Fairbrother

>
> This means that a set of ER collets will grip anything within their
> range - you don't need a metric set and an imperial set, for instance.
> They will grip milling cutters effectively. The collets themselves do
> not need a drawbar as the double taper holds them in; it is the collet
> chuck itself that needs a drawbar, at least when holding milling cutters.
>
> The different numbers are just sizes. ER25 (the set I use) goes from 1.0
> to 16.0 mm; the larger sets have a correspondingly larger range.
>
> David

Posted by David Littlewood on July 3, 2008, 5:47 pm
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>David Littlewood wrote:
>> The great advantage of ER collets is that their double taper means
>>they can close down by 1.0mm (0.5 for the very small sizes) and still
>>maintain excellent grip and concentricity. Collets with a single taper
>>only work efficiently for material of the exact diameter of the
>>collet; even normal mild steel (usually a few thou under nominal) can
>>be a problem with single taper collets.
>
>I'm not sure that it's the double taper so much as the fact that there
>are eight gripping segments, rather than three in a normal collet.
>
>In a three-segement collet the inside of the segments is round, and if
>it is used to grip a tool which is slightly smaller than the hole then
>each segment will only touch the tool on a thin line.
>
>With eight (or perhaps sixteen) segments an ER collet will grip on 8 or
>16 lines, rather than 3.
>
>Also, as there are 8/16 gaps, they can close up more than i=f there are
>three gaps.
>
The eight slits help improve grip, of course, but I believe it is the
double taper and the fact that the slits are alternately from front and
back. This means that on closing down the collet grips the work or
cutter at front and back (indeed probably all the way along) instead of
just at the front. Some text books even show this diagrammatically.

David
--
David Littlewood

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