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Thread: ER Collet Chuck
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31st Mar 2019, 11:36 PM #1Golden Member
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ER Collet Chuck
I'm nearing the end of my Quorn T&C grinder build and needed a collet style end mill holder, I had planned on using a parallel shank ER25 collet chuck so I could use my existing collets and without doing my research first I bored hole for the end mill holder as per the original plans at 1inch and then went looking for a suitable collet chuck - all of the ER25 collet chucks I came across had a 20mm diam shank, I weighed up the options - an internal sleeve in the recently bored hole or external sleeve on the collet chuck shank, ultimately I decided on machining up a complete chuck to take my existing collets.
Turned out quite good run out is less than my .001" resolution dial gauge can measure and certainly less than .0005" - I did not bother with slots for a C spanner and instead went for a coarse knurl, hand tight should be good enough as end mills only need to be held firmly enough to resist light grinding pressure. The eccentric shoulder that withdraws the collet looked like a bit of a challenge but once I had a suitable tool bit ground up it went smoothly.
I did research the taper angle on ER25 collets and the consensus looked to be 8deg or 16deg included but before I started boring the taper in the holder I checked my collets and oddly enough I measured near enough to 5deg - bit confusing but I went with the 5deg (10deg included). My two ER collet and chuck sets (both chinese made) were purchased separately about 7 or 8 yrs apart and I'm at a loss to explain why they would differ from the current accepted standard.
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1st Apr 2019, 12:20 AM #2Most Valued Member
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I found the same problem, I needed a metric sized collet for my ER25, when it got here, it was a totally different length???
//metalworkforums.com/f65/t1921...ht=ER25+collet
A pic of the 2 variants.
//metalworkforums.com/attachmen...8&d=1422679210
KrynTo grow old is mandatory, growing up is optional.
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1st Apr 2019, 10:25 AM #3Golden Member
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My imperial ER set came from the Ozme store in Adelaide as well so looks like we have the same variant, my metric set came from the old Redwood machinery on South Rd many years ago - both are Chinese made, have the 5deg angle on the collets and both have 33x2 mm thread for the nut so looks like the first example the Chinese got hold of to copy were made this way. The 5 deg taper ensures that the collets get wedged in quite tight so perhaps this is the reason that an 8 deg taper has now been adopted.
Both of my collet sets have virtually nil run out so in this respect they are quite good but I have seen on one web site that the collets and nut are regarded as consumables so if any of the collets need to be replaced or in your case added to it looks as if a complete new set will be needed.
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