A Different collet question

>>> Hi
>>> I am very new to model engineering or any engineering actually
>>> .
>>> I have never worked in an engineering occupation of any kind, I didnt
>>> even do engineering metalwork at school ( 46 years ago) instead I chose
>>> woodwork and a bit of beaten metal work .
>>>
>>> I have in the last few weeks bought myself a Myford Super 7B lathe and a
>>> Warco VMC mill and am presently building a 3" scale Little Samson
>>> traction
>>> engine which is quite a challenge with my lack of any experience ,but I
>>> am
>>> enjoying every minute of it , well almost every minute.
>>>
>>> My milling machine has an R8 spindle and with it came a set of ER32
>>> collets from 2.5mm to 20mm. This in itself was a shock, I just assumed
>>> that every thing like cutters and drills would fit into a jacobs type
>>> chuck. The collets were a nice surprise, They are easy to use and grip
>>> really well, and they seem very accurate with no wobble like you would
>>> get
>>> from a jacobs chuck.
>>>
>>> Anyway enough waffle , my question is, my collets are ER32, but I have
>>> seen for sale collets called ER25 ER20 ER16 and even ER11. So, what do
>>> the
>>> numbers mean , what is the difference in an ER32 collet and an ER11 one.
>>> Is one better than the other or are they equally as good but for
>>> different
>>> jobs?

>>
>>
>>Don
>>
>>You have the same set up as I do - happy to discuss it with you by e-mail
>>off group if I can help.
>>
>>If you are within travelling distance of London I recommend joining the
>>Society of Model and Experimental Engineers (SMEE). Bunch of great guys
>>and
>>very helpful. I did their Polly training course last year and learned a
>>lot - it's running again this year.
>>
>>Be very very careful with the ER 32 collet chuck. As Andrew says, you
>>never
>>hold a milling cutter in a Jacobs chuck becaue they are not designed to
>>resist sideways thrust and (more importantly) they don't resist the pull
>>down force on a milling cutter - it's quite scary watching your cut get
>>deeper as it progresses.
>>
>>ER collets are designed to hold over a range of diameters. My experience
>>is
>>that the ER32 is difficult to tighten to the lowest diameter, especially
>>on
>>the VMC where there is no spindle lock and especially on the smaller
>>diameters where the collet is very stiff. For example, if you want to use
>>a
>>1/4" end mill in a metric chuck then you have to use the 6 - 7 mm collet.
>>On my set up I can't tighten an ER32 down to 6.25 mm tightly enough to
>>prevent the cutter moving.
>>
>>I have the ER32 chuck which came with my mill but I vastly prefer the
>>security of an autolock chuck, where the cutter just can't move under
>>cutting load.
>>
>>Norman Billingham
>>

>
> Where ER collets really come into their scope is that many of the
> modern cutters are not working to older specs like grinding a 1/4"
> shank down to 3/16" or 1/8" then putting a thread on it.
>
> There are more and more cutters made nowdays where the shank = the
> cutter diameter and no thread.
> In effect making Clarkson chucks not as universal as ER's
>
> Not looking to start a fight over various work holding methods just
> making an observation, at the recent Bristol show, Jenny at JB Cutting
> tools had no threaded cutters on the stand at all.
> --
> Regards,
>
> John Stevenson